Download Theory_2004

18/03A
Semester 2, 2004
Page 1 of 27 pages
PART A
1.
An ANABOLIC pathway uses compounds X and Y to produces compounds A and B. Which
statement is TRUE?
A.
B.
C.
D.
E.
2.
Which of the following statements about ATP is TRUE?
A.
B.
C.
D.
E.
3.
An increase in the rate of this pathway would cause a decrease in [ADP]
An increase in the rate of this pathway would cause a parallel decrease in the rate of
fuel oxidation
An increase in the rate of this pathway would require an increased supply of NAD
The conversion of A & B to X & Y would be a catabolic pathway
Either X or Y must be a macromolecule.
A solution of ATP at room temperature will spontaneously hydrolyse to give ADP and
phosphate
The turnover of ATP (ie, the total amount that gets degraded and recreated per day) is
about 50 g
During times of need, ATP can be produced by one tissue and transported through the
bloodstream to other tissues
ATP can be stored in Golgi membrane vesicles for use during periods of high energy
demand.
The total concentration of adenine nucleotides in a healthy cell (ie, [ADP] + [ATP] +
[AMP] is always about 4-6 mM.
Both fatty acids and carbohydrate can be oxidized to carbon dioxide with the concomitant
consumption of oxygen. Which of the following is NOT a feature common to BOTH
processes?
A.
The formation of acetyl CoA in the mitochondria
B.
C.
The generation of ATP in the cytoplasm
Trapping through the addition of polar residues after transport from the blood into the
cytoplasm
A dependence on the availability of NAD
The net production of water during the whole process
D.
E.
18/03A
4.
Page 2 of 27 pages
Which statement regarding the macromolecular fuel stores is FALSE?
A.
B.
C.
D.
E.
5.
Semester 2, 2004
Glycogen, but not fat, is stored in association with water
One gram of fat releases over twice as much energy than the same amount of glycogen
The total mass of fat in the human body is about 1000-fold higher than that the total
mass of body glycogen
If all our energy was stored as glycogen, we would weigh at least 40 kg more than we
do now
Fat, but not glycogen, can be transported from liver to other tissues
Which one of the following rules/relationships is INCORRECT?
A.
B.
C.
D.
E.
ADP is used when protons flow through the F0F1ATPase
Proton re-entry into the matrix and ATP synthesis must occur simultaneously
A molecule of ATP is formed each time a proton is pumped out of the matrix
NADH cannot give hydrogens directly to oxygen
Movement of hydrogens/electrons down the electron transport chain can only occur if
protons are simultaneously being pumped from the matrix.
The following information refers to Questions 6 to 10.
Consider a suspension of brown adipocytes, supplied with plenty of oxygen and fuels.
6.
What factor is most likely to limit the rate of fuel oxidation under these conditions?
A.
B.
C.
D.
E.
The availability of glucose
The availability of NADH
The availability of acetyl CoA
The availability of ADP
The availability of fatty acids
18/03A
Semester 2, 2004
Page 3 of 27 pages
Use the options below to answer questions 7 to 10
The adipocytes were treated separately with each of the compounds below.
A.
B.
C.
D.
E.
Rotenone: an inhibitor of electron transport within Complex I
Noradrenalin: an activator of the beta-3 receptors on brown adipocytes
Methylene Blue: an acceptor of electrons from cytochrome c
Fluoroacetate: an inhibitor of the Kreb’s Cycle
Oligomycin: An inhibitor of the FoF1 ATPase
7.
Which compound (A - E) would result in the highest rate of oxygen consumption?
8.
Which compound (A - E) would result in the highest rate of ATP synthesis?
9.
Which compound (A – E) would (after a few minutes) result in the largest proton gradient
(largest difference in the [H+] across the matrix membrane)?
10.
Which compound (A – E) would cause both ubiquinone and cytochrome c to become fully
oxidised?
11.
ALL the facts listed below are features of the electron transport chain. Which feature is NOT
RELEVANT to the process of proton pumping from the mitochondrial matrix?
A.
B.
C.
D.
E.
12.
In each Complex there are proteins which have electron or hydrogen-carrying
prosthetic groups
The Complexes are free to move laterally in the inner mitochondrial membrane
Some Complexes span the membrane
In some redox reactions in the chain, protons are consumed
The inter-complex carriers ubiquinione and cytochrome c carry hydrogens and
electrons, respectively
As a check on the scanning procedure enter an answer of A to question 12 on the answer sheet.
