LMLechko

  
  
                              
 
_____ 1.  Given the following AA, the carbon labeled with the number _______is                alpha carbon.
 
     
_____ 2.  This amino acid classification is
 
a.                basic
b.                non polar
c.                acidic
d.                neutral and polar
 
 
_____ 3.  A protein with a positive lead acetate test could indicate the
    the presence of  _____________
 
_____ 4.  Nitrous Acid Test, tests for the presence of an amino nitrogen, and
          the bubbles that are produced represent which gas
 
_____ 5.  Ninhydrin would give a negative for what compd classes
 
_____ 6.  The  _______ test determines the presence of a phenol in the
          following:
 
_____ 7.  The Benedicts’ test determines the presence of a reducing sugar for
          what carbohydrates
 
_____ 8.  Tannic acid will _____ pancreatin.  Proof can be shown by testing
           starch with IKI and getting a  ______ color .
 
_____ 9.  Given the cyclic monosaccharide below, what is its origin
that is it form a aldose or a ketose.
 
____ 10. In determining the activity of pancreatin on starch with the _____   
test, brown indicates that the enzyme is active and converting the starch to glucose.
 
_____ 11. Given [enzyme] = constant and is unsaturated; increasing the
          concentration of the substrate will have a _____ effect on the
          turnover number, that is the turnover number will continue to _____
          until the enzyme is fully saturated, and then the turnover can not
          increase any more.
 
_____ 12. _____ and _____  would be an appropriate enzyme and substrate                 combination or couple.  The tip off to enzyme activity is the presence
          of a pink colour when the soln is tested with phenolphthalein.
 
_____ 13.   Given a human enzyme which is saturated, you start at 0 deg C and
            increase the temperature to 100 deg C.  The turn over number will?
 
 
 
_____ 14. The temperature _____ oC will not denature a human enzyme with an opt.
          Of 0 deg C
_____ 15. The nitrogenous base  _____  is found in RNA only.
 
_____ 16.  _____ are designed to ferry individual AAs to the ribosomes for           
          protein synthesis.
 
_____ 17. Enzymes which are made up of many peptide bonds, would test positive
          for the  _____ test; the test for complexity.
     
 
_____ 18. Enzymes which are frequently protein like in nature, can be natured
          by the factors that denature any protein, and upon denaturing, the
          enzyme turnover number will ______.
           
_____ 19. All carbohydrates have _____ rotations, which can be used to
          identify them.
 
 
_____ 20. Breaking the peptide bonds of the primary AA sequence of a protein is
          called ______.
 
_____ 21. Given the following formula:
 
                  specific rotation  =    observed rotation
                                     cell length x concentration
 
                    
_____ 22. Which one of the structures below lack a hemiacetal structure so that
          the carbohydrate can not react with Benedict’s soln.
 
 
_____ 23. Which of the following would be a proper set of RNA - RNA base pair           relationships:
 
                       
____ 24. Which of the following statements is false about all nucleic acids.
           
 
______ 25. In the general class of a ribonucleotide. which is absent.
           
     
______ 26. Which of the following could not possibly be a codon in mRNA.
 
     
_____  27. Examine of the following DNA strands.  This would represent what kind
           of change. The cause and effect relationship
 
             original ===> C-U-G-A-U-G-C-A-A-U-C
             mutated  ===> C-U-G-U-G-C-A-A-U-C-
 
_____  28. Which one of the following sample mixtures would have the
      highest proportion of saturated compounds according to the I index.
 
           
_____  29. Given the following Iodine numbers, which one of the following
           sample mixtures would have the lowest m.p.
 
     
_____ 30.   Which one of the following statements about lipids (any type) is
            false.
 
           
_____ 31. Which one of the properties of Tags
                 
_____ 32.   If 4.2 grams of bromine is used to completely react with 0.4 grams            of a lipid, the approximate Iodine number would be:
 
           
 
           
            Iodine number = (grams of Bromine - .2) x 8.0
                                  grams of fat.
 
 
______ 33.  Sometimes an unusual base inosine is found on the_____ position of
            the tRNA anticodon.
 
 
______ 34.  mRNA is made directly off the _____ with Crick Watson base paring
 
 
 
 
______ 35.  The _____ of a large block of deoxyribonucleotides on the
            informational strand would _____ the primary amino acid
            sequence of a translated protein
 
 
______ 36.  Given the monosaccharide fructose, the _____ test is specific
             for the presence of this ketohexose.
 
 
______ 37.  You are given the following two carbohydrates: galactose and
sucrose.  You test the solutions with Benedict’s soln.  Benedict’s     soln. will test.
     
______ 38.  You are told that the deoxyribonucleotide of A in a DNA
            information strand has been replaced with a C.  This would be base
            substitution and will _______ change the primary amino acid
            sequence.
 
 
______39.   The _____tests would be a good test to distinguish starch from
            galactose.
 
 
 
 
 
 
 
 
 
 
 
 
 
 
 _____ 40. Given the following modified dipeptide:  Which test/s would be
            positive:
 
_____ 41.   Given a normal strand of DNA and a mutated strand, what amino acid replaces that amino acid of the mutated strand replaces that of the normal strand.
 
                        Normal                  Mutated
 
            DNA   A-T-T-G-G-C-C-T-A       M A-C-T-G-G-C-C-T-A
           
 
 
 
_____ 42.   On the ribosome following initiation during protein synthesis, the            t-RNA bearing the new incoming amino acid pairs with the
            condon on the p position on the ribosome.
           
 
_____ 43.   Given the formula for the I index with the following data:
Determine the quantity of lipid present and the quantity of bromine added. This Iodine would be define this lipid as being an oil. 
Hint:  calculate the Iodine number.
 
 
 
            Iodine number = (grams of Br2 – 0.2) X  8.0
                                    Grams of lipid
 
 
                                  Flask and cork weight)
            Empty       with     (g lipid)  with    with   (g bromine)
                        lipid              (CH2Cl2) Br2
 
 
                   35.00       35.4                  40.1   44.0
 
 
 
 
 
 
 
_____ 44. Given the monosaccharide glucose, the measured specific rotation
           is an equilibrium balance between the Œ and õ anomeric forms of that
            carbohydrate in solution.
 
______ 45.  Carbohydrates which are common in biological systems are the D in
            configuration.
 
 
 
 
 
_____ 46.   Given the following information strand of DNA, the protein
            represented below would be the appropriate sequence:
 
 
            informational strand  C-C-T-G-A-C-G-C-G-G-T-T
 
            The protein is:  Met-Pro-Asp-Ala-Val
 
_____ 47.   The anti-codon for C-C-U: is G-G-A
 
_____48.    All final proteins start with the amino acid methionine.
 
_____ 49.   An error or a mutation in RNA can be copied into DNA and passed
            on to future generations.
 
_____ 50.   Is the following information as presented correct?  Is this the
            dipeptide, informational strand, and template configuration?
 
 
 
            Information strand  (5’è 3’)       T-A-C-C-G-A
            Template strand      (3’è5’)        A-T-G-G-C-T
            m-RNA               
(5’è3’)         U-A-C-C-G-A
            Dipeptide                           Try-Arg
 
           
 
 
 
 
As the late Jim Morrison said:  “what have they done to my fair city?” 
      
  
  
  
  
  
 

Carbohydrates

Section: 22.1

• carbohydrates: a member of a large class of naturally occurring polyhydroxy aldehydes or ketones
 name of compd. ends w/ the “ose” ending

• monosaccharides: a carbohydrate that can not be broken down into smaller units by hydrolysis with aqueous acid
o typically three to seven carbons in length
 glucose: pentylhydroxylhexanal
 fructose: pentylhydroxylhexanone
 galactose: penthylhyroxylhexanal

• disaccharide: a carbohydrate, which yields two monosaccharide on hydrolysis, identical or different. Bonds are really ether like linkages
o held together by a glycosidic bond or also called acetal bond
 lactose
 maltose
 sucrose

• polysaccharides: a carbohydrate that is composed of many monosaccharides bonded together. This is really a polymer of many monosaccharides put together end to end. Really a polymer of monosaccharides. Monomer composition or different, and if different order determines the type polysaccharide
o complex carbohydrates
 glycogen: animal
 cellulose: plant
 amylose: plant
 amylopectin: plant


• aldose: monosaccharide which contains an aldehyde functional group

• ketose: a monosaccharide which contains a ketone functional group


Naming and Examples of monosaccharides

• the number of carbons is specified by multiplicative prefixes identical to that in naming other compds

• see page

• can you find the aldehyde functional group?

