biochem 3

Patients with beriberi have reduced activities of pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase, among others, causing cardiovascular and neurological problems. Which vitamin is DEFICIENT in beriberi? Thiamine / Ascorbic acid / Pantothenic acid / Riboflavin / Niacin

Thiamine

In the eight successive reaction steps of the TCA cycle, chemical transformations produce reduced coenzymes NADH and FADH₂. Which enzyme is NOT DIRECTLY involved in NADH/NAD⁺ production? Fumarase / Isocitrate dehydrogenase / Succinate dehydrogenase / Malate dehydrogenase / Alpha-ketoglutarate dehydrogenase

Fumarase

Which coenzymes are used in reactions by alpha-ketoglutarate dehydrogenase? Thiamine pyrophosphate and lipoate / Lipoate and biotin / Lipoate, FAD, CoA, and NAD⁺ / FAD and NAD⁺ / Thiamine pyrophosphate and FAD

Lipoate, FAD, CoA, and NAD⁺

Which compound would provide the largest amount of ATP when oxidized completely to CO₂ and water? Palmitic acid / Sucrose / Glucose / Galactose / Fructose

Palmitic acid

Cytochrome c transfers electrons between which of the following? From Complex I to Complex II / From Complex II to Complex III / From Complex III to Complex IV / From Complex I to Complex III / From Complex II to Complex I

From Complex III to Complex IV

Which fuel oxidation pathway is present in red blood cells? Fatty acid beta-oxidation / Ketone body oxidation / Glycolysis / TCA / Electron transport chain

Glycolysis

Which enzyme is required to transport fatty acids into the mitochondria? Carnitine acyltransferase I / Carnitine acyltransferase II / Carnitine translocase / Acyl-CoA synthetase / None of the above

Carnitine acyltransferase I

A 26-year-old woman consumed a meal of fatty prime rib, creamy mashed potatoes, salad, bread with sweet butter, and cheesecake. A few hours later, her serum would be milky white due to high levels of: Chylomicrons / VLDL lipoprotein particles / HDL lipoprotein particles / LDL lipoprotein particles

Chylomicrons

Which best describes coenzyme Q? Its free radical form accepts four electrons / It transports electrons from either Complex I or Complex II to Complex III / It is protein-bound to the inner mitochondrial membrane / It is water-soluble quinone / All of the above

It transports electrons from either Complex I or Complex II to Complex III

Which statement is NOT correct regarding the oxidation of very-long-chain fatty acids? Oxidation initially occurs in the peroxisome / The very-long-chain fatty acyl CoA dehydrogenase is located within the peroxisomes / Oxygen is reduced to hydrogen peroxide in order to generate NADH / After a number of rounds of oxidation, shorter fatty acids are exported to mitochondria / None of the above

Oxygen is reduced to hydrogen peroxide in order to generate NADH

The inner mitochondrial membrane is impermeable to NADH. Compounds used to transport reducing equivalents across the inner mitochondrial membrane include: Oxaloacetate / Dihydroxyacetone phosphate / Malate / Glutamate / Glycerol

Malate

After oxidation of odd-chain fatty acids, carbon atoms of the fatty acids would be found in which of the following? Propionyl CoA and acetyl CoA / Malonyl CoA and propionyl CoA / NADH and FAD(H₂) / Malonyl CoA and acetyl CoA / ATP and acetyl CoA

Propionyl CoA and acetyl CoA

A freshly prepared mitochondrial suspension is treated with antimycin A (a Complex III blocker). Oxygen and malate are added. After five minutes, which components of the ETC are reduced? Complexes I and IV / Complexes III and IV / Coenzyme Q and Complex III / Complexes I and Coenzyme Q / Complexes I and III and cytochrome c

Complexes I and Coenzyme Q

In some cases of hyperlipidemia, lipoprotein lipase is defective. If a blood lipid profile is performed on patients with lipoprotein lipase deficiency, which lipids will be elevated? HDL / Cholesterol / 2-monoacylglycerol / Free fatty acids / Chylomicrons and VLDL

Chylomicrons and VLDL

Which condition inhibits fatty acid biosynthesis but encourages fatty acid degradation by beta-oxidation? Increased glucagon due to low blood glucose / High citrate level in the cytosol / High malonyl-CoA level / Increase of unphosphorylated acetyl-CoA carboxylase / The low levels of long-chain fatty acyl CoAs

