PDQ BIOCHEMISTRY - PART 10 ppsx

6. Which ONE of the following contains more of the iron found within the body? A. Transferrin B. Hemoglobin C. Myoglobin and other cytochromes D. Ferritin E. Iron found in enzymes [B] 7. Which ONE of the following concerning iron uptake by cells is INCOR- RECT? A. Iron linked to transferrin is bound to a receptor at the plasma mem- brane. B. The iron–transferrin complex is internalized and can be found in vesicles called endosomes. C. Iron is released into cytosol when the iron–transferrin complex is degraded, a process that involves the destruction of the transferrin transporter. D. Transferrin receptors and apotransferrin return to the plasma mem- brane the following liberation of iron. E. Inside cells, iron can be stored within a complex of ferritin subunits. [C. Both apotransferrin and its receptor are recycled back to the plasma membrane.] 8. Which ONE of the following concerning radioimmunoassay of ferritin is INCORRECT? A. Initially, a complex is prepared between radioactively labeled ferritin and antibodies that bind ferritin. B. The addition of a sample containing an unknown quantity of non- radioactive ferritin will lead to the binding of this ferritin to the antibodies and a displacement of radioactive ferritin from the com- plex. C. The more ferritin available in the sample, the greater is the quan- tity of radioactive ferritin released. D. The ratio of radioactivity in the ferritin–antibody complex and free ferritin should increase with the quantity of ferritin in the sample. E. The free ferritin can be separated from the ferritin–antibody com- plex to facilitate quantitating radioactivity in each. [D.Actually, the level of free radioactive ferritin rises as the radioactivity in the complex drops because unlabeled ferritin in the sample will displace radioactive ferritin from the complex.] 6 PDQ BIOCHEMISTRY Answer Answer Answer 9. Which ONE of the following concerning primary hemochromatosis is INCORRECT? A. The pathology is the result of excess iron uptake at the level of the intestinal mucosa. B. The pathology results from a genetic defect in a protein responsi- ble for iron uptake in the intestine. C. Primary hemochromatosis is accompanied by elevated levels of saturation of transferrin by iron in the plasma. D. Primary hemochromatosis is accompanied by elevated levels of serum ferritin. E. Primary hemochromatosis is primarily associated with an excessive number of blood transfusions. [E. This is secondary hemochromatosis.] 10. Which ONE of the following concerning copper is INCORRECT? A. Ceruloplasmin is a plasma protein that binds copper ions. B. Albumin in blood carries a smaller but more accessible pool of cop- per ions. C. Proteins called metallothioneins bind copper and other metal ions that enter the cytoplasm. D. Metal ions present at higher concentrations than can be adequately bound by metallothioneins represent a threat because metal ions are toxic. Excess copper ions can promote debilitating oxidation reac- tions involving various cellular molecules. E. More copper than iron is required by the body on a daily basis. [E] 11. Which ONE of the following concerning Menkes’ disease is INCOR- RECT? A. The gene responsible for the disease is found on the X-chromo- some, and male children are the only ones to have this disease. B. The deficient protein is an ATPase that is found in the liver and is responsible for the transport of copper ions out of the liver cells. C. Low levels of both serum copper ions and serum ceruloplasmin are seen in the disease. D. The ATPase that is deficient normally pumps copper out of cells uti- lizing the energy of ATP in an active transport process. E. Menkes’ disease is associated not only with a deficiency in ATPase but also with defective copper incorporation into copper-depend- ent enzymes, such as SOD and cytochrome oxidase. [B. The ATPase deficiency is found in other tissues, such as the intestine.] Multiple-Choice Review Questions 7 Answer Answer Answer 12. Which ONE of the following concerning Wilson’s disease is INCOR- RECT? A. The genetic defect is not associated with the X-chromosome, and thus, both parents of a child with Wilson’s disease are carriers of the genetic