2d - Movement into and out of cells

Question 1

What is the definition of ‘diffusion’

Answer 1

Movement of molecules from an area of high concentration to an area of low concentration

Question 2

What is the definition of ‘osmosis’

Answer 2

Movement of water molecules from an area of high concentration to an area of low concentration through a partially permeable membrane

Question 3

What is the definition of ‘active transport’

Answer 3

Movement of molecules and substances against the concentration gradient. This process requires energy from respiration.

Question 4

What are the four factors which affect the rate of movement into and out of cells?

Answer 4

• Surface area / volume ratio - Temperature - Distance - Concentration gradient

Question 5

How does the SA/vol ratio affect the rate of movement into and out of cells?

Answer 5

Larger the surface area to volume ratio, the faster the rate of diffusion since there’s larger surface area for substances to move through

Question 6

How does the Temperature affect the rate of movement into and out of cells?

Answer 6

Higher the temperature, faster the rate of diffusion since molecules have more kinetic energy, they collide more against the cell membrane

Question 7

How does the Distance affect the rate of movement into and out of cells?

Answer 7

Short the diffusion distance, faster the rate of diffusion. eg. Blood capillaries have one-cell thick walls for higher rate of diffusion

Question 8

How does the concentration gradient affect the rate of movement into and out of cells?

Answer 8

The greater the concentration gradient, the faster the rate of diffusion. This is because there is a bigger difference in the number of particles causing more collisions.

Question 9

Which movement requires a semi-permeable membrane?

Answer 9

Osmosis

Question 10

Which movement requires energy?

Answer 10

Active transport (against the concentration gradient)

Question 11

Which is the only movement which goes against the concentration gradient?

Answer 11

Active transport

Question 12

How can osmosis be investigated in a non-living organism?

Answer 12

Visking tubing:

Question 13

How can osmosis be investigated in a living organism?

Answer 13

Potato cylinders:

Question 14

How will a plant cell look like in pure water?

Answer 14

Swollen up:

Question 15

How will a plant cell look like in a solution that equals the concentration inside the cell?

Answer 15

Question 16

How will a plant cell look like that is in a solution that is more concentrated than the inside of the cell?

Answer 16

Question 17

How does a red blood cell look like in pure water?

Answer 17

Question 18

How does a red blood cell look like in a solution with an equal concentration to the inside of the cell?

Answer 18

Question 19

How does a red blood cell look like in a solution that is more concentrated than the inside of the cell?

Answer 19

Question 20

Why does a red blood cell explode in pure water?

Answer 20

Because water keeps entering the cell through osmosis, swelling the volume of the cytoplasm until it bursts.

Question 21

Why do the animal and plant cell keep the same shape and volume when placed in a solution of equal concentration?

Answer 21

Because there is no net movement of water (by osmosis) into the cell

Question 22

Why does the plant cell become flaccid when placed in a solution that is more concentrated than the inside of the cell?

Answer 22

Because water is lost from the cell by osmosis, resulting in the cell not having enough water to keep its turgidity.