1812 A Semester 2, 2005 Page 20 of 46
Faculty of SCIENCE
School of MOLECULAR AND MICROBIAL BIOSCIENCES
BCHM2072 - HUMAN BIOCHEMISTRY
Duration: 3 hours
Reading time: 10 min
SEAT NUMBER:
FULL NAME:
SID:
INSTRUCTIONS TO CANDIDATES
· Students are permitted to bring in the coloured sheets of ‘stimulus material’ provided by the School of MMB. These sheets may be annotated but MUST BE HANDED IN WITH THIS PAPER.
· This paper is CONFIDENTIAL. No part of this paper may be removed from the examination room.
· Only University supplied calculators may be used
· Answer Short Answer Questions in the spaces provided in this booklet
· Answer Multiple Choice Questions on the answer sheet provided.
· All Multiple Choice Questions are graded using the Partial Marking System. Although each question has been designed to have only ONE option which carries full marks, each option of each question may carry a partial positive or negative mark. No negative marks are incurred for questions that are left blank.
Section A covers the THEORY (lecture and assignment) Recommended time: 2 hours
Part I - SIXTY Multiple Choice Questions at 1.5 marks each.
Part II - SIX short answer questions (at 5 marks each)..
The 120 marks available in Section A will contribute 80-100% of your THEORY mark. The remaining 0-20% is contributed from the marks that you chose to accept from the assignments during the semester.
Section B covers the PRACTICAL (lab work) Recommended time, 1 hour
Part I - THIRTY FIVE Multiple Choice Questions at one mark each.
Part II – ONE short answer question (6 marks)
The 41 marks available for this Section will contribute 50% of your PRACTICAL mark for BCHM2072. The other 50% is contributed from the marks that you obtained for practical reports and laboratory tasks during the semester.
All marks are considered raw, and may be subjected to scaling, until approved by the Faculty of Science.
SECTION A - THEORY
PART I – Multiple Choice Questions worth 1.5 marks each
1. Which of the following is an ANABOLIC reaction which occurs in humans?
A Net fixation of carbon dioxide into carbohydrate
B Hydrolysis of DNA into nucleotides
C Proteolysis
D Glycogenolysis
E Lipogenesis
2. Which statement is most CORRECT?
A 1 kg of human tissue, on average, contains somewhere between 0.5 and 5mgATP
B In a healthy cell, the [ATP] is always much less than the [ADP]
C The total adenine nucleotide pool ([ATP] + [ADP] + [AMP]) in cells is about5mM
D ATP can be produced in the mitochondria of liver cells and transported in the blood for use by the muscle
E At room temperature, a 5 mM solution of ATP will completely hydrolyse into ADP and phosphate within 1 minute.
3. Which statement about fatty acid oxidation is CORRECT?
A Carnitine is a protein embedded in the cell membrane that allows fatty acids to enter from the bloodstream
B Fatty acids are covalently attached to Coenzyme A during the FAD/NAD catalysed oxidation reactions
C The oxidation reactions involving FAD/NAD occur only in the cytoplasm
D Fatty acids attached to Coenzyme A can move freely across the mitochondrial membrane
E Carnitine is consumed (two carbons at a time) during fatty acid oxidation
4. Which process occurs in the CYTOPLASM?
A Conversion of fatty acyl-CoA to acetyl-CoA
B Conversion of acetyl-CoA to malonyl-CoA
C Conversion of pyruvate to acetyl-CoA
D Conversion of oxaloacetate and acetyl-CoA to citrate
E Conversion of acetyl-CoA into ketone bodies
5. Which description of the operation of the Krebs Cycle is MOST CORRECT?
A The cycle turns acetyl-CoA into ATP
B The pathway is located in both the cytoplasm and the mitochondria
C The cycle reacts fuel molecules with oxygen to produce carbon dioxide
D The cycle generates CoA and NADH
E Most of the ATP in the cell is made directly by enzymes of the Krebs Cycle by substrate level phosphorylation.
6. Which of the following statements is INCORRECT?
A Electrons can move down the electron transport chain even if proton pumping from the matrix can not occur.
B Protons are only pumped from the matrix if electrons are passed down the electron transport chain.