defect (i.e., both parents have one chromosome that shows the genetic defect) or both parents have the disease. B. Levels of both serum copper and serum ceruloplasmin are depressed in the disease. C. Liver and urinary copper ion levels decrease in the disease as a result of defective ATPase-mediated copper transport from the liver to bile. D. Copper levels rise in the basal ganglia, and the disease is associated with neurologic signs. E. Wilson’s disease can be treated with chelation therapy using peni- cillamine. [C] 13. Using the following list, match the correct choice with the descriptions below: • Triglyceride • Lovastatin • Phospholipid • Chylomicron • Cholesterol • Atherosclerosis • VLDL • LDL receptor • LDL • Hypercholesterolemia • Lipoprotein lipase • HDL A. A drug used to lower cholesterol production by the liver B. The principal lipid found in cellular membranes C. A lipoprotein that is made by the liver and is rich in cholesterol and triglycerides D. The principal lipid component of fat E. A laboratory finding for serum that is associated with defective LDL receptor function F. The lipoprotein that carries good cholesterol and is associated with the movement of cholesterol away from the vascular system G. The lipoprotein made in the intestine using lipids synthesized from incoming products of intestinal dietary fat digestion H. A vascular disease that is associated with the accumulation of lipids, principally cholesterol, within the walls of arteries I. The enzyme found attached to vessel walls that is responsible for the hydrolysis of triglycerides carried by VLDL and chylomicrons in the circulation A = lovastatin; B = phospholipid; C = VLDL; D = triglyceride; E = hyper- cholesterolemia; F = HDL, G = chylomicrons; H = atherosclerosis; I = lipoprotein lipase. 8 PDQ BIOCHEMISTRY Answer Answer 14. Indicate which of the following statements are TRUE: A. LDL is produced from VLDL following the action of lipoprotein lipase. B. Blood cholesterol levels are universally lowered by decreasing the quantity of dietary cholesterol. C. LDL is taken up by a process known as endocytosis. D. LDL carries what is known in the media as “bad cholesterol.” E. Foam cells in atherosclerotic plaques are derived from endothelial cells. F. Those who are homozygous for the genetic defect that results in hypercholesterolemia usually die at an early age. G. Serum cholesterol levels below 5.2 mM (200 mg/L) are considered desirable. H. TIAs can be manifested by blindness in one eye or by blackouts and are indicative of transient blockages in blood flow to certain areas of the brain. I. Following the uptake of LDL and the LDL receptor, both are degraded within the cellular lysosomal system. [A, C, D, F, G, H. B is incorrect, as the liver can excessively produce and secrete cholesterol in VLDL, thus elevating blood cholesterol levels. E is incorrect, as foam cells are derived from macrophages.] CHAPTER 3 E 1. In the enzymatic reaction A → B, which one of the compounds denoted by A or B is the substrate, and which is the product? [A = substrate; B = product] 2. Which of the following are associated with catabolism? A. A conversion of more complex molecules into simpler molecules B. A need for energy supplied by ATP in the synthesis of macromole- cules C. A production of energy and synthesis of ATP D. The formation of simpler products [A, C, D. B is incorrect, as it is associated with anabolism.] Multiple-Choice Review Questions 9 Answer Answer Answer 3. Which ONE of the following is NOT a feature of the enzymatic reac- tion catalyzed by trypsin? A. The substrate for the reaction is usually a protein. B. The substrate has peptide bonds and at least one lysine or arginine amino acid residue. C. The R-group (side chain) of lysine or arginine in the substrate is vital for the binding of the substrate to the active site of trypsin. D. Serine, histidine, and aspartate are found at the active site of trypsin. E. The serine and histidine residues at the active site of trypsin func- tion to bind the lysine or arginine side chain of the substrate. [E. These residues are not involved with lysine or arginine binding; it’s actu- ally an aspartate residue that is responsible.] 