Food Supply, Plant Growth and Productivity Flashcards
What are the 3 aspects of food security?
- Access to food
- Quantity of food
- Quality of food
What has caused a demand for increased food production?
Increase in human population & concern for food security
What process is all food production ultimately dependent on?
Photosynthesis
Give some examples of plant crops.
cereals, potato, roots and legumes.
State some factors that will increase food production.
- breeding for higher yielding cultivars
- use of fertiliser
- protecting crops from pests, disease & competition
Why do livestock produce less food per unit area than crop plants?
Due to the energy loss between trophic levels (90% loss)
What is the advantage of livestock production?
Not all land is suitable for growing crops
State 2 reasons why light energy is absorbed by photosynthetic pigments.
Generate ATP and photolysis
What are 2 possible consequences of light energy that is not absorbed?
Reflected or transmitted
Name the 2 main pigments found inside chloroplasts.
Chlorophyll a and chlorophyll b
Which 2 colours are mainly absorbed by chlorophyll a and b?
red and blue wavelengths
Name the 2 pigments that make up the carotenoids.
carotene and xanthophyll
What is the advantage to plants of having carotenoids?
They extend the range of wavelengths absorbed and pass the energy to chlorophyll for photosynthesis.
What effect does absorbed light energy have on the pigment?
it excites electrons in the pigment molecule
What happens to these excited electrons?
They pass through the electron transport chain
Name the enzyme that produces ATP in the electron transport chain.
ATP synthase
What does light energy do during photolysis?
Splits water into hydrogen and oxygen
What is the fate of the oxygen?
It is evolved
What is the name of the coenzyme that hydrogen ions are transferred to.
NADP
What does NADP become when hydrogen ions have transferred to it?
NADPH
What is another name for the carbon fixation stage of photosynthesis?
The Calvin cycle
What gas is required for the Calvin cycle?
carbon dioxide
Name the enzyme that fixes carbon dioxide and what is carbon dioxide attached to?
RuBisCO
ribulose biphosphate
Name the molecule produced when carbon dioxide is fixed to ribulose biphosphate by RuBisCO.
3-phosphoglycerate (3PG)
What is added to 3-phosphoglycerate during phosphorylation?
phosphate
Where does the phosphate come from?
ATP
Where does the ATP come from?
The first stage (the electron transport chain)
Hydrogen ions are also added to 3-phosphoglycerate, where do they come from?
NADPH - from photolysis, splitting of water in the first stage
What molecule is produced when hydrogen ions and phosphate molecules are added to 3-phosphoglycerate?
glyceraldehyde-3-phosphate (G3P)
In the Calvin cycle, what 2 things does glyceraldehyde-3-phosphate become?
ribulose biphosphate
glucose
State the 4 possible fates of glucose produced during photosynthesis.
- respiratory substrate
- starch for storage
- cellulose - structural carbohydrate
- passed to other biosynthetic pathways (to produce DNA, protein & fat)
What does the absorption spectrum show?
It shows the wavelengths of light absorbed by the different pigments in the leaf.
What does the action spectrum show?
How effective the different wavelengths are at photosynthesis.
