B4 Photosynthesis and Limiting Factors (page 50)

Question 1

Photosynthesis produces what?

Answer 1

Glucose - using light.

Question 2

What do photosynthesis use energy for?

Answer 2

It uses energy to change carbon dioxide and water into glucose and oxygen.

Question 3

Where does Photosynthesis take place?

Answer 3

It takes place in Chloroplasts in green plant cells - they contain pigments like chlorophyll that absorb light.

Question 4

During photosynthesis, how is energy transferred to the chloroplasts?

Answer 4

From the environment by light

Question 5

Photosynthesis is endothermic - what do this mean?

Answer 5

it means energy is transferred from the environment in the process

Question 6

What is the ‘word equation’ for Photosynthesis?

Answer 6

Carbon Dioxide + Water &raquo_space;» Glucose + Oxygen

Question 7

What is the symbol equation for photosynthesis?

Answer 7

6CO2 + 6H20 (light)
&raquo_space;»> C6 H12 O6 + 6O2

Question 8

Plants use Glucose in five main ways, name them?

Answer 8

1) For respiration
2) Making Cellulose
3) Making amino acids
4) Stored as oils or fats
5) Stored as starch

Question 9

How do plants use Glucose for respiration?

Answer 9

Respiration transfers energy from glucose (see page 54), which enables the plants to convert the rest of the glucose into other useful substances.

Question 10

How do plants use Glucose for making Cellulose?

Answer 10

Glucose is converted into cellulose for making strong plant cell walls (see page 11).

Question 11

How do plants use Glucose to make Amino Acids?

Answer 11

Glucose is combined with Nitrate ions (absorbed from the soil) to make amino acids, which are then made into proteins.

Question 12

How do plants use Glucose to store oils or fats?

Answer 12

Glucose is turned into Lipids (fats and oils) for storing in seeds.

Question 13

How do plants use Glucose to store Starch?

Answer 13

Glucose is turned into starch and stored in roots, stems and leaves, ready to use when Photosynthesis isn’t happening, like in the winter. Starch is insoluable, which makes it much better for storing than glucose. - a cell with lots of glucose in would draw in loads of water and swell up.

Question 14

What affects the rate of Photosynthesis?

Answer 14

Limiting Factors

Question 15

How is the rate of photosynthesis affected?

Answer 15

By intensity of light, oncentration of CO2 and temperature.

Question 16

What is meant by the Limiting factor of photosynthesis?

Answer 16

any of the three factors

intensity of light
concentration of co2
temperature

(this just means that it’s stopping photosynthesis from happening any faster).

Question 17

The limiting factors have a combined effect on the rate of photosynthesis, but which factor is limiting at a particular time depends on what?

Answer 17

Depends on the environmental conditions, at night, in winter, if its warm enough, bright enough, the amount of co2 is usually limiting.

Question 18

Chlorophyll can also be a limiting factor of photosyntheses, why?

Answer 18

The amount of Chlorophyll in a plant can be affected by disease (e.g. infection with the tobacco mosaic virus) or environmental stress stuch as a lack of nutrients.

These factors can cause chloroplasts to become damaged or to not make enough Chlorphyll. This means the rate of photosynthesis is reduced because they can’t absorb as much light.

Question 19

Name the products of Photosynthsis? (2 marks)

Answer 19

Glucose (1 mark)
Oxygen (1 mark)

Question 20

Apart from temperature, name three other limiting factors of photosynthesis (3 marks)

Answer 20

Light Intensity (1 mark)
Volume of CO2 (1 mark)
amount of Chlorophyll (1 mark)