(4) Concepts and Principles of Biomedicine (CPB).doc

JC1 - 2010 M4- Concepts and Principles of Biomedicine

MCQs

Which of the following amino acids is NOT essential? CPB2 SLIDE 9 A. Alanine. B. Phenylalanine. C. Valine. D. Methionine. E. Isoleucine. ANSWER: A An essential amino acid is one which cannot be synthesized in the body. Which one of the following is a non-essential amino acid in health? CPB2 SLIDE 9 A. Leucine B. Methionine C. Tyrosine D. Valine E. Arginine ANSWER: C Protein structure is determined by the amino-acid sequence. Which of the following statements is true? CPB2 SLIDE 18 A. The alpha helix is a coiled structure with the amino-acid side-chains pointing outwards B. Disulphide bonds are formed between serine residues C. Polypeptide chains in beta-sheets are always in parallel orientation D. The peptide bond allows free rotation of the polypeptide chain to occur E. All proteins can fold correctly on their own without assistance ANSWER: A The alpha-helical structure in proteins is maintained by a number of factors, including hydrogen bonding between backbone polar groups and interactions between amino-acid side-chains. Which amino acid may disrupt the regularity of an alpha helix due to the small size of its sidechain? CPB2 SLIDE 19 A. Aspartate B. Cysteine C. Glycine D. Proline E. Tryptophan ANSWER: C Medical researchers investigating a rare but devastating inherited disease have identified the specific gene involved. Further studies identify a specific mutation of that gene which is found in the majority of sufferers. This mutation changes the activity of the protein product of the gene by disrupting the structure of a key alpha helix. This occurs because an alanine residue is changed to another residue which disrupts alpha helical structure. From the following list, choose the amino acid which is most likely to have replaced the normal alanine. CPB2 SLIDE 19 A. tyrosine B. asparagine C. lysine D. proline E. cysteine

ANSWER: D Which of the following amino acid residues is least likely to be found in an alphahelix? CPB2 SLIDE 19 A. tyrosine B. asparagine C. lysine D. glycine E. cysteine ANSWER: D Enzymes CPB2 SLIDE 33 A. they are reversibly denatured by boiling B. do not display tissue specificity C. cannot be joined covalently to carbohydrates D. are insoluble in the cytoplasm of the cell E. their secondary and tertiary structures are sensitive to pH ANSWER: E You examine a 55 year old male who has complained of stiffness in the limbs on waking and painful joints. Physical examination reveals swelling in both knee joints and in the knuckles. Further tests lead to a diagnosis of inflammatory arthritis and you prescribe a course of management which includes the use of COX inhibitors. COX inhibitors reduce the level of the inflammatory mediators known as prostaglandins by inhibiting their synthesis from arachidonic acid. Which dietary lipid is a precursor for arachidonic acid? CPB3 SLIDE 12 A. Lauric acid B. Linoleic acid ,its an essential fatty acid. C. Oleic acid D. Palmitic acid E. Stearic acid ANSWER: B A parent brings her 11 month old daughter into hospital for investigations into the reasons for mental and skeletal problems. The infant has hepatosplenomegally and is diagnosed as suffering from one of the mucopolysaccharidoses. This group of diseases is characterized by the intracellular storage of partially degraded: CPB4 SLIDE 25 A. mucins B. glycosaminoglycans C. glycogen D. gangliosides E. collagen ANSWER: B A parent brings her 11 month old daughter into hospital for investigations into the reasons for mental and skeletal problems. The infant has hepatosplenomegally and is diagnosed as suffering from one of the mucopolysaccharidoses. This group of diseases is characterized by the intracellular storage of partially degraded: CPB4 SLIDE 25