• can you find the ketone functional group?



Section 22.2 Handedness of Carbohydrates

• the simplest of the carbohydrates is the three carbon compd. glyceraldehydes
• there exists two forms:
o D-glyceraldehyde
o L-glyceraldehyde
• these compds exist chiral character
o meaning lack of plane of symmetry
o they are mirror images of each other
o same chemical properties
o all physical properties are the same except their ability to rotate a plane of polarized light
o there are called optical isomers
o the measurement of optical rotations is accomplished by a device called a polarimeter
o one will rotate light to the right and the other will rotate light to the left
o this compd. w/ one chiral center can only have two optical isomers
o if there are more chiral centers, then there are more optical isomers possibilities
o if you have 2 chiral centers, then you can have four optical isomers
 two optical isomer pairs
o thus there is a D and L erythrose and a D and L threose
o however, erythrose and threose are stereoisomerisms
 stereoisomers: some formula and connections but different spatial arrangement
 diastereomers: stereoisomers that non mirror images of each other

Section 22.3 Fisher Projections

D-sugars: monosaccharides with the OH group on the chiral atom farthest from the carbonyl group pointing to the right in a

Fisher projection. The representation “dextro” is derived from the fact that the OH group points to the right

L-sugar: monosaccharide with the OH group on the chiral atom farthest from the carbonyl group pointing to the left in a Fisher projection. The representation “levo” is derived from the fact the OH group points to the left


• see page 603

In a Fisher projection, the carbonyl group of the ketone or the aldehyde is always placed at the top of the projection

glyceraldehyde is the simplest of the monosaccharides

this means that the OH and the H groups pointing to the left and the
right of the chiral atoms are projecting into the paper and those above
and below the chiral centers are projecting out of the paper

see page 603 again

note in the D sugar form the OH group projects out of the paper
and to the right
note in the L sugar form the OH group projects out of the paper and
to the left

see examples page 606



22.4 Structure of Glucose and others

• sometimes call dextrose or blood sugar
• source of energy for almost all living organisms
• stored as a polymer as starch in plants and glycogen in animals
• hemiacetal forms from the internal condensation of an aldehyde group and an alcohol group of that sugar
• internal hemiacetal formation is possible
• the C1 and C5 carbons condense to form a six member ring which has an oxygen in the ring instead of a carbon
• see figure 22.3 page 608
• OH groups pointing left point up in the cyclic structure and those which point to the right, point down
• the hemiacetal carbon is always bonded to two oxygen atoms
• this means that the carbon is chiral
• this creates alpha and beta anomers
• in the beta form the OH group points up and in the alpha form the OH group points down
• anomers: cyclic sugars that differ only in the positions of the on the hemiacetal carbon; the alpha form has the OH group on the opposite side of the –CH2OH; the beta form has the –OH group on the same side as the –CH2OH
• anomeric carbon: the hemiacetal C atom in the cyclic sugar, the C atom bonded to an –OH group and an O in the ring
• mutarotation: change in rotation of plane polarized light resulting form the equilibrium between cyclic anomers and the open chain form of a sugar
• see page 609 for review: KNOW!


Section 22.5: Important Monosaccharides

• the monosaccharides w/ their many hydroxyl groups which permit hydrogen bonding between other monosaccharides are generally high melting, white crystalline solids
• w/ many opportunities for hydrogen bonding, they have high solubility in water and are insoluble in non-polar solvents
• most are sweet in taste and digestible as an energy source
• those of interest include:
o glyceraldehyde
o fructose
o aldohexoses
o aldopentoses
• most are in the D-family
• Glucose:
o most important of the carbohydrate of human metabolism
o final product of carbohydrate digestion
o provides acetyl groups for the Krebs’ Cycle
o hormones insulin and glucagon maintain proper glucose levels in the blood
• Galactose:
o component of the digestion of lactose
o aldohexose (see page 612)
o identical in arrangement of the carbons and hydroxyl groups in order, but orientation of the OH- group at position turned and opposed to glucose where it is turned down
o the body converts galactose to glucose
o galactose can be made from glucose to provide lactose for breast milk
o galactosemia: genetic disorder which the individual cannot process galactose, its build up may cause mental retardation, liver failure, and cataracts


• Fructose:
o see page 613
o ketohexose
o part of the glycolysis cycle
o six carbon sugar
o because of the presence of the ketone functional group and through internal condensation with carbon # 5, a five member ring results
o there are also α and β anomers
o sweeter then sucrose

• Ribose and 2-Deoxyribose
o see page 613
o both are five carbon aldehyde sugars
o found in many aspects of biological chemistry, especially DNA, RNA, and cyclic AMP

22.6 Reactions of Monosaccharide

• Reactions w/ oxidizing agents: Reducing sugars by definition
o aldehydes can be oxidized to carboxylic acids, but that reaction applies only to open chained form of the aldose monosaccharides
o if you have a given sample, the open chain will continue to react with the oxidizing agent, the equilibrium will shift, until all of the cyclic forms are consumed
o any carbohydrate that reacts w/ a reducing agent is called a reducing sugar by definition
o a ketose also behave as reducing sugar in basic solution such as Benedicts’ because of a keto-enol tautomeric shift, that is the ketone is converted to an aldehyde
o this aldehyde then can undergo oxidation
o in basic solns., all monosaccharides of either ketose or aldose origin behave as reducing sugars

• Reactions with Alcohols:
o an alcohols is a hemiacetal which can react with other alcohols to make a acetal
o a acetal has two OR groups bonded to the same carbon
o the class of compounds which reacts when a cyclic hemiacetal reacts together is called a glycoside:
 a cyclic acetal formed by the Rx of a monosaccharide with an alcohol w/ accompanied by the release of water, a condensation reaction
• the bond which o=is formed by this condensation reaction is called a glycosidic bond, by definition, the anomeric carbon must be involved in that bond
• when two monosaccharides are combined, the anomeric carbon of one carbon is reacted w/ the –OH of another monosaccharide

22.7 Disaccharides:

• when you have a disaccharide, the bond can also be α or β
• in the example on page 617 there is representation of an α and β bond types. These are stereoisomers of each other
• Maltose:
o malt sugar
o two α D-glucose molecules are linked in an alpha configuration
o note that carbons 1 and 4 are involved, hence name is called α 1-4 glycosidic bond
• Lactose:
o β-D-Galactose
o β-D-Glucose
o β-1,4 glycosidic bond
o age increases risk of lactose intolerance


• Sucrose:
o table sugar
o hydrolysis of sucrose produces:
 α-D-glucose
 β-D-fructose
• called invert sugar
• non reducing sugar because the anomeric carbons are linked together
• bond type is a 1,2 anomeric link
• can not ID as α or β link because both anomeric carbons are joined together
• only common disaccharide which is not a reducing sugar, a good ID for lab when trying to distinguish between two disaccharides

22.8 Variation on Carbohydrate Theme

• monosaccharides w/ modified functional groups are found and have many important structural applications, see page 620
• Chitin:
o structural polymer
o insect shells
o N-acetyl-D-glucosoamine
• Connective tissue Polysaccharides:
o protein fibers are embedded in a matrix of un-branched polysaccharides (mucopolysaccharides)
o these gel like polymers behave as lubricants
o repeating unit of two modified monosaccharides
 Hyaluronate: 25K units in length
 rigid material
 holds water
 synovial fluid


• Chrondroitin-6-sulfate:
o tendons and cartilage
o linked to proteins
o dietary supplements
• Heparin:
o another polymer
o anticoagulant
o various composition contain sulfate groups
o has many negative charges to bond tightly to blood clotting factors
• Glycoproteins:
o a protein that’s a short carbohydrate chain
o carbohydrate is connected to the protein by a glycosidic bond between the anomeric carbon and a side chain of the protein, the bond is of two types, a C-N glycosidic bond or C-O glycosidic bond to an oxygen atom of a side chained hydroxyl group
o major function is cell surface markers
o important in blood group identification
o the protein portion is buried in the cell membrane and the carbohydrate portion extends above the surface of the cell membrane
o see page 623
o note the common N-acetyl-D-glucose amine bade for all three blood groups
o L-fucose is found in all three blood groups
o N-acetyl-D-galactose amine is found only in blood group A
o D-galactose is found only in blood group B
o if you are an AB individual, then you have the separate glycoproteins which contain N-acetyl-galactose amine and galactose as your markers


