B2.3 Photosynthsis

Question 1

What is photosynthesis?

Answer 1

The process that produces ‘food’ in plants and algae

Question 2

What is the ‘food’ that is produced from photosynthesis?

Answer 2

Glucose

Question 3

Where does photosynthesis occur?

Answer 3

Inside chloroplasts in plant cells and algae

Question 4

What is the process of photosynthesis?

Answer 4

Chloroplasts contain a green substance called chlorophyll which absorbs sunlight and uses its energy to convert carbon dioxide and water into glucose, oxygen is also produced as a by-product

Question 5

What is the word equation for photosynthesis?

Answer 5

Carbon dioxide + water ==light energy==> glucose + oxygen

Question 6

Where are chloroplasts found?

Answer 6

In the leaves of all green plants

Question 7

What is the rate of photosynthesis affected by?

Answer 7

The intensity of light, the volume of carbon dioxide and the temperature

Question 8

What happens when one of the three factors which affect the rate of photosynthesis is too high or too low?

Answer 8

It will become the limiting factor, it’s the factor which is stopping photosynthesis from happening any faster

Question 9

When will the intensity of light become a limiting factor?

Answer 9

At night

Question 10

When will the temperature become a limiting factor?

Answer 10

In the winter

Question 11

When will the levels of carbon dioxide become a limiting factor?

Answer 11

When it is warm and bright enough, the amount of carbon dioxide is usually limiting

Question 12

How can you investigate the rate of photosynthesis?

Answer 12

Gas syringe - amount produced over a time method

Question 13

What would the control variables of an investigation on the rate of photosynthesis link to?

Answer 13

The three limiting factors of photosynthesis

Question 14

When interpreting data on the effect of light intensity and carbon dioxide on the rate of photo’, what does the graph flattening suggest?

Answer 14

That they are no longer the limiting factor, and it is another factor as the rate of photo synthesis is no longer increasing

Question 15

When interpreting data on the effect of temperature on the rate of photosynthesis, why does the graph decrease rapidly if the plant gets to hot?

Answer 15

Because the enzymes which catalyse the rate of photosynthesis are damaged/destroyed after a certain temperature, which means they can no longer work causing the rate of photo’ to plummet

Question 16

Where can you create the ideal conditions for photosynthesis?

Answer 16

In greenhouses

Question 17

How is temperature managed in greenhouses?

Answer 17

They help to trap the sun’s heat, and make sure that the temperature doesn’t become limiting

Question 18

How can temperature be managed in a greenhouse in the winter when it is too cold, and in the summer when it is too hot?

Answer 18

In the winter heaters can be used to keep temperatures at the ideal level, and in the summer, shades and ventilation can be used to cool things down

Question 19

How is light managed in greenhouses?

Answer 19

Artificial lights can be used after the sun goes down to give the plants more photosynthesis time

Question 20

How are carbon dioxide levels managed in greenhouses?

Answer 20

Paraffin heaters can be used to heat the greenhouse, which produces carbon dioxide as a by-product

Question 21

How is the general health of the plants in greenhouses managed? (2)

Answer 21

Keeping the plants enclosed in a greenhouse keeps them safe from pests and diseases, and farmers can add fertilisers to the plant’s soil to provide the minerals needed for healthy growth

Question 22

Keeping the conditions in a greenhouse at an optimum can be expensive, but why is it worth it?

Answer 22

Because keeping the conditions just right for photo’ makes the plants grow faster and a decent crop can be harvested much more often, which can then be sold

Question 23

What is glucose used for in plants? (3)

Answer 23

Respiration, making cell walls and making proteins

Question 24

How is glucose used for respiration?

Answer 24

The breakdown of glucose produces energy which can then be used to convert the rest of the glucose into other useful substances

Question 25

How is glucose used for making cell walls?

Answer 25

Glucose is converted into cellulose to make strong cell walls especially in a rapidly growing plant - these cell walls support and strengthen the cells

Question 26

How is glucose used to make amino acids?

Answer 26

Glucose is combined with nitrate ions absorbed from the soil to make amino acids

Question 27

How is glucose used for making proteins?

Answer 27

Glucose can be used to make amino acids, which are the building blocks of proteins - they can make a particular protein when joined together in a particular sequence

Question 28

How can glucose be stored in plants? (2)

Answer 28

In lipids or starch

Question 29

How can glucose be stored as lipids?

Answer 29

Glucose can converted into lipids, which are then stored in seeds (in plants) and oil droplets in cells (in algae)

Question 30

Why is glucose stored as starch?

Answer 30

So it can be used for when photosynthesis isn’t happening as much, like in the winter

Question 31

Where is starch stored in plants? (4)

Answer 31

In the roots, stems, seeds and leaves

Question 32

Why is it better for plants to store starch rather than glucose?

Answer 32

Because starch is insoluble, and a cell with lots of glucose in would draw in loads of water and swell up