B8. Photosynthesis

Question 1

Define the term photosynthesis

Answer 1

The process by which plants use light energy to produce carbon compounds such as carbohydrates

Question 2

What is the energy conversion that occurs during photosynthesis?

Answer 2

Light energy into chemical energy

Question 3

What is the role of chloroplasts in photosynthesis?

Answer 3

The role of chloroplasts is to absorb light energy during photosynthesis

Question 4

How is glucose inside plant cells?

Answer 4

Respiration
Storage, in the form of starch
The production of cellulose cell wall
Conversion into lipids and amino acids

Question 5

What is the word equation for photosynthesis?

Answer 5

carbon dioxide + water ➡ glucose + oxygen

Question 6

What is the role of water in the photosynthesis equation?

Answer 6

Water is a reactant in photosynthesis. It reacts with carbon dioxide to produce glucose and oxygen

Question 7

What are the products of photosynthesis?

Answer 7

Glucose and oxygen

Question 8

What happens to oxygen in photosynthesis?

Answer 8

Oxygen is produced as a waste products and released from leaves via the stomata.

Question 9

What is the chemical formula for glucose?

Answer 9

C₆H₁₂O₆

Question 10

Define the term endothermic reaction

Answer 10

An endothermic reaction is a chemical reaction which absorbs energy from its surroundings e.g. photosynthesis absorbs light energy

Question 11

Is photosynthesis an exothermic or endothermic reaction?

Answer 11

Endothermic

Question 12

Define the term limiting factor in the context of photosynthesis?

Answer 12

A factor that limits the rate of photosynthesis

Question 13

What are the three main factors that limit the rate of photosynthesis

Answer 13

Temperature
Light intensity
Carbon dioxide concentration

Question 14

Why does the rate of photosynthesis slow down at low temperatures?

Answer 14

Photosynthesis occurs slowly at low temperatures because molecules have little kinetic energy. This means that fewer successful collisions take place

Question 15

Why do very high temperatures cause photosynthesis to stop?

Answer 15

The enzymes that control photosynthesis denature meaning that the reaction can no longer take place

Question 16

What is the effect of increasing light intensity on the rate of photosynthesis?

Answer 16

The higher the light intensity, the faster the rate of photosynthesis

Question 17

What is the effect of increasing carbon dioxide concentration on the rate of photosynthesis?

Answer 17

The higher the carbon dioxide concentration, the faster the rate of photosynthesis

Question 18

What is shown by the inverse square law?

Answer 18

The inverse square law shows the relationship between light intensity and distance between the light source and the plant

Question 19

How can the use of a greenhouse help to increase the yield of crop plants?

Answer 19

A greenhouse can increase the yield of crop plants because levels of carbon dioxide, water, light and temperature can be controlled more carefully whilst crops are kept free of pests. This supports an increase in the rate of photosynthesis, therefore increasing the growth of plants

Question 20

How should a farmer determine the cost-effectiveness of using greenhouses to grow their crops?

Answer 20

The farmer will need to consider the cost of setting up the greenhouses as well as the running costs involved. They would then need to calculate the potential yield increase that they would expect to receive from the setup in order to work out their income.

Question 21

A practical is done to investigate the effect of light intensity on the rate of photosynthesis. What is the independent variable?

Answer 21

Light intemsity

Question 22

A practical is done to investigate the effect of light intensity on the rate of photosynthesis. What is the dependent variable?

Answer 22

The rate of photosynthesis

Question 23

A practical is done to investigate the effect of light intensity on the rate of photosynthesis. Give two control variables

Answer 23

Maintain the same environmental temperature
Using the same species, length and age of plant in each repeat
Dissolving sodium hydrogen carbonate in the water to maintain carbon dioxide levels

Question 24

In an investigation into the effect of temperature on photosynthesis, why should light intensity be controlled?

Answer 24

Light intensity should be controlled when investigating the effect of temperature on the rate of photosynthesis as light intensity is a limiting factor

Question 25

In an investigation into the effect of light intensity on the rate of photosynthesis in aquatic plants, what is the predicted outcome?

Answer 25

In an investigation into the effect of light intensity on the rate of photosynthesis, the predicted outcome that the rate of photosynthesis will increase with light intensity. This will continue until another factor becomes limiting

Question 26

Why does bubble production decrease as distance between the light source and the aquatic plant increases in a line graph?

Answer 26

The number of bubbles produced decreases as the light moves further away from the pondweed because light intensity decreases with distance; this means that the rate of photosynthesis decreases and so less oxygen is produced

Question 27

Name three uses of glucose from photosynthesis

Answer 27

Respiration Storage by conversion into insoluble starch Production of fat or oil for storage Production of cellulose, which strengthens the cell wall Production of amino acids for protein synthesis

Question 28

What mineral ion is used by plants to produce proteins?

Answer 28

As well as utilising the glucose produced in photosynthesis, plants require nitrate ions absorbed from the soil to produce proteins

Question 29

How does glucose facilitate the uptake of mineral ions in the roots of plants?

Answer 29

Glucose is transported to the root hair cells where it is used in respiration to provide energy for the uptake of mineral ions by active transport

Question 30

In what form is glucose stored in plants and animals?

Answer 30

Glucose is stored as starch in plants and glycogen in animals

Question 31

What is the function of cellulose in plant cells?

Answer 31

Cellulose provides structural support to plant cells and allows them to maintain a regular shape