Photosynthesis

Question 1

What is photosynthesis?

Answer 1

A chemical reaction that takes place inside photosynthetic organisms (e.g. plants, algae) converting light energy into chemical energy

Question 2

Write the word equation for photosynthesis

Answer 2

carbon dioxide + water → glucose + oxygen

Question 3

Write the symbol equation for

photosynthesis

Answer 3

6CO2
+ 6H2O → C6H12O6
+ 6O2 (CHECK GOOGLE IF UNSURE)

Question 4

Why is photosynthesis important?

Answer 4

It produces glucose which has a wide range of uses:

● Used in respiration to release energy

● Converted to starch and stored - broken down to glucose when the
plant requires energy

● Used to make complex organic molecules which are used for growth,
making up an organism’s biomass (transferred through food chains)

Question 5

Where does photosynthesis take place?

Answer 5

Within chloroplasts

Question 6

What type of reaction is photosynthesis?

Answer 6

An endothermic reaction that takes in

energy (in the form of light)

Question 7

What is chlorophyll?

Answer 7

A green pigment found in chloroplasts that

absorbs light

Question 8

Describe the two main stages of

photosynthesis

Answer 8

1. Chlorophyll absorbs light energy which is used to split
   water into oxygen gas (waste product) and hydrogen ions
2. Carbon dioxide combines with hydrogen ions to form
   glucose

Question 9

What factors affect the rate of

photosynthesis?

Answer 9

● Temperature
● Light intensity
● Carbon dioxide concentration

Question 10

What is a limiting factor?

Answer 10

Avariable that limits the rate of a

particular reaction

Question 11

Explain how temperature affects the rate

of photosynthesis

Answer 11

● Higher temperatures provide more KE for enzymes involved in
photosynthesis so the rate increases as temperature rises
● The optimum temperature is usually 25°C
● If the temperature becomes too high (around 45°C) enzymes
become denatured and the rate of photosynthesis decreases

Question 12

Draw a graph to show the effect of increasing

temperature on the rate of photosynthesis

Answer 12

https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FBiology%2FGCSE%2FNotes%2FEdexcel%2F6-Plant-Structures-and-their-Functions%2FFlashcards%2FFlashcards%2520-%2520Topic%25206%2520Photosynthesis%2520-%2520Edexcel%2520Biology%2520GCSE.pdf

25

Question 13

Explain how light intensity affects the rate of

photosynthesis

Answer 13

Rate of photosynthesis is directly proportional to
light intensity ∴ as light intensity increases, the
rate of photosynthesis increases

Question 14

Why does the rate of photosynthesis
eventually plateau even if light intensity
continues to increase?

Answer 14

Another factor (temperature or CO2
concentration) becomes limiting

Question 15

Draw a graph to show the effect of light

intensity on the rate of photosynthesis

Answer 15

https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FBiology%2FGCSE%2FNotes%2FEdexcel%2F6-Plant-Structures-and-their-Functions%2FFlashcards%2FFlashcards%2520-%2520Topic%25206%2520Photosynthesis%2520-%2520Edexcel%2520Biology%2520GCSE.pdf

31

Question 16

How can the effect of light intensity on the rate of

photosynthesis be measured in the lab?

Answer 16

Using a light meter
● Using the inverse square law where:

Light Intensity ∝ 1/distance^2

Question 17

Why does the rate of photosynthesis decrease as

the distance from a light source increases?

Answer 17

Light intensity is inversely proportional to the square
of the distance from the light source. Thus, as the
distance increases, light intensity decreases and the
rate of photosynthesis decreases.

Question 18

Explain how carbon dioxide concentration affects the

rate of photosynthesis

Answer 18

As carbon dioxide concentration increases,

the rate of photosynthesis increases

Question 19

Why does the rate of photosynthesis eventually
plateau even if CO2
concentration continues to
increase?

Answer 19

Another factor (temperature or light
intensity) becomes limiting.

Question 20

Draw a graph to show the effect of carbon dioxide

concentration on the rate of photosynthesis

Answer 20

https://www.physicsandmathstutor.com/pdf-pages/?pdf=https%3A%2F%2Fpmt.physicsandmathstutor.com%2Fdownload%2FBiology%2FGCSE%2FNotes%2FEdexcel%2F6-Plant-Structures-and-their-Functions%2FFlashcards%2FFlashcards%2520-%2520Topic%25206%2520Photosynthesis%2520-%2520Edexcel%2520Biology%2520GCSE.pdf

41

Question 21

Which two organisms do photosynthesis?

Answer 21

Plants and Algae

Question 22

Where is the energy of a plant stored?

Answer 22

In the glucose formed through photosynthesis.

Question 23

Define biomass

Answer 23

The total mass of an organism (this is produced by plants and algae through photosynthesis)

Question 24

What is a polymer of glucose called formed during photosynthesis?

Answer 24

Starch

Question 25

What happens to the starch after photosynthesis stops?

Answer 25

They made into simpler substances, which are moved into the cytoplasm and used to make sucrose.

Question 26

What is the purpose of sucrose?

Answer 26

Transported around the plant and used to make:

• starch (in a storage organ such as a potato)
• other molecules for the plant (such as cellulose, lipids or proteins)
• glucose for respiration