Test 3 (Gas Exchange, Digestion, Water And Ions)

Question 1

Suggest and explain two xerophytic features the leaves of a plant may have.

Answer 1

Thick cuticle to increase diffusion distance (smaller water loss)
Hair like strands to capture moist air

Question 2

Give two reasons why it was important that the student counted the number of stomata in several parts of each leaf piece

Answer 2

Some parts may have a higher number of stomata than others
They would get a mean average to compare certain areas of the leaf tissue

Question 3

Name the structure through which gasses enter and leave the body of an insect

Answer 3

Spiracles

Question 4

Name the small tubes that carry oxygen directly to and from the cells of an insect

Answer 4

Trachioles

Question 5

Explain the movement of oxygen into the gas exchange system of an insect when it is at rest

Answer 5

Spiracles open and oxygen diffuses in
Due to steep conc gradient

Question 6

Describe a biochemical test that could be performed on a sample of food to determine wether it contained triglycerides

Answer 6

Ethanol test
Dissolve substance in ethanol and add water
White colour indicates triglycerides

Question 7

How do chylomicrons leave the epithelial cell

Answer 7

By exocytosis
Because it is too large to leave by other methods

Question 8

Explain five properties of water that makes it important for organisms

Answer 8

(1) A metabolite in respiration
(2) A solvent so substances can be transported
(3) High specific heat capacity so buffers temp changes
(4) High latent heat of vaporisation so provides cooling affect
(5) Cohesion between water molecules produces surface tension supporting small organisms