C ATP synthesis at the F1ATPase requires both ADP and phosphate
D Protons will only come in through the F0F1ATPase if ATP is simultaneously being made from ADP
E Protons can pass freely across the outer mitochondrial membrane
7. Which of the following statements concerning electron transport and proton pumping is INCORRECT?
A Proton release occurs when electron carriers receive electrons from hydrogen carriers
B Cytochrome c carries only electrons
C Ubiquinone carries hydrogens from Complex I to Complex III
D Oxygen is consumed on the matrix side of the inner mitochondrial membrane
E The actual protons that move out of the matrix during electron transport come exclusively from the hydrogens on NADH
8. Which description of the components in the F0F1ATPase is INCORRECT?
A The gamma subunit rotates as protons enter the matrix
B Portions of the F0 channel rotate as protons pass through it
C The stator portion prevents free rotation of the alpha-and beta-subunits
D ATP is made on an active site on the gamma subunit
E The F1ATPase portion is located inside the matrix
The following table is relevant to Questions 9 – 13.
The table lists five situations in which there has been a change in the operation of the mitochondrial ATP generating system.
Situation / Rate of ATP Synthesis / Rate of Proton Pumping / Size of Proton Gradient / Rate of Oxygen ConsumptionA / STOPS / INCREASES / DISSIPATES / INCREASES
B / STOPS / STOPS / DISSIPATES / STOPS
C / STOPS / STOPS / STAYS HIGH / STOPS
D / CONTINUES / STOPS / STAYS HIGH / INCREASES
E / CONTINUES / CONTINUES / FALLS SLIGHTLY / STOPS
Which situation (from A-E above) would you expect to result from the following interventions?
9. An uncoupler
10. A lack of oxygen
11. Exposure to a compound which accepts electrons directly from cytochrome c
12. An inhibitor of proton movement through the F0 channel
13. An inhibitor of electron transport at Complex IV
14. Which statement regarding Basal Metabolic Rate (BMR) is CORRECT?
A Whole body BMR is generally lower in people who weigh more
B BMR contributes more to whole body energy expenditure than diet induced thermogenesis
C BMR is assessed by comparing food intake to weight gain
D BMR is inversely proportional to lean body mass
E Thyroid hormone lowers BMR
15. Which statement is CORRECT?
A Brain can use fatty acids
B Fatty acids can be converted into glucose
C Muscle glycogen is the major carbohydrate reserve for the brain
D The total amount of glycogen stored in muscle is less than the total amount stored in liver
E There is no specific protein that represents a store of amino acids
16. Both indirect calorimetry and the doubly-labeled water (D2O18) methods can be used to assess whole body energy expenditure. Which statement is CORRECT?
A Only indirect calorimetry can give an indication of which fuels are being burnt
B The doubly-labeled water method measures oxygen production
C The doubly labeled water method can be done over a shorter time frame than indirect calorimetry
D Only the doubly labeled water method can be used to determine basal metabolic rate
E Indirect calorimetry only works if the subject has consumed carbohydrates, not fat.
17. Which of the following statements regarding leptin is CORRECT?
A Leptin is secreted by the β-cells of the pancreas in response to a carbohydrate meal
B Obese subjects have a lower blood leptin concentration than non-obese subjects
C Obese subjects are hyper-responsive to leptin
D A lack of leptin will cause ravenous hunger
E In rodents, leptin inhibits thermogenesis in brown adipose tissue
18. Which of the following scenarios would MOST likely lead to flatulence (ie production of volatile short chain fatty acids and gases in the lower bowel)?
A Consumption of sucrose by someone with lactase deficiency
B Consumption of amylopectin starch
C Consumption of amylose starch
D Consumption of dairy products pre-treated with lactase
E Consumption of glucose in association with an amylase inhibitor
19. Which statement is CORRECT?
A Two days of continual exposure to a blood glucose concentration of 10 mM will cause a coma
B The reaction between proteins and glucose is not an enzyme catalysed process
C Glycosylation does not affect the function of proteins
D When blood glucose concentration is 5 mM, the rate of reaction between proteins and glucose is zero
E Hyperglycemia causes problems faster than hypoglycemia
20. Which statement is INCORRECT?
A It is not practical to measure the glycemic index of meat
B The reference food used in glycemic index determinations is normally glucose
C The glycemic index is a relative measure of the peak blood glucose concentration caused by a food
D Legumes have a lower glycemic index than white bread
E Sucrose has a lower glycemic index than amylopectin starch
The figures opposite refer to Questions 21 – 23
Each of the graphs shows the response of glucose transporter number to a glucose load in a particular part of a specific tissue. Assume that the load is completely cleared from the bloodstream in about 2 hours.
