Biochemistry Subject Review

Question 1

What type of cells exhibits altered glucose levels upon treatment with an insulin receptor antagonist?

a. Cortical neurons

b. Hepatocytes

c. Red blood cells

d. Myoblasts

Answer 1

d. Myoblasts

Question 2

The concentration of hydrogen ions [H+] in a solution is 1 x 10-7 moles/L. What is the pH of the solution?

a. 5

b. 6

c. 7

d. 8

Answer 2

c. 7

pH of solution: pH = −log [H+] = −log [1 × 10 − 7] = 7

Question 3

What characteristic is associated with eicosanoids?

a. Long half-life time

b. Mediation of fever

c. Secretion by red blood cells

d. Storage within cells

Answer 3

b. Mediation of fever

Question 4

A 25-year-old patient presents with severe pain in the groin area and describes sighting blood in the urine. The patient reports no recent trauma, has a negative sexual history, and has not previously experienced these symptoms. What condition may be responsible for the patient’s reported symptoms?

a. Phenylketonuria

b. Hartnup’s disease

c. Maple syrup urine disease

d. Cystinuria

Answer 4

d. Cystinuria

Question 5

An increased risk of hemorrhaging can be attributed to a deficiency in what vitamin?

a. Vitamin A

b. Vitamin D

c. Vitamin E

d. Vitamin K

Answer 5

d. Vitamin K

Question 6

Vitamin B6 is involved in what function in humans?

a. Vitamin B6 helps in letting amino acids and Na+ out from the cell against a concentration gradient.

b. Vitamin B6 participates in the formation of arachidonic acid from linoleic acid.

c. Vitamin B6 helps in deamination of putrescine and cadaverine.

d. Vitamin B6 acts as a coenzyme for kynureninase and thus is a part of tryptophan metabolism.

Answer 6

a. Vitamin B6 helps in letting amino acids and Na+ out from the cell against a concentration gradient.

Question 7

What vitamin deficiency is responsible for irreversible damage to the brain and the nervous system?

a. Thiamine (B1)

b. Niacin (B3)

c. Cobalamin (B12)

Answer 7

c. Cobalamin (B12)

Question 8

The conversion of phenylalanine to tyrosine is catalyzed by what?

a. Phenylalanine hydroxylase

b. Phenylalanine decarboxylase

c. Phenylalanine transferase

d. Phenylalanine deaminase

Answer 8

a. Phenylalanine hydroxylase

Question 9

Research into polymers that inhibit insulin aggregation is important in the treatment of diabetes mellitus. These polymers are added to denatured insulin to help it regain its function. What does this indicate about the denaturation of insulin?

a. The denaturation of insulin affects its primary structure.

b. The denaturation of insulin depends on disulfide bonding.

c. The denaturation of insulin is reversible.

d. The denaturation of insulin retains its function.

Answer 9

c. The denaturation of insulin is reversible.

Question 10

Birth defects, macrocytic anemia, and elevated homocysteine levels in the body are caused by a deficiency of what vitamin?

a. B12

b. B3

c. B9

Answer 10

c. B9

Question 11

The citric acid cycle is part of cellular respiration, breaking down glucose into energy the cell can use. The citric acid cycle also provides precursors for biosynthesis of fatty acids, amino acids, and other biomolecules. What kind of process is the citric acid cycle?

a. Amphibolic

b. Anabolic

c. Catabolic

d. Unregulated

Answer 11

a. Amphibolic

Question 12

Case:
Cholesterol oxidase is an enzyme that catalyzes the oxidation and isomerization of cholesterol. Cholesterol oxidase may have applications in synthesizing medicines, in the food industry, and as an insecticide. Using a Lineweaver-Burk plot, the Km was estimated to be 31 μM, with a Vmax of approximately 29 μmol/min/mL.

Question:
What would you expect the initial velocity of this reaction to be with a substrate concentration of 1 μM?

a. 0.9 μmol/min/mL

b. 0.1 μmol/min/mL

c. 1.1 μmol/min/mL

d. 10 μmol/min/mL

Answer 12

a. 0.9 μmol/min/mL

Using the Michaelis-Menten equation, initial velocity can be calculated as Vmax*[S]/(Km + [S]) where [S] is the substrate concentration. Vmax times 1 μM would be Vmax (29 μmol/min/mL) and Km + 1 μM would be 32 μM. 29 divided by 32 would be just under 1, so initial velocity would be close to 0.9 μmol/min/mL.

