Question 1

Which of the following statements best explains why naturally occurring unsaturated fatty acids are usually found in the cis configuration rather than the trans configuration?

Accepted Answer

Cis double bonds introduce kinks in the hydrocarbon chain, increasing membrane fluidity and preventing tight packing.

Question 2

Based on the structures shown, which type of fatty acid would have the highest melting temperature?

Accepted Answer

A saturated fatty acid with 18 carbons

Question 3

Given the following fatty acids, which one is most likely to be liquid at room temperature?

Accepted Answer

Linolenate (18:3, Δ9,12,15)

Question 4

A fatty acid is described as 18:2 Δ9,12. What does this notation indicate?

Accepted Answer

The fatty acid has 18 carbons and two double bonds at carbons 9 and 12.

Question 5

Which of the following best describes the structure of a triacylglycerol molecule?

Accepted Answer

Three fatty acyl chains esterified to a glycerol backbone

Question 6

Why are triacylglycerols less soluble in water than free fatty acids?

Accepted Answer

Their head group is less charged, making them more hydrophobic.

Question 7

Which of the following statements about glycerophospholipids is correct?

Accepted Answer

They typically have a saturated fatty acid at position 1 and an unsaturated fatty acid at position 2 of glycerol.

Question 8

What structural property allows fatty acids to form micelles in aqueous solution?

Accepted Answer

Their wedge-shaped structure with a single hydrophobic tail and a polar head group

Question 9

Which of the following best explains why phospholipids form bilayers rather than micelles?

Accepted Answer

Phospholipids are more cylindrical, allowing them to pack together in a bilayer structure.

Question 10

Which of the following is a function of cholesterol in biological membranes?

Accepted Answer

It increases membrane fluidity at low temperatures and decreases fluidity at high temperatures.

Question 11

What is the effect of adding cholesterol to a pure phospholipid bilayer, as shown in the calorimetry graph?

Accepted Answer

The transition temperature (Tm) is not changed, but the transition is broadened.

Question 12

Which of the following statements about LDL particles is correct?

Accepted Answer

They transport cholesterol from the liver to peripheral tissues.

Question 13

Which of the following best describes the role of apolipoprotein B-100 in LDL particles?

Accepted Answer

It targets LDL particles to specific cell types for uptake.

Question 14

Which of the following is a key difference between integral membrane proteins and peripheral membrane proteins?

Accepted Answer

Integral membrane proteins span the bilayer and interact with the hydrophobic core, while peripheral proteins associate with polar head groups.

Question 15

Which of the following best explains why HDL is considered 'good cholesterol'?

Accepted Answer

HDL collects cholesterol from the blood and transports it back to the liver for excretion.

Question 16

Which of the following is a correct statement about the amphipathic nature of membrane lipids?

Accepted Answer

They contain both hydrophobic tails and hydrophilic head groups, allowing them to form bilayers in water.

Question 17

Which of the following best describes the structure of cholesterol?

Accepted Answer

A rigid molecule with four fused hydrocarbon rings and a short hydrocarbon tail

Question 18

Which of the following is a consequence of the presence of cis double bonds in fatty acids?

Accepted Answer

They introduce kinks in the hydrocarbon chain, lowering the melting temperature.

Lipids, Membranes, and Cellular Transport: Structure, Function, and Regulation

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