A. mucins B. collagen C. gangliosides D. glycosaminoglycans E. glycogen ANSWER: D Enzymes are highly selective biocatalysts. They act by: CPB7 SLIDE 5 A. Increasing the rate of a reaction B. Altering the equilibrium of a reaction C. Increasing the ambient temperature D. Increasing the amount of its available substrate E. Decreasing the rate of a reaction ANSWER: A Protein kinases are enzymes that phosphorylate amino acid side chains of proteins in ATP-dependent reactions. A protein kinase can be classified as which of the following: CPB7 SLIDE 14 A. Hydrolase B. Isomerase C. Lyase D. Transferase E. Ligase ANSWER: D A competitive inhibitor of an enzyme: CPB7 SLIDE 30 A. raises the Vmax B. raises the Km C. lowers the Vmax D. covalently modifies the enzyme E. combines with allosteric sites on the enzyme ANSWER: B A drug company researcher is developing new drugs to treat a specific infectious disease by synthesising inhibitors to enzymes found only in the pathogenc organism. One particular compound shows promise and she carries out kinetic experiments to identify the specific type of inhibition that the compound exhibits. The experiments show that the apparent Vmax of the enzyme-catalysed reaction is not changed by the inhibitor. The mode of inhibition is CPB7 SLIDE 30 A. Allosteric B. Competitive C. Covalent D. Non-Competitive E. Uncompetitive ANSWER: B A non-competitive inhibitor of an enzyme: CPB7 SLIDE 32 A. lowers the apparent Vmax B. raises the apparent Km C. has a structure similar to the transition state

D. covalently modifies the enzyme E. binds to the active site of the enzyme ANSWER: A A biochemical pathway converts molecule W into molecule Z in a series of enzyme catalyzed reactions: W  X  Y  Z. Molecule Z binds to the enzyme that converts W to X at a site remote from the active site and by doing so, decreases the activity of the enzyme. Thus, with regard to this enzyme, Z acts as CPB7 SLIDE 36 A. An allosteric inhibitor –slight remote from the active site. B. A coenzyme C. A competitive inhibitor D .An intermediate E. A substrate ANSWER: A Aripiprazole is a dopamine receptor partial agonist used in the treatment of schizophrenia. Which of the following statements is INCORRECT? A partial agonist CPB10 SLIDE 28 A. Produces sub-maximal responses B. Has a lower efficacy than full agonists C. Can reverse constitutive activation D. May have different potencies than full agonists E. Bind to the same receptors as full agonists ANSWER: C In the absence of other drugs, pindolol increases heart rate by activating adrenoreceptors. However, when the heart rate has been increased by adrenaline, pindolol causes a dose-dependent reversible decrease in heart rate. From this information, pindolol is probably a: CPB10 SLIDE 28 A. non-competitive antagonist B. competitive antagonist C. physiological antagonist D. chemical antagonist E. partial agonist ANSWER: E The affinity of a ligand is: CPB11 SLIDE 9 A. a measure of its safety B. the log dose response curve C. identical to the dose which causes the maximal effect D. related to the concentration of the ligand which will produce a half-maximal response E. a measure of the intrinsic activity ANSWER: D The affinity of a ligand is: CPB11 SLIDE 9 A. a measure of its safety B. the log dose response curve C. identical to the dose which causes the maximal effect

