3.1 - Food Supply, Plant Growth and Productivity

Question 1

Food Security Definition

Answer 1

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

Question 2

Food Production

Answer 2

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

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

Question 3

How To Increase Food Production

Answer 3

• breeding of higher yielding cultivators
• use of fertilisers
• protect crops from pests, diseases and competition

Question 4

Energy Loss

Answer 4

All food production is dependant on photosynthesis. As you move along a food chain, energy is lost between each trophic level and the next.

This means that livestock produce less food per unit area of land compared to plant production as there is more energy lost between the extra trophic level.

Question 5

Factors That Control Photosynthesis And Plant Growth

Answer 5

• Soil factors e.g. area farmed, fertilisers, soil quantity, drainage
• Crop factors e.g. pests, disease, competition, cultivar
• Environmental factors e.g. temperature, light intensity, carbon dioxide concentration, rainfall

Question 6

Breeders Try To Develop Crops With:

Answer 6

• Higher nutritional values
• Resistance to pests and diseases
• Physical characteristics suited to rearing and harvesting
• Ability to thrive in particular environmental conditions

Question 7

Photosynthesis Definition

Answer 7

Production of food by green plants using light energy.

Question 8

Fate of Photosynthetic Pigments

Answer 8

• Reflected
• Transmitted (light passes through lead)
• Absorbed: used for photolysis and generating ATP

Question 9

Photosynthetic Pigments

Answer 9

• Chlorophyll a
• Chlorophyll b (most of light absorption uses chlorophyll)
• Carotenoids: extend the range of wavelengths absorbed in photosynthesis and pass the energy to chlorophyll

Question 10

Absorption Spectra

Answer 10

The colours of light absorbed by photosynthetic pigments can be measured using a spectroscope or colorimeter.

Chlorophyll a and b absorb the blue (400-500nm) and red (600-700nm) regions.

Carotenoids absorb blue-green (400-600nm) regions.

Question 11

Action Spectra

Answer 11

Shows the wavelengths of light which are used in the photosynthesis.

Question 12

Stages of Photosynthesis
1. Energy Capture & Photolysis

Answer 12

1. Light energy absorbed by pigments causes electrons to become ‘excited’
2. The electrons are passed through the electron transport chain in the chloroplast’s membrane
3. ATP is generated using ATP synthase when energy is released by the electrons moving through the membrane.
4. Energy released from the electrons is used to split water into hydrogen and oxygen
5. Hydrogen is picked up by coenzyme NADP to become NADPH
6. Hydrogen and ATP are transferred onto the next stage and oxygen is released as a by-product

Question 13

Stages of Photosynthesis
2. Calvin Cycle

Answer 13

1. Carbon dioxide is captured from the air by RuBisCo and combined with Ribulose Biphosphate (RuBP) to form 3-phosphogylcerate (3PG)
2. 3PG is phosphorylated by ATP and combined with hydrogen from NADPH to form glyceraldehyde-3-phosphate (G3P.) NADPH is converted back to NADP
3. G3P is either used to produce glucose or is used to regenerated more RuBP

Question 14

Fate of Glucose

Answer 14

Glucose can be used as:
a respiratory substrated
a storage carbohydrate - starch
a structural carbohydrate - cellulose

Other carbohydrates produced in photosynthesisi are used in other biosynthetic pathways to form a variety of metabolites such as DNA protein and fat.