64 WJEC Biology AS Level - Marianne Izen - 2nd Edition (1.3 Cell Membranes And Transport)

Question 1

How do cells transport materials in bulk?

Answer 1

A cell transports materials in bulk:

into the cell, by endocytosis
out of the cell, by exocytosis.

Question 2

How does endocytosis occur?

Answer 2

Endocytosis occurs when material is engulfed by extensions of the cell membrane and cytoplasm, surrounding it, making a vesicle.

Question 3

What are the types of endocytosis?

Answer 3

There are two types of endocytosis:

1. Phagocytosis
2. Pinocytosis

Question 4

Describe phagocytosis.

Answer 4

Phagocytosis is the uptake of solid material that is too large to be taken in by diffusion or active transport.

When granulocytes engulf bacteria, a lysosome fuses with the vesicle formed and enzymes digest the cells.

The products are absorbed into the cytoplasm.

Question 5

Describe pinocytosis.

Answer 5

Pinocytosis is the uptake of liquid by the same mechanism, although the vesicles produced are smaller.

Question 6

Describe exocytosis.

Answer 6

Exocytosis is the process by which substances may leave the cell, having been transported through the cytoplasm in a vesicle, which fuses with the cell membrane.

Question 7

What is often secreted via exocytosis?

Answer 7

Digestive enzymes are often secreted in this way.

Question 8

Draw a diagram to show:
pinocytosis

Answer 8

Question 9

Draw a diagram to show:
phagocytosis

Answer 9

Question 10

Draw a diagram to show:
exocytosis

Answer 10

Question 11

What is required for endocytosis and exocytosis?

Answer 11

Energy: When endocytosis or exocytosis occurs, the cell membrane has to change shape and this requires energy. These processes are therefore active, using ATP, generated by the cell’s respiration.

Fluid cell membrane: In both cases, the cell membrane flows. The property of fluidity of the cell membrane is essential for these processes to occur.

Question 12

Endocytosis (Key-Term)

Answer 12

The active process of the cell membrane engulfing material, bringing it into the cell in a vesicle

Question 13

Exocytosis (Key-Term)

Answer 13

The active process of a vesicle fusing with the cell membrane, releasing the molecules it contains.

Question 14

Phagocytosis (Key-Term)

Answer 14

The active process of the cell membrane engulfing large particles, bringing them into the cell in a vesicle

Question 15

Pinocytosis (Key-Term)

Answer 15

The active process of the cell membrane engulfing droplets of fluid, bringing them into the cell in a vesicle

Question 16

Endocytosis and exocytosis are ——-processes, using —–

Answer 16

Endocytosis and exocytosis are active processes, using ATP.