Category: The Transfer of Energy
Life depends on continuous transfers of energy.
In this unit we start with photosynthesis. Splitting it into the light dependent reactions (LDR), and the Light Independent reactions (LIR).
LDR take place in the thylakoid membranes of the chloroplasts. Light energy is absorbed by chlorophyll, and results in electron transfer, which in turn creates a proton gradient, and the enzyme ATP synthase to produce ATP. The LDR also produces reduced NADP, which together with carbon dioxide enter the Calvin cycle and produce triose phosphate which can be converted to other organic molecules such as glucose. There are also three required practicals on the cross board CPAC linked to photosynthesis.
In aerobic respiration, the breakdown of glucose as a respiratory substrate starts with glycolysis in the cytoplasm, which then links to the mitochondria. Krebs cycle occurs in the mitochondrial matrix, finishing off with the Electron Transport Chain producing ATP.
This unit extends to the transfer of energy between organisms, as Net Primary Productivity (NPP) . this is Gross Primary Productivity ( GPP) minus respiratory losses. This extends to animals ( consumers) when N ( Net production) is equal to chemical energy ingested, minus losses in faeces, urine and respiration. Farming practices are designed to make these transfers most efficient.
Finally, nutrients alo cycle through the ecosystem, and at A Level biology , these focus on the Nitrogen cycle and the Phosphorus cycle. This is extended to A level by the role of saprobionts and mycorrhizae.