Question 12

Case:
The Notch signaling pathway is critical in development and cancer. Post-translational modifications are a key way the activity and output of this signaling pathway can be fine-tuned. Phosphorylation of the intracellular domain of Notch generally increases its ubiquitination and marks it for proteasomal degradation. Phosphatase Eya1 acts on a specific threonine residue in the Notch intracellular domain.

Question:
How would enhanced Eya1 activity affect Notch stability and Notch signaling?

a. Decreased Notch stability, decreased Notch signaling

b. Decreased Notch stability, increased Notch signaling

c. Increased Notch stability, decreased Notch signaling

d. Increased Notch stability, increased Notch signaling

Answer 12

d. Increased Notch stability, increased Notch signaling

Question 13

In a 60-year-old patient with liver cirrhosis, detoxification of ammonia is impaired and damaging the brain. Which of the following can transport ammonia in a non-toxic form?

a. Serine

b. Aspartate

c. Cysteine

d. Glutamine

Answer 13

d. Glutamine

Question 14

Hydrolysis of what bond releases energy from the ATP molecule?

a. Glycosidic bond

b. Peptide bond

c. Phosphoanhydride bond

d. Phosphodiester bond

Answer 14

c. Phosphoanhydride bond

Question 15

Which of the following hemolytic anemias is due to an inborn error of metabolism?

a. Hereditary spherocytosis

b. Hereditary elliptocytosis

c. Glucoso-6 phosphate dehydrogenase deficiency

d. Fetal Rh incompatibility

e. Thalassemia syndrome

Answer 15

c. Glucoso-6 phosphate dehydrogenase deficiency

Question 16

After drinking a chocolate milk-based drink (sweetened with table sugar), what is/are the major carbohydrate product(s) that enter the blood after digestion?

a. Glucose

b. Glucose and fructose

c. Galactose, fructose, and glucose

d. Glucose and galactose

Answer 16

c. Galactose, fructose, and glucose

Question 17

Adenosine triphosphatases (ATPases) are ion pumps that span the lipid bilayer. Like all proteins, ATPases are composed of many amino acids. Where would you expect to find the most isoleucine residues in an ATPase?

a. Interacting with the hydrophilic lipids

b. Interacting with the hydrophobic lipids

c. Interacting with the hydrophilic phosphate groups

d. Interacting with the hydrophobic phosphate groups

Answer 17

b. Interacting with the hydrophobic lipids

Question 17

Selenocysteine can only be incorporated into protein by recoding a UGA codon. This recoding requires a selenocysteine insertion sequence in the mRNA 3’UTR and the presence of what specific molecule?

a. The ribosome specific for selenocysteine

b. The RNA polymerase specific for selenocysteine

c. The selenoprotein specifically made by selenocysteine

d. The tRNA specific for selenocysteine

Answer 17

d. The tRNA specific for selenocysteine

Question 18

Serine is necessary for the proper formation of the myelin sheath (fatty tissue that wraps around the axons of nerve cells).

What problems can be caused by serine synthesis disorders in newborns?

a. Hypermyelination and macrocephaly

b. Hypermyelination and microcephaly

c. Hypomyelination and macrocephaly

d. Hypomyelination and microcephaly

Answer 18

d. Hypomyelination and microcephaly

Question 19

How are polypeptide chains of silk fibroin, a fibrous protein, arranged?

a. Tertiary structure

b. ß-pleated sheets

c. α-helix

d. Primary structure

Answer 19

b. ß-pleated sheets

Question 20

The oxidative phosphorylation system is highly regulated to provide the appropriate level of ATP needed in the cell. ATP synthase is less active when phosphorylated. A mutation of protein kinase C (the enzyme that phosphorylates ATP synthase) has been identified as more active than normal.

What effect will this mutated protein kinase C most predictably have on ATP synthase activity and ATP levels in the cell?

a. Decreased ATP synthase activity and ATP levels

b. Decreased ATP synthase activity, increased ATP levels

c. Increased ATP synthase activity, decreased ATP levels

d. Increased ATP synthase activity and ATP levels

Answer 20

a. Decreased ATP synthase activity and ATP levels

Question 21

The urea cycle takes place in the mitochondria of the liver, where excess ammonia is degraded into urea for excretion. In the initial step of the cycle, ammonia (along with bicarbonate and 2 molecules of ATP) is converted into which of the following molecules?

a. Citrulline

b. Ornithine transcarbamoylase

c. Carbamoyl phosphate

d. Fumarate

e. Arginine

Answer 21

c. Carbamoyl phosphate

Question 22

How do the antiparallel beta sheets in the mature mammalian cystatin-related epididymal spermatogenic protein differ from the parallel beta sheets in the immature protein?

a. The amino end and the carboxyl end of each beta strand are aligned.

b. The amino end of one beta strand is aligned with the carboxyl end of the next beta strand.

c. The amino ends are at an acute angle to the carboxyl ends of the beta strands.

d. The amino ends are perpendicular to the carboxyl ends of the beta strands.

