Unit 3 KA1 Flashcards
3 aspects of food security
Quantity, quality and access.
Green revolution
Traditional farming changed to intensive farming in the 1960s.
Increased food production due to mechanisation and the use of chemicals - pesticides and fertilisers.
Food security challenges
A rapidly rising global population
Malnourishment, resulting in people trapped in a cycle of poverty
Rising demand for energy - biofuels grown instead of food
Rising oil prices, making use of machinery more expensive
Climate change and drought.
Food security solutions
Develop better crop varieties through selective breeding or GM.
Protect crops from weeds and pests.
Remove factors that limit plant growth using fertilisers or irrigation schemes.
Develop new agricultural areas as a result of global warming
Birth control to limit human population growth.
Agricultural production
Crop plants are photosynthetic - they pass energy/molecules along food chains to human consumers.
Crop plants include cereals (rice, wheat and maize), tubers (potatoes) and legumes (beans).
Agricultural food chains
Agricultural food chains are more efficient if humans eat plants, rather than animals, generating more energy per hectare.
This reduces energy loss as there are fewer trophic levels.
Only steep rocky hillsides unsuitable for agriculture should be used for livestock production.
Photosynthesis
Used by green plants to trap light energy for the production of carbohydrates (sugars and starch) and other molecules.
Visible light
A type of electromagnetic radiation, which travels in waves.
Wavelengths (the distance between the crests of the waves) are measured in nanometres (nm)
Biologically important wavelengths occur between 380 and 750nm.
This is known as ‘visible light’ and can be seen as colours by the human eye.
Fate of light hitting a leaf
It may be absorbed by pigments, reflected or transmitted.
Pigment
A substance that absorbs visible light. eg chlorophyll a and b, carotenoids
Different pigments extend the range of wavelengths absorbed, and pass the absorbed energy to chlorophyll.
Chromatography
Technique used to separate the different pigments extracted from leaves, based on their solubility.
Spectrophotometer (spectroscope)
Used to measure how much light of each wavelength is absorbed by a particular pigment.
Data collected is used to plot an absorption spectrum.
Action spectrum
Shows how effective the different wavelengths of light are at causing photosynthesis.
Rate of photosynthesis can be measured by collecting oxygen released by a pond plant, in different wavelengths of light.
Close correlation between absorption and action spectra demonstrates the importance of pigments in photosynthesis.
Chloroplast
Organelle found in leaf cells, which is the site of photosynthesis.
The light reaction occurs in the stacked membranes, the Calvin cycle in the stroma.
Photosynthesis overview
Light is captured by chlorophyll and is used to split water into oxygen (waste product) and hydrogen, and to produce ATP.
ATP and hydrogen are used in the Calvin cycle to produce carbohydrates by combining them with absorbed carbon dioxide.
Light dependent reaction
A flow of high energy electrons (from chlorophyll) pumps H+ ions across the membrane, creating a high concentration inside the chloroplast.
The H+ ions return via ATP synthase, along a concentration gradient, generating ATP.
Photolysis
Energy from the flow of electrons is used to split water releasing oxygen as a waste product and hydrogen.
NADP
Hydrogen from photolysis is transferred to the co-enzyme NADP, reducing it to NADPH. The hydrogen is used in the Calvin cycle.
Calvin cycle
A series of enzyme controlled (temperature dependent) reactions that occur in the stroma of the chloroplast.
The ATP and hydrogen generated in the light dependent stage are used to produce carbohydrates.
Production of G3P
3PG combines with hydrogen released from NADP, and is phosphorylated by ATP forming glycerate-3-phosphate (G3P).
Phosphorylation by ATP provides the energy to drive the reaction.
RuBP
Accepts carbon dioxide and turns into the intermediate compound 3-phosphoglycerate (3PG).
RuBisCo
Enzyme that catalyses the addition of carbon dioxide to RuBP
Uses of G3P
G3P is either used to regenerate RuBP or is used to make sugars such as glucose.
Uses of sugar
Respiration - provides energy for growth and reproduction.
Used to build complex carbohydrates - cellulose (cell walls) and starch (starch grains, which act as an energy store).
Used in other metabolic pathways to build amino acids (and therefore protein), DNA and fats.
