B10 Photosynthesis

Question 1

who can carry out photosynthesis

Answer 1

green plants and algae

Question 2

photosynthesis equation

• endo or exothermic, why?

Answer 2

carbon dioxide + water —light energy—> glucose + oxygen

• endothermic (energy transferred from the environment when light is absorbed by chlorophyll)

Question 3

photosynthesis process

Answer 3

carbon dioxide taken in by leaves, water taken up by roots
chlorophyll traps the light energy needed for photosynthesis
the energy is used to convert the carbon dioxide and water into glucose

Question 4

limiting factors of photosynthesis

Answer 4

temperature, light intensity, carbon dioxide concentration, amount of chlorophyll

Question 5

interaction of limiting factors

Answer 5

Question 6

inverse square law

Answer 6

as distance from light source increase, light intensity decreases

light intensity prop. to 1/distance^2

Question 7

uses of glucose produced in photosynthesis

Answer 7

converted into insoluble starch for storage (in leaves, tubers and bulbs)
for respiration to release energy (can be used for active transport etc)
produce lipids for storage
produce amino acids for protein synthesis (nitrate ions also needed)
produce cellulose to strengthen cell walls

Question 8

C02 and photosynthesis

Answer 8

Question 9

light intensity and photosynthesis

Answer 9

Question 10

journey of carbon atom to becoming starch (6)

Answer 10

 diffuses through stomata
 into air spaces in leaf
 into plant cells / cell in the spongy mesophyll
 into chloroplasts
 joins / bonds with water / hydrogen and oxygen
 to make glucose
 glucose is converted to starch (for storage)

Question 11

three (3) reasons why plants convert glucose into starch

Answer 11

 starch provides a store of energy
 glucose is soluble and would affect movement of water
 into and out of plant cells by osmosis
 starch is insoluble and does not disturb plant’s water balance

Question 12

design an investigation to study the effect of light intensity on the rate of photosynthesis

Answer 12

Question 13

explain the role of chloroplasts in photosynthesis (3)

Answer 13

 contain chlorophyll
 which absorbs light energy
 reaction is endothermic
 used to break bonds between carbon dioxide and
water

Question 14

temperature and photosynthesis

Answer 14

Question 15

hydroponics

Answer 15

growing plants using a water-based nutrient solution instead of soil

allow the grower to optimise mineral
ions given to plants. Mineral ions are required to synthesise other essential molecules from the glucose produced during photosynthesis.