22.9 Important Polysaccharides

• Cellulose:
o see page 624
o fibrous structure that provides support in plants
o made up of β-D-glucose units in repeated fashion
o links are called β 1-4 glycosidic bonds
o see anti-parallel arrangement
o hydrogen bonding holds the structure together
o we as humans can not digest cellulose because we lack the enzyme β-cellulase

• Starch:
o General properties
 polymer of α-D-glucose
 joined by α 1-4 glycosidic links
 fully digestible because α-amylase
 found only in plant material:
• beans
• potato
• wheat
• rice
o amylose:
 20% of the total plant starch
 somewhat soluble in hot water
 several hundred to 1000 units of α-D-glucose linked together by α 1-4 glycosidic bonds
 coils in helical arrangement, not anti-parallel sheets
 w/o branching


o amylopectin:
 80 % of the starch
 identical monomer construction
 up to 100,000 monomer units
 α 1-6 branch to an α-D-glucose occurs approximately on each 25th α-D-glucose unit, branches can also be 100,000 units long
 digested in small intestine by α-amylase which catalyzes the α 1-4 links

o Glycogen:
 animal starch
 energy storage in the liver and muscles
 when used as energy source, the glucose is converted to glucose-6-phosphate for glycolysis
 branch points as in amylopectin but every 10 units
 size is 1,000,000 units
 readily mobilized form of glucose storage
 designed to increase the amount of glucose that is immediately available following between meals
 important for blood glucose levels and regulation
 reservoir of glucose for strenuous muscle activity
 the α 1-6 branch is broken down by a debranching enzyme called α 1-6 gluosidase which is found in the liver
 other debrancing enzymes, collectively called pancreatins complete the activity in the small intestine

This is a practice test. summary of similar questions to be found on the final. Does not have every single topic though.


_____1. What functional group/s could be found in the open chain configuration of a monosaccharide?

a. hydroxyl
b. aldehyde
c. ketone
d. both aldehyde and ketone groups present at the same time
e. aldehyde or a ketone


_____ 2. Given the following structure, this sugar represents.





a. alpha anomer
b. beta anomer
c. open chain configuration
d. none of the above


_____3. The bond, which forms between an UDP-glucose (activated glucose) molecule and glycogen is called a (n) ________ bond. This is the process of adding one glucose molecule to long glycogen chain, adding one glucose molecule at a time.

a. amine
b. amide
c. peptide
d. alcoholic
e. glycosidic


_____ 5. The reaction described as being _______ and is called ___________.

a. condensation; glycolysis
b. condensation; gluconeogenesis
c. condensation; glycogenesis
d. condensation; glycogenolysis
e. condensation; pentose phosphate shunt
a.b. none of the above meet the criteria described

_____ 6. Given that you are of the blood group O, what lipid classification is found on the outer surface of the RBC membrane are responsible for the antigenic response.

a. phospholipids
b. glycolipids
c. glycoproteins
d. cholesterol
e. none of the above

_____ 7. Amylose (starch) has the following glycosidic links:

a. alpha 1,4 and alpha 1,6.
b. alpha 1,4 and beta 1,6.
c. beta 1,4 and beta 1,6.
d. beta 1,4 and alpha 1,6.
e. no specific links, all link are random

_____ 8. Hydrolysis of glycogen produces what product/s?

a. fructose
b. glucose
c. galactose
d. fructose and glucose
e. fructose, glucose, and galactose

_____ 9. An ester of a longed-chained fatty acid and a long chained alcohol falls into what general compd. Classification?

a. carbohydrate
b. lipid
c. protein
d. oxyacid
e. wax


_____ 11. CH3-CH=CH-(CH2)16-C-OH represents a __________.
"
O

a. unsaturated fatty acid
b. saturated fatty acid
c. wax
d. triacylglycerol
e. none of the above

For questions 12, 13, 14 consider the following compd. below C=O omitted for simplicity

H
|
H-C-O-C-(CH2)16-CH=CH-CH3
| O
H-C-O-C-(CH2)16-CH=CH-CH3
| O
H-C-O-C-(CH2)16-CH=CH-CH3
| O

H

_____ 12. The compd. described above is classified as a ________.

a. wax
b. triacylglycerol (note: alternate name is triacylglyceride)
c. phosphoglyceride
d. sphingolipid
e. steroid

_____ 13. If this compd. were treated with NaOH, the products would be ___________ .

a. glycerol and water
b. glycerol and three fatty acids
c. glycerol and three Na salts of the fatty acids
d. esters and mixture of three Na salts of fatty acids
e. ester and fatty acids
a.b. none of the above


_____ 14. If I told you that the Iodine number = 20, the compd. is probably

a. probably solid at RT
b. probably liquid at RT
c. can not tell


_____ 15. Which component is not found in phospholipids?

a. fatty acids
b. glycerol
c. glucose
d. phosphate
e. all of above

_____ 16. Sphingosine contains __________ .

a. glycerol
b. two fatty acids
c. phosphate group
d. amino alcohol
e. all of the above


_____ 17 Mammalian glycolipids do not contain _______________, in their backbone

a. glycerol
b. sphingosine
c. fatty acid
d. carbohydrate
e. contains all of the above











benzene group
_____ 18. The following amino acid is ____. |
H2N-C-C=O Hint :examine R group
| |
a. non-polar H OH
b. neutral and polar
c. basic
d. acidic
e. ask Mickee.

_____ 19. Mitochondria function in _________________.

a. energy production
b. protein synthesis
c. glycolysis
d. genetic instructions
e. waste disposal

_____ 20. ATP serves as ____________, in energy transfer reactions.

a. a nucleotide unit in RNA and DNA
b. a end products of gluconeogensis
c. a end product of transamination
d. a enzyme
e. a energy currency

_____ 21. The enzymes for protein digestion are called?

a. peptidases.
b. amylases.
c. hexokinases.
d. glyosidases.
e. nucleases.

_____ 22. Glycolysis________ .

a. requires oxygen, end product is only pyruvate
b. represents the anaerobic anabolism for glucose, ATP production, and
NADH, H+ production, and pyruvate formation
c. represents the splitting off of glucose residues from glycogen
d. represents the anaerobic catabolism of glucose to lactate and ATP production
e. represents the anaerobic catabolism of glucose to pyruvate and
nothing else

_____ 23. The end result of beta-oxidation (fatty acid spiral) of FAs?

a. glucose
b. NAD+
c. acetyl-SCoA
d. glycerol
e. FAD









_____ 24. Identify the chiral carbon in the compd. below.

H a. a only
| b. b only
a Cl-C-H c. c only
| d. a and b
b Cl-C-OH e. b and c
|
c H-C-H
|
H

______ 25. Given the following enzyme substrate relationship:


amylase and glycogen

Which of the tests listed below demonstrates that the enzyme amylase
would be active

a. glucose test strip is positive for glucose
b. IKI (starch Iodine test) is dark blue for carbohydrate
c. phenolphthalein turns pink due to ammonia formation
d. no Rx because wrong substrate-enzyme relationship
e. not enough information to answer the question

_____ 26. Active transport has a(n) ________ requirement

a. ATP
b. GTP
c. CTP
d. UTP
e. all above are required for active transport


____ 27. Methionine, which is common to many proteins, would test positive with the _________ reagent.

a. Xanthropetic
b. Millons
c. Lead acetate
d. Biuret
e. Seliwanoff

______ 33. Following treatment with Pb (lead), what will happen to any enzyme? _________ .

a. the enzyme will denature and all activity stops
b. nothing will happen
c. the enzyme will be activated
d. the sulfur groups will react with lead
e. a and d



_______ 34. A major control element in the metabolism of lipids, carbohydrates, and proteins is ___________ .

a. acetyl-SCoA
b. pyruvate
c. acyl-SCoA
d. all of the above
d. none of the above




________ 39. This following conversion Rx is an example of an __________ reaction.

+ H2O
cyclopentene ----------> cyclopentanol

a. hydration
b. reduction
c. halogenation
d. substitution
e. none of the above


______ 42. _________ is the common functional group identification for an alcohol.

a. R'-O-R"
b. ROH
c. R-O-SH
d. RCOOH
e. none of the above


_______ 43. The conversion of glucose 6 phosphate into fructose 6 phosphate is an example of a(n) _____ enzyme.

a. isomerase
b. hydratase
c. reductase
d. oxidase
e. none of the above

_______ 44. Albumin can function as ___________ >

a. a buffer
b. a lipid carrier
c. a single amino acid
d. a buffer and lipid carrier
e. a buffer, lipid carrier, and an amino acid


