Mass Transport In Plants + Animals

Question 1

Name factors which reduce haemoglobin’s affinity for oxygen.

Answer 1

High CO2 concentration, lower pH, high temperature

Question 2

Describe the structure of arteries.

Answer 2

• thick muscular elastic walls which can recoil to maintain high blood pressure
• inner layer known as endothelium and is folded which allows it to recoil, regulate blood pressure in arteries
• branch out into smaller arterioles which transport blood into capillaries

Question 3

Describe how the structure of capillaries is adapted to provide short diffusion pathway.

Answer 3

• endothelium which is one cell thick+ narrow lumen providing short diffusion pathway
• also narrow lumen slows movement of blood allowing more time for diffusion, pushes red blood cells against capillary wall so shorter diffusion pathway

Question 4

Describe how else capillary structure is adapted to function.

Answer 4

• small gaps between cells allowing larger molecules to squeeze out making wall permeable
• form large networks known as capillary beds which provide large surface area for exchange

Question 5

Describe the formation of tissue fluid.

Answer 5

• high hydrostatic pressure at the arteriole end of capillaries so water and small molecules are forced out of the capillaries through pores down hydrostatic pressure gradient to form tissue fluid
• at venous end water potential in tissue fluid is higher that in the capillaries so water diffuses down concentration gradient back into capillaries.
• lymphatic system collects excess tissue fluid and returns it to the circulatory system

Question 6

What factors affect tissue fluid formation?

Answer 6

-high blood pressure leads to excess tissue fluid
- low protein concentration in blood, water potential gradient isn’t steep so less water re enters capillary by osmosis

Question 7

Describe ringing experiments.

Answer 7

• ring of bark including phloem is removed from a tree trunk
• region above the removed section begins to swell
• samples of liquid taken and analysed for sugar to prove that the removal of phloem has led to inhibition of transport of organic substances