18/03A
13.
Obese individuals are relatively resistant to the actions of leptin
Leptin increases energy expenditure in rodents but not so much in humans
Leptin is secreted by the alpha-cells of the pancreas after a meal
A lack of leptin induces hyperphagia
Blood leptin levels are generally higher in obese individuals
Which statement about Basal Metabolic Rate (BMR) is CORRECT?
A.
B.
C.
D.
E.
16.
The flow of protons through F0 is required to turn the gamma-subunit.
The alpha- and beta-subunits of F1 DO NOT rotate as protons enter the matrix.
The F1 portion is located on the matrix face of the inner mitochondrial membrane.
ATP is made by the gamma-subunits.
About three protons are required to make one ATP
Which statement regarding leptin is INCORRECT?
A.
B.
C.
D.
E.
15.
Page 4 of 27 pages
Which statement regarding the F0F1ATPase is INCORRECT?
A.
B.
C.
D.
E.
14.
Semester 2, 2004
BMR never comprises more than 30% of whole body energy expenditure
BMR refers to the energy used as a consequence of GLUT-1 catalysed glucose
metabolism
BMR is the average daily amount of energy expended by a standard 70 kg person at
20oC
BMR is decreased in response to thyroid hormone
BMR is lower in obese subjects than in lean subjects of the same weight
Which of the following statements regarding the Glycemic Index (GI) is CORRECT?
A.
B.
C.
D.
E.
Amylose starch has a higher GI than amylopectin starch
Sucrose does not have a GI because it is a disaccharide containing fructose
It is not practical to measure the GI of foods containing less than 1% (w/w)
carbohydrate
The GI of lactose is 100
High GI foods often cause flatulence
Semester 2, 2004
18/03A
Page 5 of 27 pages
CH 2OH
Opposite is the structure of glucose presented as a Haworth
projection. Consider this structure, and the structures (A – E),
when answering Questions 17-18
O
H
H
OH
H
H
OH
H
A
B
CH 2OH
O
OH
OH
OH
O
OH
CH 2OH
OH
OH
D
CH 2OH
CH 2OH
O
H
OH
H
OH
O
H
H
OH
OH
H
E
CH 2OH
H
H
OH
beta-D-glucose
H
H
C
OH
OH
OH
OH
CH 2OPO3H
O
H
H
OH
OH
H
H
OH
H
OH
OH
17.
Which structure (A – E) is a keto sugar?
18.
Which structure (A – E) is the non-enzymic product of -D-glucose in solution?
Semester 2, 2004
18/03A
19.
Which of the facts below is NOT an important reason why the concentration of blood glucose
needs to be kept at approximately 5 mM?
A.
B.
C.
D.
E.
20.
an increased number of GLUT-2 transporters on the muscle cell surface
a loss of GLUT-4 transporters from the muscle Golgi apparatus
insulin-stimulation of glucose uptake into the liver
an increase in GLUT-1 expression in brain cells
rapid trapping of glucose in muscle cells by glucokinase
Which of the following properties is NOT a feature of a typical rate limiting enzyme and/or
flux generating step?
A.
B.
C.
D.
E.
23.
Amylose
Sucrose
Maltose
Lactose
Cellulose
Glucose uptake into tissues following a carbohydrate meal is facilitated by:
A.
B.
C.
D.
E.
22.
The skin, red blood cells and kidney have an obligatory requirement for glucose
The extent of protein glycosylation is directly proportional to time of exposure to
glucose
The glycosylation of proteins is a non-enzymatically controlled reaction
Glucose is a relatively reactive molecule
The brain does not possess GLUT-4 transporters: it only has GLUT-1 transporters.
Which of the following does NOT have a free anomeric carbon atom?
A.
B.
C.
D.
E.
21.
Page 6 of 27 pages
The step is irreversible
The concentration of the substrate is very much greater than the Km of the enzyme
The enzyme operates under Vmax conditions
The activity of the enzyme can be regulated by changes in gene expression
The enzyme is regulated by the concentration of substrate alone
As a check on the scanning procedure enter an answer of A to question 23 on the answer sheet.
18/03A
24.
