Mechanism of Enzyme Action

• Molecules in a solution move and collide randomly. For a reaction, molecules need to collide in the correct orientation
• When high temperatures and pressures are applied --> the speed of the molecules increase, this means the no. of successful collisions and rate of reaction will increase 

Each enzyme catalyses 1 biochemical reaction --> enzymes are specific 

• Activation energy --> energy supplied for a reaction to start. Sometimes it is so large that it prevents the reaction happening under normal conditions 
• Enzymes help the molecules collide successfully, this means the activation energy required is reduced 

• the area within the tertiary structure of an enzyme (active site) has a shape complementary to the shape of a specific substrate molecule 
• only a specific substrate will 'fit' the active site of an enzyme to form an enzyme-substrate complex 

• The active site and substrate are held in such a way that the right atom groups are close enough to react. The R-groups within active site interact with the substrate- puts strain on the temporary bonds --> this helps the rate of reaction 

• The active site of an enzyme actually changes shape slightly as the substrate enters- induced fit hypothesis
• It is a modified version of the lock and key hypothesis 

• The intial reaction between the enzyme and substrate is weak
• The weak interactions rapidly induce changes in the enzymes tertiary structure that strengthens binding- strain on the substrate molecule
• This can weaken a particular bond/bonds in the substrate = activation energy lowered for the reaction

Enzymes that act within cells. They play an essential role in both the structure and function of cells and whole organisms 

Example:

-synthesis of polymers from monomers e.g. making polysaccharides from glucose requires enzymes

• Hydrogen peroxide is a toxic product of many metabolic pathways
• The enzyme catalse ensures hydrogen peroxide is broken down into oxygen and water quickly, preventing accumulation
• Found in both plant and animal tissues 

Enzymes that are released from cells to break down large nutrient molecules into smaller molecules- digestion (so, they work outside the cell that made them)

• Both single-celled and multicellular organisms rely on extracellular enzymes to make use of polymers for nutrition 

Single-celled Organisms:

• e.g. bacteria and yeast release enzymes into their immediate environment 
• They break down larger molecules e.g. proteins and the smaller molecules produced e.g. amino acids and glucose are then absorbed by the cells

Multicellular Organisms:

• many eat food to gain nutrients- large molecules have to be digested so smaller enzymes can be absorbed into the bloodstream 
• They're transported around the body to be used as substrates in cellular reactions
• e.g. amylase and tipsin