4. Which ONE of the following defines the turnover number (kcat) for an enzyme? A. The number of substrate molecules turned into product by an enzyme molecule in a unit of time B. The affinity of the substrate for the enzyme C. The rate at which new molecules of the enzyme are made by the cell D. The equilibrium constant for the conversion of the substrate into the product [A] 5. The members of the oxidoreductase class of enzymes are most likely to use which of the following coenzymes? A. NADH B. Vitamin C C. Folic acid D. FADH 2 E. NADPH [A, D, E] 6. Trypsin is a member of which of the following enzyme classes? A. Isomerase B. Hydrolase C. Transferase D. Ligase E. Oxidoreductase [B] 10 PDQ BIOCHEMISTRY Answer Answer Answer Answer 7. Which ONE of the following concerning the measurement of enzymatic rate is INCORRECT? A. Enzyme assays are carried out with mixtures of substrates and a source of the enzyme to be studied (e.g., serum or plasma). B. Enzyme rates can be monitored by measuring the formation of product molecules with time. C. Enzyme rates can be increased by elevating substrate concentration, but there is a maximal velocity that will be approached at high sub- strate concentrations. D. Changes in temperature and pH will affect enzyme rate, as may the presence of drugs or pharmaceuticals in samples (e.g., plasma or serum) taken for enzyme assay. E. If an enzyme rate falls off with time, it is likely because the maxi- mum velocity for the enzyme is being approached. [E. The fall-off is caused by loss of substrate concentration, product inhi- bition, or enzyme instability.] 8. An enzyme assay for alcohol dehydrogenase contains ethanol, NAD + , and a sample of serum adjusted to a final volume of 1 mL. Which ONE of the following is INCORRECT? A. With time, NADH is produced in the assay mixture, and this can be monitored by measuring the increase in optical density (OD) at 340 nm. B. If NADH replaced NAD + in the assay mixture, there would be no increase in OD with time. C. A doubling of the serum volume within the 1-mL assay mixture should result in a doubling of the enzyme rate as measured by increase in OD at 340 nm. D. The change in OD noted at 340 nm should allow a calculation of the rate of formation of NADH. E. For every NADH formed in the assay, two molecules of ethanol are used as the substrate. [E. For each molecule of ethanol converted to acetaldehyde, one molecule of NAD + is converted to NADH.] Multiple-Choice Review Questions 11 Answer Answer 9. A coupled assay for hexokinase involves a mixture that contains a homogenized sample of liver biopsy, ATP, glucose, NADP + , and the enzyme glucose-6-phosphate dehydrogenase (GPDH), which is present in excess. Which ONE of the folowing is INCORRECT? A. Glucose-6-phosphate can be used by hexokinase in the reduction of NADP + to NADPH. B. The rate of glucose-6-phosphate production can be measured by the rate of NADPH formation as followed by change in OD at 340 nm. C. If GPDH were present at concentrations that were less than that of the hexokinase, then the coupled assay would only reflect the amount of GPDH present. D. The rate of NADPH production can be decreased by lowering the concentration of glucose initially in the assay. E. If ATP were omitted from the assay mixture, no change in OD at 340 nm would be seen. [A. Hexokinase does not reduce NADP + .] 10. Which ONE of the following concerning the end-point analysis for the determination of blood alcohol levels is INCORRECT? A. The purpose of the end-point analysis is not the measurement of enzyme rate; rather, it is the use of an enzyme to facilitate the meas- urement of ethanol. B. End-point analysis of ethanol can involve a mixture of depro- teinated serum, NADH, and excess alcohol dehydrogenase. C. The net change in optical density at 340 nm reflects the concentra- tion of NADH generated by the enzyme. D. The concentration of NADH can be used to calculate the micro- moles of NADH in the assay volume. E. The number of micromoles of NADH in the assay corresponds to the number of micromoles of ethanol in the assay, and this can be used to calculate the concentration of ethanol in the original vol- ume of serum added to the assay. [B. NAD + , not NADH, is required.] 