Question 1

Which of the following best describes the structure of the plasma membrane in eukaryotic cells?

Accepted Answer

A double layer of phospholipids with hydrophilic heads facing outward and hydrophobic tails facing inward

Question 2

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

Accepted Answer

It will shrink because water moves out of the cell to the area of higher solute concentration

Question 3

Which of the following statements about facilitated diffusion is correct?

Accepted Answer

It moves large or polar molecules down their concentration gradient with the help of specific membrane proteins

Question 4

Which equation correctly represents the relationship between surface area (SA) and volume (V) for a spherical cell, and why is this relationship important?

Accepted Answer

$$SA = 4 \pi r^2$, V$$ = \frac{4}{3} \pi $$r^3$$; as cells grow, volume increases faster than surface area, limiting efficient diffusion$

Question 5

During an experiment, dialysis tubing filled with a starch solution is placed in a beaker of iodine solution. After 30 minutes, the inside of the tubing turns blue-black. What does this indicate about the movement of molecules?

Accepted Answer

Iodine diffused into the tubing and reacted with starch

Question 6

Which of the following best explains why cells are typically small in size?

Accepted Answer

Smaller cells have a higher surface area-to-volume ratio, allowing for more efficient diffusion of materials

Question 7

Which process requires energy in the form of ATP to move molecules across the plasma membrane?

Accepted Answer

Active transport

Question 8

A cell is placed in a solution and water moves into the cell, causing it to swell. Which term best describes the solution relative to the cell?

Accepted Answer

Hypotonic

Question 9

Which of the following is NOT a factor that affects the rate of simple diffusion across a plasma membrane?

Accepted Answer

Presence of ATP

Question 10

Which component of the plasma membrane is primarily responsible for cell recognition and communication?

Accepted Answer

Carbohydrates on the external surface

Question 11

A scientist observes that chloride ions move across a cell membrane only when a specific protein is present, and this movement does not require ATP. Which transport mechanism is being observed?

Accepted Answer

Facilitated diffusion

Question 12

Which of the following best describes osmosis?

Accepted Answer

Movement of water from low solute concentration to high solute concentration across a semipermeable membrane

Question 13

The sodium-potassium pump is an example of which type of membrane transport?

Accepted Answer

Active transport

Question 14

If a cell's surface area is $$100 \ \mu m^2$ and its volume is 125$$ \ \mu $$m^3$$, what is its surface area-to-volume ratio, and why is this ratio important?

Accepted Answer

$$1.25$$, which means the cell can efficiently exchange materials with its environment$

Question 15

Which of the following scenarios best illustrates active transport?

Accepted Answer

Sodium ions being pumped out of a nerve cell against their concentration gradient using ATP

Question 16

Which of the following statements about the movement of water and solutes across a semipermeable membrane is correct?

Accepted Answer

Water moves from low solute concentration to high solute concentration, while solutes move down their concentration gradients

Question 17

Which of the following is a real-world example of facilitated diffusion?

Accepted Answer

Glucose entering muscle cells via GLUT transporters

Question 18

A dialysis bag containing protein and reducing sugars is placed in pure water. After 30 minutes, reducing sugars are detected outside the bag, but protein is not. What does this indicate about the membrane's properties?

Accepted Answer

The membrane is permeable to reducing sugars but not to protein

Question 19

Which of the following best explains why increasing temperature generally increases the rate of diffusion across a plasma membrane?

Accepted Answer

Higher temperature increases the kinetic energy of molecules, causing them to move faster

Question 20

Which of the following is a function of proteins in the plasma membrane?

Accepted Answer

Providing stability and transporting molecules across the membrane

Plasma Membrane Structure, Diffusion, Osmosis, and Cell Size

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