Examination III Key

Transcription

Examination III Key
MCMP 208 Exam III Key - 1
Examination III Key
MCMP 208 – Biochemistry for Pharmaceutical Sciences I
April 8, 2015
Correct answers in multiple choice questions are indicated in RED and underlined.
Correct answers to essay questions are indicated in RED in comic book font.
In some cases and explanation is provided in BLUE/BLUE
MATCHING. For problems 1 to 3, a set of numbered answers is provided immediately below. For each
problem, select from the list of answers the single choice that best matches the item described in the
problem. Mark that answer on your answer sheet. An answer may be used more than once or not at all.
[3 points each]










Cholesterol
Cholic acid
Prostaglandin
Leukotriene
Saturated fatty acid
ω-3 fatty acid
ω-6 fatty acid
Sphingomyelin
Phosphatidylserine
Phosphatidylcholine
1.

R and R′: hydrocarbon chains
2.

3.

MCMP 208 Exam III Key - 2
MULTIPLE CHOICE. For problems 4 to 23, select from the list immediately following each question the
single most correct choice to complete the statement, solve the problem, or answer the question. Mark that
answer on your answer sheet. [3 points each]
4. What are the constituent(s) of the core of lipoproteins?







Apolipoprotein Amphipathic
Triacylglycerol Hydrophobic
Phospholipids Amphipathic
Cholesterol Amphipathic
Cholesterol ester Hydrophobic
 and 
 and 
The core of lipoproteins is composed of insoluble hydrophobic molecules, while the shell of
lipoproteins is composed of amphipathic molecules.
5. Which of the following statements is INCORRECT about biological membranes?





Membranes serve as a barrier to ionic and polar substances.
Proteins and lipids can diffuse and interact in the membrane.
Tissue and various cell membranes have a distinctive lipid composition.
Unsaturated fatty acyl groups decreases the fluidity of membranes.
The transverse movement (flip-flop) of membrane lipids is catalyzed by enzymes.
Unsaturated fatty acyl groups make poor packing, which increases the fluidity of membranes.
6. Transmembrane helices of integral membrane proteins are composed of mostly ____________ residues.






small
hydrophobic
polar
charged
branched
aromatic
Transmembrane helices of integral membrane proteins contact the hydrophobic layer of the membrane.
The hydropathy plot of the amino acid sequence of an integral membrane protein is used to identify
transmembrane helices.
7. Which of the following is a transporter with a uniport mechanism?






Glucose transporter Uniport
ATP–ADP transporter Antiport
Na+/K+-ATPase Antiport
Na+/glucose cotransporter Symport
Acetylcholine receptor Not a transporter
Voltage-gated Na+ channel Not a transporter
MCMP 208 Exam III Key - 3
8. Which of the following is a secondary active transporter?






Glucose transporter Passive
ATP–ADP transporter Passive
Na+/K+-ATPase Primary active
Na+/glucose cotransporter Secondary active
Acetylcholine receptor Not a transporter
Voltage-gated Na+ channel Not a transporter
9. Which organ or tissue is the greatest contributor of lipids into the blood circulation during times of
prolonged fasting?






liver
brain
intestines
adipose
mammary
muscle
10. Lipoproteins released into the blood differ in many ways from the lipoprotein remnants that are
endocytosed from the blood for recycling of their components. Of these differences, the greatest
change(s) is(are) that remnants have lost most of their







apolipoproteins
cholesterol and cholesterol esters
phospholipids
phospholipids, cholesterol and cholesteryl esters
phospholipids and apolipoproteins
phospholipids and triacylglycerol
triacyglycerol, cholesterol and cholesteryl esters
The PL and protein are the “packaging” on the surface so the droplet can travel in the circulation, but
they are not consumed by the rest of the body. While some proteins are lost during the depletion of TG
and cholesterol because the particle diameter decreases, the loss of protein is much smaller than the loss
of TG, cholesterol, and cholesterol esters.
11. Before β-oxidation of palmitate can occur in the mitochondrial matrix, it must be converted to







palmitoyl-CoA outside the mitochondrial matrix
palmitoyl-CoA inside the mitochondrial matrix
palmitoyl-ACP outside the mitochondrial matrix
pallmitoyl-ACP inside the mitochondrial matrix
palmitoyl-carnitine outside the mitochondrial matrix
palmitoyl-carnitine inside the mitochondrial matrix
palmitoyl-CoA then palmitoyl-carnitine outside the mitochondrial matrix, then palmitoyl-CoA inside
the mitochondrial matrix
 palmitoyl-CoA then palmitoyl-carnitine inside the mitochondrial matrix, then palmitoyl-CoA outside
the mitochondrial matrix
 palmityl-pyrophosphate outside the mitochondrial matrix
 palmityl-pyrophosphate inside the mitochondrial matrix
MCMP 208 Exam III Key - 4
12. All acylation of alcohol or amino groups occurring during the biosynthesis of triglycerides,
phospholipids, and sphingolipids involve transfer of acyl groups from








