Question 1

Which of the following best describes the amphipathic nature of phospholipids in biological membranes?

Accepted Answer

They have both hydrophobic fatty acid tails and hydrophilic phosphate heads.

Question 2

A scientist increases the temperature of a cell membrane. What is the most likely effect on membrane fluidity and permeability?

Accepted Answer

Both fluidity and permeability will increase.

Question 3

Which type of lipid is characterized by a bulky, four-ring structure and is a component of animal cell membranes?

Accepted Answer

Steroids

Question 4

Why do unsaturated fatty acids increase membrane fluidity compared to saturated fatty acids?

Accepted Answer

Unsaturated fatty acids have double bonds that create kinks, preventing tight packing.

Question 5

Which equation best represents the process of diffusion across a membrane?

Accepted Answer

$$J = -D \frac{dC}{dx}$$

Question 6

A cell membrane contains a high proportion of cholesterol. What is the expected effect on membrane permeability?

Accepted Answer

Permeability will decrease.

Question 7

Which of the following molecules would most easily diffuse across a pure phospholipid bilayer?

Accepted Answer

O$$_2$$

Question 8

What is the primary function of the plasma membrane in cells?

Accepted Answer

It acts as a selective barrier separating the cell interior from the external environment.

Question 9

Which statement about the movement of phospholipids within the bilayer is correct?

Accepted Answer

Lateral diffusion is common, but transverse diffusion ('flip-flop') is rare.

Question 10

A patient has a genetic mutation that causes their cell membranes to have only saturated fatty acids. What is a likely consequence?

Accepted Answer

Their membranes will be less fluid and less permeable.

Question 11

Which of the following best explains why ions such as Na$$^+$$ and Cl$$^-$$ have low permeability across lipid bilayers?

Accepted Answer

They are charged and hydrophilic, so they cannot easily pass through the hydrophobic core.

Question 12

Which of the following is NOT a major type of lipid found in biological membranes?

Accepted Answer

Triglycerides

Question 13

A researcher observes that a cell's membrane permeability increases after adding a certain lipid. Which lipid was most likely added?

Accepted Answer

An unsaturated phospholipid

Question 14

Which of the following best describes the structure of a glycolipid?

Accepted Answer

A lipid with a carbohydrate (oligosaccharide) head group

Question 15

Which of the following is a correct statement about the selective permeability of phospholipid bilayers?

Accepted Answer

Small, nonpolar molecules cross easily; large or charged molecules cross with difficulty.

Question 16

Which of the following would most likely decrease the permeability of a cell membrane?

Accepted Answer

Increasing the proportion of saturated fatty acids

Question 17

Which real-world scenario best illustrates the importance of membrane compartmentalization in eukaryotic cells?

Accepted Answer

Lysosomes digesting cellular waste without harming other organelles

Question 18

Which of the following is the correct chemical structure for a triglyceride (fat) molecule?

Accepted Answer

$$	ext{Triglyceride: Glycerol} + 3 	ext{Fatty Acids} ightarrow 	ext{Ester Bonds}$$

Question 19

Which property of phospholipids is most responsible for the spontaneous formation of bilayers in water?

Accepted Answer

Their amphipathic nature, with hydrophilic heads and hydrophobic tails

Lipids and Membranes: Structure, Function, and Permeability

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