D. related to the concentration of the ligand which will produce a half-maximal response E. a measure of the intrinsic activity ANSWER: D A 55-year-old woman with congestive heart failure is to be treated with a diuretic drug. Drugs X and Y have the same mechanism of diuretic action. Drug X in a dose of 5 mg produces the same magnitude of diuresis as 500mg of drug Y. This suggests that: CPB11 SLIDE 11 A. drug Y is less efficacious than drug X B. drug X is approximately 100 times more potent than drug Y C. toxicity of drug X is less than that of drug Y D. drug X is a safer drug than drug Y E. drug X will have a shorter duration of action than drug Y ANSWER: B Regarding competitive antagonists, which of the following is FALSE: CPB11 SLIDE 21 A. they have intrinsic activity equal to zero B. they bind reversibly C. they can be displaced by an excess of agonist D. they potentiate the actions of an agonist E. they shift the agonist dose-response curve to the right ANSWER: D Regarding competitive antagonists, which of the following is FALSE: CPB11 SLIDE 21 A. they have intrinsic activity equal to zero B. they bind reversibly C. they can be displaced by an excess of agonist D. they bind to a different site than the agonist E. they shift the agonist dose-response curve to the right ANSWER: D Regarding competitive antagonists, which of the following statements is FALSE: CPB11 SLIDE 21 A. their effects cannot be overcome with increasing the concentration of agonist B. bind to the same site as the agonist C. bind reversibly to the receptor D. have an intrinsic activity of zero (0) E. shift the agonist dose-response curve to the right. ANSWER: A Which of the following statements is FALSE? The therapeutic index CPB11 SLIDE 36 A. is a measure of the safety of the drug B. is defined as a ratio of the effective dose in 50% of the population versus toxic dose in 50% of the population C. has a higher value the more selective a drug is in producing the desired response

D. can be derived from the cumulative frequency distribution of individual-effective concentration curves E. With a low value will indicate a high level of adverse effects at clinical doses ANSWER: B A 55-year-old woman with atrial fibrillation is to be treated with digoxin. Careful monitoring of the blood concentration of digoxin is required, as doubling the effective concentration may be enough to produce harmful effects of the medication. The degree of safety of a drug is described by the: CPB11 SLIDE 37 A. therapeutic index B. dissociation constant (Kd) C. dose that causes toxicity in half a population (TD50) D. dose that causes a half-maximal effect (ED50) E. maximal effective concentration ANSWER: A A substance has an LD50 of 10 mg/kg. What would be the fatal dose in an average man? CPB11 SLIDE 36 A. 0.07 mg B. 0.7 mg C. 7 mg D. 0 mg E. 700 mg ANSWER: E A 55-year-old woman with congestive heart failure is to be treated with a diuretic drug. Drugs X and Y have the same mechanism of diuretic action. Drug X in a dose of 5 mg produces the same magnitude of diuresis as 500mg of drug Y. The safety index of a drug is described by the: CPB11 SLIDE 37 Choose one answer. A. dissociation constant (Kd) B. dose that causes toxicity in half a population (TD50) C. maximal effective concentration D. Therapeutic index E. dose that causes a half-maximal effect (ED50) ANSWER: D Therapeutic index is: CPB11 SLIDE 37 A. the ratio of the toxic dose of a drug to the effective dose of a different drug B. is a measure of the safety of a drug C. the recommended dose of a drug D. is the dose of a drug required to produce a response in 50% of the population E. the dose of a drug that causes toxicity in 50% of the population ANSWER: B Therapeutic index is: CPB11 SLIDE 37 A. the ratio of the toxic dose of a drug to the effective dose of a different drug B. is a measure of the safety of a drug C. the recommended dose of a drug D. is the dose of a drug required to produce a response in 50% of the population

