Photosynthesis and Energy Flashcards
Describe the light reactions of photosynthesis
During the light reactions, light energy from the sun is trapped by chlorophyll in chloroplasts and is converted into chemical energy which is used to generate ATP.
Water is split to produce Hydrogen and Oxygen. Oxygen diffuses out of the cell.
Describe carbon fixation
A series of enzyme-controlled reactions, which use hydrogen and ATP (produced by the light reactions) are combined with carbon dioxide to produce sugar.
Describe the fate of the sugar produced by photosynthesis
The chemical energy in sugar is available for respiration or the sugar can be converted into other substances, such as starch for storage, and cellulose which is structural and used in cell walls.
Identify the limiting factors of photosynthesis
Anything that limits the rate of a reaction is known as a limiting factor. The three limiting factors for photosynthesis are:
Carbon dioxide concentration
Light intensity
Temperature
If any factor limits the rate of photosynthesis, then this will have an overall negative impact on plant growth and will slow the overall rate of photosynthesis.
Describe what happens to energy from one level to the next in a food chain
As energy transfers from one level of the food chain to the next, only 10% of the energy is passed on through growth.
90% of the energy is lost as:
heat
movement
undigested materials
Describe a pyramid of numbers and a pyramid of energy
A pyramid of numbers is a diagram that represents the number of organisms at each stage of the food chain.
A pyramid of energy is a diagram that represents the amount of energy present at each stage of the food chain.
Compare a pyramid of numbers and energy
A pyramid of numbers is always representative, due to the size of the organisms present.
Pyramids of energy will be represented as true pyramids no matter the size of the organisms because energy is always lost at each stage of the food chain.
Describe the impact of the human population on food production
An increasing human population requires an increasing food yield.
Describe a fertiliser and the impact on food production
Fertilisers can help increase the food yield as they provide chemicals such as nitrates which increase crop yield.
Describe a pesticide and the impacts on food production
Pesticides can increase crop yield, by killing unwanted animals and plants that would reduce crop yield.
Describe how plants use and obtain nitrates
Nitrates are dissolved in the soil and absorbed by the plants through the roots.
Plants use nitrates to produce amino acids which are used to make proteins.
Describe how animals obtain amino acids
Animals consume plants or other animals to gain the amino acids needed for protein synthesis.
Describe the relationship between nitrates and fertiliser
Fertilisers can be added to the soil to increase the nitrate concentration.
Describe the impact on biodiversity when fertilisers leach into fresh water
Fertilisers can leach into fresh water rivers and streams. This adds unwanted extra nitrates into the water. This leads to a series of events causing Eutrophication.
Fertilisers leach into rivers and streams adding nitrates
The algal population increases causing algal blooms
Algal bloom on the surface of the water reduces the light, killing aquatic plants
Dead plants and dead algae become food for bacteria
Bacteria in the water increases
Bacteria use up a large quantity of oxygen form the river
Reducing the oxygen for other living organisms
Decreasing biodiversity
State the impact of genetically modified crops
The use of genetically modified crops can reduce the use of fertilisers and pesticides.
