Question 1

Which of the following best describes the process by which cells respond to external stimuli via receptors that act through second and third messengers?

Accepted Answer

Signal transduction pathway

Question 2

Which of the following is NOT a recognized type of cell surface receptor?

Accepted Answer

Voltage-gated sodium pump

Question 3

Which of the following is a correct pairing of a receptor type, its ligand, and a second messenger?

Accepted Answer

G protein-coupled receptor; epinephrine; $$cAMP$$

Question 4

Which of the following is NOT a reason why glycolysis is considered a core metabolic pathway?

Accepted Answer

It is the only pathway that produces $$CO_2 in $$the cytosol

Question 5

Why is AMP a positive allosteric regulator of phosphofructokinase-1 (PFK-1), while ATP is a negative effector?

Accepted Answer

AMP signals low energy, activating glycolysis; ATP signals high energy, inhibiting glycolysis

Question 6

A patient with a severe deficiency of phosphoglycerate mutase is unable to sustain intense exercise. Which of the following best explains this?

Accepted Answer

The block in glycolysis prevents sufficient ATP production during anaerobic exercise

Question 7

Would an individual with phosphoglycerate mutase deficiency be expected to suffer from lactic acid buildup in the muscle during intense exercise?

Accepted Answer

No, because glycolysis is blocked before pyruvate and lactate can be formed

Question 8

Why does paper lose its shape and strength when soaked in water, but not when soaked in oil?

Accepted Answer

Water disrupts hydrogen bonds between cellulose fibers, while oil does not

Question 9

Which of the following metabolic states promotes flux through the pentose phosphate pathway?

Accepted Answer

High demand for NADPH

Question 10

What is the primary function of glutathione in red blood corpuscles?

Accepted Answer

It reduces reactive oxygen species, protecting cells from oxidative damage

Question 11

How is the activity of glucose-6-phosphate dehydrogenase (G6PD) connected to glutathione levels in red blood cells?

Accepted Answer

G6PD produces NADPH, which is required to regenerate reduced glutathione

Question 12

Why does glycolysis yield 3 net ATP molecules when starting from glucose-1-phosphate (from glycogen breakdown), but only 2 net ATP from dietary glucose?

Accepted Answer

Glucose-1-phosphate enters glycolysis as glucose-6-phosphate, bypassing the ATP-consuming hexokinase step

Question 13

Consuming large amounts of alcohol when blood glucose is low can cause hypoglycemia. Which of the following best explains this effect?

Accepted Answer

Alcohol metabolism increases $$NADH$$, inhibiting gluconeogenesis by shifting pyruvate and oxaloacetate to lactate and malate

Question 14

Which glycolytic enzymes are bypassed in gluconeogenesis, and what are their corresponding bypass enzymes?

Accepted Answer

Hexokinase (by glucose-6-phosphatase), phosphofructokinase-1 (by fructose-1,6-bisphosphatase), pyruvate kinase (by pyruvate carboxylase and PEP carboxykinase)

Question 15

Activation of protein kinase A (PKA) by $$cAMP$$ after glucagon or epinephrine stimulation has which effect on glycogen metabolism?

Accepted Answer

Inhibits glycogen synthase and activates glycogen phosphorylase

Question 16

What is the net effect of PKA activation on glycogen storage in the body?

Accepted Answer

Decreases glycogen storage

Question 17

Caffeine inhibits $$cAMP$$ phosphodiesterase. What effect does this have on the actions of glucagon and epinephrine?

Accepted Answer

It increases their effects by prolonging $$cAMP$$ signaling

Question 18

A patient with G6PD deficiency is prescribed primaquine for malaria. What is the most likely biochemical consequence in their red blood cells?

Accepted Answer

Increased oxidative damage due to insufficient NADPH for glutathione reduction

Question 19

Which of the following best explains why individuals with G6PD deficiency are more resistant to malaria?

Accepted Answer

Their red blood cells are more susceptible to oxidative stress, which impairs malaria parasite survival

Biochemistry II Practice Exam 1 – Guided Study Support

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