E. the dose of a drug that causes toxicity in 50% of the population ANSWER: B A rapid response is typical of nicotinic cholinergic receptors because: CPB12 SLIDE 11 A. they are ligand gated ion channels B. they are G-protein coupled receptors C. acetylcholinesterase only slowly metabolises acetylcholine D. choline acetyltransferase only slowly metabolises acetylcholine E. monoamine oxidase only slowly metabolises acetylcholine ANSWER: A A rapid response is typical of nicotinic cholinergic receptors because: CPB12 SLIDE 11 A. they are ligand gated ion channels B. they are G-protein coupled receptors C. acetylcholinesterase only slowly metabolises acetylcholine D. choline acetyltransferase only slowly metabolises acetylcholine E. monoamine oxidase only slowly metabolises acetylcholine ANSWER: A Activation of receptor –operated channels (ROCs) allows for fast transmission of signals, based on ion movement. The channels form a pore complex, which opens on binding of ligand to the receptor. In relation to ligand binding to ROCs, which of the following statements is an accurate reflection of this process? CPB12 SLIDE 15 A. One molecule of ligand is sufficient to open the channel. B. The channel is gated by the second transmembrane domain of each subunit. C. Movement of ions with all ROCs is from outside-to-in only. D. ROCs always cause depolarization of excitable membranes E. The rate of signal transmission by ROCs is in the order of minutes ANSWER: B Which of the following statements is FALSE? CPB13 SLIDE 5 A. G-protein-coupled receptors have seven transmembrane domains B. G-proteins exist in an active state as a heterotrimer C. on activation of the receptor, G-proteins bind to the third intracellular loop. D. the alpha-subunit of the G-protein activates second messenger cascades E. activation of adenylyl cyclase results in the production of cyclic AMP ANSWER: B Which of the following statements about receptors is correct: CPB13 SLIDE 9 A. tyrosine kinase receptors have seven transmembrane domains B. receptor-operated ion channels modulate gene transcription C. seven transmembrane domain (7TM) receptors are located in the nucleus D. seven transmembrane domain (7TM) receptors are coupled to G proteins E. classical steroid hormone receptors are membrane-bound ANSWER: D Receptor mechanisms CPB13 SLIDE 9

A. tyrosine kinase receptors have seven transmembrane domains B. receptor-operated ion channels modulate gene transcription C. seven transmembrane domain (7TM) receptors are located in the nucleus D. seven transmembrane domain (7TM) receptors are coupled to G proteins E. steroid receptors are localized to the cell membrane ANSWER: D Activation of Receptor Tyrosine Kinases (RTKs) results in the regulation of gene expression by a series of phosphorylation events in a signaling cascade. Regarding RTKs, which of the following statements is FALSE? CPB13 SLIDE 33 A. RTKs have one transmembrane domain B. Two ligand molecules bind to each receptor to invoke activation C. RTKs form dimers when activated D. Tyrosine kinase domains in the cytoplasmic tail of the RTKs cross-phosphorylate other RTKs E. Phosphorylated motifs in the RTK cytoplasmic tail act as docking sites for adapter proteins ANSWER: B Tyrosine kinase receptors CPB13 SLIDE 35 A. are ion channel proteins B. are receptors for growth factors C. are part of the Krebs cycle D. are G-protein-coupled receptors E. include adrenergic receptors ANSWER: B Regarding ascorbate (vitamin C), which of the following is true? CPB14 SLIDE 6 A. Its deficiency is a major cause of pernicious anaemia. B. It is required for hydroxyproline formation in cells. C. Is a major fat soluble vitamin. D. Is most abundant in red meats. E. May cause night blindness if deficient. ANSWER: B What proportion of total caloric intake should be derived from carbohydrate in a healthy human diet? CPB14 SLIDE 12 A. 5%. B. 15%. C. 35%. D. 55%. E. 80%. ANSWER: D In a healthy human adult diet, carbohydrate should comprise what proportion of total calorie intake? CPB14 SLIDE 12 A. 55% B. 40% C. 20% D. 80%