Increased glucagon due to low blood glucose

Dietary triglyceride is initially found in which lipoprotein particle? Very low density lipoprotein (VLDL) / Chylomicrons / Low density lipoprotein (LDL) / High density lipoprotein (HDL) / Intermediate density lipoprotein (IDL)

Chylomicrons

The major regulatory step in fatty acid synthesis is: Condensation of acetyl-CoA with malonyl-CoA / Formation of acetyl-CoA from pyruvate / Transport of fatty acyl-carnitine into the mitochondria / The reaction catalyzed by acetyl-CoA carboxylase / The reduction of a β-ketoacyl to a β-hydroxyacyl group

The reaction catalyzed by acetyl-CoA carboxylase

Which statement about VLDL is WRONG? It contains triacylglycerol converted from excess carbohydrates in the liver / Its main apolipoprotein component is apoB-48 / VLDL remnants contain lower amounts of triacylglycerol than VLDL / The hepatic uptake of VLDL remnants is mediated by apoE receptor in the liver / None of the above

Its main apolipoprotein component is apoB-48

Which comparative description between sphingomyelin (SM) and phosphatidylcholine (PC) is correct? The presence of a phosphate in PC, but not in SM / The same number of fatty acid chains is found in both PC and SM / The presence of an ether linkage in PC, but not in SM / The head groups are different between PC and SM / PC has the glycerol backbone, whereas SM has the sphingosine backbone

PC has the glycerol backbone, whereas SM has the sphingosine backbone

Which statement is INCORRECT regarding the ABO blood group system? Safe to give Type A blood for a patient whose blood type is AB / People with type O blood are universal donors / People with Type A blood naturally have antibodies to B antigens in their blood serum / People with type AB blood have both A and B antigens and produce antibodies to both / None of the above

People with type AB blood have both A and B antigens and produce antibodies to both

An isolated preparation of liver mitochondria is incubated with oxygen and sodium azide (an inhibitor blocking the ETC between Complex IV and coenzyme Q). Addition of which compound will restore oxygen consumption? Pyruvate / Succinate / Citrate / NADH / Malate

Succinate

Which is the main lipid component stored in adipose tissues? Triglyceride / Cholesterol / Glycolipid / Phospholipid / None of the above

Triglyceride

Which reduces the risk for developing coronary artery disease? High LDL / High VLDL / High IDL / High HDL / None of the above

High HDL

Which apolipoprotein activates lipoprotein lipase? Apo B-48 / Apo B-100 / Apo E / Apo A-1 / Apo C-II

Apo C-II

Which statement about HDL is correct? HDL is only synthesized in the liver / HDL transports triacylglycerols to peripheral tissues / HDL picks up cholesterol and converts it to its cholesterol ester / HDL cannot be endocytosed by the liver / None of the above

HDL picks up cholesterol and converts it to its cholesterol ester

All of the following statements are true EXCEPT: Complex II accepts two electrons from FADH₂ of succinate dehydrogenase of the TCA cycle / Complex I donates two electrons to Coenzyme Q / If the ATP/ADP ratio is low enough, the oxidation of succinate will produce about 1.5 ATPs / When succinate is oxidized, protons are pumped at Complex I / When succinate is oxidized, protons are pumped at Complex IV

When succinate is oxidized, protons are pumped at Complex I

The Urea Cycle is stimulated by: N-Acetyl glutamate and Arginine / N-Acetyl glutamate and Alanine / Pyruvate and Arginine / Oxaloacetate and Arginine / N-Acetyl glutamate and Oxaloacetate

N-Acetyl glutamate and Arginine

A patient with elevated plasma AST and ALT levels is diagnosed with hyperammonemia. Which best describes a practical therapeutic approach to restore normal plasma ammonia levels? Thiazolidinedione enhances synthesis of carbamoyl phosphate synthetase I, thereby accelerating the clearance of ammonia / Benzoate reacts with glycine to form Hippurate, which is rapidly excreted / Glucocorticoids restore proper amino acid metabolism, balancing ammonia production with urea synthesis / Hippurate inhibits glutamate dehydrogenase and glutaminase reactions / Benzoate inhibits transamination reactions to prevent ammonia production

Benzoate reacts with glycine to form Hippurate, which is rapidly excreted

The hyperammonemia patient suffers a seizure. What was most likely the immediate cause? Accumulation of urea produced toxic serum NH₄⁺ / Excess arginine acted as a GABA antagonist / Glutamine depletion caused excitotoxicity / Elevated serum ammonia entered the CNS and depleted α-ketoglutarate / Hyperammonemia inhibited synaptic vesicle release

