H Biology - Unit 3 - KA1 - Food Supply, Plant Growth, and Productivity

What is food security?

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

How should food be produced?

Any food should be produced sustainably

What should food production not do?

Food production must not damage or destroy the natural resources needed for agriculture

What are the three factors affecting food production?

The three factors affecting food production are;

• Photosynthesis

• Plant growth

• Breeding crops for particular traits

How can food production be affected through photosynthesis?

Food production can be affected through photosynthesis by;

• Light intensity

• CO₂ concentration

• Temperature

• Water availability

How can food production be affected through plant growth?

Food production can be affected through plant growth by;

• Higher yielding cultivars

• Fertilisers

• Protecting crops from diseases and pests

• Protecting crops from competition

How can food production be affected through breeding crops for particular traits?

Food production can be affected through breeding crops for particular traits by breeding crops that have;

• High nutritional values

• Resistance to pests and disease

• The ability to thrive in difficult conditions such as droughts or flooding

• Physical features that are good for growing and harvesting such as big leaves or a strong stem.

What are the things farmers can influence that affect food production?

The things farmers can influence that affect food production are;

• Photosynthesis

• Plant growth

Why do livestock produce less food per unit area than crops?

Livestock produces less food per unit area than crops due to loss of energy between trophic levels

How many fates of light are there?

There are three fates of light

What are the three fates of light?

The three fates of light are;

• Absorption

• Transmission

• Reflection

What are the three pigments in leaves that absorb light?

The three pigments in leaves that absorb light are;

• Chlorophyll A

• Chlorophyll B

• Carotenoids

What do absorption spectra show?

Absorption spectra show the absorption of light by different pigments over the range of visible wavelengths of light

What do each of the pigments absorb in the absorption spectra?

Each of the pigments absorb a different range of wavelength of light

What do carotenoids do?

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

What does action spectra show?

Action spectra show the rate of photosynthesis over the range of visible wavelengths of light.

What are the stages of photosynthesis?

The stages of photosynthesis are;

• Light reaction 1

• Light reaction 2

• Carbon fixation

What occurs in Light Reaction 1

In Light Reaction 1;

• Light energy absorbed excites the electrons in the pigment molecule

• The high energy electrons are transferred along the electron transport chain. This releases energy.

• The energy released is used by the enzyme ATP synthase to generate ATP.

What occurs in Light Reaction 2?

In Light Reaction 2;

• The energy released in Light Reaction 1 is used for photolysis

• Oxygen is produced. This diffuses out of the cell.

• The hydrogen produced joins coenzyme NADP to form NADPH.

What are the essential molecules for Carbon Fixation?

The essential molecules for Carbon Fixation are;

• ATP from Light Reactions

• NADPH from Light Reactions

• CO₂ from the atmosphere

• RuBisCO enzyme

• RuBP

How many reactions are there in Carbon Fixation

There are three reactions in Carbon Fixation

What is Reaction 1 in Carbon Fixation?

Reaction 1 in Carbon Fixation;

The enzyme RuBisCO fixes CO₂ by attaching it to RuBP. This produces 3PG.

What is Reaction 2 in Carbon Fixation?

Reaction 2 in Carbon Fixation;

The 3PG produced is phosphorylated by ATP and combined with hydrogen ions from NADPH to form G3P.

What is Reaction 3 in Carbon Fixation?

Reaction 3 in Carbon Fixation;

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

Carbon fixation

Carbon fixation:

• The enzyme RuBisCO fixes CO₂ by attaching it to RuBP. This produces 3PG.

• The 3PG produced is phosphorylated by ATP and combined with hydrogen ions from NADPH to form G3P.

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

What are the fates of sugar in photosynthesis?

The fates of sugar in photosynthesis are being used;

• As respiratory substrate

• To synthesise carbohydrates

• As starch for storage

• As cellulose for cell walls

• In biosynthetic pathways which make DNA, proteins, and fat.

When answering photosynthesis questions what coenzyme must you say?

When answering photosynthesis questions you must say NADP