E. 10% ANSWER: A What proportion of total caloric intake should be derived from carbohydrate? CPB14 SLIDE 12 A. 80% B. 15% C. 35% D. 55% E. 5% ANSWER: D The optimal response in the treatment of hyperlipidemia is: CPB14 SLIDE 13 A. an increase in LDL and HDL B. a decrease in LDL and HDL C. an increase in LDL and decrease in HDL D. a decrease in LDL and increase in HDL E. none of the above ANSWER: D Foam cells are characteristic constituents of atheromatous plaques. These cells usually contain a high concentration of which of the following? CPB14 SLIDE 14 A. Triglycerides B. Cholesterol esters C. Free fatty-acids D. Apolipoprotein B100 E. Phospholipids ANSWER: B The main lipid constituent of the standard human diet is: CPB14 SLIDE 16 A. Fat- soluble vitamins. B. Saturated fatty acids. C. Cholesterol. D. Triglyceride (triacylglycerols). E. Lecithin. ANSWER: D Regarding dietary vitamin B12, which of the following statements is TRUE? CPB15/16 SLIDE 19 A. It must be ingested daily in milligram quantities. B. It is found abundantly in green vegetables. C. It requires a gastric factor for its intestinal absorption. D. It is absorbed in the upper duodenum. E. It causes a microcytic anaemia if deficient. ANSWER: C For next 3 questions: A 55 year old male subject presented at outpatients complaining of lack of energy, weakness and feeling generally run down. He was pale and a medical history indicated he had a partial gastrectomy 2.5 years previously to remove a malignant growth. A blood sample, taken for haematological analysis, indicated a

low haemotcrit, confirmed by a low RBC count. A blood film indicated the presence of many megaloblastic cells and a diagnosis of megaloblastic anaemia was suggested. CPB15/16 SLIDES 19, 20 What is the most likely cause of anaemia in this patient? A. Poor uptake of dietary iron. B. Inadequate levels of intrinsic factor. C. Poor digestion of dietary protein. D. Fat malabsorption. E. No dietary vitamin B12. ANSWER: B The best way to treat this patient's anaemia is: A. To increase dietary folate B. To increase dietary B12 C. To increase dietary iron D. To administer intrinsic factor intramuscularly E. To administer vitamin B12 intramuscularly ANSWER: E What vitamin would best supplement this treatment? A. Vitamin C B. Thiamin C. Folic acid D. Biotin E. Vitamin D ANSWER: C A 52 year old man attends his GP. The patient is an alcoholic and suffers from malnutrition. He tells the doctor that he has noticed that his eyes are feeling very dry and that he has recently started to have difficulty seeing at night. The doctor sends his patient to an ophthalmic consultant who confirms that the patient has xerophthalmia, due to a vitamin deficiency. Which vitamin deficiency results in this eye condition? CPB15/16 SLIDE 24 A) Vitamin C B) Thiamine C) Folic acid D) Vitamin A E)Vitamin D ANSWER: D A 52 year old man attends his GP. The patient is an alcoholic and suffers from malnutrition. He tells the doctor that he has noticed that his eyes are feeling very dry and that he has recently started to have difficulty seeing at night. The doctor sends his patient to an Ophthalmic consultant who confirms that the patient has xerophthalmia, due to a vitamin deficiency. Which vitamin deficiency results in this eye condition? CPB15/16 SLIDE 24 A. Thiamine B. Vitamin D C. Vitamin C

D. Vitamin A E. Folic acid ANSWER: D A patient suffering from Vitamin A deficiency is most likely to suffer from: CPB15/16 SLIDE 24 A. Rickets B. Scurvy C. Wernicke's Encephalopathy D. Night blindness E.Clotting defects ANSWER: D Regarding vitamin D which of the following is false: CPB15/16 SLIDE 25 A. it is active in the body as calcitriol B. it is a water soluble substance C. it can be synthesized in the human body D. deficiency symptoms may appear in renal dialysis subjects E. it brings about increased intestinal calcium absorption ANSWER: B For next 2 questions: A 63 year old woman presents with muscle weakness. On investigation her plasma calcium level was 1.80 mmol/L (reference range 2.15 to 2.60), plasma inorganic phosphate level 0.80 mmol/L (reference range 0.8 to 1.2) and the plasma alkaline phosphatase activity was raised at 850U/L. What is the most likely origin of the alkaline phosphatase enzyme: HIS12 SLIDE 3 A. Osteoclasts in the bone B. Gastrointestinal tract C. Hepatocytes in the liver D. Skeletal muscle E. Osteoblasts in the bone ANSWER: E The most likely cause of this patient’s symptoms and biochemical findings is: CPB15/16 SLIDE 25 A. Primary hyperparathyroidism B. Liver failure C. Hypoparathyroidism D.Vitamin D deficiency E. Renal failure ANSWER: D Nurse Murphy reported that the steatorrhea began 5/6 weeks previously. A laboratory report indicated a prolonged prothrombin clotting time in her blood. Which vitamin deficiency is she most likely to have? CPB15/16 SLIDE 28 A. Vitamin K. B. VitaminB12. C. Vitamin D.