Answer 22

b. The amino end of one beta strand is aligned with the carboxyl end of the next beta strand.

Question 23

For the reactions containing transaminases, which of the following is a common nitrogen acceptor? a. Alanine b. α-ketoglutarate c. Glutamate

Answer 23

b. α-ketoglutarate

Question 24

Which of the following anemia syndromes results from a membrane defect during the erythropoiesis process? a. Hereditary spherocytosis b. Folate-deficient anemia c. Glucoso-6-phosphate dehydrogenase deficiency d. Sickle cell disease e. Thalassemia syndrome

Answer 24

a. Hereditary spherocytosis

Question 24

Glycolysis is the process of converting the six-carbon molecule glucose into two three-carbon molecules, generating ATP and NADH. What three-carbon molecule is the final product of glycolysis? a. Citrate b. Fructose c. Lactate d. Pyruvate

Answer 24

d. Pyruvate

Question 25

What explains anemia as a result of vitamin B6 deficiency? a. The role of vitamin B6 in the production of arachidonic acid from linoleic acid b. The role of vitamin B6 in the production of delta-aminolevulinic acid c. The role of vitamin B6 as a coenzyme for diamine oxidase

Answer 25

b. The role of vitamin B6 in the production of delta-aminolevulinic acid

Question 25

What pattern of inheritance would be expected for individuals affected by glucose-6-phosphate dehydrogenase deficiency? a. Males will not be affected. b. Females will not be affected. c. Males will be only mildly affected. d. Mostly males will be affected. e. Mostly females will be affected.

Answer 25

d. Mostly males will be affected.

Question 26

Which cellular transporter is mostly responsible for transportation of vitamin C? a. GLUT3 b. GLUT4 c. SVCT1 d. SVCT2

Answer 26

d. SVCT2

Question 27

In SDS-polyacrylamide gel electrophoresis (SDS-PAGE), proteins are separated based on what? a. Secondary structure b. Tertiary structure c. Net charge d. Molecular mass

Answer 27

d. Molecular mass

Question 28

A 32-year-old man presents with severe muscle cramps. His laboratory result shows a deficiency of muscle glycogen phosphorylase. Which of the following is his most probable diagnosis? a. Pompe's disease b. McArdle's disease c. Hers disease d. Tarui disease

Answer 28

b. McArdle's disease

Question 29

What process is taking place when aspirin is used to reduce the activity of the enzyme responsible for inflammation? a. Enzyme catalysis b. Enzyme degradation c. Enzyme inhibition d. Enzyme substrate complex

Answer 29

c. Enzyme inhibition

Question 30

What enzyme is found in both the glycolysis pathway and the gluconeogenesis pathway? a. Malate dehydrogenase b. Phosphoenolpyruvic acid carboxykinase c. Phosphoglucoisomerase d. Pyruvate carboxylase

Answer 30

c. Phosphoglucoisomerase

Question 31

Which of the following is a synthetic form of vitamin K? a. Phytomenadione b. Menaquinone c. Menadione

Answer 31

c. Menadione

Question 32

What enzyme is used in both gluconeogenesis and glycolysis? a. 3-phosphoglycerate kinase b. Glucose 6-phosphate c. Hexokinase d. Pyruvate kinase

Answer 32

a. 3-phosphoglycerate kinase

Question 33

Which intermediary of the cholesterol biosynthesis pathway plays an important role in protein prenylation? a. DPP (3,3-dimethylallyl pyrophosphate) b. Farnesyl pyrophosphate c. Geranyl pyrophosphate d. Isopentenyl pyrophosphate

Answer 33

d. Isopentenyl pyrophosphate

Question 34

A hospital lab indicates a urine sample pH of 5.0 in a patient presenting with symptoms of kidney stones. What is the actual hydrogen ion concentration of the urine sample? a. 5.0^-10M b. 5.0M c. 10^-5M d. 10^5M e. 5%

