Transport in cells

Question 1

What is diffusion?

Answer 1

the net movement of particles from a higher area of concenration to lower area of concentration

Question 2

What three main factors affect the rate of diffusion?

Answer 2

• concentration gradient (larger gradient = faster diffusion)
• temperature (higher temp. = faster diffusion)
• Surface area (large sa = faster diffusion)

Question 3

give examples of substances transported by diffusion in the lungs and kidney

Answer 3

Lungs - oxygen diffuses into blood from the lungs, and carbon dioxide diffuses into the lungs from the blood, both down their concentration gradient
Kidney - urea diffuses from cells into blood from plasma so it can be excreted in urine

Question 4

how are single cell organisms adapted for diffusion?

Answer 4

they have a large surface area to volume ratio, which maximises the rate of diffusion of molecules to meet the organisms needs

Question 5

How is surface area to volume calculated?

Answer 5

surface area = number of sides x (side length x side width)

volume = length x width x depth

ratio = surface area:volume

Question 6

what four factors increase the effectiveness of a gas exchange surface?

Answer 6

• large surface area
• thin membrane (short diffusion path)
• efficient blood supply (animals)
• ventilation (animals)

Question 7

What is osmosis?

Answer 7

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

Question 8

what is meant when a solution is isotonic to a cell?

Answer 8

the concentrations of the external and internal (inside the cell) solutions are the same

Question 9

what is meant a solution is hypertonic to a cell?

Answer 9

the concentration of the external solution is higher than the internal solution (inside the cell)

Question 10

What may happen when an animal cell is placed in a hypertonic solution?

Answer 10

water moves to the cell, causing it to burst

Question 11

what may happen when an animal is placed into a very hypertonic solution?

Answer 11

water moves out of the cell, causing the cell to shrivel up

Question 12

What may happen when a plant is placed in very hypertonic solution?

Answer 12

water moves out of the cell by osmosis and the vacuole and cytoplasm decrease in size. the cell membrane may pull away from the wall, causing the cell to become plasmolysed

Question 12

How do plant leaves and stems remain rigid?

Answer 12

turgor pressure - water moves in by osmosis, causing the vacuole to swell and the cytoplasm to press against the cell wall

Question 13

what is active transport?

Answer 13

the movement of molecules from a more dilute solution to a more concentrated solution against a concentration gradient, using energy from respiration

Question 14

how do plant root cells use active transport?

Answer 14

root hair cells use active transport to take up mineral ions from a more dilute solution in soils, ions such as magnesium and nitrates are required for healthy growth

Question 15

How is active transport used to absorb the products of digestion?

Answer 15

active transport is used to transport glucose from a lower concentration in the gut to a higher concentration in the blood. glucose is then transported to the tissues where it can be used for respiration