Scientific Foundations

Recall Questions

1. Which of the following enzymes catalyzes the first committed step of glycolysis?

   1. Hexokinase
   2. Phosphofructokinase-1 (PFK-1)
   3. Aldolase
   4. Pyruvate kinase

2. Which of the following steps in glycolysis generates ATP?

   1. Conversion of glucose to glucose-6-phosphate
   2. Conversion of fructose-6-phosphate to fructose-1,6-bisphosphate
   3. Conversion of 1,3-bisphosphoglycerate to 3-phosphoglycerate
   4. Conversion of pyruvate to lactate

3. In glycolysis, what is the net gain of ATP molecules per molecule of glucose?

   1. 1
   2. 2
   3. 4
   4. 6

4. Which coenzyme is reduced during glycolysis and later used in oxidative phosphorylation?

   1. NADP⁺
   2. NAD⁺
   3. FAD
   4. Coenzyme A

5. What is the fate of pyruvate under anaerobic conditions in muscle cells?

   1. It is converted to acetyl-CoA.
   2. It is converted to lactate.
   3. It enters the citric acid cycle.
   4. It is converted to ethanol.

6. Which of the following enzymes catalyzes a substrate-level phosphorylation in glycolysis?

   1. Hexokinase
   2. Phosphofructokinase-1 (PFK-1)
   3. Pyruvate kinase
   4. Aldolase

7. The Cori cycle allows the liver to produces glucose from which of the following?

   1. Acetyl-CoA
   2. Lactate
   3. Ribose 5-phosphate
   4. Glycogen

8. Which of the following enzymes is responsible for the breakdown of glycogen into glucose-1-phosphate?

   1. Glycogen synthase
   2. Glycogen phosphorylase
   3. Glucokinase
   4. Phosphoglucomutase

9. Which of the following hormones stimulates glycogen breakdown in the liver?

   1. Insulin
   2. Epinephrine
   3. Glucagon
   4. Cortisol

10. The debranching enzyme in glycogenolysis has which two enzymatic activities?

    1. Transferase and glucosidase
    2. Kinase and phosphatase
    3. Synthase and phosphorylase
    4. Epimerase and isomerase

11. Which of the following molecules directly inhibits glycogen phosphorylase in muscle cells?

    1. Glucose-6-phosphate
    2. AMP
    3. ATP
    4. Calcium

12. In glycogen synthesis, what is the activated form of glucose that is added to the growing glycogen chain?

    1. Glucose-1-phosphatee
    2. Glucose-6-phosphate
    3. UDP-glucose
    4. Fructose-6-phosphate

13. What enzyme activates glycogen phosphorylase?

    1. Protein kinase A
    2. Glycogen synthase kinase
    3. Phosphoprotein phosphatase
    4. Phosphorylase kinase

14. Which enzyme in gluconeogenesis is not involved in glycolysis?

    1. Phosphofructokinase-1
    2. Pyruvate kinase
    3. Glucose-6-phosphatase
    4. Hexokinase

15. Which precursor for gluconeogenesis is produced in muscles during anaerobic respiration?

    1. Glycerol
    2. Lactate
    3. Acetyl-CoA
    4. Fructose-2,6-bisphosphate

16. Which enzyme catalyzes the final step of gluconeogenesis, converting glucose-6-phosphate to free glucose?

    1. Hexokinase
    2. Phosphofructokinase-1
    3. Glucose-6-phosphatase
    4. Aldolase

17. Which cofactor is required by pyruvate carboxylase during the conversion of pyruvate to oxaloacetate in gluconeogenesis?

    1. Biotin
    2. NADH
    3. FAD
    4. TPP (Thiamine pyrophosphate)

18. The oxidative phase of the pentose phosphate pathway generates which of the following?

    1. NADH
    2. FADH₂
    3. NADPH
    4. ATP

19. What is the main purpose of NADPH produced in the pentose phosphate pathway?

    1. ATP synthesis
    2. Oxidative phosphorylation
    3. Reductive biosynthesis and maintaining glutathione in its reduced form
    4. Glycogen synthesis

20. Which virus is responsible for COVID-19?

    1. Influenza
    2. SARS-CoV-2
    3. HIV
    4. SARS-CoV-2

21. What is the primary mode of transmission for SARS-CoV-2?

    1. Fecal-oral route
    2. Vector-borne transmission
    3. Droplet and airborne transmission
    4. Bloodborne transmission

22. Which of the following tests is used to diagnose an active SARS-CoV-2 infection?

    1. PCR (Polymerase Chain Reaction) test
    2. ELISA (Enzyme-Linked Immunosorbent Assay)
    3. Western blot
    4. Rapid strep test

23. Which of the following is a common symptom of COVID-19?

    1. Erythema multiforme
    2. Persistent cough
    3. Numbness in the feet
    4. Jaundice

24. What type of vaccine was first widely used to protect against COVID-19?

    1. Inactivated virus vaccine
    2. Subunit vaccine
    3. mRNA vaccine
    4. Live attenuated vaccine

25. What is the primary mechanism of action of mRNA vaccines against COVID-19?

    1. Directly inactivates the virus
    2. Inhibits viral replication
    3. Neutralizes toxins produced by the virus
    4. Stimulates an immune response by translation of the viral spike protein