E.
C.
D.
E.
Insulin is essential for glycogen synthesis in muscle, but not liver
The concentration of glucose 6-phosphate can rise high enough in liver to stimulate
glycogen synthase, but this does not happen in muscle
A build up of glucose 6-phosphate inhibits further glucose trapping in muscle, but not
liver
In liver, but not muscle, glucose is only made into glucose 6-phosphate if it is going to
be made into glycogen.
The intracellular [glucose] is always equal to blood [glucose] in liver cells, but not
muscle cells
Which of the following changes DOES NOT occur during lipogenesis (the conversion of
glucose to fatty acids)?
A.
B.
C.
D.
E.
27.
Glycogenesis is stimulated by phosphorylation of glycogen synthase
NADPH is required for the conversion of glucose 6-phosphate to glycogen
Insulin directly stimulates phosphofructokinase to provide ATP for glycogenesis
The consumption of ATP during glycogenesis results in an increased flux through
glycolysis
A new molecule of glycogenin is required each time a branch point is made in the
growing glycogen chain.
Which statement regarding the disposal of glucose by liver and muscle is INCORRECT?
A.
B.
26.
Page 7 of 27 pages
Which statement regarding the conversion of glucose to glycogen in muscle is CORRECT?
A.
B.
C.
D.
25.
Semester 2, 2004
The polymerization of acetyl CoA carboxylase (ACC) increases
The production of malonyl CoA increases
The cleavage of citrate in the cytoplasm decreases
The consumption of NADPH increases
The consumption of ATP increases
If you added 14C malonyl CoA, labelled in the carboxylic acid carbon (see diagram below), to
cells undergoing fatty acid synthesis to palmitate (C16) where would you expect to recover the
label?
-OO14C-CH2-CO-S-CoA
malonyl CoA
A.
B.
C.
D.
E.
On the odd numbered carbons of palmitate
None of the carbon atoms in palmitate
On the carboxyl carbon (carbon 1) of palmitate
On the even numbered carbons of palmitate
On the omega-carbon (carbon 16) of palmitate
18/03A
Semester 2, 2004
Page 8 of 27 pages
The following information refers to Questions 28-29.
The following enzymes (A – E) are all involved in the synthesis of fatty acids from glucose.
A.
B.
C.
D.
E.
Glucose 6-phosphate dehydrogenase
ATP citrate lyase
Acetyl CoA carboxylase
Pyruvate dehydrogenase
Phosphofructokinase
28.
Which enzyme (A – E) is DIRECTLY regulated by the availability of NADP+?
29.
Which enzyme (A – E) catalyses the step after which the products cannot be reconverted back
into glucose?
30.
During the synthesis of fatty acids from acetyl CoA, which type of reaction DOES NOT
happen?
A.
B.
C.
D.
E.
31.
Which of the following statements regarding fat digestion is INCORRECT?
A.
B.
C.
D.
E.
32.
Hydration of a double bonded carbon
Reduction of a ketone (C=O) to an alcohol (C-OH)
Carboxylation
Decarboxylation
Reduction of a double bonded carbon (-CH=CH-)
Triglyceride is not soluble in water
Bile salts are made in the liver but stored in the gall bladder
Bile salt production involves adding polar residues on to cholesterol
Lipoprotein lipase, attached to the inside of the gut wall, hydrolyses dietary fat
The hydrolysis products of fat are re-esterified back to lipid by the intestinal cells
before export into the blood stream.
Person A is eating a normal fat diet but taking a drug which inhibits fat digestion. Person B is
eating a diet in which the fat has been replaced by Olestra. Which statement is INCORRECT?
A.
B.
C.
D.
E.
In both people, there would be little rise in level of chylomicrons in the blood stream
after a meal.
Both people would experience flatulence
The faeces of both individuals would be relatively buoyant
Fat soluble vitamin uptake would be compromised in both subjects.
Bile salts would not be produced in either person.
18/03A
Semester 2, 2004
Page 9 of 27 pages
33.
Which of the following is NOT a fate of cholesterol in mammalian tissues?
A.
Acetyl CoA
B.
Incorporation into VLDL.
C.
Incorporation into plasma membranes
D.
Cholesterol esters
E.
Steroid hormones
34.
Dietary cholesterol is transported from the liver:
A.
B.
