Question 1

Which of the following statements best explains why unsaturated fatty acids have a lower melting temperature ($$T_m) $$than saturated fatty acids of the same chain length?

Accepted Answer

The presence of double bonds in unsaturated fatty acids introduces kinks, preventing tight packing.

Question 2

A fatty acid is named 18:2(Δ9,12) according to IUPAC nomenclature. Which of the following correctly describes this molecule?

Accepted Answer

It is an 18-carbon fatty acid with two cis double bonds between carbons 9-10 and 12-13.

Question 3

Which of the following best describes the role of cholesterol in biological membranes?

Accepted Answer

Cholesterol disrupts membrane fluidity at high temperatures and stabilizes it at low temperatures.

Question 4

A patient has a genetic defect that impairs the function of the GLUT4 transporter. Which of the following is the most likely consequence?

Accepted Answer

Decreased glucose uptake in skeletal muscle and adipose tissue in response to insulin.

Question 5

Which of the following best explains why ATP hydrolysis is highly exergonic?

Accepted Answer

The products of ATP hydrolysis are more stable due to resonance stabilization and reduced electrostatic repulsion.

Question 6

Which of the following statements about the sodium-potassium ATPase (Na⁺/K⁺ pump) is correct?

Accepted Answer

It hydrolyzes ATP to move 3 Na⁺ out and 2 K⁺ into the cell, generating both concentration and charge gradients.

Question 7

Which of the following best describes the function of phosphofructokinase-1 (PFK-1) in glycolysis?

Accepted Answer

It catalyzes the committed step of glycolysis and is allosterically activated by fructose-2,6-bisphosphate.

Question 8

A cell is exposed to a hormone that activates a G-protein coupled receptor (GPCR), leading to increased cAMP levels. Which of the following is the most likely downstream effect?

Accepted Answer

Activation of protein kinase A (PKA), leading to phosphorylation of target proteins.

Question 9

Which of the following best explains why gluconeogenesis requires unique enzymes for certain steps compared to glycolysis?

Accepted Answer

Some steps in glycolysis are highly exergonic and essentially irreversible under cellular conditions, requiring bypass reactions in gluconeogenesis.

Question 10

Which of the following is a correct description of the role of NADPH produced in the pentose phosphate pathway?

Accepted Answer

NADPH is primarily used for reductive biosynthesis and antioxidant defense.

Question 11

A mutation causes the bifunctional enzyme phosphofructokinase-2/fructose-2,6-bisphosphatase to be constitutively active in its kinase domain. What is the most likely metabolic consequence?

Accepted Answer

Increased levels of fructose-2,6-bisphosphate, stimulating glycolysis and inhibiting gluconeogenesis.

Question 12

Which of the following best describes the difference between primary and secondary active transport?

Accepted Answer

Primary active transport directly uses ATP hydrolysis, while secondary active transport uses the energy stored in ion gradients.

Question 13

Which of the following is true regarding the regulation of glycogen metabolism by insulin and glucagon?

Accepted Answer

Insulin promotes glycogen synthesis by activating glycogen synthase, while glucagon promotes glycogen breakdown by activating glycogen phosphorylase.

Question 14

Which of the following best describes the effect of increasing the length of fatty acid chains in membrane phospholipids?

Accepted Answer

It decreases membrane fluidity by increasing van der Waals interactions.

Question 15

Which of the following equations correctly calculates the free energy change ($$\Delta G) $$for the transport of an ion across a membrane, considering both concentration and charge gradients?

Accepted Answer

$$\Delta G = RT \ln \left( \frac{[C]_	ext{in}}{[C]_	ext{out}} ight) + zF\Delta \Psi$$

Question 16

Which of the following best describes the function of the Cori cycle?

Accepted Answer

It transports lactate from muscle to liver, where it is converted back to glucose.

Question 17

Which of the following statements about membrane transport is correct?

Accepted Answer

Facilitated diffusion requires a protein carrier and moves molecules down their concentration gradient without energy input.

Question 18

Which of the following best explains why reactions far from equilibrium are often sites of metabolic regulation?

Accepted Answer

These reactions are essentially irreversible under cellular conditions, making them effective control points.

Question 19

Which of the following is a correct pairing of a lipoprotein particle and its primary function?

Accepted Answer

Chylomicrons: transport dietary triglycerides from the intestine to peripheral tissues.

Comprehensive Study Guide: Lipids, Membranes, Metabolism, and Regulation in Biochemistry

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