Gas Exchange

Question 1

What’s an amoeba?

Answer 1

Single cellular organism that can alter its shape

Question 2

What’s Fick’s Law?

Answer 2

Rate of diffusion= (SA x difference in concentration)/length of diffusion path

Question 3

Process of gas exchange in insects

Answer 3

• Air enters through holes called spiracles
• Oxygen diffuses down concentration gradient along trachea
• Trachea are closely surrounded by cells which direct diffusion
• The trachea branch into smaller tubes named tracheoles which deliver oxygen to respiring cells

Question 4

Name the 3 methods of moving gases in the tracheal system

Answer 4

• Diffusion as when cells respire, oxygen is used up and carbon dioxide is produced, creating a concentration gradient from the tracheoles to the atmosphere
• Mass transport; an insect contracts and relaxes their abdominal muscles to move gases on mass
• Respire anaerobically (when in flight) to produce lactate; lowers water potential of cells so water moves from tracheoles into cells via osmosis, decreasing volume in the tracheoles so more air can be drawn in

Question 5

Insect adaptations for efficient gas exchange

Answer 5

• Large number of tracheoles; large surface area
• Tracheoles have thin walls; short diffusion distance
• Tracheae provide tubes full of air; faster diffusion through the air to gas exchange surface

Question 6

Insect adaptations to prevent water loss

Answer 6

• Small SA to volume ratio
• Waterproof exoskeleton
• Spiracles which can open and close to reduce water loss

Question 7

3 features of a gas exchange surface

Answer 7

• Large SA to volume ratio
• Short diffusion distance
• Maintained a concentration gradient

Question 8

Fish adaptations for efficient gas exchange

Answer 8

• Filaments and lamellae; large SA to volume ratio
• Thin epithelium; short diffusion distance
• Counter current flow; maintains concentration gradient

Question 9

Describe the counter current exchange principle

Answer 9

When water flows over the gills in the opposite direction to the flow of blood in the capillaries

Question 10

Advantage of the counter current exchange principle

Answer 10

Ensures concentration gradient is maintained across entire length of the gill lamellae

Question 11

Function of palisade mesophyll

Answer 11

Where photosynthesis mainly occurs in the leaf

Question 12

What happens in the stomata?

Answer 12

Oxygen diffuses out and carbon dioxide diffuses in

Question 13

How would a plant reduce water loss?

Answer 13

-Guard cells control the opening and closing of the stomata

• Small SA to volume ratio
• Waxy cuticle to prevent evaporation
• Hairy leaves reduce water potential gradient

Question 14

Process of inspiration

Answer 14

• External intercostal muscles contracts, internal intercostal muscle relaxes
• Ribs are pulled upwards and outwards, whilst the diaphragm contracts and flattens
• This increases thoracic volume, decreasing air pressure so air is forced into the lungs

Question 15

Process of expiration

Answer 15

• External intercostal muscles relax, external intercostal muscles contract
• Ribs are pulled downwards and inwards, whilst the diaphragm relaxes and is pushed back into a dome shape
• This decreases thoracic volume, increasing air pressure, so air is forced into the atmosphere

Question 16

What happens in the alveoli?

Answer 16

Place where oxygen is absorbed into the blood

Question 17

Adaptions of alveoli

Answer 17

• Very large surface area; higher rate of diffusion
• Thin alveolar epithelium; short diffusion distance
• Surrounded by network of capillaries; short diffusion distance