Exchange

Question 1

How does an organism’s size relate to their SA:V ratio?

Answer 1

A larger organism typically has a lower SA:V ratio

Question 2

How do large organisms adapt to having a smaller SA:V ratio?

Answer 2

Changes that increase surface area
Body parts become larger (e.g. elephant ears)
Specialised gas exchange surface

Question 3

Name 3 features of an efficient gas exchange surface

Answer 3

1. Large surface area
2. Short distance
3. Steep concn gradient maintained by blood supply

Question 4

Describe the 3 main features of an insect’s gas transport system

Answer 4

Spiracles = holes that are open or closed for gas / water exchange
Trachea = large tubes supported by rings to prevent collapsing
Tracheoles = smaller branches dividing off the trachea

Question 5

Explain the process of gas exchange in insects

Answer 5

Gases move in / out trachea through spiracles
Diffusion gradient allows oxygen to diffuse into body tissue while carbon dioxide diffuses out
Muscle contractions in the trachea allows mass movement of air in / out

Question 6

Describe the 2 main features of a fish’s gas transport system

Answer 6

Gills = supported by arches along gill filaments stacked in piles
Lamellae = right angles to gill filaments which increases surface area (allows countercurrent exchange system)

Question 7

What is the countercurrent exchange system?

Answer 7

Where blood and water flow across the gill filaments in opposite directions

Question 8

Explain the process of gas exchange in fish

Answer 8

Fish opens mouth for water to flow
Fish closes mouth to increase pressure
Water passes over lamellae as oxygen diffuses into bloodstream
Carbon dioxide diffuses into water and out the gills

Question 9

Describe 3 adaptations of a leaf that allows for efficient gas exchange

Answer 9

1. Thin = short diffusion pathway + large SA:V ratio
2. Stomata = allows gases to easily enter
3. Air spaces = facilitates photosynthesis

Question 10

How do plants limit water loss via the stomata?

Answer 10

Guard cells allow them to open and close when needed to prevent water loss or let oxygen in

Question 11

Describe the 5 main features of the human gas exchange system

Answer 11

Nasal cavity = secretes mucus which traps dust / bacteria
Trachea = carries air to the bronchi
Bronchi = allows passage of air to bronchioles
Bronchioles = allow passage of air into alveoli
Alveoli = site of gaseous exchange

Question 12

Explain the process of inspiration

Answer 12

External intercostals contract (pulling ribs up and out)
Diaphragm contract + flattens
Thorax volume increases
Air pressure outside lungs > inside
Therefore air moves in

Question 13

Explain the process of exhalation

Answer 13

Internal intercostals contract (bringing ribs down and in)
Diaphragm relaxes and domes upwards
Thorax volume decreases
Air pressure outside lungs < inside
Therefore air moves out

Question 14

Define digestion

Answer 14

Hydrolysis of larger, insoluble molecules into smaller molecules that can be absorbed across cell membranes

Question 15

Which enzymes are involved in carbohydrate digestion and where are they found?

Answer 15

Amylase in the mouth
Maltase, sucrase and lactase in the membrane of the small intestine

Question 16

What happens to lipids before being digested?

Answer 16

Must be emulsified by bile salts produced in the liver

Question 17

What are the roles of the 3 enzymes involved in protein digestion?

Answer 17

Endopeptidases = break between specific amino acids in the middle of the polypeptide chain
Exopeptidases = break between specific amino acids at the end of the polypeptide chain
Dipeptidases = break dipeptides into amino acids

Question 18

Which molecules require co-transport?

Answer 18

Amino acids and monsaccharides

Question 19

Why do lipids not require co-transport?

Answer 19

Molecules are non-polar
Easily diffuse across the membrane of epithelial cells