Elevated serum ammonia entered the CNS and depleted α-ketoglutarate

Which amino acids are both ketogenic and glucogenic? Isoleucine and Tyrosine / Isoleucine, Histidine, and Tyrosine / Valine and Arginine / Valine, Histidine, and Arginine / Valine, Arginine, and Tyrosine

Isoleucine and Tyrosine

Match the disease: Inability to generate tyrosine in a hydroxylation reaction from its precursor. Tyrosinemia II / Maple Syrup Urine Disease / Phenylketonuria / Alkaptonuria / Homocysteinemia

Phenylketonuria

Match the disease: Deficiency of branched-chain α-ketoacid dehydrogenase complex. Tyrosinemia II / Maple Syrup Urine Disease / Phenylketonuria / Alkaptonuria / Homocysteinemia

Maple Syrup Urine Disease

Match the disease: Deficiency in cystathionine β-synthase. Tyrosinemia II / Maple Syrup Urine Disease / Phenylketonuria / Alkaptonuria / Homocysteinemia

Homocysteinemia

Cats were fasted overnight then given a meal of all amino acids except arginine. Within 2 hours, blood ammonia rose from 18 to 540 µg/dL. Controls fed complete amino acids (or arginine replaced by ornithine) had no symptoms. What was the role of fasting in this experiment? Promote feeding on the meal of defined amino acids / Remove confounding signals from the analysis of ammonia / Induce the catabolism of amino acids for production of glucose / Promote the mobilization of glucose from glycogen / Trigger the synthesis of essential amino acids

Induce the catabolism of amino acids for production of glucose

Same cat experiment. What caused ammonia levels to rise? The absence of arginine prevented the conversion of amino groups to urea / Depleted energy stores could not support the production of urea / Arginine was not available to transport amino groups into the liver / Protein synthesis was blocked by the absence of arginine or its precursor / Arginine and ornithine stimulated the release of ammonia by glial cells

The absence of arginine prevented the conversion of amino groups to urea

Arginine, glutamine, histidine and proline are metabolized through which compound before their carbon skeletons enter the TCA cycle? Glutamate / Alanine / Pyruvate / Acetyl CoA / Propionyl CoA

Glutamate

What pair of amino acids carry most of the nitrogen in the bloodstream between peripheral tissues and the liver? Alanine and aspartate / Glutamate and ornithine / Asparagine and glutamine / Alanine and glutamine / Alanine and asparagine

Alanine and glutamine

Actively working muscle generates fumarate as an anaplerotic factor for the TCA cycle. The carbons of the fumarate are primarily derived from which molecule? Pyruvate / Aspartate / Alanine / Acetyl CoA / Glucose

Aspartate

Which compound provides a reserve of high-energy bonds used to maintain ATP levels during short bursts of movement? Acetyl-CoA / Creatinine / Fructose-1-phosphate / Phosphocreatine / Succinyl-CoA

Phosphocreatine

Which enzyme catalyzes fixation of nitrogen from ammonia/ammonium? Asparaginase / Carbamoyl phosphate synthetase I / Glutaminase / Alanine transaminase / Arginase

Carbamoyl phosphate synthetase I

Elevated homocysteine in the blood is associated with deficiency of which vitamin? Vitamin B3 / Vitamin B12 / Thiamine / Lipoic acid / Vitamin C

Vitamin B12

Synthesis of urea requires NH₄⁺, bicarbonate, aspartate, and 3 ATPs. Identify the correct locations for utilization. NH₄⁺, bicarbonate, aspartate in mitochondria and 3 ATPs in cytoplasm / NH₄⁺, bicarbonate, aspartate, 1 ATP in mitochondria and 2 ATPs in cytoplasm / NH₄⁺, bicarbonate, aspartate, 2 ATPs in mitochondria and 1 ATP in cytoplasm / NH₄⁺, bicarbonate, 2 ATPs in mitochondria, and aspartate and 1 ATP in cytoplasm / NH₄⁺, aspartate, 2 ATPs in mitochondria, and bicarbonate and 1 ATP in cytoplasm

NH₄⁺, bicarbonate, 2 ATPs in mitochondria, and aspartate and 1 ATP in cytoplasm