3.1 Specialised Exchange Surfaces

Question 1

All organisms need to do what?

Answer 1

Exchange with their environment

Question 2

All cells need to take in what?

Answer 2

Oxygen and glucose for aerobic respiration and other metabolic processes

Question 3

Cells also need to excrete what?

Answer 3

Waste products like carbon dioxide and urea

Question 4

The smaller an organism the greater it’s what?

Answer 4

Surface area to volume ratio

Question 5

The greater the surface area to volume ratio the greater the efficiency of what?

Answer 5

Diffusion of gases

Question 6

Why do unicellular organisms not need specialised exchange surfaces?

Answer 6

Substances can diffuse directly in or out of their cell surface membrane
Small diffusion distance
Large sa:v

Question 7

In multicellular organisms why is diffusion across the outer membrane too slow?

Answer 7

Large diffusion distance
Small sa:v
High metabolic rate - need constant supply of glucose and O2

Question 8

What do multicellular organisms need?

Answer 8

Specialised exchange surfaces

E.g. Alveoli in lungs

Question 9

What are the features of an efficient exchange surface?

Answer 9

Large surface area
Thin surface
Concentration gradient (blood supply/ventilation)
Moist surface

Question 10

Why do most multicellular organisms respire aerobically?

Answer 10

Higher energy requirements and aerobic provides 19x more ATP than anaerobic

Question 11

Give an example of a exchange surface with large sa:

Answer 11

Root hairs

Gives roots large sa increasing water absorption and mineral ions