Organisation

Question 1

A leaf is an organ made of tissues. What is a tissue?

Answer 1

a group of cells with a similar structure / function

Question 2

Describe how you would test a sample of food to show it contains protein.
Give the reason for any safety precautions you would take.

Answer 2

grind up the food
add Biuret reagent to food (sample)
protein turns solution from blue to purple / lilac

Safety:
wear goggles to protect eyes
clean up spills immediately
Biuret is an irritant / corrosive / poisonous

Question 3

Describe the route taken by oxygenated blood from the lungs to the body cells.

Answer 3

(blood) travels through (the) pulmonary vein
(blood) enters left atrium
(blood) enters (the) left ventricle
(blood) leaves the heart via / through (the) aorta

Question 4

Explain how the villi and the alveoli are adapted to absorb molecules into the bloodstream.

Answer 4

-both have a large surface area
villi have many microvilli, alveolar walls are not flat / are folded to maximise diffusion (of gases) / absorption of (food) molecules
-both have many capillaries / good blood supply / capillaries near the surface, to maintain concentration / diffusion gradient
-both have thin walls / walls that are one cell thick / one cell thick surface, to provide a short diffusion distance (for molecules to travel)
villi have many mitochondria, to provide energy for active transport (of food molecules)

Question 5

Enzymes speed up chemical reactions.
Explain how amylase breaks down starch.

Answer 5

starch / substrate fits into active site (of enzyme)
shape of active site is unique / complementary to substrate
bonds between sugar molecules are broken

Question 6

When light intensity is high potassium ions are moved into the guard cells.
Describe how the movement of potassium ions into the guard cells causes the stoma to open.

Answer 6

(potassium) ions make cell more concentrated / less dilute
water moves into the (guard) cell by osmosis
cell swells (so stoma opens)
as inner wall is less flexible than outer wall

Question 7

Describe how the root hair cells are adapted for absorption

Answer 7

have (many root) hairs
(which) give a large surface area (for absorption)

Question 8

Explain why translocation is important to plants

Answer 8

sugars are made in the leaves
so they need to be moved to other parts of the plant for respiration / growth /storage

Question 9

Explain why active transport is necessary in root hair cells.

Answer 9

for movement of minerals / ions against their concentration gradient