______ 45. In blood serum, _________ ratio would represent an ideal condition.

a. a high HDL/LDL > 1
b. a low HDL/LDL > 1
c. a high VLDL/HDL > 1
d. a low VLDL/HDL > 1
e. none of the above

_______ 46. The following amine is classified as a _________ .

a. primary CH2-CH3
b. secondary |
c. tertiary H-N-CH3
d. quantenary |
e. penetenary CH3

_______ 47. A drug that interacts with a receptor to produce or enhance its normal response is called a(n) ________.

a. agonist
b. amino acid derivative
c. antagonist
d. hormone
e. steroid

______ 48. Which compd. classification would not be found on the inner surface of a cell membrane, since there is no requirement for an antigenic response?

a. carbohydrates alone
b. glycoproteins alone
c. glycolipids alone
d. glycoproteins and glycolipids
e. all above could be found in any combination


_____ 49. All of the following types of molecules function as chemical messengers except: ________________ .

a. polypeptide hormones such as insulin
b. steroid hormones such as progesterone
c. neurons, including axons and dendrites
d. amino acid derivatives classified as catecholamines
e. neurotransmitters such as acetylcholine

_____ 50. Which statement about a polypeptide hormone is incorrect?

a. hormone class produced by the pituitary
b. an example is vasopressin
c. insulin is an example
d. sex hormones are an example
e. may include the releasing hormones









_____ 51. All of the following are for energy transfer reactions in biochemical
processes except?

a. glycogen must be easily accessible
b. stored energy must be released in a controlled manner, i.e. steps
c. energy for endergonic reactions require ATP
d. NAD+ can be used to drive unfavorable chemical reactions
e. mark this if all of the above are true


_____ 52. The biochemical process in which three individual fatty acids are combined with glycerol to make a triacylglycerol is ______ and called ______.

a. Anabolism; lipogenesis
b. Anabolism; fatty acid spiral
c. Catabolism; lipogenesis
d. Catabolism; fatty acid spiral
e. none of the above

_____ 54. ATP is the molecule most often used for the transfer of energy. Which one of the following statements is false?

a. a relatively large amount of energy is release upon hydrolysis of its two phosphoric acid bonds. i.e. explosive, 1000 kcal
b. its hydrolysis release an intermediate amount, 7.3 kcal
c. it can be produced directly from glycolysis
d. its production is an energy requiring process through the cytochrome
system
e. mark this if all of the above are true.


______ 55. Coupling two different chemical reactions together, such as the hydrolysis of ATP, (the expenditure of ATP), a release of energy so that urea can be made from the Urea cycle, a synthetic process, is necessary because __________________.

a. it lowers the activation energy of both of the reactions
b. it increases the activation energy of both reactions
c. converts an exergonic reaction to an endergonic reaction
d. converts an endergonic reaction into and exogonic reaction
e. an exergonic reaction drives an endergonic one

_____ 56. Which statement concerning the co-enzymes NAD+ is true when:

NAD+ ---------- NADH, H+

a. this is a process of oxidation
b. this is a process of reduction
c. this is a process of hydration
d. this is a process of hydrogenation
e. none of the above

_____ 57. Every turn of the citric acid cycle directly produces NADH, H+?

a. 1
b. 2
c. 3
d. 4
e. 5

_____59. The fourth stage of metabolism, in which the high energy molecules from stage three (Kreb's cycle) are oxidized to produced ATP is referred to as

a. active transport
b. reductive phosphorylation
c. oxidative phosphorylation (electron transport)
d. glycolysis
e. none of the above

_____ 60. The driving force, which provides the energy for the synthesis of ATP in the fourth stage of metabolism, is the _____.

a. the endergonic conversion of ADP to ATP
b. the hydrogen ion concentration difference between the inner and outer mitochondria membranes
c. the concentration of oxygen in the cell
d. the concentration of glucose in the cell
e. all of the above


_____ 61. The terminal acceptor in the fourth stage of metabolism for the
hydrogens from NADH, H+ is a molecule of ____.
(Hint: it is group VI AND period 2 molecule and water is produced)

a. water
b. carbon dioxide
c. pyruvate
d. oxygen
e. sulfu
f.
_____ 63. The fatty acid spiral as it relates to the catabolism of a fatty acid can best be described as one in which _______ .

a. the product of the first reaction is the starting material for
for the next reaction in a linear fashion
b. a complicated series of chemical reactions which regenerate the
the same starting material for the spiral sequence
c. no connections between any of the reactants or products in the
continuous spiral sequence.
d. the same set of enzymes, sequentially tearing down fatty acids in preparation for their entry in the Kreb's cycle as acetyl-SCoA
e. The same set of enzymes, adding two carbons one step at a time to the length of fatty acids chains , preparing them to be added to a glycerol molecule for lipogenesis.

______ 64. The reaction in which ATP is converted to ADP with the release of energy is described as being _____ and classified as ____.

a. hydrolysis; and exergonic
b. hydrolysis; and endergonic
c. combustion; and exergonic
d. combustion; and endergonic
e. hydration; exergonic








_____ 65. Which of the following pathways pairs are reciprocally regulated?

a. glycolysis and gluconeogensis
b. glycogenesis and glycogenolysis
c. beta oxidation (fatty acid spiral) and lipogenesis
d. all of the above are
e. none of the above are

______ 66. Urea form deamination of amino acids is used the production of?

a. purines
b. pyrimidines
c. purines and pyrimidines
d. glucose
e. fructose

______ 67. Under anaerobic conditions, pyruvate (pyruvic acid) is directly converted to __________.

a. ethanol or lactate
b. acetyl-SCoA
c. citrate
d. steroids
e. a purine ribonucleotide (all types)

______ 68. Glycerol 3-phosphate, is the link to glycolysis from which
hydrolysis product of the triacylglycerols?

a. fatty acids
b. glycerol
c. fatty acids and glycerol
d. amino acids
e. none of the above

______ 69. Overproduction of insulin causes ____, a state in which the concentration of circulating plasma glucose is _____ than normal.

a. hypoglycemia; lower
b. hypoglycemia; higher
c. hyperglycemia; lower
d. hyperglycemia; higher
e. none of the above

_____ 70. In an individual who is starving or fasting for prolonged periods of time,the body meets its energy requirements for glucose by the process of _____, and then by the process of _______.

a. glycolysis; gluconeogenesis
b. glycogenolysis; gluconeogenesis
c. gluconeogenesis; glycogenesis
d. glycogenesis; lipogenesis
e. lipogenesis; glycogenolysis








______ 71. The pentose phosphate shunt is responsible for the production of
________ under high demands for DNA replication and transcription.
Hint: What goes into making the polymer chains of DNA and RNA. What are the starting materials required?

a. ribose sugars
b. pyruvate
c. citrate
d. glucose
e. none of the above


_____ 72. The co-enzymes involved in carbohydrate catabolism depend on a supply of _______ and carbohydrate anabolism depends on a supply of _______.

a. NAD+; NADH,H+
b. NADP+:NADPH, H+
c. NAD+; NADPH, H+
d. NADH,H+; NAD+
e. NADPH,H+; NADP+

______ 73. Muscles operating under anaerobic conditions produce high concentrations of lactate, lactate is converted to glucose, in a process called ______ .

a. the Corri cycle
b. the Kreb's cycle
c. the Fatty acid spiral
d. pentose phosphate shunt
e. none of the above


______ 74. If acetyl-SCoA is in higher concentration than can be handled by the Kreb's Cycle, ketone bodies are produced, which one is really a ketone?

a. 3-hydroxybutyrate
b. acetoacetate
c. acetone
d. 5-hydroxybutyrate
e. none are ketones

_____ 75. Ketone bodies can originate from the carbon skeletons of _______ .

a. carbohydrates
b. lipids
c. proteins
d. lipids and proteins
e. carbohydrates and protein

