UNIT 1 - KA6

Metabolic pathways are interrogated and controlled pathways of enzyme - catalysed reactions within a cell

Anabolic reactions build up large molecules from small molecules and require energy

Catabolic reactions break down large molecules into smaller molecules and release energy

Metabolic pathways can have reversible steps, irreversible steps and alternative routes

Metabolic pathways are controlled by the presence or absence of particular enzymes and the regulation of the rate of reaction of key enzymes

The activation energy is the energy required to break chemical bonds during a chemical reaction.

Higher activation energy needed with no enzymes :(

Lower activation energy is needed with enzymes :)

Check jotter

1) lower the activation energy (required for a reaction) 2) SPEED UP the rate of reaction 3) DO NOT change and can be reused

Enzymes are the body’s catalysts and without them the biochemical reactions essential for life would be unable to proceed at a fast enough rate to sustain life

Enzymes are said to be specific which means that each enzyme only works on one substrate

The substance and enzyme works on is called it’s substrate

Amylase - starch - (Maltose/glusoce) simple sugars Lipase - LIPDS (fats) - fatty acids and glycerol Protease (eg pepsin) - protein - amino acids

A model that explains how enzymes and substrates react when mixed is the INDUCED FIT model

Induced fit occurs when the active site changes shape to better fit the substrate after the substrate binds

1- substrate with High affinity for active site binds to active site. Substrate becomes bound to active site 2- once the substrate binds induced fit occurs as the enzymes active site has changed shape to better fit the substrate (enzyme substrate complex formed). 3- substrate is broken down to end products 4- end products released 5- enzyme has returned to original shape. End products have low affinity allowing them to leave the active site

1 - temperature 2 - pH 3 - substrate concentration 4 - inhibitors

• the reaction rate is lower at w because the substrate concentration is lower. So there are less substrate molecules to react with the available active sites. The reaction rate is quicker at x

• as substrate concentration increases from x-y more substrate is available to bind to free enzyme active sites so reaction rate increases. At z there are no free enzyme active sites available so even if substrate concentration is increased the reaction cannot go any faster

Check jotter

Substrate — ——> product Enzyme

Substrate <——— product Enzyme

Substrate <——— product