Which graph represents:
21. The number of GLUT-4 transporters in the vesicles of the Golgi apparatus in muscle cells
22 The number of GLUT-2 transporters on the cell membrane of liver cells
23 The number of GLUT-1 transporters on the cell membrane of brain cells
24. Which statement is INCORRECT?
A Anomeric forms of monosaccharides result from ring formation
B Glyceraldehyde and dihydroxyacteone are both trioses
C Interconversion of glucose and galactose occurs spontaneously in solution
D Glucose, fructose and galactose are all hexoses
E Conversion of glucose 6-phosphate to fructose 6-phosphate involves changing an aldose into a ketose
25. Which of the following enzymes is most likely to catalyse a ‘rate limiting step’ in a pathway
A High Vmax enzyme that catalyses irreversible conversion of SàP with the prevailing [S] being about the same as the Km of the enzyme.
B High Vmax enzyme that catalyses reversible conversion of SàP with the prevailing [S] being about the same as the Km of the enzyme
C High Vmax enzyme that catalyses reversible conversion of SàP with the prevailing [S] being about 2-fold the Km of the enzyme
D Moderate Vmax enzyme that catalyses reversible conversion of SàP with the prevailing [S] being about 2-fold the Km of the enzyme
E Low Vmax enzyme that catalyses irreversible conversion of SàP with the prevailing [S] being about 20-fold the Km of the enzyme
26. Which process requires ATP?
A Addition of glucose from UDP-glucose to a growing glycogen chain
B Conversion of glucose residues in glycogen to glucose 6-phosphate
C ANY of the reactions in the fatty acyl synthase complex (ie, from malonlyl-CoA to fatty acyl-CoA)
D Carboxylation of acetyl-CoA to give malonyl-CoA
E Decarboxylation of pyruvate to acetyl-CoA
27. Which statement about the balance between glycogenesis and glycolysis in muscle after a carbohydrate meal is CORRECT?
A Consumption of ATP in glycogenesis stimulates glycolysis
B Insulin stimulates dephosphorylation of phosphofructokinase
C Glucose 6-phosphate concentration rises about 100-fold and stimulates glycogen synthase
D Production of ATP in glycolysis is the major driving force for glycogenesis
E A rise in the level of ATP stimulates glycogen synthase
28. Which statement describes a genuine feature of glucokinase which is NOT shared by hexokinase?
A Glucokinase irreversibly produces glucose 6-phosphate from glucose
B Glucokinase is inhibited by a build up of glucose 6-phosphate
C Glucokinase is stimulated by phosphorylation
D Glucokinase can work on any hexoses
E Glucokinase is not saturated by 10 mM glucose
29. Which statement about the synthesis of glycogen from glucose is INCORRECT?
A The formation of UDP-glucose is facilitated by the joining of two phosphates to form pyrophosphate
B In UDP-glucose, the glucose residue is joined to UDP at the C-1 end of glucose.
C Glycogen synthesis occurs in the cytoplasm
D Activated glucose residues on UDP-glucose form glycosidic bonds with the C-4 ends of the growing glycogen chain
E UTP is regenerated by the reaction of UDP and ATP
30. Which statement is CORRECT?
A A rise in intracellular glucose concentration is sufficient to increase the rate of glycogenesis in liver
B Liver does not have branching enzyme
C The size of a glycogen molecule is unlimited in liver
D Glucose transport into liver requires insulin
E Liver glycogenesis can occur without a concomitant increase in a catabolic pathway
31. Which statement is CORRECT?
A Only the liver can dispose of fructose
B Fructose is trapped as fructose 6-phosphate in the liver
C A fructokinase deficiency would severely deplete ATP levels in liver after a meal containing fructose
D The liver cannot convert fructose into glucose
E The aldolase involved in liver fructose metabolism is slow in comparison to the rate of fructose trapping
32. In white adipose tissue, which process is NOT stimulated by insulin?
A The rate of glucose uptake
B Pyruvate dehydrogenase activity
C Acetyl-CoA carboxylase acitvity
D Expression of fatty acyl synthase
E Lipolysis
33. Hydroxycitrate is an inhibitor of ATP-citrate lyase. What would be the MOST LIKELY consequence of adding hydroxycitrate to cells undergoing lipogenesis?
A The movement of acetyl-CoA into the cytoplasm would decrease
B Production of ATP would stop
C Mitochondrial acetyl-CoA levels would rapidly deplete