Biochemistry Practice Test 1

Biochemistry Practice Test Handout

• The handout is only valid for the March 2023 PLE batch and will be rendered obsolete for the next batch since it is updated regularly.
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Thermodynamics

• The entropy of a system can never decrease; it can decrease when the entropy of the surroundings increases by at least as much.
• The entropy of a system decreases when the system is isolated, and the process is irreversible.

Chromatography

• Ion-exchange chromatography is a type of chromatographic technique used to extract a substrate, which is an antimicrobial agent found in milk.
• The substrate is extracted using a column of charged resin.

Heat Transfer

• The three modes of heat transfer are: radiation, conduction, and convection.
• The correct order of heat transfer experienced by a patient who went inside a house with hot smoke, touched a hot steel doorknob, and felt the heat around his neck is: radiation, conduction, and convection.

State Functions

• All of the following are state functions, except: temperature.

Biochemical Reactions

• The compound responsible for the greenish-yellow color of a patient's phlegm participates in three reaction steps: propagation, termination, and initiation.
• The correct order of this three-step reaction is: initiation, propagation, and termination.

Enzymes

• Aldose reductase is responsible for the cloudy lens opacities in a patient with diabetes.
• Glucose-6-phosphatase is deficient in a patient who presents with leg cramps, myoglobinuria, hyperuricemia, and hyperbilirubinemia.
• Phospholipase A2 is directly affected by the active metabolite of nitroprusside.

Biochemistry and Pathology

• Cholera toxin causes massive diarrhea by continually synthesizing cAMP.
• Anabolic pathways are stimulated in the fed state, and they require energy.
• The deficiency of glutathione synthetase explains the recurrent infections in a patient.

Pharmacology

• The active metabolite of nitroprusside directly affects phospholipase A2.
• Hydrogen peroxide is used to clean wounds, and its mechanism of action is the formation of free radicals.
• The enzyme affected by the active metabolite of nitroprusside is phospholipase A2.### Enzyme Deficiencies
• Glucose-6-phosphate dehydrogenase deficiency is associated with myocardial disease.
• Isocitrate dehydrogenase deficiency is associated with cardiac muscles.
• NADPH oxidase deficiency is associated with myeloperoxidase.
• Angiotensin-converting enzyme 2 deficiency is associated with cardiac disease.

Inherited Disorders

• Galactokinase deficiency is associated with cataract formation.
• Galactose-1-phosphate uridyltransferase (GALT) deficiency is associated with classic galactosemia.
• McArdle disease is caused by a deficiency in glycogen phosphorylase.
• Pyruvate kinase deficiency is associated with hemolytic anemia.

Lipid Metabolism

• Increased lipoprotein lipase activity is associated with reduced mortality risk from atherosclerotic cardiovascular disease.
• Statins inhibit the enzyme HMG-CoA reductase.
• HMG-CoA reductase is the rate-limiting enzyme in the biosynthesis of unesterified fatty acids.
• Squalene is an important intermediate in the biosynthesis of unesterified fatty acids.
• Carnitine is an important intermediate in the biosynthesis of unesterified fatty acids.

Cardiovascular Disease

• Bisoprolol is used to treat hypertension.
• Elevated total cholesterol and LDL cholesterol levels are associated with increased cardiovascular disease risk.
• Xanthomas are associated with familial hypercholesterolemia.
• Autosomal recessive hypercholesterolemia is characterized by a mutation in the LDL receptor gene.

Diabetes Mellitus

• Type 1 diabetes mellitus is associated with elevated serum ketones.
• Hepatocytes secrete ketone bodies into the circulation due to the absence of the enzyme HMG-CoA lyase.
• Beta-hydroxybutyrate dehydrogenase is involved in the metabolism of ketone bodies.

Lipid Storage Diseases

• Fabry disease is caused by a deficiency of alpha-galactosidase.
• Gaucher disease is caused by a deficiency of glucocerebrosidase.
• Krabbe disease is caused by a deficiency of galactocerebrosidase.
• Niemann-Pick disease is caused by a deficiency of sphingomyelinase.
• Tay-Sachs disease is caused by a deficiency of hexosaminidase A.

Hormones

• Dihydrotestosterone (DHT) plays a role in male-pattern baldness.
• DHT promotes development of the prostate and is involved in the development of the testes.

Nutrition

• Essential fatty acid deficiency is associated with a dry and scaly rash.
• Lauric acid is a direct derivative of an essential fatty acid.
• Prostaglandin H2 is involved in the metabolism of essential fatty acids.

Toxicology

• Carbon monoxide toxicity is associated with competitive binding to heme.
• Carbon monoxide toxicity is associated with oxidation of Fe2+.### Biochemistry Case Studies
• A 37-year-old male presents with pain, swelling, and redness in the right big toe, likely due to gout caused by hyperuricemia.
• The patient has a history of chronic alcoholism and drank expensive whiskey, which may have contributed to the development of gout.
• Laboratory findings include hyperuricemia and scleral icterus.

Defects in Proteins

• A defect in Fibrillin can cause Marfan syndrome.
• A defect in Type III collagen can cause Ehlers-Danlos syndrome.
• A defect in Type II collagen can cause osteogenesis imperfecta.
• A defect in Type I collagen can cause Ehlers-Danlos syndrome.
• A defect in Laminin can cause muscular dystrophy.

Amino Acids

• Isoleucine is an essential amino acid.
• Phenylalanine is an essential amino acid.
• Homogentisic acid is a byproduct of the breakdown of phenylalanine.
• Homocysteine is a byproduct of the breakdown of methionine.

Enzyme Defects

• A defect in AST (Aspartate Transaminase) can cause liver damage.
• A defect in Phenylalanine Hydroxylase can cause phenylketonuria (PKU).
• A defect in Dopamine Hydroxylase can cause Menkes disease.
• A defect in Homogentisate Oxidase can cause albinism.
• A defect in Tyrosinase can cause albinism.

Other Biochemical Defects

• Rubenstein-Taybi syndrome is caused by a defect in the CREB-binding protein (CBP) gene, which affects histone acetyltransferase activity.
• Alzheimer disease is characterized by the accumulation of beta-amyloid and neurotoxic amyloid beta peptide.
• Sickle cell disease is caused by a point mutation that changes glutamate to lysine on the beta-subunit of hemoglobin.
• Hemoglobin S has an increased hydrophobicity compared to normal hemoglobin, leading to the sickled phenotype.
• Phenytoin can cause vitamin D deficiency.

Metabolic Disorders

• Uremia is characterized by the accumulation of urea and other nitrogenous waste products in the blood.
• Porphyria is a group of disorders caused by defects in the heme biosynthetic pathway.
• Gout is caused by the overproduction of uric acid.
• PKU is caused by a defect in phenylalanine hydroxylase, leading to the accumulation of phenylalanine in the blood.
• Carbamoyl Phosphate Synthetase I deficiency is a urea cycle disorder that can cause hyperammonemia.

Toxicology

• Carbon monoxide can bind to hemoglobin, causing carboxyhemoglobin and leading to tissue hypoxia.
• Lead can inhibit heme biosynthesis, leading to anemia and neurological symptoms.

Miscellaneous

• CREB-binding protein (CBP) gene is involved in histone acetyltransferase activity, which helps to expose the promoters of genes.
• Hemin can be used to treat porphyria by increasing the production of heme.
• Glucose can be used to treat porphyria by increasing the production of heme.