Question 1

Which structural feature of a phospholipid is responsible for its amphipathic nature, as shown in the image?

Accepted Answer

The presence of both a polar head group and non-polar fatty acid tails

Question 2

In the structure of a phospholipid, what is the main difference between the two fatty acid chains depicted in the image?

Accepted Answer

One is saturated (straight) and the other is unsaturated (bent)

Question 3

How does the presence of an unsaturated fatty acid (bent tail) in a phospholipid affect membrane fluidity?

Accepted Answer

It increases membrane fluidity by preventing tight packing of phospholipids

Question 4

Which part of the phospholipid, as shown in the image, interacts with water molecules in an aqueous environment?

Accepted Answer

The polar head group

Question 5

If a mutation caused both fatty acid chains in a phospholipid to be saturated, what would be the likely effect on the plasma membrane at low temperatures?

Accepted Answer

The membrane would become more rigid and less fluid

Question 6

Which chemical group is attached to the phosphate in the phospholipid head, as indicated by 'X' in the image?

Accepted Answer

It varies and can be choline, serine, or ethanolamine

Question 7

Why do phospholipids spontaneously form bilayers in water?

Accepted Answer

Their hydrophilic heads interact with water while hydrophobic tails avoid water, leading to bilayer formation

Question 8

Which of the following best describes the role of phospholipids in the plasma membrane?

Accepted Answer

They form a selectively permeable barrier that separates the cell from its environment

Question 9

What would happen to a cell membrane composed entirely of phospholipids with saturated fatty acid tails at high temperatures?

Accepted Answer

The membrane would become less fluid than normal, but cholesterol could help stabilize it

Question 10

Which equation best represents the dehydration reaction that forms the ester linkage between glycerol and a fatty acid in a phospholipid?

Accepted Answer

$$\mathrm{Glycerol} + \mathrm{Fatty\ Acid} \rightarrow \mathrm{Phospholipid} + \mathrm{H}_2\mathrm{O}$$

Structure and Function of Large Biological Molecules & Cell Membranes

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