Food supply, plant growth and productivity 3.1

Question 1

What is food security?

Answer 1

Food security is the ability of human populations to access food of sufficient quality and quantity.

Question 2

What leads to a demand for increased food production?

Answer 2

Increase in human population and concern for food security leads to a demand for increased food production.

Question 3

What must food production be?

Answer 3

Food production must be sustainable and not degrade the natural resources on which agriculture depends.

Question 4

What is all food production dependant on?

Answer 4

All food production is dependent
ultimately upon photosynthesis.

Question 5

What does agricultural production depend on?

Answer 5

Agricultural production depends on factors that control photosynthesis and
plant growth.

Question 6

What are the factors that control plant grow that increased food production id dependant on?

Answer 6

Increased food production will
depend on factors that control plant growth — breeding of higher yielding cultivars, use of fertiliser, protecting crops
from pests, diseases and competition.

Question 7

What are some plant crop examples?

Answer 7

Plant crop examples include cereals, potato, roots
and legumes.

Question 8

What are some characteristics that breeders seek to develop in crops?

Answer 8

Breeders seek to develop
crops with higher nutritional values, resistance to pests and diseases, physical characteristics suited to rearing and harvesting as well as those that can thrive
in particular environmental conditions.

Question 9

What produces more food: crop plants or livestock?

Answer 9

Livestock produce less food per unit area than crop plants due to loss of energy between trophic levels.

Question 10

Where is livestock production possible?

Answer 10

Livestock production is often possible in habitats unsuitable for growing crops.

Question 11

What is photosynthesis?

Answer 11

Light energy is absorbed by
photosynthetic pigments to generate ATP
and for photolysis

Question 12

What happens to the light energy not absorbed?

Answer 12

Light energy not absorbed is transmitted or reflected.

Question 13

What is the use of having to different pigments ( chlorophyll a, chlorophyll b and carotenoids)?

Answer 13

Each pigment absorbs a different range of wavelengths of light.

Question 14

What is the use of carotenoids?

Answer 14

Carotenoids extend the range of wavelengths absorbed and pass the energy to chlorophyll for photosynthesis.

Question 15

What happens to absorbed light energy in the pigment molecule?

Answer 15

Absorbed light energy excites electrons in the pigment molecule.

Question 16

What happens to the excited electrons in the pigment molecule?

Answer 16

Transfer of these electrons through the electron transport chain releases energy to generate ATP by ATP synthase

Question 17

What is the absorbed energy also used for?

Answer 17

Energy is also used for
photolysis, in which water is split into oxygen, which is evolved, and hydrogen ions, which are transferred to the coenzyme NADP.

Question 17

What happens in the carbon fixation stage?

Answer 17

In the carbon fixation stage (Calvin cycle), the enzyme RuBisCO fixes carbon dioxide
by attaching it to ribulose bisphosphate (RuBP).

Question 18

What happens to the 3PG produced in the carbon fixation stage?

Answer 18

The 3-phosphoglycerate (3PG)
produced is phosphorylated by ATP and combined with hydrogen ions from NADPH to form glyceraldehyde-3-
phosphate (G3P).

Question 19

What is G3P used for?

Answer 19

G3P is used to regenerate RuBP and for the synthesis of glucose.

Question 20

What may glucose be used as?

Answer 20

Glucose may be used as a respiratory substrate, synthesised into starch or
cellulose or passed to other biosynthetic pathways.

Question 21

What may these biosynthetic pathways lead to?

Answer 21

These biosynthetic pathways can lead to the formation of a variety of metabolites such as DNA, protein and fat.