26. Which of the following is the primary role of the tricarboxylic acid cycle (TCA cycle) in cellular metabolism?

    1. To produce ATP directly through substrate-level phosphorylation
    2. To generate high-energy electron carriers for oxidative phosphorylation
    3. To synthesize glucose from fatty acids
    4. To catalyze the breakdown of amino acids into ammonia

27. Which coenzyme is essential for the function of the α-ketoglutarate dehydrogenase complex?

    1. Biotin
    2. Pyridoxal phosphate
    3. Thiamine
    4. Vitamin K

28. In the context of the TCA cycle, which molecule is regenerated to continue the cycle after the production of oxaloacetate?

    1. Citrate
    2. Succinate
    3. Fumarate
    4. Isocitrate

29. Which of the following enzymes is a part of the TCA cycle and also plays a role in the electron transport chain?

    1. Succinate dehydrogenase
    2. Citrate synthase
    3. Malate dehydrogenase
    4. Aconitase

30. Mutations in enzymes that catalyze reactions in the TCA cycle often lead to lactic acidosis. Why do cells produce lactate if pyruvate is the end product of glycolysis?

    1. Pyruvate is less soluble than lactate
    2. Lactate is more easily converted to glucose in the liver
    3. The conversion of pyruvate to lactate generates NAD⁺
    4. Cells can more easily convert lactate to fatty acids

31. Which of the following is the primary function of the electron transport chain (ETC) in oxidative phosphorylation?

    1. Conversion of glucose to pyruvate
    2. Production of NADH and FADH₂ from acetyl-CoA
    3. Transfer of electrons from NADH and FADH₂ to oxygen, creating a proton gradient
    4. Direct synthesis of ATP from ADP and inorganic phosphate

32. Which of the following molecules is the final electron acceptor in the electron transport chain?

    1. NADH
    2. FADH₂
    3. Oxygen
    4. Carbon dioxide

More challenging questions

1. The following three questions refer to the image below of a cross-section of a peripheral nerve. What best describes the structure seen in the image?

   

   1. Myelinated nerve
   2. Unmyelinated nerve
   3. Neuron cell body
   4. Axon terminus

   Show Explanation

   Note the large nucleus of a cell which appears to encapsulate several small structures. The small structures are axons in cross-section. This indicates the cells is a Schwann cell. The Schwann cells does not form a thick wrapping around the axons (myelin) so this is an unmyelinated nerve.

2. In the image above, what is arrow 1 one pointing to?

   1. Elastic fibers
   2. Proteoglycans
   3. Neuron cell body
   4. Collagen fibrils

   Show Explanation

   Note the arrow is pointing to the extra cellular matrix. In cross section, collagen fibrils appear round and show a regular spacing between each other.

3. In the image above, what protein would be expect to find in the cell membrane of the region indicated by arrow 2?

   1. Integrins
   2. Cadherins
   3. Claudins
   4. Connexins

   Show Explanation

   Note the arrow is pointing the section of the Schwann cell membrane that faces the extracellular matrix. Cells use integrins to interact with components of the extracellular matrix.

4. Which of the following best characterizes a biochemical reaction with positive ΔG in metabolic pathways?

   1. Never happens
   2. Generates ATP
   3. Coupled with reaction that has a negative ΔG
   4. Don't require enzymes

   Show Explanation

   Reactions with a positive ΔG are energetically unfavorable and will not proceed unless coupled to a reaction that has a negative ΔG. Importantly, the sum of the ΔGs for both reactions must be negative.

5. You are treating patients with hypertension and prescribe a phosphodiesterase inhibitor to relax the smooth muscle around blood vessels to increase their diameter and reduce their resistance to blood flow. You notice in some of the patients an increase in serum glucose levels even when they have not eaten in a while. What does this suggest about glycogen breakdown in the body?

   1. Stimulated by protein kinase A
   2. Stimulated by protein kinase C
   3. Stimulated by cytosolic calcium
   4. Stimulated by MAP kinase

   Show Explanation

   Phosphodiesterase converts cAMP to 5'-AMP. Because protein kinase A is activated by cAMP, phosphodiesterase decrease the amount of active protein kinase A. Inhibiting phosphodiesterase would increase the amount of active protein kinase A and suggests that glycogen breakdown is stimulated by protein kinase A.

6. A 40 year old male who weighs 75 kg has a serum sodium concentration of 190 meq/L. What is the water deficit in the patient?

   1. 8 liters
   2. 10 liters
   3. 12 liters
   4. 16 liters

   Show Explanation

   First calculate total body water = 75 * 0.6 = 45 liters. Next, calculate the water deficit:

   Water deficit = TBW_t=0(([Na⁺]_t=0/[Na⁺]_normal) - 1)

   Water deficit = 45((190/140) - 1) = 16.07