2.5.4- How Substances Cross Membranes Using Active Processes

Question 1

Define the word ‘endocytosis’.

Answer 1

Bulk transport of molecules that are too large to pass through the membrane or via protein channels or carriers, into a cell.

Question 2

Define ‘exocytosis’.

Answer 2

Bulk transport of molecules that are too large to diffuse through the membrane or cross the membrane via protein channels or carrier proteins- OUT of a cell.

Question 3

To move energy against the substances concentration gradient, more energy is needed than…

Answer 3

The kinetic energy of the molecules.

Question 4

How is the energy to actively transport substances provided to cells.

Answer 4

Energy is provided by the hydrolysis of ATP- it’s broken down into ADP and P

Question 5

Why is Active Transport needed?

Answer 5

It is needed when cells or organelles need to accumulate more of an ion than could be achieved by simple or facilitated diffusion alone.

Question 6

Carrier proteins have specific regions or sites that…

Answer 6

Reversible combine with only certain solute molecules or ions.

Question 7

List two regions or sites that are present in carrier proteins.

Answer 7

> A region that reversibly combines with only certain solute molecules or ions.
A region that binds to and allows ATP hydrolysis.

Question 8

Why is energy in the form of ATP required for carrier proteins?

Answer 8

The energy helps the proteins to change its shape- so that it can carry the ion from one side of the membrane to the other.

Question 9

Explain why energy in the form of ATP is required (and made by chloroplasts in plants) for use by guard cells.

Answer 9

To actively transport potassium ions into guard cells- ion influx lowers the water potential of guard cells so more water enters from surroundings via osmosis and the guard cells swell so their tips bulge, opening the stomata between them.

Question 10

Bulk transport requires…

Answer 10

Energy in the form of ATP

Question 11

What are the two general types of bulk transport.

Answer 11

Endocytosis

Exocytosis

Question 12

Bulk transport processes are different from

Diffusion processes across a selectively permeable membrane as…

Answer 12

The material does not pass through the plasma membrane.

Question 13

explain how the process of endocytosis takes place.

Answer 13

A segment of the plasma membrane surrounds and encloses the particle(s) and brings it into the cell in a vesicle.

Question 14

What are the two types of endocytosis?

Answer 14

Phagocytosis

Pino(endo)cytosis.

Question 15

What is phagocytosis?

Answer 15

The intake of solid matter by endocytosis

Question 16

What is pino(endo)cytosis?

Answer 16

When cells ingest liquids by endocytosis.

Question 17

Explain why ATP is needed in the process of bulk transport? Give two reasons.

Answer 17

To provide the energy to form the vesicles and to move them using motor proteins along the cytoskeleton threads

Question 18

Explain briefly how exocytosis happens.

Answer 18

A vesicle containing the matter is moved towards the plasma membrane where the plasma and vesicle membranes fuse, causing the fused site to open and the contents of the secretory vesicle to be released on the other side of the membrane.

Question 19

Describe and explain an example of exocytosis in the body.

Answer 19

At the synapses of neurones where chemicals in vesicles are moved to the presynaptic membrane, by motor proteins along cytoskeleton threads, where the vesicle and plasma membrane dude and the neurotransmitter chemicals are released to the synaptic cleft.

Question 20

How much ATP is hydrolysed for every step a motor protein takes along a cytoskeleton thread?

Answer 20

One Molecule of ATP is hydrolysed.

Question 21

Define active transport.

Answer 21

The movement of substances against the concentration gradient across a cell membrane, with the use of energy in the form of ATP