IB Biology - 8.1: Metabolism

what is metabolism?

all of the enzyme catalysed chemical reactions in an organism

anabolic reactions

create larger molecules

form bonds

condensation reaction

requires energy

e.g photosynthesis

catabolic reactions

breaking down larger molecules into smaller ones

breaks bonds

hydrolysis reaction

releases energy

e.g. cell respiration

metabolic pathways

the sequence showing the steps of a metabolic reaction

mostly in chains or cycles

what are the two enzyme substrate models?

induced fit model and the lock and key model

endergonic reactions

products have more energy than reactants

energy is absorbed in this reaction

anabolic

exergonic reactions

products have less energy than reactants

energy is released in this reaction

catabolic

what is inhibition?

the act of decreasing/eliminating the effects of any enzyme

competitive inhibition

a molecule that is similarly shaped to the specific substrate of an enzyme attaches to the active site and blocks the substrate from joining with the enzyme

this can be overcome by increasing substrate concentration

non competitive inhibition

also known as allosteric inhibition

a molecule attaches to the allosteric site of an enzyme changing the conformation the enzyme

feedback inhibition (end product inhibition)

prevents the cell from producing more of a substance when there is already a sufficient amount of it in the cell

end product of the metabolic pathway will act as an allosteric inhibitor to one of the enzymes

example of competitive inhibition

we use the drug sulphanilamide to block bacteria from using one of their enzymes to build up their cell wall

example of non competitive inhibition

mercury binds easily to proteins (including enzymes) and changes the shape of these proteins. this is very harmful.

examples of feedback inhibition

E-coli needs enzymes to produce isoleucine \n if isoleucine is already present in high amounts, it inhibits the first enzyme and the production process stops.