D. Folate. E. Pyridoxine(B6). ANSWER: A A microcytic anaemia is most likely to be caused by deficiency of which of the following? CPB15/16 SLIDE 44 A. Dietary folate. B. Dietary B12. C. Dietary vitamin K. D. Dietary iron. E Essential fatty acids. ANSWER: D Raised levels of ammonia in the blood could arise from which of the following? CPB18 SLIDE 16 A. Folate deficiency. B. Deficiency of the enzyme carbamoyl phosphate synthetase. C. Low carbohydrate diet. D. High protein diet. E. Lack of dietary essential amino acids. ANSWER: B Phenylketonuria (PKU) is an inherited disorder of amino-acid metabolism due to deficient activity of the enzyme phenylalanine hydroxylase. The cofactor that may be deficient in some cases of phenylketonuria is: CPB18 SLIDE 22 A. Pyridoxal phosphate (Vitamin B6) B. Tetrahydrofolate C. Dihydropteridine D. Biotin E. Thiamine pyrophosphate ANSWER: C Fasting blood glucose levels were ordered for this patient. Hormones allow the body to control triglyceride metabolism in the “ fed “ and “fasted” state. Which of the following catalyses the first step in triglyceride breakdown? CPB20 SLIDE 14 A. Glucagon. B. Diacylglycerol acyl transferase. C. Hormone-sensitive adipose tissue lipase. D. Insulin. E. Acetyl CoA carboxylase. ANSWER: C The TCA cycle: CPB21/22 SLIDE 19 A. is a series of irreversible reactions B. takes place in lysosomes C. is regulated by levels of NADH and ATP D. does not exist in muscle cells E. generates oxidized coenzymes ANSWER: C

The body’s energy is derived from intracellular metabolism. The inner mitochondrial membrane is impermeable to reduced coenzymes like NADH+H+. Which of the following systems does the cell use to transport these reducing equivalents generated in the cytosol across the inner mitochondrial membrane? CPB 21/22 SLIDE 22 A. ATP synthase. B. Adenine nucleotide carrier. C. Pyruvate carrier . D. Malate –aspartate shuttle. E. Phosphate carrier. ANSWER: D In order to synthesise the energy source ATP in the mitochondria, the cell needs to oxidize reduced co-enzymes such as NADH. This is done via the electron transport chain in the inner mitochondrial membrane. The inner mitochondrial membrane is impermeable to NADH. Therefore, the cell uses which of the following to transport reducing equivalents generated in the cytosol across the inner mitochondrial membrane? CPB 21/22 SLIDE 22 A. ATP synthase B. Malate-aspartate shuttle C. Adenine nucleotide carrier D. Pyruvate carrier E. Phosphate carrier ANSWER: B Match the numbered question to a lettered response. Each response may be used once, more than once or not at all. A.Plasma proteins. B. Liver glycogen. C. Triglycerides. D. Muscle glycogen. E. Plasma cholesterol. The largest energy store in the human body. Found in human plasma associated mainly with VLDL. Breaks down to blood glucose under the influence of glucagon. Found in human plasma associated mainly with LDL. Breaks down causing a rise in blood lactate levels. ANSWER: D, C, B, E, D Match the numbered question to a lettered response. Each response may be used once, more than once, or not at all. A. Chylomicron B. HDL C. LDL D. IDL

E. VLDL A positive risk factor for vascular disease in humans The most triglyceride-rich protein in the body. Levels reduced in humans undergoing treatment with statins. ANSWER: B, A, C Match the numbered question to a lettered response. Each response may be used once, more than once, or not at all. Many poisons inhibit ATP synthesis. For example, Dinitrophenol prevents ATP synthesis by interfering with the proton gradient while electron flow remains intact. A. B. C. D. E.

