3.1 Food Supply, Plant Growth and Productivity

Question 1

Define ‘Food Security’

Answer 1

The ability of a population to access food of sufficient quality and quantity

Question 2

What are the three factors that influence food security?

Answer 2

• Food Quantity
• Food Quality
• Food Access

Question 3

Why is food security becoming harder to achieve?

Answer 3

Due to the increasing rate of population growth and lack of available land to grow food

Question 4

What does food availability depend on?

Answer 4

Sustainable Agricultural Methods

Question 5

What does ‘Sustainable’ mean in relation to plant growth

Answer 5

Sustainable - does not degrade the natural resources on which agriculture depends on

Question 6

How can you increase crop production without expanding the area?

Answer 6

• Grow High Yielding Cultivars
• Applying fertilisers
• Reducing pests/diseases

Question 7

Livestock production produces … due to energy lost between trophic levels.

Answer 7

Livestock production produces less food per unit area than crop plants due to energy lost between trophic levels

Question 8

What advantage is there to using livestock over crop plants?

Answer 8

Livestock production is often possible where crop plants cannot be grown, i.e. a very steep hill.

Question 9

What is the word equation for photosynthesis?

Answer 9

Carbon Dioxide + Water —> Glucose + Oxygen

Question 10

What are some factors that affect the rate of photosynthesis?

Answer 10

Carbon dioxide availability
Temperature
Light intensity

Question 11

Why are plants produce more food per unit area than livestock?

Answer 11

Due to the energy loss at each tropic level

Question 12

Why are livestock sometimes chosen over plant production in certain areas?

Answer 12

Chosen in areas unsuitable for plant growth due to ability to grow (eg. mountains)

Question 13

What is plant productivity?

Answer 13

Rate at which light energy is converted to glucose in photosynthesis

Question 14

What is the biological yield of a plant?

Answer 14

Total increase in biomass

Question 15

What are the two stages in photosynthesis?

Answer 15

Light Dependant Stage

Calvin Cycle

Question 16

Where does the light dependant stage take place?

Answer 16

Chloroplasts

Question 17

Where does the Calvin Cycle take place?

Answer 17

Chloroplasts

Question 18

What are the three fates of light hitting a leaf?

Answer 18

• Absorbed
• Reflected
• Transmitted

Question 19

What is the main photosynthetic pigment?

Answer 19

Chlorophyll a

Question 20

What regions of the absorption spectrum does chlorophyll A absorb light from?

Answer 20

Red & Blue

Question 21

What are the two accessory pigments called?

Answer 21

Carotenoids

Question 22

State an advantage of having accessory pigments

Answer 22

Extend the absorption spectrum and pass energy to chlorophyll

Question 23

Which regions of the absorption spectrum do the carotenoids absorb?

Answer 23

Yellow and Green

Question 24

Define the ‘Absorption Spectrum’

Answer 24

Absorption spectrum shows which colours of light are absorbed by the photosynthetic pigments

Question 25

Define the ‘Action Spectrum’

Answer 25

Action Spectrum shows the rate of photosynthesis at each light wavelength (colour).

Question 26

How can pigments in a leaf be extracted?

Answer 26

Thin Layer Chromatography

Question 27

What is the role of light energy in the production of ATP?

Answer 27

Light energy excites the electrons and puts them in a high energy state

Question 28

Which co-enzyme is responsible for picking up hydrogen?

Answer 28

NADP

Question 29

What does NADP become after picking up hydrogen?

Answer 29

NADPH

Question 30

What two products of the light dependant stage enter the calvin cycle?

Answer 30

NADPH and ATP

Question 31

What is the energy used for in photolysis?

Answer 31

To split water into hydrogen and oxygen

Question 32

ATP synthase is an enzyme that …

Answer 32

ATP synthase is an enzyme that generates ATP by the flow of Hydrogen ions passing through it

Question 33

Describe what happens to oxygen after photosynthesis?

Answer 33

Oxygen exits the plant via the stomata.

Question 34

List the steps of the light dependent stage of photosynthesis?

Answer 34

1 - Consists of a series of carrier proteins attached to the inner mitochondrial membrane.
2 - electrons become excited
3 - electrons transferred along an electron transport chain releasing energy.
4 - Energy is used by the enzyme ATP synthase to generate ATP
5 - Energy is also used for photolysis (split water) into hydrogen and oxygen
6 - Hydrogen picked by coenzyme NADP to make NADPH for carbon fixation stage.
7 - Oxygen evolved as gas through stomata

Question 35

Describe the steps of carbon fixation (calvin cycle) of photosynthesis?

Answer 35

1 - the enzyme RuBisCO fixes carbon dioxide by attaching it to ribulose bisphosphate (RuBP) to produce 3-phosphoglycerate (3PG)
2 - The 3-phosphoglycerate (3PG) produced is phosphorylated by ATP and combined with hydrogen ions from NADPH to form glyceraldehyde-3-phosphate (G3P). Both the hydrogen and the ATP are generated during the light dependent stage.
3 - G3P is used for the synthesis of glucose and the regeneration of RuBP.

Question 36

What is the full chemical name of the 3PG, which is involved in photosynthesis?

Answer 36

3-phosphoglycerate (3PG)

Question 37

What is the full chemical name of the G3P, which is involved in photosynthesis?

Answer 37

glyceraldehyde-3-phosphate (G3P)

Question 38

What are the fates of the glucose produced as a result of photosynthesis?

Answer 38

1 - used as a respiratory substrate to generate energy (ATP)
2 - converted to cellulose (structural carbohydrate)
3 - converted into starch (storage carbohydrate)
4 - used in other biosynthetic pathways (to make DNA, protein etc.)