B2 Cell transport

Question 1

Name three factors which affect the rate of diffusion

Answer 1

concentration gradient;
temperature;
surface area

Question 2

How are villi adapted for exchanging substances?

Answer 2

1. long and thin - increases surface area
2. on cell thick membrane - short diffusion pathway
3. Good blood supply - maintains a steep concentration gradient

Question 3

How are the lungs adapted for efficient gas exchange?

Answer 3

1. Alveoli - large surface area
2. Moist membrane - increases rate of diffusion
3. One cell thick membrane - short diffusion pathway
4. Good blood supply - maintains a steep concentration gradient

Question 4

How are fish gills adapted for efficient gas exchange?

Answer 4

1. Large surface area for gases to diffuse across;
2. Thin layer of cells - short diffusion pathway;
3. Good blood supply - maintains a steep concentration gradient

Question 5

What is osmosis?

Answer 5

Diffusion of water from a dilute solution to a concentrated solution through a partially permeable membrane

Question 6

Give a use of osmosis in a plant

Answer 6

Movement of water into the root hair cell

Question 7

What is active transport?

Answer 7

Movement of particles against a concentration gradient using energy from respiration

Question 8

Why is active transport needed in plant roots?

Answer 8

Concentration of mineral ions in the soil is lower than the concentration in the root hair cells;
mineral ions must move against the concentration gradient to enter the root hair cells

Question 9

What is the purpose of active transport in the small intestine?

Answer 9

Sugars can be absorbed when the concentration of sugar in the small intestine is lower than the concentration of sugar in the blood

Question 10

Why how and why temperature affects the rate of diffusion?

Answer 10

the higher the temperature the faster the rate of diffusion;
because the particles have more (kinetic) energy and move faster

Question 11

What is meant by a partially permeable membrane?

Answer 11

A membrane which only allows small molecules such as water to diffuse through it

Question 12

Name three processes substances can use to move across an exchange surface?

Answer 12

diffusion
active transport
osmosis

Question 13

Name two exchange surfaces in humans

Answer 13

1. alveoli in the lungs
2. Villi in the small intestine