C.
D.
E.
35.
Ketone bodies are transported to tissues:
A.
B.
C.
D.
E.
36.
Freely dissolved in solution without attachment to a carrier.
In chylomicrons
On carnitine
In HDLs
In VLDLs
An inhibitor of the interaction of VLDL with target tissues would:
A.
B.
C.
D.
E.
37.
On carnitine
In chylomicrons
In HDLs
Freely dissolved in solution without attachment to a carrier.
In VLDLs
Inhibit the uptake of dietary fat in the intestine
Inhibit the transport of fat from the liver to the tissues
Increase the production of LDLs in the bloodstream
Inhibit the release of fatty acids from adipose tissue
Increase the uptake of dietary cholesterol by cells from LDLs
Below is a number of strategies used to lower serum cholesterol levels. Which strategy is
designed to encourage cells to express more LDL-receptors?
A.
B.
C.
D.
E.
Increasing the consumption of omega-3 fatty acids.
Reducing the intake of meat and dairy products
Treatment with resins that block bile salt reabsorbtion
Treatment with statins
Ingesting sterols of plant origin
Semester 2, 2004
18/03A
Page 10 of 27 pages
Use graphs (A – E) to answer Questions (38-40)
A volunteer has starved for 3 days and a number of biochemical measurements have been made over
the course of that time. Time “0” is the beginning of the post absorptive period (ie. when the last meal
has been completely absorbed).
A
100
80
60
40
20
100
80
60
40
20
0
0
0.5
1
1.5
2
2.5
B
120
% Activity/
concentration
% Activity/
concentration
120
0
3
0
0.5
Time (days)
1.5
2
2.5
3
Time (days)
C
120
120
100
100
% Activity/
concentration
% Activity/
concentration
1
80
60
40
20
0
D
80
60
40
20
0
0
0.5
1
1.5
2
2.5
3
0
Time (days)
0.5
1
1.5
2
2.5
3
Time (days)
E
120
% Activity/
concentration
100
80
60
40
20
0
0
0.5
1
1.5
2
2.5
3
Time (days)
38.
Which graph (A – E) represents the concentration of glucose in the bloodstream?
39.
Which graph (A – E) represents the blood ketone body concentration?
40.
Which graph (A – E) represents the phosphorylation of liver glycogen phosphorylase?
Semester 2, 2004
18/03A
The graph below does NOT represent:
% Activity/ concentration
41.
Page 11 of 27 pages
120
100
80
60
40
20
0
0
0.5
1
1.5
2
2.5
3
Tim e (days)
A.
B.
C.
D.
E.
42.
Which statement regarding the stimulation of glycogenolysis during starvation is
INCORRECT?
A.
B.
C.
D.
E.
43.
The rate of glucose output from the liver
The liver glycogen content
The activity of muscle pyruvate dehydrogenase
The blood insulin level
The intracellular liver concentration of fructose 2,6 bisphosphate
Phosphorylase kinase phosphorylates phosphorylase
cAMP-dependent kinase is not activated by phosphorylation
One phosphorylase molecule is activated for every one glucagon molecule that binds to
a liver glucagon receptor
Glucagon does not stimulate a rise in [cAMP] in muscle
Muscle cannot convert glucose 6-phosphate into glucose for release into the blood
stream.
Which statement regarding white adipose tissue after three days of starvation is CORRECT:
A.
B.
C.
D.
E.
Phosphodiesterase will be fully active
Hormone sensitive lipase will be phosphorylated
The release of fatty acids into the blood stream will be decreasing relative to day one
The rate of glycerol release is enough to sustain the production of 120 of glucose per
day
cAMP-dependent protein kinase will be inhibited
18/03A
44.
D.
E.
liver phosphoenolpyruvate carboxykinase is activated
liver pyruvate carboxylase is inhibited
muscle beta-oxidation is inhibited
glucose transport into muscles is prevented
muscle pyruvate dehydrogenase is stimulated
Which statement regarding the process of beta-oxidation is CORRECT?
A.
B.
C.
D.
E.
47.
In the early post-absorbtive period, the brain uses about 120g of glucose per day
Fatty acids are released once all body glycogen stores have been used up
Although we store most of our energy as fat, we cannot convert fatty acids into
carbohydrate
Net gluconeogenesis is possible from part of triacylglycerol
The brain cannot use fatty acids as they do not pass across the blood-brain barrier.