Answer 34

c. 10^-5M pH = −log (H+) We have a urine sample with a pH of 5.0. To determine the actual hydrogen ion concentration, move the 5.0 as a negative exponent to base 10: H+ = 10^−5

Question 35

Glycogen phosphorylase is the enzyme responsible for removing the terminal glucose residue from a glycogen chain, producing glucose-1-phosphate. Glycogen phosphorylase is activated by phosphorylation, which is carried out by the enzyme phosphorylase kinase. Glycogen phosphorylase has been investigated as a potential target for the treatment of type 2 diabetes. How would you expect a therapy for type 2 diabetes to affect this enzyme? a. Effective therapy would dephosphorylate and inhibit glycogen phosphorylase. b. Effective therapy would dephosphorylate and activate glycogen phosphorylase. c. Effective therapy would phosphorylate and activate glycogen phosphorylase. d. Effective therapy would phosphorylate and inhibit glycogen phosphorylase.

Answer 35

a. Effective therapy would dephosphorylate and inhibit glycogen phosphorylase.

Question 35

Steroid hormones are synthesized from cholesterol, and some sex steroids can be converted into other sex steroids. In fact, the majority of estradiol in men is produced from testosterone in their fat tissue. What type of process converts testosterone to estradiol? a. Aromatization b. Dehydrogenation c. Hydroxylation d. Reduction

Answer 35

a. Aromatization

Question 35

What clinical condition can result from folic acid deficiency? a. Hemolytic anemia b. Macrocytic anemia c. Microcytic anemia d. Iron-deficiency anemia e. Thalassemia syndrome

Answer 35

b. Macrocytic anemia

Question 35

Which of the following is a tryptophan-derived hormone? a. Serotonin b. Thyroxine c. Thyroid stimulating hormone d. Norepinephrine

Answer 35

a. Serotonin

Question 36

What form of zinc is present in shampoos for the treatment of seborrhoeic dermatitis? a. Zinc oxide b. Chelated zinc c. Zinc pyrithione

Answer 36

c. Zinc pyrithione

Question 37

What vitamin B subtype is required as a precursor to coenzyme A? a. Niacin (B3) b. Thiamine (B1) c. Biotin (B7) d. Pantothenic acid (B5)

Answer 37

d. Pantothenic acid (B5)

Question 38

DPP-4 inhibitors work by stimulating insulin secretion and inhibiting the secretion of what other pancreatic hormone? a. Amylase b. Glucagon c. Pancreatic polypeptide d. Somatostatin

Answer 38

b. Glucagon

Question 38

What is the term for the quantitive measure of the ability of a molecule to acquire electrons? a. Gibbs free energy b. Oxidation rate c. Reduction potential d. Thermodynamics

Answer 38

c. Reduction potential

Question 39

A patient presents with poor wound healing, bleeding gums, and petechiae. Which of the following vitamins may be deficient? a. Vitamin B3 b. Vitamin B7 c. Vitamin B12 d. Vitamin C

Answer 39

d. Vitamin C

Question 39

Howship's lacunae are a feature of what? a. Osteoblasts b. Osteoclasts c. Osteocytes d. Osteogenesis

Answer 39

b. Osteoclasts

Question 39

Cyclin-dependent kinase 9 (CDK9) is a key metabolic regulator and a candidate drug target for several types of cancer. CDK9 inhibitors have been shown to decrease the ability of prostate cancer cells to metabolize glucose, instead making them dependent on alternative energy sources. Given in combination with a CDK9 inhibitor, what would you predict would be lethal to prostate cancer cells? a. Fatty acid oxidation inhibitors b. Gluconeogenesis inhibitors c. Glycolysis inhibitors d. TCA cycle inhibitors

Answer 39

a. Fatty acid oxidation inhibitors

Question 39

Case: Polyphenols have anti-inflammatory properties and act in a variety of ways to exert these functions. They are known to inhibit enzymes that produce reactive oxygen species, and they upregulate endogenous antioxidant enzymes. Polyphenols have an effect on catalase. Question: What effect do polyphenols have on catalase, and why? a. Polyphenols inhibit catalase because it degrades hydrogen peroxide. b. Polyphenols inhibit catalase because it produces hydrogen peroxide. c. Polyphenols upregulate catalase because it degrades hydrogen peroxide. d. Polyphenols upregulate catalase because it produces hydrogen peroxide.

Answer 39

c. Polyphenols upregulate catalase because it degrades hydrogen peroxide.