transport in cells

Question 1

What is diffusion?

Answer 1

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

Question 2

What three main factors affect the rate of diffusion?

Answer 2

● Concentration gradient - larger gradient, faster
diffusion.
● Temperature - higher temperature, faster diffusion, particles have more kinetic energy, moving faster.
● Surface area - larger surface area, faster diffusion.

Question 3

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

Answer 3

● Lungs: oxygen diffuses into the 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 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 organism’s 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 concentrated solution through a semi 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 cell) solutions are the same.

Question 9

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

Answer 9

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

Question 10

What is meant when a solution is hypotonic to a cell?

Answer 10

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

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. The cell membrane may pull away from the cell wall,
causing the cell to become flaccid.

Question 15

What is active transport?

Answer 15

The 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

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 17

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

Answer 17

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 in
respiration.

Question 18

How have fish adapted to diffuse oxygen into their bodies?

Answer 18

oxygen rich water passes into their mouth, flows over gills, where the oxygen is transported into the blood stream.

Question 19

How do gills pass oxygen to the blood?

Answer 19

covered in fine filaments, where gas passes into and out of the blood. deoxygenated blood is passed into the filament. oxygen diffuses from the water into the blood, oxygenated blood returns to body.

Question 20

How are the filaments of a fish adapted to increase the rate of diffusion?

Answer 20

The filaments give the gills a massive surface area. they have a thin membrane to provide a short diffusion pathway. efficient blood supply, to take the blood away, ensuring the concentration gradient is always high.