______ 76. Enzymes, which hydrolyze triacylglycerols, are called: _______.

a. lipases
b. proteases
c. amylases
d. nucleosides
e. none of the above




_____ 77. Chemical digestion of lipids begins where?

a. mouth
b. stomach
c. mouth and stomach
d. small intestine
e. large intestine

_____ 78. After treating triacyglycerols with lipases, they pass into the cells of the villi of the small intestine where they are than repackaged as _____________ for transport to the liver. This is the exogenous source of lipids, and these carries are dedicated solely to that the transport exogenous source of lipids.

a. chylomicrons
b. ultra-high-density-lipoproteins
c. high-density-lipoproteins
d. low-density-lipoproteins
e. very-low-density lipoproteins

______ 79. The lipoprotein carrier, which is, dedicated to the transport of lipids, which are derived form, an excess of dietary protein and carbohydrate is the ______.

a. very low density lipoproteins
b. low density lipoproteins
c. medium density lipoproteins
d. high density lipoproteins
e. chylomicrons

_____ 80. The first step in the complete hydrolysis of TAGs produces _______ .

a. glycerol and three fatty acids
b. partial break down to phospholipids, fatty acids and glycerol
c. re-esterification back to TAGs
d. triacylglycerols are directly converted to cholesterol
e. direct conversion of glycerol to pyruvate and fatty acids to
acetyl-SCoA

_____ 81. If lipid catabolism produces more acetyl-SCoA than the Kreb's Cycle
can consume because of reduced need for ATP, (increasing ATP concentration) than the process of ______________ occurs.

a. gluconeogensis
b. ketogenesis
c. lipogenesis
d. steroid synthesis
e. none of the above












_____ 82. In the process of lipogenesis, which coenzyme would be involved in this catabolic process? Id which direction that co-enzyme must operate. (Hint: the process of synthesis is always reduction. Each of the added fatty acids must be reduced with hydrogen as they are added. Oxidation and reduction must always occur at the same time. This is redox!!) Think what happens to coenzyme when it undergoes oxidation.

a. NAD+ ---------> NADH, H+
b. NADH, H+ ------> NAD+
c. NADP+ --------> NADPH,H+
d. NADPH, H+ ------> NADP+
e. only the shadow knows for sure (none of the above)

_____ 83. If the concentration of ATP in the cell controls the conversion of
conversion of glucose to glucose 6 phosphate, this is an example of
what kind of control mechanism. (Hint: control based on a inhibitor, which does not resemble the substrate, which was changed to product at the active site).

a. allosteric
b. competitive
c. non-competitive
d. helper competitive
e. lock and key

______ 84. Which statement best summarizes the digestive process of proteins?

a. amine groups are removed from all amino acids during this process.
b. all peptide links are hydrolyzed to produce an amino acid pool
c. stomach acids denature proteins
d. amino acids are combined to make new proteins and enzymes
e. none of the above

_____ 85. Which of the following enzymes are not involved in the hydrolysis of the peptide bonds?

a. pepsin
b. trypsin
c. amylase
d. carboxypeptidase
e. chymotrypsin

_____ 86. The amino acid pool is a collection of _________ .

a. all the amino acids available from the diet
b. amino acids produced from the break down of proteins and reused.
c. essential amino acids from diet
d. nonessential amino acids made by the organism
e. all the free amino acids in the body, either essential or
nonessential
a.b. all the amino acids in the both, both essential and nonessential; found either as free amino acids or found in proteins.








_____ 87. The common feature of the catabolism of all amino acids is the following: (Hint: think about how energy is going to be produced)

a. removal of an amino group and the remaining carbon skeleton
can end up as intermediates, which can be converted to pyruvate,
acetyl-SCoA, and other components of the Kreb's cycle.
b. the direct hydrolysis of peptide linkages and the production of carbon dioxide.
c. the hydrolysis of peptide linkages to add amino acids to the amino
acid pool; with the production of urea.
d. diversion of the remaining carbon skeletons; shuttle them into the
process of gluconeogenesis
e. diversion of the remaining carbon skeletons directly into ketone bodies.

______ 88. Carbon Dioxide a waste product of the Citric Acid Cycle and the breakdown of amino acids into carbon skeletons are carbon dioxide and amino groups. Ammonia and carbon dioxide. These are converted to ________ .

a. urea via the Urea cycle
b. lipids via the lipogenesis cycle
c. carbohydrates through glycolysis
d. proteins though protein synthesis
e. DNA, via replication

_____ 89. An essential amino is part of the amino acid pool, it is described as being; _______________________ .

a. required in the synthesis of all proteins
b. must be obtained in the diet, species can not manufacture.
c. can be omitted from the diet without any consequences
d. must be provided in the diet if the organism has a
genetic deficiency which prevents the formation of
as specific amino acid, if the organism normally
makes all the common 20 amino acids.
e. has a simple carbon skeleton.

______90. The formation of urea is described as being _____ and would require ______ in order for it to proceed favorably.

a. anabolic; ATP
b. anabolic; ADP
c. catabolic; ATP
d. catabolic; ADP
e. neither catabolic or anabolic; neither ATP or ADP

_____ 91. A amino acid which whose carbon skeleton can be converted to a
Kreb's Cycle intermediate, which later becomes a ketone body is called a ________ .

a. ketogenic amino acid
b. glucogenic amino acid
c. ketone
d. aldehyde
e. ester





_____ 92. The ammonia which is produced from the removal of the amino groups from amino acids can be used for the synthesis of _______ among other intermediates. Choose one from below.

a. purines and pyrimidines
b. purines only
c. pyrimidines only
d. acetyl-SCoA
e. fumarate

_____ 93. The inability to make tyrosine from phenylalanine is a genetic
defect called: ________ .

a. PKU
b. UPK
c. KPU
d. Xenobiotics
e. AIDS

______ 94. The catabolism of the amino acid carbon skeletons (amino acids which have had their amino groups removed; occurs in the _______ .

a. mitochondria
b. cytoplasm
c. mitochondria and cytoplasm
d. chloroplasts
e. mitochondria, chloroplasts, and cytoplasm

______ 95. If a chemical messenger which is carried by the blood stream
is capable of passing through the cell membrane of a cell, the
chemical messenger is probably _______ messenger.

a. lipid soluble
b. water-soluble
c. could be lipid or water-soluble
d. lipase soluble
e. carbohydrate based

______ 96. If a protein contains the following amino acid sequence, the
protein would most likely have the following characteristics?

H2N-Ala100-Glu50-Met-Try-Val-Leu-C00H

a. containing both non polar and acid amino acids
b. containing polar and acidic groups
c. dominated completely by non polar groups
d. cominated completely by acid amino acids
e, none of the above

______ 97. Myoglogin which is found in muscle tissue proper, frequently called muscle hemoglobin, would be what kind of protein?

a. storage
b. transport
c. structural
d. protective
e. contractile


98. List the order of events for protein synthesis:

I. transcription
II. initiation
III. termination
IV. elongation
V, translocation

a. I, II, III, IV, V
b. I, II, IV, V, III
c. I, II, V, IV, III
d. I, III, II, IV, V
e. none of the above

Chapter 22

Carbohydrate Metabolism


• the principal role of glucose is as a fuel to yield the energy carried by ATP
• muscle cells, nerve cells, and red blood cells rely on glucose as an energy source
• the final stages of ATP production begin with acetyl-SCoA, a common intermediate in the catabolism of all food sources
• the process of digestion takes the following course
1. digestion begins in the mouth with the enzyme alpha amylase
which starts of the process of breaking down complex starches
to sucrose, lactose, maltose
2. this digestive process continues in the stomach for about
1 hour where more digestion is taking place
3. these partially digested carbohydrates move into the small
intestine, where the disaccharides are broken down into
monosaccharides, which can be easily absorbed
typical enzymes include:
a. maltase
b. sucrase
c. pancreatin
d. alpha amylase
4. these monosaccharides are than absorbed by the villi of the
small intestine and then enter the blood stream


