Photosynthesis in one sentence (5 marks)

Photosynthesis is a chemical reaction that takes place in the chloroplasts

in green plant cells, where light energy is used to convert carbon dioxide and

water into glucose and oxygen.

Specification Link

• Demonstrate an understanding of how limiting factors affect the rate of photosynthesis, including:

a) light intensityb) CO2 concentrationc) temperature• Investigate how factors, including the effect of

light intensity, CO2

Biggest Greenhouse in the UK

Why would farmers spend so much money building this greenhouse?

Rate of photosynthesis depends on the growing conditions.

Things that slow photosynthesis down are called limiting factors.

What are the limiting factors of photosynthesis?

What is the ideal combination of factors for the maximum rate of photosynthesis?

What is a limiting factor?

enough light

What will happen to the rate of photosynthesis if one of these factors is restricted?

The rate of photosynthesis will be below the maximum possible rate.

The restricted factor controls how quickly photosynthesis occurs and so limits the rate. It is

called the limiting factor.

enough carbon dioxide ideal temperature (not too hot or cold)

Photosynthesis and light – limiting factors

How does the amount of light affect the rate of photosynthesis on this labelled graph?

As the amount of light increases, so does the rate. The limiting factor is light.

light intensity

rate

of p

hoto

synt

hesi

s

Here, increasing the amount of light has no affect on the rate. The limiting factor is now carbon dioxide or temperature.

What must be increased for the rate to increase?

1

2

1

2

Photosynthesis and carbon dioxide – limiting factors

How does the amount of carbon dioxide affect the rate of photosynthesis on this labelled graph?

As the amount of carbon dioxide goes up, so does the rate. The limiting factor is carbon dioxide.

concentration of carbon dioxide

rate

of p

hoto

synt

hesi

s

Here, increasing the amount of carbon dioxide has no affect on the rate. Light or warmth is now the limiting factor.

What must be increased for the rate to increase?

1

21

2

Photosynthesis and temperature – limiting factors

How does temperature affect the rate of photosynthesis on this labelled graph?

1. As temperature increases, so does the rate because photosynthetic enzymes work best in the warmth. Here, the limiting factor is temperature.

temperature

rate

of p

hoto

synt

hesi

s

0oC 45oC

Most plant enzymes are destroyed at about 45°C. Here, photosynthesis stops and the rate falls to zero.What is the limiting factor?

1

2

1

2

Photosynthesis InvestigationIn this investigation, you are going to study the photosynthesis of pondweed (Elodea).

Using the apparatus shown in the diagram, the photosynthesis can be measured by the number of bubbles of oxygen produced by pondweed in a certain amount of time.

clamp

pondweed

sodium hydrogencarbonate

solution

bubbles of oxygen

test tube

beaker

Investigating limiting Factors

• Aim- To see how light intensity can affect the rate of photosynthesis.

Distance of Lamp Amount of Bubbles in 1 Minute

Extension- Write a conclusion for your experiment, if your experiment did not work very well then explain why you think this is and suggest possible improvements.