RP4- Permeability of cell mem

Question 1

Suggest how the increase in temperature of the water caused the release of the red pigment from cells of the beatroot. (2)

Answer 1

• damage to cell-surface mem
• proteins denature
• ↑ fluidity of phospholipid bilayer

Question 2

The cells of beetroot contain a red pigment. A student investigated the effect of temperature on the loss of red pigment from beetroot. He put discs cut from beetroot into tubes containing water. He maintained each tube at a different temperature. After 25 minutes, he measured the percentage of light passing through the water in each tube.
The student put the same volume of water in each tube.
Explain why it was important that he controlled this experimental variable. (2)

Answer 2

• too much water–> ↓ conc. of pigment, ↑ light passes through
• so results are comparable

Question 3

The cells of beetroot contain a red pigment. A student investigated the effect of temperature on the loss of red pigment from beetroot. He put discs cut from beetroot into tubes containing water. He maintained each tube at a different temperature. After 25 minutes, he measured the percentage of light passing through the water in each tube.
Describe a method the student could have used to monitor the temperature of the water in each tube. (1)

Answer 3

Take readings during experiment using thermometer.

Question 4

In mammals, in the early stages of pregnancy, a developing embryo exchanges substances with its mother via cells in the lining of the uterus. At this stage, there is a high concentration of glycogen in cells lining the uterus.
Suggest and explain two ways the cell-surface membranes of the cells lining the uterus may be adapted to allow rapid transport of nutrients. (2)

Answer 4

1. folded mem- ↑ s.a.
2. large no. of** protein channels + carriers** for facilitated diffusion / co-transport
3. large no. of carrier proteins for A.T.

Question 5

Give 2 variables the student should control in her experiment with beetroot cynlinders. (2)

Answer 5

1. length & diameter/ s.a./ vol
2. time in solution

Question 6

How could you reduce the uncertainty of the experiment which uses a measuring cylinder to take a reading of 10cm3? (1)

Answer 6

use an instrument w/ smaller intervals