transport in cells

Question 1

what is diffusion

Answer 1

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

Question 2

what three main factor affect the rate of diffusion

Answer 2

1. concentration gradient (larger gradient, faster diffusion)
2. temperature (higher temp - faster diffusion)
3. surface area (larger sa - faster diffusion)

Question 3

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

Answer 3

lungs: oxygen diffused into the blood from the lungs and carbon dioxide diffused into the lungs from the blood, both down their concentration gradient.
kidney: urea diffuses from cells into blood plasma so it can be excreted in urine.

Question 4

how are single celled organisms adapted for diffusion

Answer 4

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

Question 5

what four factors increase the effectiveness of a gas exchange surface

Answer 5

1. large surface area
2. thin membrane (short diffusion path)
3. efficient blood supply (animals)
4. ventilation (animals)

Question 6

what is omosis?

Answer 6

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

Question 7

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

Answer 7

the concentrations of the solutions externally and internally are the same

Question 8

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

Answer 8

the concentration of the external solution is lower than that of internal solution

Question 9

what may happen when an animal cell is placed in a hypotonic solution

Answer 9

water moves into the cell, causing it to burst

Question 10

what may happen when an animal cell is placed in a very hypotonic solution

Answer 10

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

Question 11

how do plant leaves and stems remain rigid

Answer 11

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

Question 12

what may happen when an plant cell is placed in a very hypotonic 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 cell wall, causing the cell to become plasmolysed

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 hair 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 the transported to the tissues where it can be used in respiration.