Question 1

Which of the following best explains why fats are considered hydrophobic molecules?

Accepted Answer

They are composed mostly of hydrocarbons, which form nonpolar covalent bonds.

Question 2

A triglyceride is formed by which of the following chemical reactions?

Accepted Answer

Dehydration synthesis between three fatty acids and one glycerol molecule

Question 3

Which of the following statements about saturated and unsaturated fatty acids is correct?

Accepted Answer

Saturated fatty acids are typically found in animal fats and lack double bonds between carbon atoms.

Question 4

Which of the following best describes the structure of a phospholipid in a biological membrane?

Accepted Answer

Two fatty acids and a phosphate group attached to glycerol, forming a hydrophilic head and hydrophobic tails

Question 5

A patient is diagnosed with a genetic disorder that causes their cell membranes to be excessively rigid. Which of the following changes in membrane composition is most likely responsible?

Accepted Answer

Increased proportion of saturated fatty acids

Question 6

Which of the following best explains why cholesterol is important for membrane fluidity in animal cells?

Accepted Answer

Cholesterol acts as a buffer, preventing changes in fluidity as temperature changes.

Question 7

A red blood cell is placed in a hypotonic solution. What will most likely happen to the cell, and why?

Accepted Answer

It will swell and potentially burst because water will enter the cell by osmosis.

Question 8

Which of the following best describes the function of aquaporins in the plasma membrane?

Accepted Answer

They facilitate the rapid diffusion of water molecules across the membrane.

Question 9

Which of the following is an example of passive transport across a biological membrane?

Accepted Answer

Diffusion of oxygen from the blood into body tissues

Question 10

A cell is placed in a solution containing a higher concentration of solutes than the cytoplasm. Which of the following terms best describes the solution, and what is the expected movement of water?

Accepted Answer

Hypertonic; water moves out of the cell

Question 11

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It involves the movement of molecules down their concentration gradient via transport proteins.

Question 12

Which of the following best explains why ions such as Na$$^+$$ and K$$^+$$ cannot easily cross the plasma membrane without assistance?

Accepted Answer

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

Question 13

A plant cell is placed in a hypertonic solution. Which of the following will most likely occur?

Accepted Answer

The cell will lose water, and the plasma membrane will pull away from the cell wall (plasmolysis).

Question 14

Which of the following best describes the sodium-potassium pump (Na$$^+/K$^+$$ ATPase) in animal cells?

Accepted Answer

It uses ATP to move Na$$^+$$ out of the cell and K$$^+$$ into the cell against their concentration gradients.

Question 15

Which of the following is a function of membrane proteins?

Accepted Answer

They facilitate cell-cell recognition, signal transduction, and transport of substances.

Question 16

A scientist observes that a certain molecule crosses the plasma membrane rapidly and without the assistance of a transport protein. Which of the following is most likely true about this molecule?

Accepted Answer

It is small and nonpolar.

Question 17

Which of the following best describes the fluid mosaic model of membrane structure?

Accepted Answer

Membranes consist of a phospholipid bilayer with proteins embedded and moving laterally within the layer.

Question 18

Which of the following scenarios best illustrates the concept of selective permeability in biological membranes?

Accepted Answer

Oxygen and carbon dioxide diffuse rapidly, while ions require specific transport proteins to cross.

Question 19

A cell is actively transporting glucose against its concentration gradient. Which of the following processes is most likely involved?

Accepted Answer

Active transport using a carrier protein and ATP

Question 20

Which of the following best explains why plant cells do not burst when placed in a hypotonic solution, unlike animal cells?

Accepted Answer

Plant cells have a rigid cell wall that resists excessive water uptake.

Lipids, Membranes, and Membrane Transport in General Biology

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