acyl carrier protein
serum albumin
apolipoproteins
lipid droplets
coenzyme A
pyrophosphate
CDP
pyridoxal phosphate
13. The molecule with the structure shown to the right is synthesized
malonoyl-CoA
 in order to serve as the starting molecule for extension into fatty acids by addition of subsequent
acetate units
 in order to make it easier to produce a carbanion of acetate during fatty acid synthesis
 in order to make condensation into ketone bodies more energetically favorable
 during glyeroneogenesis
 in order to make sphinganine
 in order to shuttle acetate units out of the mitochondria
 during catabolism of odd chain length and branched fatty acids
14. The olefin bonds in fatty acids which are biosynthesized entirely in human cells







are created during the oligomerization process and simply left in the fatty acid
are created during the oligomerization process by condensing an unsaturated 4-carbon acid
are added in the endoplasmic reticulum after the oligomerization process
are added in the peroxisomes before the oligomerization process
are added only during the catabolism of fatty acids
include both cis and trans configurations, depending on the specific fatty acid length
None of the above are correct.
15. In mammals, including humans, fatty acid biosynthesis in lactating mammary tissue differs from fatty
acid synthesis occurring in other tissues in that fatty acid synthesis in the lactating mammary gland






occurs exclusively in the endoplasmic reticulum
sometimes occurs in the mitochondria
frequently produces fatty acids longer than 16 carbons
frequently produces fatty acids shorter than 16 carbons
frequently produces fatty acids with odd numbers of carbons
frequently produces branched chain fatty acids
MCMP 208 Exam III Key - 5
16. Hormonal regulation of the biosynthesis and catabolism of fatty acids occurs primarily at
 acetyl coenzyme A carboxylase
 acyl coenzyme A ligase
 hormone sensitive lipase
 lipoprotein lipase
 carnitine acyl transferase
 fatty acid synthase
 pyruvate dehydrogenase
ACC not only is where fatty acid synthesis is regulated, but because mitochondrial FA oxidation is
regulated by Acylcarnitine transferase, and it is inhibited by malonyl-CoA, ACC activity also regulates
mitochondrial fatty acid oxidation.
17. Nitrogenous bisphosphonates are






intermediates in the biosynthesis of glycolipid
intermediates in the biosynthesis of isoprenoids
drugs used to treat hypercholesterolemia
drugs used to treat obesity
drugs that block protein prenylation
drugs that block mono-oxygenases
18. A person who has a positive nitrogen balance likely





is suffering from protein malnutrition
has recently suffered from trauma or severe burns or has had major surgery
has difficulty absorbing amino acids from ingested foods
is growing, pregnant, or lactating
None of the above are correct.
19. Neutral (zwiterionic) phosphoglycerolipids differ in their synthesis from some acidic
phosphoglycerolipids in that neutral phosphoglycerolipids are nearly always made by





head group transfer to DAG involving the CDP-activated head group
acylation of the lysophospholipid
addition of the head group to phosphatidic acid
head group exchange with a molecule of phospholipid
head group transfer to CDP-DAG from the phosphorylated head group
20. Methionine is









an essential amino acid that is also glucogenic It’s carbons are converted to proprionyl-CoA
a non-essential amino acid that is also glucogenic
is a semi-essential amino acid that is also glucogenic
an essential amino acid that is also ketogenic
a non-essential amino acid that is also ketogenic
is a semi-essential amino acid that is also ketogenic
an essential amino acid that is both ketogenic and glucogenic
a non-essential amino acid that is both ketogenic and glucogenic
is a semi-essential amino acid that is both ketogenic and glucogenic
MCMP 208 Exam III Key - 6
21. Homocysteine is









converted into cysteine by removal of a methylene group from homocysteine
converted into cysteine by addition of a methylene group to homocysteine
converted into cystathionine by the addition of serine to homocysteine
made from cystathionine by removal of a cysteine from homocysteine
made from methionine by the addition of a cysteine to methionine
made from methionine by the addition of a serine to methionine
made from methionine by the addition of a methyl group to methionine
used to make one-carbon groups that are bound to THF
used to make phosphatidylcholine from phosphatidyethanolamine
22. The proteasome is a supramolecular structure







responsible for the multistep process of fatty acid synthesis
involved in membrane-vessicle fusion during membrane remodeling
responsible for degrading all molecules endocytosed by cells
responsible for ATP-dependent protein degradation
responsible for determining the half-life of all proteins
responsible for the synthesis and initial post-translational modifications to proteins
involved in movement of proteins into and out of the cell nucleus
23. L-α-amino acids that serve as intermediates in the biosynthesis of arginine from the first non-nitrogenous
molecule in its biosynthetic pathway are