12 PDQ BIOCHEMISTRY Answer Answer 11. For the following pathologic states, select appropriate diagnostic serum enzymes: • Myocardial infarction (MI) • Duchenne’s muscular dystrophy • Viral hepatitis • Alcoholic pancreatitis A. Creatine kinase (CK) MB dimer B. Amylase C. AST D. ALT E. Creatine kinase (CK) MM dimer F. LDH G. Raised LD 1 /LD 2 ratio H. LD 5 [MI = A, C, G; Duchenne’s MD = E; viral hepatitis = C, D, H; alcoholic pan- creatitis = B] 12. Which ONE of the following statements concerning the sensitivity and specificity of a serum diagnostic enzyme is INCORRECT? A. It is very important to have tables of values for serum enzymes that match an individual, with respect to age, gender, and race, before a decision can be made that a particular serum enzyme level is ele- vated. B. If the level of elevation for a serum diagnostic enzyme is set too high, it is likely that all those diagnosed with the pathologic condi- tion will indeed have the disease, but a significant number of indi- viduals (false negatives) will be missed. C. If the level of elevation for a serum diagnostic enzyme is set too low so that there will be no false negatives, there will likely be false pos- itives (i.e., those who do not have the disease but are judged to have the pathologic condition). D. As the number of false negatives increases, the sensitivity of the diagnostic enzyme decreases. E. As the number of false positives increases, the specificity of the diag- nostic enzyme increases. [E. The specificity actually declines with the number of false positives.] Multiple-Choice Review Questions 13 Answer Answer 13. Which of the following does NOT describe useful applications of enzymes or enzyme assays? A. Genetic diseases that lead to deficiencies in enzymes can be shown by enzyme assays (e.g., Tay-Sachs disease). B. Diagnostic enzymes can be used to monitor the course of a disease and also possibly the response to therapy. C. Recombinant enzymes can be used therapeutically,for example, the use of intravenous PAF acetylhydrolase to remove the inflammatory compound PAF. D. The hydrolase papain can be used to clear away necrotic tissue. E. Streptokinase and tissue plasminogen activator can be used to fight bacterial infection. [E. These enzymes are used as clot busters.] CHAPTER 4 1. Many of the coagulation factors in their active states are members of which family of enzymes? A. Serine proteases B. Lysine hydrolases C. Alanine transferases D. Hexokinases E. Aminotransferases [A] 2. The exposure of which cellular protein initiates the intrinsic path of coagulation? A. Thrombomodulin B. Tissue factor (TF) C. Protein C D. Coagulation factor V E. Antithrombin [B] 3. Which of the following have their action at a membrane surface? A. Factor IXa B. Tissue factor complex (TFC) C. Factor Xa D. Factor VIIIa E. Factor Va F. Factor XIIIa G. Protein C [All except F: Factor XIIIa is active at the fibrin surface.] 14 PDQ BIOCHEMISTRY Answer Answer Answer Answer 4. Which of the following are found in the extrinsic pathway of the coag- ulation cascade? A. Factor XIIa B. Kallikrein C. Factor XIa D. Protein S E. TFC F. Plasmin [A, B, C] 5. The PTT will test for deficiencies in which of the following? A. Factor II B. Factor XII C. Factor X D. Factor V E. Factor VIII F. Factor IX G. Kallikrein [A, C, D] 6. Warfarin is an oral anticoagulant that interferes with the function of which vitamin? A. Vitamin A B. Niacin C. Vitamin K D. Vitamin C E. Folic acid [C] 7. The complex that includes thrombomodulin and protein C will lead to the inactivation of which factors? A. Factor IIa B. Factor XIIIa C. Factor Va D. Factor VIIa E. Factor VIIIa F. Factor IXa [C, E] Multiple-Choice Review Questions 15 Answer Answer Answer Answer [...]... product of DHFR is FH4.] 