Question 1

Which of the following best explains why unsaturated fatty acids generally have lower melting temperatures ($$T_m) $$than saturated fatty acids?

Accepted Answer

The presence of double bonds in unsaturated fatty acids introduces kinks, preventing tight packing and reducing van der Waals interactions.

Question 2

A fatty acid is named as 18:2(Δ9,12) according to IUPAC conventions. Which of the following statements is TRUE about this fatty acid?

Accepted Answer

It is a polyunsaturated fatty acid with double bonds at carbons 9 and 12 (counting from the carboxyl end).

Question 3

Which of the following best describes the structural difference between cis and trans fatty acids?

Accepted Answer

Cis fatty acids have hydrogen atoms on the same side of the double bond, causing a bend, while trans fatty acids have them on opposite sides, resulting in a straighter chain.

Question 4

Which of the following statements about triacylglycerols is correct?

Accepted Answer

Triacylglycerols are composed of three fatty acids esterified to a glycerol backbone and serve primarily as energy storage molecules.

Question 5

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

Accepted Answer

Cholesterol decreases membrane fluidity by rigidifying the membrane at low temperatures and prevents packing at high temperatures.

Question 6

A cell maintains a concentration gradient of potassium ions ($$K^+) $$across its membrane. Which equation would you use to calculate the free energy change ($$\Delta G) $$for transporting $$K^+$$ from outside to inside, considering both concentration and charge gradients?

Accepted Answer

$$\Delta G = RT \ln \left( \frac{[K^+]_{in}}{[K^+]_{out}} \right) + zF\Delta \Psi$$

Question 7

Which of the following best describes the difference between passive and active transport across membranes?

Accepted Answer

Passive transport moves molecules down their concentration gradient without energy input, while active transport moves molecules against their gradient and requires energy.

Question 8

Which of the following is an example of secondary active transport?

Accepted Answer

The glucose-sodium symporter, which uses the sodium gradient established by the $$Na^+/K^+$$ ATPase to transport glucose into the cell.

Question 9

Which of the following best describes the function of G-proteins in signal transduction?

Accepted Answer

G-proteins function as molecular switches, cycling between active (GTP-bound) and inactive (GDP-bound) states to relay signals from receptors to effector enzymes.

Question 10

Which of the following statements about ATP is correct?

Accepted Answer

ATP contains high-energy phosphoanhydride bonds, which release energy upon hydrolysis due to charge repulsion and resonance stabilization of products.

Question 11

Which of the following best describes the role of NADPH in cellular metabolism?

Accepted Answer

NADPH is primarily used in anabolic pathways, such as fatty acid synthesis, as a reducing agent.

Question 12

Which of the following is a key regulatory step in glycolysis, often referred to as the committed step?

Accepted Answer

The conversion of fructose-6-phosphate to fructose-1,6-bisphosphate by phosphofructokinase-1 (Step 3).

Question 13

During anaerobic glycolysis in muscle cells, why is the conversion of pyruvate to lactate necessary?

Accepted Answer

To regenerate NAD$$^+$$, allowing glycolysis to continue in the absence of oxygen.

Question 14

Which of the following best describes the reciprocal regulation of glycogen synthesis and breakdown by insulin and glucagon?

Accepted Answer

Insulin stimulates glycogen synthesis, while glucagon stimulates glycogen breakdown.

Question 15

Which of the following is a product of the oxidative phase of the pentose phosphate pathway?

Accepted Answer

NADPH

Question 16

Which enzyme is responsible for the synthesis of fructose-2,6-bisphosphate (F2,6BP), a key regulator of glycolysis and gluconeogenesis?

Accepted Answer

Phosphofructokinase-2 (PFK-2)

Question 17

Which of the following statements about the regulation of glycolysis and gluconeogenesis is correct?

Accepted Answer

Fructose-2,6-bisphosphate activates glycolysis and inhibits gluconeogenesis.

Question 18

Which of the following best describes the fate of glucose-6-phosphate in liver cells?

Accepted Answer

It can be used for glycogen synthesis, glycolysis, or the pentose phosphate pathway.

Question 19

Which of the following statements about the Cory Cycle is correct?

Accepted Answer

The Cory Cycle describes the conversion of lactate produced in muscle to glucose in the liver, which is then transported back to muscle.

Comprehensive Study Notes: Lipids, Membranes, and Carbohydrate Metabolism

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