Gcse Biology Paper 1 Photosynthesis

Question 1

What is photosynthesis?

Answer 1

-the process by which plants synthesise
Glucose using light energy from the sun

• light energy is converted into chemical energy

Question 2

Where do photosynthesis take place

Answer 2

• Within chloroplasts in leaf palisade cells

- they contain chlorophyll, a pigment which absorbs light energy

Question 3

Word equations for photosynthesis (word and symbol)

Answer 3

Light
Carbon dioxide + water —> glucose +oxygen

6CO2 + 6H2O → C6H12O6 + 6O2.

Question 4

Is photosynthesis exothermic or endothermic reaction? Why?

Answer 4

Endothermic- energy is transferred from the environment to chloroplasts by light

Question 5

How can you show that a plant gives off oxygen during photosynthesis ?

Answer 5

• use a water plant , collect gas bubbles produced during photosynthesis.
• the gas will relight a glowing splint as it contains oxygen

Question 6

Examples of leaf adaptions which maximise the rate of photosynthesis

Answer 6

• Broad leaves- maximises surface area
• Thin leaves- short diffusion path
• chlorophyll present- trap light energy
• Veins - transports water to leaves via xylem, remove photosynthesis products via phloem
• air spaces- allows CO2 to enter and O2 to leave
• Guard cells- control opening of stomata for gaseous exchange and prevent water loss

Question 7

Four factors that affect the rate of photosynthesis

Answer 7

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

Question 8

How does temperature affect the rate of photosynthesis?

Answer 8

Increasing the temperature increases the rate of photosynthesis as the kinetic energy of particles is increased.

• the rate decreases past a certain temperature as enzymes become denatured

Question 9

How does light intensity affect the rate of photosynthesis

Answer 9

Increasing the light intensity increases the rate of photosynthesis until another factor becomes limiting

Question 10

How does carbon dioxide affect the rate of photosynthesis

Answer 10

Increasing the carbon dioxide concentration increases the rate of photosynthesis (until another factor becomes limiting)

-as CO2 is required to make gluecose

Question 11

How does the amount of chlorophyll affect the rate of photosynthesis?

Answer 11

-decreasing the amount of chlorophyll (e.g due to lack of magnesium) decreases the rate of photosynthesis as chlorophyll is required to absorb light energy

Question 12

What is limiting factor

Answer 12

An environmental factor which can restrict the rate of photosynthesis e.g light intensity

Question 13

Explain how you can calculate the rate of photosynthesis by measuring by oxygen production

Answer 13

• Set up bubble potometer apparatus (pondweed in a sealed tube of water,attached to a capillary tube and gas syringe).
• oxygen gas produced causes the bubble in the capillary tube to move. The distance moved by the bubble is used to calculate the volume of oxygen produced.

Question 14

How can farmers use their knowledge of limiting factors to increase their profits ?

Answer 14

They can control temperature, light intensity and CO2 concentration to achieve the fastest possible rate of photosynthesis ,leading to greater yield

Question 15

State the 5 uses of gluecose produced during photosynthesis

Answer 15

• Respiration
• Starch for storage
• Cellulose for strength
• amino acids and protein synthesis (combined with nitrates)
• Lipids for energy storage in seeds

Question 16

relationship between the distance of a light source from a plant and light intensity?

Answer 16

Inverse square law -light intensity = 1/ distance 2