Exchange Of Materials

Question 1

Describe how phospholipids are arranged in a plasma membrane.

Answer 1

The hydrophobic amino acid tails face onwards and the hydrophilic heads face outwards.✔️

Question 2

Cells that secrete enzymes contains a lot of RER and Golgi apparatus;

i) describe how the RER is involved in the production of enzymes.
ii) describe how the Golgi apparatus is involved in the secretion of enzymes.

Answer 2

i) RER has ribsomes for protein synthesis

ii) they modify and package the enzymes into vesicles which are passed to the surface of the cell ✔️✔️

Question 3

Give two structures in a kidney cell that have adapted for rapid absorption of glucose and explain how it’s adapted.

Answer 3

1. Microvilli - to create a large surface area for diffusion
2. Lots of mitochondria by the microvilli - provides ATP for active transport ✔️✔️

Question 4

The absorption of glucose into the cell leads to the movement of water into the cell. Explain how.

Answer 4

Glucose will lower the water potential of the cell so the water can move in via osmosis ✔️✔️

Question 5

During an experiment to measure osmosis in strawberries, they cut the strawberries into slices, why?

Answer 5

• allow for more cells to be exposed creating a large surface area for absorption.
• increases water loss

Question 6

Explain the structure of gills.

Answer 6

• Made of gill filaments
• many Gill filaments are lamellae
• lamellae increase surface area
• counter current flow✔️

Question 7

Explain counter current flow

Answer 7

•Blood that is already well oxygenated meets with water which has max conc of O2 therefore diffusion from water to blood takes place✔️

Question 8

Explain why countercurrent flow is so effective.

Answer 8

• the diffusion gradient for oxygen uptake is maintained across the whole Gill lamallae ✔️

Question 9

Explain the difference between counter current and parallel flow.

Answer 9

80% of oxygen is available in counter current whereas 50% is available in parallel ✔️