• see diagram Figure 23.2


Metabolic Pathways of Glucose


Name Function

glycolysis conversion of glucose to pyruvate

gluconeogenesis synthesis of glucose from amino acids, pyruvate,
and non carbs

glycogenesis synthesis of glycogen from glucose

gylcogenolysis breakdown of glycogen to glucose

Pentose Phosphate conversion of glucose to five carbon sugar phosphates
shunt


• when glucose enters the cell, it is immediately converted into a form called glucose-6phosphate
• this helps keep glucose in the cell by the addition of a phosphate group
• this also permits glucose to enter two different pathways, one for the conversion of glucose to pyruvate and processes called glycolysis and the other for the placement of glucose in storage as glycogen a processed called glycogenesis or can be used for the formation of lipid, a process called lipogenesis
• in some cells, glucose can enter the pentose phosphate pathway

 sometimes glucose is converted to lactate when oxygen is not present in sufficient concentration, this is necessary to regenerate the oxidized form of the coenzyme NAD+
 sometimes pyruvate is converted back to glucose in a process called gluconeogenesis


Glycolysis

• this is a process which involves ten enzymatic-catalyzed reactions that breakdown one glucose molecule into two molecules of pyruvate
• this process is sometimes called Embden-Meyerhoff
• however, other people were involved and their names are not affixed
• occurs in the cytosol of all human cells

Steps 1 through 3

 once glucose enters the cell, it is immediately phosphorylated by an enzyme called a kinase with an investment of one ATP molecule
 this process is highly exergonic
 this product acts as an allosteric inhibitor of the kinase, if G6P builds up, then glucose is shunted into storage
 G6P is isomerized to F6P
 F6P is phosphorylated by a kinase to FDP or fructose 1,6 bisphosphate

Steps 4 and 5

 Fructose 1,6 bisphosphate is broken down into to two three carbon molecules each of which contains a phosphate group, this enzyme is called an aldolase
 at the conclusion of these first five steps, two ATP molecules have been invested in this process
 dihydroxyacetone phosphate and D-glyceraldehyde 3 phosphate exist in equilibrium with each other


Steps 6 – 10 Energy Generation Steps

 the purpose of these steps is to generate ATP
 Step 6 adds a phosphate to G3P to make a molecule of GDP
 this is a critical step because here we make the reduced coenzyme of NADH which can be used in oxidative phosphorylation
 Step 7 is called a substrate level phosphorylation because in this step, the phosphate group found on carbon # 1 is transferred to an molecule of ADP to make a molecule of ATP
 Step 8 and 9 deal with internal re-arrangement and dehydration to yield a critical product called phosphenopyruvate


Step 10

 critical step, phosphoenolpyruvate, here is a phosphate transfer pathway, another substrate level phosphorylation. The final product is now pyruvate, which can enter the mitochondria if oxygen is present.

Remember steps 6 – 10 are repeated twice, this means that there is now a net of
of two ATPs from this cycle.


Summary of Glycolysis

conversion of glucose into two pyruvates

production net of two ATPs by substrate level phosphorylation

production of two molecules of NADH, which can be used in the mitrochondria



Fate of Pyruvate

 ultimate fate depends on the presence or absence of oxygen

Aerobic Oxidation

 pyruvate is carried across the mitrochondria into the matrix of the mitrochondria by carrier protein
 in this matrix it is converted to acetyl-SCoA
 this process involves the use of oxidized NAD which is converted to NADH, which could be used in the generation of additional ATP

Anaerobic Reduction to Lactate

 if a cell which is aerobic becomes oxygen starved, the NADH produced in step 6 page 669
 in step 10 of glycolysis pyruvate accumulated in high concentration because electron transport has slowed
 this is an alternative mechanism in the cytosol to regenerate NAD, but to keep glycolysis going, however, at the cost of ATP formation
 lactate can be converted to pyruvate at any time in the cell or removed from the cell and brought back as glucose in the Cori cycle page 674 in the liver

Alcoholic Fermentation

 the process of fermentation occurs in the absence of oxygen, as in the case of yeast being used to add alcohol content to a bottle of wine
 pyruvate is converted to ethanol and carbon dioxide



Energy Output for the Complete Metabolism of Glucose

predicated on the following:

 glycolysis
 conversion of pyruvate to acetyl-SCoA
 conversion of two acetyl-SCoA to four molecules of carbon dioxide in the citric acid cycle
 the passage of reduced coenzymes through electron transport. These coenzymes originate from glycolysis, pyruvate oxidation, and the citric acid cycle
 the amount of energy produced varies from 30 – 32 to as high as 38. Some determination put the value at 36. The actual amount is dependent upon whether or not the analysis occurs in a eukaryotic or a prokaryotic cell. It appears that 2 ATPS are lost in a shuttle process/glucose unit moving ATP out of the mitochondria

Regulation of Glucose Metabolism

hypoglycemia = lower than normal blood glucose levels

hyperglycemia = higher than normal blood glucose levels

 normal blood glucose levels are 65 – 110 mg/dl. A deciliter is 100 ml
 if blood glucose levels are too low, memory loss and fatigue are frequent symptoms
 if blood sugar levels are too high there is frequent low blood pressure and significant urine output
 regulation is the result of two hormones from the pancreas, which control blood glucose levels. These hormones are antagonistic toward each other in the control of blood glucose levels
 if the glucose levels start to rise in the blood because of a heavy meal, there is a release of insulin from the beta cells of the pancreas. this release has four major effects on the glucose level within the blood stream:
1) glucose starts to enter cells more rapidly, apparently, the semi-permeable membrane of the cell has become more permeable to glucose by opening up more gates or making the gates more accessible
2) breakdown of glucose by glysolysis is accelerated, apparently insulin through a secondary messenger accelerates the entry of glucose into glycolysis by accelerating the phosphorylation of glucose with ATP in the presence of a kinase
3) glycogen synthesis increases to help rid the body of excess glucose
4) synthesis of lipids and proteins occurs, this is an alternate form of storage form of excess glucose
 under conditions of falling glucose levels, the following four events occur:
1) glucose entry into cells slows
2) glycogen in the liver starts to breakdown to release more glucose
3) breakdown of lipids and proteins to form glucose, as process called
gluconeogenesis
4) then gluconeogenesis accelerates



Glycogen Metabolism: Glycogenesis and Glycogenolysis

 glycogenesis occurs when glucose concentrations are high
 the process begins with G6P
 G6P is isomerized to G1P
 G1P is attached to UTP with concurrent loss of a phosphate group
 the resulting Glucose-UDP can transfer glucose to a glycogen chain
 in removing from storage, a single glucose molecule has a phosphate group added to it w/o an investment of ATP
 both synthesis and degradation of glycogen are regulated by the concentration of cAMP. Elevation of the cAMP levels enhances the conversion of glycogen to glucose-1-P by inhibiting the enzyme glycogen synthetase and increasing the glycogen breakdown by activating the enzyme called glycogen phosphorylase
 the converse is of course true
 the resulting molecule is G1P which can enter glycolysis after it is mutated to G6P by an enzyme called phosphoglucomutase


see overhead

• the process is different in muscle cells and in liver cells
• in muscle cells G6P directly enters the glycolysis pathways
• in liver cells, G6P is converted to glucose which can enter the blood stream directly and then this glucose must be transported into the cell for conversion back to G6P which can then enter glycolysis

Glucose from Non carbohydrates: Gluconeogenesis

Cori Cycle

reactions of 1, 3, and 10 are too exergonic to be reversed directly, they require alternate pathways

glycerol from triacyglycerols is converted to dihydroxyacetone phosphate which in turn is converted to G3P at step 5

carbon atoms from protein breakdown enter at levels as indicated



Pentose Phosphate Pathway (Shunt)

a biochemical pathway that produces a ribose, NADPH and other sugar intermediates from glycolysis, an alternative to glycolysis

the chief function is to produced NADPH an coenzyme needed for the synthesis of
lipids

occurs mainly in those places where lipids are produced in high concentration

the other major function is to produce ribose sugars for the synthesis of nucleic acids

two phase process:

1. the oxidative phase converts glucose to Ribulose-5-phosphate

2. the reductive phase converts ribulose-5-phosphate to G3P and F6P which are part of glycolysis in a multi-step process

28.1 Digestion of Protein
The end result of protein digestion is the hydrolysis of all peptide bonds to produce amino acids.

28.2 Amino Acid Metabolism: An Overview
The amino acid pool, the entire collection of free amino acids throughout the body, occupies a central position in amino acid metabolism.

Each of 20 amino acids degrades in its own way. However, the general scheme is the same for each one.
Amino Acid Catabolism:
Removal of the amino group.
Use of nitrogen in the synthesis of new nitrogen compounds.
Passage of nitrogen into the urea cycle.
Incorporation of the carbon atoms into compounds that can enter the citric acid cycle.


