T1 transport in cells

Question 1

what is diffusion

Answer 1

net movement of particles from an area of higher concentration to an area of lower concentration

Question 2

three main factors affecting the rate of diffusion

Answer 2

concentration gradient - larger, faster

temperature - higher, faster

surface area - larger, faster

Question 3

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

Answer 3

lungs: O2 diffuses into blood from the lungs and CO2 diffuses 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

large surface area to volume ratio - maximises the rate of diffusion of molecules to meet the organism’s needs

Question 5

how is surface area to volume calculated

Answer 5

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

volume = length x width x depth

ratio = surface area : volume

Question 6

what 4 factors increase the effectiveness of a gas exchange surface

Answer 6

large surface area

thin membrane (short diffusion path)

efficient blood supply

ventilation

Question 7

what is osmosis

Answer 7

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

concentrations of the external and internal solutions are the same

Question 9

what is meant when a solution is hypertonic to a cell

Answer 9

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

Question 10

what is meant when a solution is hypotonic to a cell

Answer 10

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

Question 11

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

Answer 11

water moves into the cell, causing it to burst

Question 12

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

Answer 12

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

Question 13

how do plant leaves and stems remain rigid

Answer 13

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

Question 14

what may happen when a plant cell is placed in a very hypertonic solution

Answer 14

water moves out of the cell by osmosis and the vacuole and cytoplasm decrease in size

cell membrane may pull away from the cell wall, causing the cell to become plasmolysed

Question 15

what is active transport

Answer 15

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

Question 16

how do plant root hair cells use active transport

Answer 16

take up mineral ions from a more dilute solution in soils.

ions such as magnesium and nitrates are required for healthy growth

Question 17

how is active transport used to absorb the products of digestion

Answer 17

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 in respiration