7 - Mass transport

Question 1

Describe the cohesion-tension theory of water transport in the xylem. (5)

Answer 1

Water lost from leaves through transpiration
Lowers water potential of mesophyll cells
Water pulled up xylem (creating tension)
Water molecules stick together by hydrogen bonds
Forming (continuous) water column
Adhesion of water (molecules) to walls of xylem

Question 2

What kind of protein is haemoglobin?

Answer 2

Quaternary

Question 3

Describe the structure of haemoglobin?

Answer 3

• 4 polypeptide chains
• Each contains one prosthetic haem group
• Each haem group binds to one oxygen

Question 4

What is the Bohr effect?

Answer 4

Haemoglobin’s oxygen affinity is inversely related to the concentration of carbon dioxide

A higher CO2 level causes the curve to shift right

Question 5

Describe the cooperative nature of haemoglobin.

Answer 5

The first oxygen to bind causes a change in structure which makes it easier for the second to bind. The second oxygen does the same to make to make the third easier to bind. The fourth oxygen is harder to bind due to collision theory.

Question 6

If a type of haemoglobin has a high affinity to oxygen, what does this mean?

Answer 6

Oxygen is more easily loaded and less easily unloaded. Therefore the curve is further to the left.

Question 7

Which blood vessel leaves the heart with deoxygenated blood?

Answer 7

Pulmonary artery

Question 8

Describe the movement of blood in the human circulatory system.

Chambers, organs, vessels, valves

Answer 8

Deoxygenated blood enters right atrium through vena cava
Enters right ventricle through atrioventricular valve
Leaves through semi-lunar valve and pulmonary artery to lungs
Oxygenated blood enters left atrium through pulmonary vein
Enters left ventricle through atrioventricular valve
Leaves through semi-lunar valve and aorta to body

Question 9

Describe atrial systole and its associated pressure changes.

Answer 9

Atria contract
Blood forced into ventricles
Pressure in ventricles increases
Atrioventricular valves close

Question 10

Describe ventricular systole and its associated pressure changes.

Answer 10

Ventricles contract
Pressure in ventricles increases further, higher than pulmonary artery/aortic pressure
Blood forced into vessels

Question 11

Describe diastole.

Answer 11

Chambers relax
Blood enters heart

Question 12

Describe the structure of arteries and arterioles related to their function.

Answer 12

Thick muscle layer to withstand high pressure
Thick elastic layer to maintain high blood pressure
Narrow lumen to maintain high blood pressure

Question 13

Describe the structure of arteries and arterioles related to their function.

Answer 13

Thick muscle layer to withstand high pressure
Thick elastic layer to maintain high blood pressure
Narrow lumen to maintain high blood pressure

Question 14

Describe the structure of veins.

Answer 14

Thin smooth muscle layer
Thin elastic layer
Wider lumen
Valves prevent backflow

Question 15

What is a capillary bed?

Answer 15

A network of capillaries

Question 16

Describe the structure of capillaries.

Answer 16

Thin walls
Narrow lumen
Walls have pores which allow blood plasma to leak out and form tissue fluid

Question 17

Which vessel transports water and mineral ions through a plant?

Answer 17

Xylem

Question 18

What is transpiration?

Answer 18

Evaporation of water from leaves creating tension

Question 19

Which vessel transports organic substances in plants?

Answer 19

Phloem

Question 20

What factors is the rate of transpiration affected by?

Answer 20

Light, temperature, humidity, wind

Question 21

What mechanism moves organic substances from source nodes to sink nodes?

Answer 21

Transpiration

Question 22

Mass flow + ringing + tracers

Answer 22

Need to make!!

Question 23

Describe the mass flow hypothesis.

Answer 23

1. Sucrose actively transported into phloem
2. By companion cells
3. Lowers water potential in phloem so water enteres by osmosis
4. High pressure
5. Mass flow towards sink
6. At sink, sugars are unloaded