The Cori-Cycle to operates when:
A.
B.
C.
D.
E.
46.
Page 12 of 27 pages
Which of the following statements regarding our fuel stores is INCORRECT?
A.
B.
C.
45.
Semester 2, 2004
The transport of fatty acids into the cell is totally dependent on a membrane carrier
The movement of fatty acids into the mitochondrial matrix is stimulated by malonyl
CoA
The beta-oxidation of a 16-carbon fatty acyl CoA would result in the production of 8
FADH2 and 8 NADH molecules
Matrix carnitine and cytosolic carnitine pools cannot mix
The coupling of fatty acids to Coenzyme A involves consumption of ATP
As a check on the scanning procedure enter an answer of A to question 47 on the answer sheet.
Semester 2, 2004
18/03A
Page 13 of 27 pages
Use the Table below to answer Questions 48-51.
Options A – E show the rates of various enzymes and pathways during exercise. The scale goes from
minimum (-) to maximum (+++++).
Activity
A
B
C
D
E
beta-oxidation of
fatty acids
-
-
++
+++
-
Krebs cycle
-
+++
++
++++
-
Muscle
phosphorylase
+++++
+++
-
+
+++++
Muscle
-
+++
-
++
++++
-
++
-
++
-
Phosphofructokinase
Muscle pyruvate
dehydrogenase
48.
Which option (A – E) shows the pattern of fuel utilization after 30 minutes of jogging
(moderate, aerobic exercise)?
49.
Which option (A – E) shows the pattern of fuel utilization during a sprint?
50.
Which option (A – E) shows the pattern of fuel utilization after 1 hour of running in a
competitive long distance race (eg, a marathon race)?
51.
Which option (A – E) is NOT possible under any exercise scenario?
52.
What is NOT one of the fates of amino acids arising from the digestion of dietary protein?
A.
B.
C.
D.
E.
Deamination to produce carbon skeletons
Conversion to glucose in the liver
Synthesis of new protein
Conversion to fat in the liver
Conversion to alanine in the muscle and storage as poly-alanine
18/03A
53.
B.
C.
D.
E.
Complete oxidation of one acetyl CoA in the Krebs Cycle produces 4 NADH and 1
FADH2
The major rate limiting steps are the reactions from succinate to oxaloacetate
The sequence of reactions from succinate to oxaloacetate are similar to those involved
in fatty acid sythesis
The Krebs Cycle does not produce any ATP directly
During one turn of the cycle, neither of the carbon atoms released as carbon dioxide
have come from the acetyl CoA molecule that entered the cycle.
Which of the following statements about protein folding in the ER is correct?
A.
B.
C.
D.
E.
56.
240 g/day of protein comprised of all amino acids
60 g/day of protein comprisedof a all amino acids
120 g/day of protein deficient in lysine
120 g/day of protein deficient in alanine
60 d/day of protein deficient in both alanine and glutamate
Which statement regarding the Krebs Cycle is CORRECT?
A.
55.
Page 14 of 27 pages
For a 60 kg female which of the follow type of protein intake would be LEAST desirable?
A.
B.
C.
D.
E.
54.
Semester 2, 2004
The hydrophobic signal peptide is buried in the core of the protein as it folds.
The reducing environment inside the ER ensures rapid formation of disulfide bonds in
proteins undergoing folding.
Peptidyl disulfide isomerase forms covalent bonds with substrate proteins.
ATP hydrolysis catalysed by the signal recognition particle is used to drive protein
folding.
UDP:glucosyl transferase removes glucose residues from glycoproteins which have
folded correctly
During biosynthesis of glycosylphosphatidylinositol (GPI) -anchored proteins:
A.
B.
C.
D.
E.
The GPI anchor becomes covalently linked to the S atom of a cysteine residue on the
protein.
Dolichol phosphate is displaced by the GPI anchor in a transesterification reaction.
Inositol triphosphate is released and then acts to mobilise Ca2+ from intra-cellular
stores.
Glucose residues are trimmed from the GPI anchor.
The GPI anchor is linked to the C-terminal of the protein in a transamidation reaction.
18/03A
57.
B.
C.
D.
E.
