Biochemistry Quiz
Questions: 16 · 10 minutes
1. In a eukaryotic cell, where does glycolysis occur?
Mitochondrial matrix
Mitochondrial intermembrane space
Nucleus
Cytosol
2. A solution changes from pH 7 to pH 6. What happens to its hydrogen ion concentration?
It increases by a factor of 10.
It increases by a factor of 2.
It decreases by a factor of 10.
It remains unchanged because both values are near neutral.
3. Cyanide inhibits complex IV of the mitochondrial electron transport chain. Which immediate pattern is most likely?
NADH oxidation accelerates and oxygen consumption rises.
The citric acid cycle accelerates because the NAD+ supply increases.
Oxygen consumption falls, NADH accumulates, and oxidative ATP production declines.
ATP synthase produces more ATP because the proton gradient becomes steeper.
4. A red blood cell is placed in a solution with the same effective osmolarity as its cytoplasm. What is the expected result?
Water enters continuously, causing the cell to burst.
Water leaves continuously, causing the cell to shrink.
Solute movement stops because molecular motion ceases.
Water moves in both directions with no net change in cell volume.
5. Which substance can cross the hydrophobic core of a phospholipid bilayer most readily by simple diffusion?
Glucose
Oxygen
Sodium ion
Alanine at physiological pH
6. A reversible competitive inhibitor is added to an enzyme reaction. Under standard Michaelis–Menten assumptions, what change is expected?
Both apparent Km and Vmax decrease.
Apparent Km increases while Vmax remains unchanged.
Both apparent Km and Vmax increase.
Apparent Km stays the same while Vmax increases.
7. A mutation changes a charged amino acid in an enzyme's substrate-binding pocket to a nonpolar amino acid. What is the most direct possible consequence?
The enzyme must begin catalyzing every reaction more quickly.
The protein's peptide bonds are automatically hydrolyzed.
Substrate binding may weaken if the original charge contributed to recognition.
The reaction's equilibrium constant must reverse.
8. A pure noncompetitive inhibitor binds equally well to the free enzyme and enzyme–substrate complex. What is its expected kinetic effect?
Vmax remains unchanged while Km increases.
Vmax increases while Km decreases.
Vmax decreases while Km remains unchanged.
Both Vmax and Km increase.
9. When lactate is oxidized to pyruvate by lactate dehydrogenase, what happens to NAD+?
It is hydrolyzed into ADP and phosphate.
It donates reducing equivalents and becomes NADH.
It transfers a phosphate group and becomes ATP.
It accepts reducing equivalents and becomes NADH.
10. How does an enzyme typically increase the rate of a biochemical reaction?
It makes the reaction's overall free-energy change more negative.
It lowers the activation energy by providing an alternative reaction pathway.
It permanently shifts the reaction equilibrium toward the products.
It raises the temperature immediately around each substrate molecule.
11. Which type of bond directly joins amino acids in the primary structure of a protein?
Glycosidic bond
Phosphodiester bond
Peptide bond
Hydrogen bond
12. During an overnight fast, glucagon acts on the liver. Which response helps maintain blood glucose?
Increased glycogen breakdown and gluconeogenesis
Increased fatty acid synthesis and reduced glycogen breakdown
Increased glucose uptake through insulin-dependent transporters
Increased glycogen synthesis and reduced gluconeogenesis
13. Which feature distinguishes RNA from DNA under ordinary cellular conditions?
RNA generally contains ribose and uracil rather than deoxyribose and thymine.
RNA contains phosphate, whereas DNA does not.
RNA is built from amino acids rather than nucleotides.
RNA cannot form complementary base pairs.
14. The final product of a metabolic pathway binds reversibly to a regulatory site on an early enzyme and reduces its activity. What does this illustrate?
Substrate-level phosphorylation
Irreversible protein denaturation
Competitive activation at the enzyme's active site
Allosteric feedback inhibition
15. A globular protein is heated enough to denature it without breaking its peptide bonds. Which change is most likely?
Its amino acid sequence is replaced with a new sequence.
Its higher-order folding is disrupted while its primary structure largely remains intact.
Every covalent bond in the protein is cleaved.
Its amino acids are converted into nucleotides.
16. What is the name of the process that uses a DNA template to produce RNA?
Transcription
Translation
Replication
Reverse transcription