Our body don’t store nitrogen-containing compounds. The amino nitrogen from dietary protein has just two fates.
It may be used in the synthesis of nitrogen containing molecules such as,
- Nitric oxide - Hormones
- Neurotransmitters - Nicotinamide
- Heme - Creatin phosphate
- Purine and pyrimidine bases
Or the amino group must be incorporated into urea and excreted.

28.3 Amino Acid Catabolism: The Amino Group
The first step in amino acid catabolism is removal of amino group. In this process, known as transamination, the amino group of the amino acid and the keto group of an a-keto acid change places.
There are a number of transaminase enzymes. Most are specific for a-ketoglutarate as the amino group acceptor and work with several amino acids. The a-ketoglutarate is converted to glutamate, and the amino acid is converted to an a-keto acid.
28.3 Amino Acid Catabolism: The Amino Group
The first step in amino acid catabolism is removal of amino group. In this process, known as transamination, the amino group of the amino acid and the keto group of an a-keto acid change places.
There are a number of transaminase enzymes. Most are specific for a-ketoglutarate as the amino group acceptor and work with several amino acids. The a-ketoglutarate is converted to glutamate, and the amino acid is converted to an a-keto acid.

The ionized ammonia formed in the oxidative deamination reaction proceeds to the urea cycle for conversion to urea that is eliminated in the urine. The pathway of nitrogen from an amino acid to urea is summarized in Fig 28.3.
28.4 The Urea cycle
Ammonia is highly toxic to living organisms and must be eliminated safely. Fish excrete ammonia through their gills directly into the surrounding water and mammals converts ammonia to non-toxic urea via the urea cycle.
The conversion of ammonia to urea takes place in the liver. From there urea is transported to the kidneys and transferred to urine for excretion. The biochemical pathway for urea synthesis is shown in Fig 28.4.

28.5 Amino Acid Catabolism: The carbon Atoms
The carbon atoms of each protein amino acid are converted to pyruvate, acetyl SCoA, or one of the citric acid cycle intermediates by distinctive pathway, Fig 28.5. Eventually, all the carbon skeleton carbon atoms are used generate energy by passing through the citric acid cycle and gluconeogenesis pathway to form glucose or by entering the ketogenesis pathway to form ketone bodies.

The carbon atoms of the amino acids are converted to the seven compounds shown in the following Fig 28.5. Each of these compound is either an intermediate in the citric acid cycle or a precursor to citrate.
28.6 Biosynthesis of Nonessential Amino Acids
Humans are able to synthesize about half of the 20 amino acids found in proteins. These are known as nonessential amino acids, because they don’t have to be supplied by our diet.
The remaining amino acids, known as the essential amino acids, are synthesized only by plants and microorganisms. Humans must obtain these essential amino acids from food.

All of the nonessential amino acids derive their amino acid from glutamate.
Glutamate is also the molecule that picks up the ammonia in amino acid catabolism and carries it to the urea cycle.
Glutamate can be made by reductive amination, the reverse of oxidative deamination.
Glutamate also provides nitrogen for the synthesis of other nitrogen containing molecules such as purine and pyrimidine.

Glutamine is made from glutamate, asparagine is made by the reaction of glutamine with aspartate.
The amino acid tyrosine, classified both as essential and nonessential amino acid since we can synthesize it from phenylalanine.
We have a high nutritional requirements for phenyl alanine, and several metabolic diseases are associated with defects in the enzymes needed to convert it to tyrosine and other metabolites. The best known of these diseases is phenylketonuria (PKU).

Phenylketonuria (PKU) results in elevated concentration of phenylalanine, phenylpyruvate, and several other metabolites in the blood serum and urine.
Undetected PKU causes mental retardation by the second month of life.
All hospitals in the United States now routinely screened newborn babies for treatable PKU.
Treatment consists of a phenylalanine free formula for infants and for adults diet free of any meat or other protein containing food.
Chapter Summary
Protein digestion begins in the stomach and continues in the small intestine.
The result of digestion is the complete hydrolysis of proteins to free amino acids.
Each amino acid is catabolized by a distinctive pathway, but in most of them amino acid is removed by transamination, usually to form glutamate.
The amino group of glutamate is removed as ammonia by oxidative deamination.
Chapter Summary Contd.
The carbon atoms of proteins are converted to fatty acids or glycogen for storage, or for synthesis of ketone bodies.
The net result of urea cycle is the conversion of ammonium ion to urea.
Essential amino acids must be obtained from our diet since our body can not synthesize them.
Our body can synthesize nonessential amino acids. The nitrogen in these amino acids is commonly supplied by glutamate.

Lipid transport mechanisms
Chylomicrons
Serum albumin
VLDL
LDLHDL


Sources of triglycerides for metabolism
Diet
Storage in adipose tissue
Synthesis in the liver
Chylomicrons
The least dense of the lipoproteins of the transport mechanisms
Required for the exogenous lipid transport to the liver

Serum albumin
Responsible for the transport of endogenous lipid transport form fat cells
VLDL
Transport of TAGs manufactured by the liver to fat cells and other cells, tissues, organs where they may be needed
LDL
Higher in the density of lipid transport mechanisms
Often called bad cholesterol
Carries cholesterol from the liver to peripheral tissues where it can be used in
Steroid hormones
Cholesterol synthesis for cell membranes


HDL
Highest of the density of protein carriers
Responsible for the transport of cholesterol from worn out cells to the liver for destruction as bile salts
Often called good cholesterol
25.3 Triacylglycerol Metabolism:An Overview
Fig 25.6 The metabolic pathways for triacylglycerols are summarized.


The fate of glycerol is carried to the liver where it is converted to
DHAP which is then converted to glyceraldehyde 3-phosphate
- Glycolysis – energy generation
- or Gluconeogenesis – glucose formation
- Triacylglycerol synthesis: starts with DHAP conversion to glycerol-3-phosphate
Glycerol-3-phosphate then has two fatty acids added to make a diacylglycerolphosphate
This diacylglycerol phosphate has the phosphate group cleaved and another fatty acid added


Acetyl SCoA participates in:
- Triacylglycerol synthesis
- Ketone body synthesis
- Synthesis of steroids and other lipids
- entrance into the Citric acid cycle and then used for oxidative phosphorylation to make ATP

25.4 Storage and Mobilization of Triacylglycerols
After a meal, blood glucose levels are high, insulin level rises, and glucogen levels drop. Glucose is entering cells and glycolysis is proceeding actively. Under this conditions, insulin activates the synthesis of TAG for storage from glycerol 3-phosphate and fatty acid acyl group carried by coenzyme A.

TAG Mobilization
After the digestion of a meal is finished, blood glucose levels drop so the insulin level drops and glucagon level rise.
The lower insulin level and higher glucagon level together activate triacylglycerol lipase, the enzyme that controls hydrolysis of stored TAG.
When there is a short supply of glycerol 3-phosphate, indicates glycolysis is not producing sufficient energy, the fatty acids and glycerols which are the products of TAG hydrolysis are released to the bloodstream for transportation to the energy-generating cells, the cells which are in need
25.5 Oxidation of Fatty Acids
Oxidation of fatty acid in a cell that needs energy proceeds by the following three steps:
Step 1. Fatty acid is activated by conversion to fatty acyl-SCoA, a form that can be broken down more easily.
Step 2. Fatty acyl-SCoA is transported into the mitochondial matrix where energy generation takes place.
Step 3. Oxidation occurs by repetition of the series of four reactions.
25.6 Energy from Fatty Acid Oxidation
The total energy out put from fatty acid catabolism is measured by the total number of ATPs produced. First we need to know the total number of acetyl-SCoA produced. Each acetyl-SCoA produces 10 ATPs. Each b-oxidation produces 4 ATPs. Number of repetition is always one less than the number of acetyl-SCoa produced since the last repetition of b-oxidation cleaves a four carbon chain to give two acetyl-SCoa. Also we must subtract 2ATPs spent in activation of fatty acid.

For example, a 12 carbon fatty acid, Lauric acid, produces 78 ATPs.

12 carbon atoms/2 = 6 acetyl-SCoA
10 ATPs/acetyl-SCoA x 6 acetyl-SCoA = 60 ATPs
-2 ATPs for fatty acid activation
6 acetyl-SCoA – 1= 5 b-oxidation
4 ATPs / b-oxidation = 20 ATPs
Total ATPs produced = 60 + 20 -2 = 78.

