Exchange and Transport

Question 1

What maintains the diffusion gradient of gases in + out of a cell?

Answer 1

Mitochondria have lowest conc of O2 + highest conc of CO2

Question 2

Why do large organisms have internalized gas exchange systems?

Answer 2

They have small surface area to volume ratio

Question 3

Why don’t small organisms have internal exchange systems?

Answer 3

Have a large surface area to volume ratio

Question 4

What three ways do insects minimize water loss?

Answer 4

1. Waterproof shell
2. Small surface area
3. Close spiracles

Question 5

How does Oxygen reach the cells of an

Insect?

Answer 5

• enter into spiracle
• diffuses through trachea + tracheoles down conc gradient
• abdominal muscles contract for ventilation of air to maintain conc gradient

Question 6

How is diffusion kept efficient between the tracheoles + surrounding cells?

Answer 6

Every cell very short distance from tracheoles

Question 7

Describe the two main structures in fish gills

Answer 7

Gill filaments + lamellae on them

Question 8

What is countercurrent flow?

Answer 8

Water flows in opposite direction to blood in the gill lamellae

Question 9

What is the purpose of the gill lamellae?

Answer 9

Increase surface area for gas exchange

Question 10

How is a steep diffusion gradient maintained in fish?

Answer 10

Ventilation of oxygen

Mass transport of O2 carried away from gills by blood

Question 11

Explain how the countercurrent flow creates a diffusion gradient across the whole length of the gill lamellae

Answer 11

• O2 blood meets water that has max O2 = diffusion

- no O2 blood meets water that still has some O2 left = diffusion

Question 12

What would happen if the blood + water flowed in the same direction across the gill lamellae?

Answer 12

Gas exchange reaches equilibrium + diffusion only occurs across part of gill lamellae

Question 13

Why is countercurrent flow important in the gas exchange in fish?

Answer 13

Maintains a concentration gradient for diffusion across the whole length of gill lamellae

Question 14

What is the purpose of the tracheoles?

Answer 14

Thin + permeable walls = short diffusion distance to surrounding cells

Question 15

Oxygen still diffuses into the leaf when it is dark, why?

Answer 15

It’s constantly being used by cells in respiration

Question 16

Why are the diffusion gradients maintained in the leaf?

Answer 16

Mitochondria respiring + chloroplasts photosynthesis

Question 17

How does the structure of the leaf allow for efficient gas exchange?

Answer 17

• Cells close to external air, flat leaf

- diffusion in gas spaces = quicker than in water

Question 18

Why does the leaf have no specialized gas exchange system?

Answer 18

Large surface area to volume ratio

Question 19

What adaptations does a leaf have for rapid diffusion?

Answer 19

• thin + flat = SA + cells not far from external air
• stomata on underside of leaf
• interconnecting air spaces in mesophyll

Question 20

What do plants do to control gaseous exchange and water loss?

Answer 20

Guard cells close stomata

Question 21

What two factors determines whether a large organism has an internalized gas exchange network?

Answer 21

• if the SA:V ratio is small

- how active organism is

Question 22

What are 3 features of transport systems in large organisms?

Answer 22

1. Blood to carry materials
2. Tubular vessels that contain blood + distribute
3. Valves to ensure movement in one direction

Question 23

Why does the oxygenated blood return back to the heart from the lungs instead of just circulating round the rest of the body?

Answer 23

Low pressure after lungs = too slow

Question 24

Why do the substances + gases in the blood need to be delivered to cells in mammals quickly?

Answer 24

Mammals have a high body temp => high metabolism

Question 25

What basic structure of layers do all arteries, arterioles and veins have + what is the purpose of each layer?

Answer 25

- tough outer layer: pressure - muscle: contract - elastic: stretch/recoil, pressure - endothelium: friction - lumen: carries blood

Question 26

Which vessel carries out exchange of material?

Answer 26

Capillaries

Question 27

How do the proportions of an artery differ to veins and relate to its function?

Answer 27

- thicker muscle layer than veins = constrict blood flow to arterioles - thicker elastic layer than veins = stretch + recoil + smooth/high pressure smooth - thick wall = pressure bursting - no valves = high pressure

Question 28

How does the structure of an arteriole differ to an artery + link to its function?

Answer 28

- thicker muscle layer: vasoconstriction | - thinner elastic layer: pressure is lower

Question 29

How does the structure of a vein link to its function?

Answer 29

- thin muscle layer: carrying blood away from tissues - thin elastic layer: pressure too low - thin wall: flattened easily = aid flow of blood - valves: prevent back flow

Question 30

How does the structure of the capillaries link to their function?

Answer 30

- endothelium layer = short diffusion distance - branched = SA - narrow diameter = permeate tissues - narrow lumen = blood cells flat - spaces in endothelial = white blood cells escape

Question 31

Name 3 substances tissue fluid contains

Answer 31

Amino acids, glucose, oxygen

Question 32

What is hydrostatic pressure?

Answer 32

- Pressure created by the blood moving from the arteries, arterioles, to capillaries - forces tissue fluid out of blood

Question 33

What two forces oppose the movement of tissue fluid out of the capillaries?

Answer 33

- hydrostatic pressure of tissue fluid | - lower water potential of blood (few proteins)

Question 34

What type of filtration occurs at the arteriole end of the capillary?

Answer 34

Ultrafiltration (large molecules left in blood)

Question 35

Why does tissue fluid return to the venous end of the capillary?

Answer 35

- lower hydrostatic pressure inside capillary than surrounding tissue fluid - low water potential because of many proteins in blood = gradient = osmosis

Question 36

How is the composition of the tissue fluid different when it returns to the capillaries?

Answer 36

CO2 + waste materials from cells

Question 37

What two forces move the tissue fluid through the lymphatic system to the heart?

Answer 37

Hydrostatic pressure + contraction body muscles

Question 38

Why don't red blood cells + plasma proteins move out of the capillaries?

Answer 38

Too large