Ubiquinone Glycerol phosphate shuttle Cytochrome b NADH Cyanide

Hydrogen carrier Oxidation of this yields 3 ATP ANSWER: A, D Muscle cells have many mitochondria and contain high levels of glycolytic enzymes in their cytosol. This enables them to utilise energy sources and ultimately generate the ATP which is necessary for muscle contraction. A. Pyruvate Dehydrogenase B. Cytochrome c C. Ubiquinone D. Actin E. Creatine phosphate Energy source used during muscle contraction Electron carrier ANSWER: E, B DNA is the repository of genetic information, which is expressed through the processes of transcription and translation, and mainly effected through the activities of proteins. The base sequence of a strand of DNA used as the template for RNA polymerisation is CTAGATGC. What is the sequence of the RNA product? (all sequences are written 5’ to 3’) A. GAUCUACG B. GCAUCUAG C. GCUACAUG D. CATGATGC

E. GCATCTAG ANSWER: B DNA is the repository of genetic information, which is expressed through the processes of transcription and translation, and mainly effected through the activities of proteins. The base sequence of a strand of DNA used as the template for RNA polymerisation is 5’CTAGATGC. What is the sequence of the RNA product? (all sequences are written 5’ to 3’){ A. 3’GAUCUACG5’ B. GCAUCUAG reversed. C. GCUACAUG D. CATGATGC E. GCATCTAG ANSWER: B Regarding therapy with digoxin, which of the following is FALSE: A. has an effect on the electrical activity of the heart B. is associated with arrhythmias C. is a negative inotrope D. has a low therapeutic index E. serious toxicity may be treated with a specific antibody ANSWER: C Familial type II diabetes is a genetic disease. A number of genetic diseases are known in which the base sequence of a gene has been altered so that it can no longer be transcribed into RNA. Which of the following occcurs in normal gene transcription.? A. The RNA polymerase enzyme recognises and binds to the promoter sequence. B. The process needs a primer. C. Both DNA strands of every gene is transcribed. D. The building blocks of the RNA are deoxyribonucleotides. E. The RNA polymerase reads the template in the 5’ to 3’ direction. ANSWER: A In a patient suffering from Type I Diabetes (hypoinsulinaemia) A. blood glucose levels are less than 4.5 mmol/L B. lipogenesis (fat synthesis) is increased C. tissue glycogen levels will fall D. there will be a decreased frequency of urination E. glucagon levels are decreased ANSWER: C Which of the following regarding therapy with digoxin is FALSE: A. has an effect on the electrical activity of the heart B. is associated with arrhythmias C. is a negative ionotrope D. has a low therapeutic index E. serious toxicity may be treated with a specific antibody ANSWER: C

The phase of the cell cycle that is resistant to most chemotherapeutic agents is: A. M phase B. G2 phase C. S phase D. G0 phase E. G1 phase ANSWER: D Which of the following regarding therapy with digoxin is FALSE: A. has an effect on the electrical activity of the heart B. is associated with arrhythmias C. is a negative ionotrope D. has a low therapeutic index E. serious toxicity may be treated with a specific antibody ANSWER: C A 37 year-old man is prescribed a benzodiazepine for severe anxiety. Treatment with this class of drug will: A. increase cAMP production B. reduce cGMP production C. increase the frequency of opening of Cl- channels linked to GABAA receptors D. reduce the duration of opening of Cl- channels linked to glutamate receptors E. inhibit GABA transaminase [GABA-T] ANSWER: C Excess carbohydrate intake by the body results in its being converted to body fat. Which liver enzyme is crucial to this process? A. Lactate dehydrogenase B. Phosphorylase C. Citrate lyase D. Transaminase E. Lipoprotein lipase ANSWER: C Which of the following is NOT a recognized function of thyroid hormone: A. Raises the body temperature B. Stimulates growth in children C. Increases cardiac output volume D. Stimulates lipolysis E. Increases the pulse rate ANSWER: D An individual on a high calorie, high carbohydrate diet would show increased activity of which of the following liver enzymes? A. Lactate dehydrogenase B. Aldolase C. Glyceraldehyde 3-phosphate dehyrogenase D. Glucose 6-phosphatase E. Acetyl CoA carboxylase