Fig 25.8 Summary of pathways of nutrients through anabolism and catabolism
25.7 Ketone Bodies and Ketoacidosis
If catabolism produces more acetyl-SCoA than the citric acid cycle can handle, excess acetyl-SCoA is converted to 3-hydroxybutyrate and acetoacetate by liver’s mitochondria.
Acetoacetate undergoes spontaneous non-enzymatic decomposition to acetone.
3-hydroxybutyrate, acetoacetate, and acetone together known as ketone bodies even though only one of the three compds is actually a ketone

Ketone bodies are produced by a process known as ketogenesis occurs in four enzyme catalyzed steps.
Under well-fed, healthy conditions, skeletal muscles derive a small portion of their energy needs from acetoacetate because glucose is supplying all the energy demands of the active cell
In a situation when energy production from glucose is not adequate due to starvation or because glucose is not metabolized due to diabetes the production of ketone bodies accelerates since acetoacetate and 3-hydroxybutyrate can be converted to acetyl-SCoA for oxidation in the citric acid cycle.

Under condition of diabetes, ketone bodies are produced faster than utilized, a condition known as ketosis.
Because two of the three ketone bodies are carboxylic acids, continued ketosis lead to serious condition known as ketoacidosis. The blood’s buffers are over whelmed and blood pH drops. An individual suffers from dehydration due to increased urine flow, labored breathing since acidic blood is a poor carrier of oxygen, and depression. Ultimately, if untreated, the condition leads to coma and death.
25.8 Biosynthesis of Fatty Acids
The biochemical pathway for synthesis of fatty acids from acetyl-SCoA is known as lipogenesis. Fatty acid synthesis and catabolism are similar in that they both proceed two carbon atoms at a time. But the two pathways are not exactly reverse to each other.
The following two reactions set the stage for lipogenesis: (1) transfer of an acyl group from acetyl-SCoA to a acyl carrier protein (ACP) and (2) Conversion of acetyl-SCoA to malonyl-SCoA.

Once acetyl-SACP and malonyl-SACP are generated a series of four reactions lengthens the fatty acid chain by adding two carbon atoms with each repetition. Fatty acids with up to 16 carbon atoms (palmitic acid)are produced by this method. Larger fatty acids are produced from palmitoyl-SCoA with the aid of specific enzyme.
Chapter Summary
Triacylglycerols (TAGs) from the diet are broken into small droplets in the stomach and enter the small intestine, where they are emulsified by bile acids and forms micelles.
Pancreatic lipases partially hydrolyze the TAGs in micelles.
Small fatty acids and glycerols from TAGs hydrolysis are absorbed directly in to the blood stream.
Chapter Summary Cond.
Insoluble hydrolysis products are reassembled into TAGs. These TAGs are reassembled into lipoprotein chylomicrons and absorbed into the lymph system for transport to the bloodstream.
In addition to chylomicrons
Very-low-density-lipoproteins (VLDLs) carry TAGs synthesized in the liver to peripheral tissues for energy generation or storage.
Low-density-lipoproteins (LDLs) transport cholesterols from the liver to peripheral tissues for cell membranes or steroid synthesis.
Chapter Summary Contd.
High-density-lipoproteins (HDLs) transport cholesterols from peripheral tissues back to the liver for conversion to bile acids that are used in the digestion or excreted.
Dietary TAGs undergo hydrolysis to fatty acids and glycerol-3-phospahate by enzymes. Fatty acids undergo b-oxidation to acetyl-SCoA or resynthesis into TAGs for storage.
Acetyl-SCoA can participate in resynthesis of fatty acids (lipogenesis), formation of ketone bodies (ketogenesis), steroid synthesis, or energy generation via citric acid cycle and oxidative phosphorylation.(10 step pathway)
Chapter Summary Contd.
Glycerols can participate in glycolysis, gluconeogenesis, or TAG synthesis.
Synthesis of TAGs for storage is activated by insulin when glucose levels are high, typical when following a heavy meal.
Utilization of lipids occurs when glucose levels are low and the enzyme glucagon now kicks in, typical when carbohydrates reserves are low or starvation conditions exist
Fatty acid oxidations are activated by conversion to fatty acyl Coenzyme A. The fatty acyl-COA are transported into the mitochondrial matrix and are then oxidized two carbon atoms at a time to acetyl-SCoA by repeated trips through the b-oxidation spiral.
Chapter Summary Contd.
The ketone bodies (3-hydroxybutyrate, acetoacetate, and acetone) are produced when the energy generation from citric acid cycle cannot keep up with the quantity of acetyl-SCoA that is available which can enter the citric acid cycle. This is a “dump pathway” so the cells in need of energy can convert 3-hydroxybutyrate to acetyl-SCoA. In this way, acetyl-SCoA is made available for energy generation when glucose is short supply.

This is the end

25.1 Digestion of Triacylglycerols
Lipid metabolism is the second most important source of energy in our body. Majority of the lipids in our diet are triacyglycerols (TAG), therefore, metabolism of triacylglycerols, which are stored in our fatty tissue, constitute a chief energy reserve source

When eaten, triacylglycerols pass through the mouth virtually unchanged and enter into the stomach where the heat and churning action of the stomach breaks lipids into smaller droplets.
Mechanical action of the churning of the stomach
The lipids leave the stomach in a package called chyme



The hydrophobic lipid droplets are packaged in the small intestine various kinds of
Lipoproteins. This is necessary in order for the hydrophobic lipids to move about in aqueous environments.

The efforts of the small intestine
The lipids must be prepared to be attacked by the enzymes of the small intestine
Here bile salts are added in the duodenum to help the action of the lipases
These behave as detergents
These resemble soaps which allow the lipids to become more soluble in the aqueous environment
Finally the low pH of the chyme is raised to pH = 8

Partially digested lipids (mechanical) are partially hydrolyzed in the upper intestine with the help of bile released by the gallbladder and the enzyme pancreatic lipases to mono and diacylglycerols, fatty acids and a small amount of glycerol which is then absorbed in the cells of the small intestine through facilitated diffusion. Glycerol and some of the smaller fatty acids are absorbed in the cells of the villi

These water soluble smaller fatty acids and glycerols enter into the blood stream and carried to the liver through the intestinal veins and enter the hepatic portal vein which goes to the liver where chemicals processes occur:
Glycerol is converted to through DHAP
This can be used to make glycogen
DHAP is Isomerized to glyceraldehyde-3-phosphate to make ATP through glycolysis
The smaller fatty acids are combined with with the glycerol which has been converted to glycerol-3-phosphate and return to storage

Digestion of the larger lipids
The still-insoluble acylglycerols and larger fatty acids are emulsified once again with biles salts
They are then packaged into water soluble lipoproteins known as chylomicrons
These lipids are released from the chylomicrons once they have entered the cell of the small intestine
These mon and diacyglycerides are converted back to triglycerides in the cells of the small intestine
These triglycerides are repackaged into chylomicrons again
Which are then absorbed by the lacteals
They are then sent to inferior vena cava by passing the liver

What are the chylomicrons?
Chylomicrons are too large to enter blood stream through capillary walls of the small intestine. Instead, they pass through the cells of the small intestine and are then absorbed by the lymphatic system and carried to the thoracic duct, where the lymphatic system is emptied into the superior vena cava.

Fig 25.4 Pathways of lipids through the villi

Fig 25.4 Pathways of lipids through the villi


Fig 25.5 Transport of lipids

Lipid transport mechanisms
Chylomicrons
Serum albumin
VLDL
LDLHDL


Sources of triglycerides for metabolism
Diet
Storage in adipose tissue
Synthesis in the liver
Chylomicrons
The least dense of the lipoproteins of the transport mechanisms
Required for the exogenous lipid transport to the liver

Serum albumin
Responsible for the transport of endogenous lipid transport form fat cells
VLDL
Transport of TAGs manufactured by the liver to fat cells and other cells, tissues, organs where they may be needed
LDL
Higher in the density of lipid transport mechanisms
Often called bad cholesterol
Carries cholesterol from the liver to peripheral tissues where it can be used in
Steroid hormones
Cholesterol synthesis for cell membranes


HDL
Highest of the density of protein carriers
Responsible for the transport of cholesterol from worn out cells to the liver for destruction as bile salts
Often called good cholesterol