FOOD SUPPLY, PLANT GROWTH AND PRODUCTIVITY U3 Flashcards
Describe food security
Food security is the ability of human populations to access food of sufficient quality and quantity.
State why food production has to be increased and how this can be achieved
An increase in human population and concerns for food security leads to a demand for increased food production.
Food production must be sustainable and not degrade the natural resources on which agriculture depends.
Food production can be increased by:
breeding of higher yielding cultivators
use of fertilisers
protect crops from pests, diseases and competition
Breeders seek to develop crops with:
high 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.
Describe agricultural production in terms of crops and plant growth
The area to grow crops is quite limited.
All food production is dependent on photosynthesis and factors which control photosynthesis.
Examples of crops grown include cereals, potatoes, roots and legumes.
Compare livestock produce to crop plants
Livestock produce less food per unit area than crop plants due to a loss of energy between trophic levels.
Livestock production is often possible in habitats unsuitable for growing crops.
State the 3 fates of light energy and name the main photosynthetic pigments
Light energy can be:
Reflected
Absorbed by photosynthetic pigments to generate ATP
Transmitted
Explain the absorption spectra of the photosynthetic pigments
Each photosynthetic pigment absorbs different wavelengths of light. The absorption spectra shows the wavelength of light that each pigment absorbs.
Carotenoids extend the range of wavelengths absorbed and pass the energy to chlorophyll for photosynthesis.
Compare the absorption spectra with the action spectra
The action spectra shows the relative rate of photosynthesis at different wave lengths of light.
Describe how light energy generates ATP when absorbed by the photosynthetic pigment
Absorbed light energy excites electrons in the pigment molecule. The transfer of these electrons through the electron transport chain releases energy to generate ATP by ATP synthase.
Describe photolysis
Photolysis uses light energy to split water into hydrogen ions and oxygen.
Oxygen is evolved (released) and hydrogen ions are transferred to the co-enzyme NADP to form NADPH.
Describe carbon fixation
The enzyme RuBisCO fixes carbon dioxide by attaching it to ribulose bisphosphate. (RuBP) producing 3-phosphoglycerate (3PG).
The 3-phosphoglycerate is phosphorylated by ATP and combined with hydrogen ions from NADPH to form lyceraldehyde-3-phosphate (G3P).
Glyceraldehyde-3-phosphate is used to regenerate RuBP and for the synthesis of glucose.
State the uses of glucose
Glucose can be used as a respiratory substrate, synthesised into starch or cellulose or passed to other biosynthetic pathways.
The biosynthetic pathways can lead to the formation of variety of metabolites such as DNA, protein and fat.