7 Which ONE of the following concerning N5, N10-methylene FH4 is INCORRECT? A N5, N10-methylene FH4 serves as a one-carbon donor for the enzyme thymidylate synthase B The carbon donated by N5, N10-methylene FH4 is used as the -CH3 group found in the thymine ring structure of the product thymidylate (dTMP) C N5, N10-methylene FH4 is formed from FH4, produced by the action of the... Adenylate cyclase B Gs-heterotrimer C Gi-heterotrimer D PIP2 phospholipase C E Gsα-subunit–GTP F Adrenaline receptor G Cholera toxin Answer [A, B, E, F] 28 PDQ BIOCHEMISTRY 9 From the compounds noted below, what are the two products of PIP2 phospholipase C, an enzyme that participates in certain signal transduction pathways? A Diacylglycerol B Inositol C IP3 D GTP E cAMP F TXA2 Answer [A, C] 10 Which ONE of... of fructose 1,6-bisphosphatase and glucose-6-phosphatase E AMP serves as an allosteric inhibitor for PFK-1 in glycolysis and an allosteric activator for fructose 1,6-bisphosphatase F Effects that follow glucagon binding to its receptor include the increased activity of fructose 2,6-bisphosphatase, increased rates of gluconeogenesis, and an inactivation of PK Answer [E AMP activates PFK-1 while inhibiting... fructose 1,6-bisphosphatase.] 20 Which of the following are found within the signalling pathway initiated by adrenaline binding to its receptor in fat cells? A Adenylate cyclase B cAMP C PKA D PKC E Gsα-subunit-GTP F Diacylglycerol Answer [A, B, C, E] 21 Which of the following are products of fatty acid β-oxidation? A NADPH B Acetyl-CoA C Pyruvate D NADH E FADH2 Answer [B, D, E] 32 PDQ BIOCHEMISTRY. .. following amino acids from homocysteine? A Alanine B Glycine C Phenylalanine D Cysteine E Methionine Answer [E] 4 A deficiency in vitamin B12 can lead to a build-up in which one of the following folate derivatives? A N5-methyl FH4 B N5 ,1 0- methylene FH4 C N10-hydroxymethyl FH4 D FH2 E FH4 Answer [A This is the form that is used by the methyltransferase that depends on MeCbl.] 5 Which ONE of the following concerning... Multiple-Choice Review Questions 21 7 Which of the following is/are true? A Mutations that lead to alterations in amino acid residues close to the heme binding sites in - or β-globins can seriously alter hemoglobin function B The sickle cell trait is the result of a missense mutation C Those who are homozygotes for β-thalassemia rarely survive to maturity D α-Thalassemias are usually more severe than β-thalassemias... pyruvate D Major products of the hexose monophosphate (HMP) shunt are the five-carbon sugar ribose-5-phosphate and NADPH E Acetyl-CoA, formed by the action of β-oxidation using fatty acylCoA molecules as substrates, can be converted into glucose Answer [E While pyruvate and lactate can serve as substrates in gluconeogenesis, acetyl-CoA cannot be directly used as a substrate.] 5 Which of the following statements... presents practice problems http://esg-www.mit.edu:8001/esgbio/7001main.html The Biology Project: Biochemistry The Biology Project, which originates from the University of Arizona, has a substantial, high-quality biochemistry component, directed more at undergraduate students than at medical students It contains problem sets http://www.biology.arizona.edu /biochemistry/ biochemistry.html The Merck Manual,... D is incorrect, as there are four genes for α-globin, compared Answer with two for β-globin Thus, it would require mutations in all four genes for α-globin before a deficiency in this protein was manifested.] 8 From the following, pick out the substrates for ALA synthase A Succinyl-coenzyme A (CoA) B Isoleucine C Heme D Glycine E Porphobilinogen F Acetyl-CoA Answer [A, D] 9 The first tetrapyrrole structure... insulin to limit the activity of hormone-sensitive lipase B There is a very high rate of fatty acid production and a high rate of β-oxidation C Glucagon stimulates the liberation of fatty acids from fat cells D Rising levels of mitochondrial acetyl-CoA lead to increased synthesis of acetoacetyl-CoA E There is a drop in the activity of the carnitine shuttle F β-Hydroxybutyrate is made by reduction of . concerning N 5 ,N 10 -methylene FH 4 is IN- CORRECT? A. N 5 ,N 10 -methylene FH 4 serves as a one-carbon donor for the enzyme thymidylate synthase. B. The carbon donated by N 5 ,N 10 -methylene FH 4. deficiency in vitamin B 12 can lead to a build-up in which one of the following folate derivatives? A. N 5 -methyl FH 4 B. N 5 ,10 -methylene FH 4 C. N 10 -hydroxymethyl FH 4 D. FH 2 E. FH 4 [A. This. cobalamin can lead to an inadequate pro- duction of dUMP that adversely affects DNA synthesis. E. N 5 ,N 10 -methylene FH 4 can also be formed from N 5 ,N 10 -methenyl FH 4 . [D. It is the production