Dephosphorylation of a JAK kinase allows the binding of a STAT transcription factor,
mediated by its SH2 domains.
JAK kinases use GTP to phosphorylate small GTP-binding proteins such as Ras.
Phosphorylation of STAT proteins allows them to dimerise through their SH2 domains.
JAK-dependent phosphorylation of calmodulin leads to inhibition of Ca2+-dependent
protein kinases.
Entry of JAK kinases to the nucleus is followed by phosphorylation of the 2’ OH
groups of the deoxyribose residues of chromosomal DNA.
In general, binding of growth factors to receptors with intra-cellular tyrosine kinase domains
might be expected to:
A.
B.
C.
D.
E.
61.
An influx of Ca2+ through activation of a ligand-gated ion channel.
Translocation of the receptor:cytokine complex to the nucleus.
Autophosphorylation of a tyrosine kinase bound to the receptor.
Dissociation of the receptor from a dimer to a monomer form.
Inhibition of intra-cellular adenyl cyclase.
Which of the following statements about the JAK-STAT signalling pathway is correct?
A.
60.
They all contain seven strands of beta-sheet which span the cell membrane.
They all mediate signal transduction through G-protein coupled events.
Their extra-cellular domains are alpha-helical bundles.
They are all GPI-anchored proteins.
Typically, binding of cytokines to their receptors leads to dissociation of the receptors
into their active monomeric forms
Binding of a cytokine to a cytokine receptor would be generally expected to lead to:
A.
B.
C.
D.
E.
59.
Page 15 of 27 pages
A common structural theme in the cytokine family of receptors is:
A.
B.
C.
D.
E.
58.
Semester 2, 2004
Lead to tyrosine kinase-catalysed dephosphorylation of phosphoproteins.
Lead to activation of the Ras protein kinase through the action of the Raf adaptor
protein.
Lead to the activation of protein kinase C because of decreased levels of intra-cellular
Ca2+.
Culminate in the phosphorylation of transcription factors by a MAP kinase.
Lead to enhanced expression of protein kinase A.
As a check on the scanning procedure enter an answer of A to question 61 on the answer sheet.
18/03A
62.
Page 16 of 27 pages
During activation of protein kinase C:
A.
B.
C.
D.
E.
63.
Semester 2, 2004
An influx of Ca2+ from the nucleus to the cytoplasm leads to conversion of protein
kinase C into its active form.
Production of IP3 leads to the opening of a ligand-gated ion channel in the membrane
of the endoplasmic reticulum.
Protein kinase C enters the nucleus after a steroid hormone binds to it
Calmodulin-activated protein kinase binds to the IP3 receptor through its SH2 domain.
Diacyl glycerol is phosphorylated and becomes incorporated into the cell membrane.
One of the characteristic features of G-protein coupled receptors is:
A.
B.
C.
D.
E.
Their primary role is signal transduction within cells of the immune system.
Normally, small GTP-binding proteins like Ras bind to G-protein coupled receptors
during their activation.
G-protein coupled receptors are heterotrimers of alpha-, beta- and gamma-chains.
In most cases, their monomeric forms are inactive.
They contain seven membrane-spanning alpha-helices.
18/03A
PART B: To be answered by ALL students.
Page 17 of 27 pages
Part B: Short Answer Questions to be answered by ALL students.
Answer these questions in the space provided in this booklet.
64.
What ways are principles and advantages/disadvantages of TWO different methods of
measuring whole body energy expenditure? (5 marks)
18/03A
PART B: To be answered by ALL students.
Page 18 of 27 pages
HINT: A sketch of the process by which lipogenesis occurs (no structures, just names!) will help you
answer the questions below. (5 marks)
65.
The overall, balanced equation for the synthesis of palmitate (a 16-carbon fatty acid) from
glucose is:
9 glucose + 8 O2  2 palmitate + 22 CO2 + 22 H20
i)
Why is there no mention of ATP or NADPH in this equation?
ii)
Palmitate is a highly reduced hydrocarbon chain – so why is mentioned in this equation?
iii)
At what steps were the carbon dioxide molecules released?
iv)
Roughly, what percentage of the energy in glucose is lost in doing this conversion
(Mw palmitate = 256, Mw glucose = 180)
v)
How does lipogenesis affect the respiratory quotient?
18/03A
66.
PART B: To be answered by ALL students.