glutamate, glutamine, and aspartate
glutamate, ornithine, and aspartate
glutamate, ornithine, citrulline, and argininosuccinate
glutamate, proline, ornithine, citrulline, and argininosuccinate
glutamate, ornithine, citrulline, asparatate, and argininosuccinate
glutamate, proline, and aspartate
An intermediate is a molecule made in the pathway that is also consumed in the pathway, with both
of those events happening after the starting material and before production of the final product.
Aspartate is consumed, but not produced by the arginine biosynthesis pathway, so is not an
intermediate (it is an input to the reactions of the pathway, just as are ATP, bicarbonate, and water.)
ESSAY PROBLEMS. Write your answers to problems 24 to 30 in the space immediately below each
problem (or in the blanks for problem 25).
24. [3 points] Triacylglycerol is the main constituent of both butter and olive oil. However, butter is solid,
and olive oil is liquid at room temperature. Explain briefly the chemical basis of this difference.
Olive oil has a higher content of unsaturated fatty acids than butter. Unsaturated
fatty acids makes poor packing compared with saturated fatty acids. Poor packing
decreases the melting point.
MCMP 208 Exam III Key - 7
25. [3 points] The action of ATP–ADP transporter is shown below. Fill the blanks in the following questions.
ADP3-
ADP3-
ATP4-
ATP4-
(a) [2 points] When ATP and ADP are exchanged in the direction indicated above, the net charge of
______-1_______ moves from Side _____2____ to Side _____1_____.
(b) [1 points] When Side ____2______ has a more negative membrane potential, the exchange in the
direction indicated above is more favorable.
26. [3 points] Explain briefly the molecular origin of cystic fibrosis.
Patients with cystic fibrosis have mutations in a membrane channel. The mutations
interfere with the folding of the channel protein, and the amount of the active channel
is insufficient in the patients.
27. [6 points] There are six entry points into metabolism for the catabolism of amino acids. Each of these
entry points is either glucogenic or ketogenic, but not both. List these metabolic entry points. Also, for
each entry point, indicate if that entry point is for glucogenic amino acids (or fragments of amino acids)
or if it is for ketogenic for amino acids (or fragments of amino acids) by placing the word (glucogenic or
ketogenic) next to the entry point in your answer.
α-ketoglutarate
oxaloacetate
pyruvate
fumarate
succinyl-CoA
glucogenic
glucogenic
glucogenic
glucogenic
glucogenic
acetyl-CoA
ketogenic
MCMP 208 Exam III Key - 8
28. [5 points] Of the 20 L-α-amino acids used for protein synthesis, list those that are made directly from the
carbons in α-ketoglutarate (without having to go through any other pathways in intermediary or
carbohydrate metabolism.) For each of the amino acids you list, indicate which category the synthetic
pathway length belongs in, choosing only from these three categories of length (in terms of number of
steps catalyzed by different enzymes): “1 or 2 steps”; “3 or 4 steps”; “more than 4 steps”.
Glutamate
Glutamine
Proline
Arginine
1 or 2 steps
1 or 2 steps
Either “3 or 4 steps” or “more than 4 steps” are allowed as correct. This
is because the cyclization reaction (Schiff base formation) is likely to be
spontaneous and not catalyzed by an enzyme, hence only 4 enzymes are
needed from α-KG, though it may take 5 reactions.)
more than 4 steps
29. [6 points] Complex lipids can be described as oligomers of oligomers. When this is concept is applied to
cholesterol, it is actually an oligomer of an oligomer of an oligomer.
a. [2 points] What is the name of the metabolite produced by the first stage of oligomerization
(before it is further modified for use in the next stage)?
3-Hydroxy-3-methylglutaryl-CoA also acceptable are HMG-CoA and HMG-coenzyme-A
HMG-CoA is made from three molecules of acetyl-CoA. Even though the two condensations are not
identical types of condensations, this is still an oligomerization
b. [2 points] What is the name of the metabolite produced by the second stage of oligomerization?
Farnesy-pyrophosphate This is made from three isoprenes (one dimethylallyl-PP and
two isopentenyl-PPs), added in two identical condensation reactions.
c. [2 points] What is the name of the metabolite produced by the third stage of oligomerization
(before it is further modified)?
Squalene This is made from two farnesyl-PP.
30. [5 points] This question is about ketone bodies.
a. [2 points] What are the names OR structures of the ketone body molecules?
Acetoacetate
β-hydroxybutyrate
Note that either the correct structure or the name of the molecule will be awarded
credit for each of the two keto bodies. Also, structures of either the acid or carboxylate
forms will be considered correct as well as the acid or conjugate base names.
MCMP 208 Exam III Key - 9
b. [1 point] In what organ/tissue are ketone bodies synthesized?
Liver or hepatocytes
c. [1 point] When are ketone bodies synthesized?
During prolonged fasting
d. [1 point] Why are ketone bodies synthesized?
To reduce consumption of blood glucose by the brain. Ultimately, this reduced utilization
of blood glucose spares body protein which must be broken down for use by the liver to
make blood glucose.