Chapter 3 Movement of Substances across the plasma membrane

Subtopic: 3.1 Movement across the Plasma Membrane

WORKSHEET

NAME:_________________ CLASS:___________ DATE:_____________

Part A: Answer all questions.

1. Diagram 1 shows a fluid-mosaic model of a plasma membrane.

a) On Diagram 1, label structures P, Q, R, S and T. [5 marks] b) Molecules can pass through structure Q in Diagram 1 by facilitated diffusion.

(i) State Three characteristics of the molecule that can pass through structure Q. ____________________________________________________________________________________________________________________________________________________________________________________________[3 marks]

(ii) Explain how molecules pass through structure Q. ______________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________[3 marks]

c) State one characteristics of the plasma membrane based on the model in Diagram 1.

_______________________________________________________________________________________________________________________________________[1 mark]

2. Diffusion is the movement of molecules from an area of ____________ concentration to an area of _____________ concentration.

3. Osmosis is the movement of ____________ across a differentially permeable membrane.

Part B: Answer all questions. Choose the best option for each question.

1. What is meant by the plasma membrane exhibiting fluidity?

A. The hydrophobic tails point towards each other in the middle of the bilayer.

B. The hydrophilic heads are attracted to water in the extracellular fluid and cytoplasm.

C. The phospholipid bilayer forms a membrane that is not static but dynamic.

D. The membrane proteins are suspended in the phospholipid bilayer.

2. Which of the following not a process of diffusion?

A. Net movement of molecules from a region of higher concentration of molecules to a region of lower concentration of molecules.

B. Net movement of ions from a region of higher concentration of ions to a region of lower concentration of ions.

C. Net movement of water molecules from a region of higher solute concentration to a region of lower solute concentration.

D. Net movement of water molecules from a region of higher water concentration to a region of lower water concentration.

3. Which of the following is not a passive transport?

A. Simple diffusion

B. Sodium-potassium pump

C. Facilitated diffusion

D. Osmosis

4. What are the molecules that can pass through the phospholipid bilayer of the plasma membrane by simple diffusion?

I. Fatty acids

II. Vitamin A

III. Carbon dioxide molecules

IV. Oxygen molecules

A. I only

B. I and II only

C. I, II and III only

D. I, II, III and IV

ANSWERSHEET

Part A:

1. a) P: Cholesterol; Q: Carrier protein; R: Channel / pore protein;

2. S: Hydrophilic head; T: Hydrophobic tail

b)

(i) Polar molecule / Water-soluble / Not lipid-soluble / Small size

(ii) ~ There is a concentration gradient on both sides of the

plasma membrane.

~ The molecule will bind to the binding site of carrier protein.

~ The carrier protein changes shape to transport molecules

across the plasma membrane.

~ The molecule will move from a region of higher solute

concentration to a region of lower solute concentration.

c) Semi-permeable / selectively permeable

2. High; low3. water

Part B:

1. C

2. C

3. B

4. D