ANSWER: E A 65 year old man presented to A&E suffering from sudden onset of a crushing retrosternal pain that radiated along the medial aspect of his left arm. He was pale and perspiring. On questioning the man told the doctor that he had suffered from retrosternal discomfort in the past, which passed with rest. The muscle involved has all of the following traits except: A. striations B. intercalated discs C. desmosones D. non branching fibres E. involuntary ANSWER: D Glycerol is a gluconeogenic substrate in human liver. An enzyme which allows it to interact with the gluconeogenic sequence, thereby generating blood glucose, also plays a role in regenerating cytoplasmic NAD+ which is essential for the maintenance of glycolysis. Which of the following enzymes fulfils this important role? A. Glycerol kinase B. Phosphoglyceromutase C. Glyceraldehyde 3-phosphate dehydrogenase D. Glycerol 3-phosphate dehydrogenase E. Triose phosphate isomerase ANSWER: D Regarding nitric oxide (NO), which of the following is TRUE: A. acts on the endothelium B. binds to membrane bound guanylate cyclase C. causes smooth muscle cell contraction D. acts to increase cGMP levels E. can be used as a general anesthetic ANSWER: D UNANSWERED QUESTIONS: Calcium A. Reabsorption in renal tubules is increased by PTH. B. Binding to albumin is increased by lowering the pH. C. In plasma is largely complexed with phosphate. D. Absorption is enhanced in patients with steatorrhoea. E. Is synthesised by osteoblasts. Which statement regarding inositol triphosphate (IP3) is false? A. Is a hormone 2nd messenger in many cells. B. Is formed in cells together with diacylglycerol. C. Is formed in cells from phosphatidyl inositol bisphosphate (PIP2). D. Levels rise in cells exposed to cortisol. E. Causes calcium ion release from intracellular stores.

Regarding cyclic AMP which statement is incorrect? A. Is a substrate for phosphodiesterase. B. Is converted to ATP by the enzyme, adenylate kinase. C. Levels rise in hepatocytes exposed to glucagon. D. Levels rise in adipocytes exposed to adrenalin. E. Activates protein kinaseA. Which statement regarding the hexose monophosphate shunt is false? A. Is required for de novo nucleotide synthesis. B. Requires ribose-5-phosphate as an intermediate. C. Is active in all tissues in the human body. D. Requires the activity of glucose 6-phosphate dehydrogenase. E. Generates NADPH in cells. Q. 32 Regarding ketone bodies which statement is true? A. They are a form of long chained fatty acids. B. They are formed mainly in adipose tissue. C. They are abundant in the blood of human neonates. D. Their levels fall in the blood of starving individuals. E. They are mainly consumed by the liver. Q. 33 Which statement on the urea cycle is false? A. It is active in the kidneys under acidotic conditions. B. Involves the enzyme, arginase. C. If malfunctioning, causes hyperammonaemia in humans. D. Involves ornithine. E. Involves aspartate. Q. 35 Following the release of insulin from the pancreas all the following are likely to be reduced except; A. Tissue cAMP levels. B. Glucokinase activity. C. Triglyceride Lipase activity. D. Glycogen Phosphorylase activity. E. Glucose 6 phosphatase activity.