CB6a paper 2

Question 1

Equation for photosynthesis

Answer 1

Carbon dioxide + water -> glucose + oxygen
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Energy is transferred by light

Question 2

Where does photosynthesis occur?

Answer 2

In the chloroplasts which contains chlorophyll which traps energy transferred by light

Question 3

Is photosynthesis an exothermic or endothermic reaction

Answer 3

Endothermic

Question 4

What do glucose molecules form when they link together

Answer 4

A polymer called starch

Question 5

How long does starch stay the chloroplasts

Answer 5

Until photosynthesis ends

Extra info
The starch is then broken down into simpler substances which are moved into the cytoplasm and used to make sucrose (another type of sugar molecule). Sucrose is then transported around the plant.

Question 6

Sucrose is transported around the plant and used to make…

Answer 6

Starch
Other molecules for the plant
Glucose for respiration (to release energy)

Question 7

Where are the palisade cells located

Answer 7

Near the top of the leaves and contain many chloroplasts

Question 8

Leaf adaptations. Leaves contain microscopic pores called

Answer 8

Stomata (singular =stoma)

Question 9

What does stomata allow

Answer 9

Carbon dioxide to diffuse into the leaf

Question 10

Sucrose is transported around the plant and used to make…

Answer 10

Starch
Other molecules for the plant
Glucose for respiration (to release energy)

Question 11

Where are the palisade cells located

Answer 11

Near the top of the leaves and contain many chloroplasts

Question 12

Leaf adaptations. Leaves contain microscopic pores called

Answer 12

Stomata (singular =stoma)

Question 13

What does stomata allow

Answer 13

Carbon dioxide to diffuse into the leaf

Question 14

What are the stomata opened and closed by

Answer 14

Specialised guard cells

Question 15

When does the stoma open

Answer 15

In the light when water flows into pairs of guard cells, making them rigid (allowing the stoma to open)

Question 16

Positive of leaves thickness

Answer 16

They are thin, allowing carbon dioxide to not have to diffuse far into the leaf before reaching the callers that need it

Question 17

What is a limiting factor

Answer 17

A factor that prevents a rate increasing

Question 18

State three limiting factors for photosynthesis

Answer 18

Carbon dioxide concentration
Temperature
And light intensity

Question 19

The water absorbed by plant roots is used for

Answer 19

Carrying dissolved mineral ions
Photosynthesis
Keeping cells rigid
Cooling the leaves

Question 20

Water passes into the cytoplasm of root hair cells by

Answer 20

Osmosis

Question 21

Transpiration

Answer 21

The flow of water into a root, up the stem and out of the leaves

Question 22

Xylem vessels

Answer 22

Tiny continuous pipes leading from plants roots up into its leaves

Question 23

Water is pulled up the xylem vessels in the stem, as

Answer 23

water evaporates from the xylem vessels in the leaves

Question 24

Fact

Answer 24

The concentration of water vapour in the air spaces is higher inside than outside. So water molecules diffuse down the concentration gradient out of the leaf. A bigger difference between the gradients makes the gradient steeper, thus increasing the rate of diffusion. So any factor that affects the concentration of water outside the stomata, will increase transpiration. These factors are:
Wind (moves water molecules away from stomata)
Low humidity in air (less water vapour )

Question 25

Four factors that increase transpiration are:

Answer 25

Wind
Low humidity levels
Higher temperature
Greater light intensity

Question 26

Why are xylem vessels rigid

Answer 26

Because they have thick side walls and rings of lignin. So water pressure in the cells does not burst them.

Question 27

Rigid xylem helps to support…

Answer 27

The plant