4.2.3 Food farming and Populations

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Explain that light energy is used during photosynthesis to produce complex organic molecules

Plants are autotrophic as they use inorganic (no carbon) molecules and external energy sourves to produce own organic (carbon) molecules- glucose strach, amino acids and fatty acids.These are then avaliable to higher trophic levels that feed on them- primary+secondary consumers. These are known as hetereotrophs.

Plants use photosynthesis to trap sunlight and use this energy to convert water and carbon dioxide into glucose, oxygen and ATP. Therefore they have converted light energy into potential energy.

The sugar produced is then converted into ATP and use to fuel processes such as active transport and protein synthesis in the plant. This all involves the action of light-harvesting pigment chloropyhll 

Explain how respiration in humans and animals depend upon the products of photosynthesis.

photosynthesis produces the byproducts glucose and oxygen which are required for respiration. glucose is needed to be broken to produce ATP molecules and oxygen needed to be the final receiver of the electrons in electron transport chain which become a water molecule.

Outline light dependent stage of photosynthesis

The site of reactions happens on the pigments held on thylakoid membrane on the chloroplst, these harvest energy from photons of sunlight.pigments are grouped together in specialised structures called photosystems (heres energys converted) They include many different pigments which trap light wavelenghts of differing energy values. There a 2 photosystems each which chloropyll as their primary pigment  and a network of associated accessory pigment.

energy from the sun energies the electrons in chlorophyll, there are then boosted to a higher energy level in the photosystems. These electrons cant remain energised so return to their lowel enery level through a series of electron transport systems in thylakoid membranes as they do this they realease energy.

eletrons expelled from the chloropyhll go through one or two electron transport systems resulting in the formation of ATP and reduced NADP (a coenzyme which picks up potential energy and hydrogen atoms making it reduced. The energy for this will be provided by the ATP. ATP formation is made by phosphorylation of ADP and Pi. The light energy is also used to split water molecules to provide a source of electrons and hydrogen ions (photolysis) It realeases oxygen as waste and supplies hydrogen to coenzyme NADP.

Outline light idependent stage of photosynthesis

enzyme-driven metabolic pathway known as the calvin cycle which takes place in the stroma of chloroplasts which involves reduction of atmospheric co2 into sugars.

co2 diffuses into leaf, across the plasma membrane and into stroma of chloroplasts

enzyme rubisco (ribulose bisphosphate carboxylase) combines with co2 molecule  to a 5 carbon sugar RuBP (ribulose biphosphate)

this produces an unstable 6-carbon intermediate which splits into two 3-carbon molcules of GP ( glycerate 3-phosphate).

The GP molecules are then reduced to triose phosphate using hydrogen atoms for reduced NADP and the ATP from phosphorylation.

most of tp molecules continue into the cycle…


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