B8. Photosynthesis

Question 1

What is the word equation for photosynthesis?

Answer 1

Carbon dioxide + Water —-> Glucose + Oxygen

Note: Sunlight and chlorophyll are also needed.

Question 2

What type of reaction is photosynthesis?

Answer 2

It is an ENDOthermic reaction. This means is requires an input of energy from the environment.

Question 3

What is the energy transfer in photoysnthesis?

Answer 3

Light energy is converted to chemical energy (in glucose).

Question 4

What is the chemical equation for photosynthesis?

Answer 4

6CO2 + 6H20 —–> C6H12O6 + 6O2

Question 5

What is the name of the (food) chemical made in photosynthesis?

Answer 5

Glucose

Question 6

What is the chemical formula for glucose?

Answer 6

C6H12O6

Question 7

What do plants use glucose for?

Answer 7

• Used for respiration to release energy
• Converted into insoluble starch for storage until it is needed
• Used to produce fat, or oil for storage
• Used to make other carbohydrates e.g. cellulose which strengthens the cell wall
• Used to produce amino acids for protein synthesis.

Question 8

In photosynthesis, what is a limiting factor?

Answer 8

When a process (e.g. photosynthesis) depends on two or more factors (/substances), the rate of that process is limited by the factor which is in shortest supply.

Question 9

Which factors could limit the rate of photosynthesis?

Answer 9

• Light intensity
• Availability of water
• Temperature
• Carbon dioxide concentration
• Amount of chlorophyll in the leaves

Question 10

In what layer of the leaf does photosynthesis take place?

Answer 10

The palisade layer

Question 11

Which organelle in plant cells produce chlorophyll?

Answer 11

Chloroplast

Question 12

What is the function of chlorophyll?

Answer 12

It is a green chemical that traps sunlight energy.

Question 13

How are water levels controlled in the plant?

Answer 13

The volume of water is controlled by the guard cells that open and close the stomata.

Question 14

Why are leaves very thin?

Answer 14

This allows for a short diffusion pathway for the exchange of gases.

Question 15

Which substances does the plant tissue xylem transport?

Answer 15

Water molecules and dissolved minerals

Question 16

Why are there air spaces in the spongy mesophyll layer?

Answer 16

For faster exchange of gases

Question 17

What do plants store excess glucose as?

Answer 17

Starch

Question 18

What is the chemical test for starch?

Answer 18

Add 2-3 drops of iodine to the sample, if the colour changes from red/orange to blue-black starch is present.

Question 19

What is meant by the ‘rate of photosynthesis’?

Answer 19

The rate of photosynthesis is how quickly photosynthesis takes place (or how quickly a plant converts water and carbon dioxide to glucose and oxygen)

Question 20

What is a limiting factor?

Answer 20

When are process relies on two or more factors, if one or more of these factors are in limited supply the rate will not increase. These are called limiting factors.

Question 21

What could be limiting factors of photosynthesis?

Answer 21

• Carbon dioxide concentration
• Water availability
• Light intensity
• Chlorophyll
• Temperature

Question 22

Name 3 ways a student could measure the rate of photosynthesis?

Answer 22

Measure:

1) the rate ofoxygenoutput
2) the rate ofcarbon dioxideuptake
3) the rate ofcarbohydrateproduction

Question 23

What is meant by an ‘inverse relationship’ between two variables.

Answer 23

As one variable increases the other decreases.

For e.g. in the photosynthesis experiment as the distance of the light source from the plant increases, the light intensity decreases.

Question 24

Which variable gets plotted on the x axis?

Answer 24

The independent variable

Question 25

Which variable gets plotted on the y axis?

Answer 25

The dependent variable

Question 26

How might farmers increase the carbon dioxide concentration in a greenhouse?

Answer 26

• Use paraffin heaters on a small scale.
• On a larger scale, use carbon dioxide wastes from industrial processes that has been cleaned up before use.
• Can use liquid carbon dioxide, applied through pipes, though this can be expensive.

Question 27

Which type of microorganism can be used to increase CO2 concentrations in greenhouses?

Answer 27

Fungi can be used, grown as amyceliumin bags around the greenhouse, that add carbon dioxide through their respiration.

Question 28

Explain 2 ways water volume could be increased in commercial plant greenhouses.

Answer 28

• Irrigation systems.

- Plants are sometimes grown in liquid systems called hydroponics.

Question 29

Compare the normal concentration of atmospheric carbon dioxide to carbon dioxide in a greenhouse.

Answer 29

• The normal concentration for atmospheric carbon dioxide varies between 0.03 % and 0.04 %.
• The concentration of carbon dioxide in greenhouses is often kept at around 0.1 per cent

Question 30

In a plant cell, when the rate of respiration = the rate of photosynthesis this is called the ___________ point.

Answer 30

Compensation point

Question 31

Give an advantage of growing crops in a commercial greenhouse.

Answer 31

• Much higher yields of crops can be obtained.

- Plants can be grown all year round.

Question 32

Give an disadvantage of growing crops in a commercial greenhouse.

Answer 32

• Manipulating the conditions can be very expensive.

- Very time consuming and workers need to be trained.