Page 19 of 27 pages
To sustain a high rate of fatty acid oxidation in muscles it is necessary to have a large demand
for ATP synthesis and a rapidly working Krebs Cycle. However, this is not the case in liver.
Why? (5 marks)
18/03A
67.
PART B: To be answered by ALL students.
Page 20 of 27 pages
The following strategies are often employed by athletes. Explain why. Justify your answers on
biochemical terms but use NO MORE than one or two sentences for each strategy. (5 marks)
Dietary creatine supplementation
Dietary carnitine supplementation
Consumption of sodium bicarbonate before a race
Dietary Coenzyme Q supplementation
Consumption of caffeine before a race
18/03A
68.
PART B: To be answered by ALL students.
Page 21 of 27 pages
The insulin sensitivity and fasting blood glucose concentration of about 40 subjects was
measured. The graph opposite shows the result. Each circle is a separate individual. (5 marks)
i)
What is the name and principle of the technique which would have been used to measure
the insulin sensitivity of each individual?
ii)
What do THESE results tell us about the relationship between hyperglycemia and insulin
resistance?
iii)
On a separate graph, draw the results that you would expect to see if an oral glucose
tolerance test was given to individuals in each of the ‘groups’ A, B & C
18/03A
PART B: To be answered by ALL students.
Page 22 of 27 pages
high
A
Insulin
Sensitivity
C
B
low
4
8
12
fasting blood [glucose] (mM)
16
18/03A
69.
PART B: To be answered by ALL students.
Page 23 of 27 pages
Explain the molecular processes linking the binding of a growth factor to its receptor to the
arrival of the transcription factor NF-B in the nucleus.
*BCHM2902 students should include in their answers a discussion of the importance of
ubiquitin in these processes*. (5 marks)
18/03A
Part C: To be done by BCHM2002 & BCHM2102 students ONLY. Page 24 of 27 pages
PART C: To be answered by BCHM2002 & BCHM2102 students ONLY.
70.
i) Give an example of how a phosphorylation cascade can simultaneously inactivate and
activate different target enzymes. (3 marks)
ii) Briefly compare the features of phosphorylation cascades to other regulatory systems (ie,
allosteric modulation and gene expression control). (3 marks)
iii) PFK is not directly activated by protein kinase A dependent phosphorylation. What
problems would you foresee if it was? (2 marks)
18/03A
Part D: To be done by BCHM2902 Advanced students ONLY.
Page 25 of 27 pages
PART D: To be answered by BCHM2902 (ADVANCED) students ONLY.
71.
Galactose is mainly processed by the liver. On entry into liver cells, galactose is
phosphorylated by galactokinase to galactose 1-phosphate (Gal 1-P). The galactose moiety in
Gal 1-P is then swapped for glucose on UDP-Glucose, giving UDP-Galactose and Glucose 1phosphate (Glu 1-P). The Glu 1-P can enter 'normal' glucose metabolic pathways, whilst
UDP-Galactose can be converted into UDP-Glucose using the enzyme UDP-Glucose 4epimerase.
Galactokinase
Galactose
Galactose 1-P
UDP-Glucose
UD-glucose4- epimerase
Transferase
Glucose 1-P
UDP-Galactose
Normal Glucose
Metabolism
In other tissues, excess galactose is converted into the dead end product galacticol by aldose
reductase. A build up of galacticol in tissues, especially nerve cells, is very damaging.
Two defects in galactose metabolism are known: Gdef a deficiency in galactokinase and Edef
a deficiency in UDP-glucose 4-epimerase.
These conditions can be identified by giving a galactose tolerance test (intravenous infusion of
galactose).
18/03A
Part D: To be done by BCHM2902 Advanced students ONLY.
Page 26 of 27 pages
i)
Explain how the galactose tolerance test would help identify each condition? HINT:
Consider the response of blood galactose, blood glucose and blood lactate levels in
each case, and in control subjects. (5 marks)
ii)
What general/daily metabolic problems and/or symptoms would you expect to see in
someone with each of the two conditions? (2 marks)
iii)
What treatment or management strategy would you recommend for each condition?
(1 mark)
18/03A
Part D: To be done by BCHM2902 Advanced students ONLY.
THIS IS THE END OF YOUR QUESTIONS
Page 27 of 27 pages