enzymes

what is the function of an enzyme?

act as a biological catalyst to speed up metabolic reactions in living organisms by lowering the activation energy

what does intracellular mean?

produced and used within the cell

e.g. catalase

what does extracellular mean?

produced inside but used outside the cell

e.g. amylase catalysing hydrolysis of starch and trypsin catalysing hydrolysis of peptide bonds

example of the process of enzyme breaking down sucrose :

• substrate sucrose, contains glucose and fructose bonded together

• substrate binds to enzyme active site

• forms enzyme substrate complex

• the binding places stress on bond lowering the activation energy

• bond breaks

• products are released

what is the induced fit model?

states that when a substrate binds with the active site the enzyme changes shape to fit the substrate unlike the lock and key model

effect of temperature on enzyme activity :

• optimum warm temperature means increased kinetic energy and more successful bindings

• temperature too high mean more kinetic energy causing bonds to break breaking the tertiary structure and denature the enzyme

what does denatured mean?

tertiary structure has been broken causing the active site to change

Q10 =

rate at higher temperature / rate at lower temperature

effect of ph on enzyme activity :

• mid optimum ph

• too high ph causes H+ and OH- ions to break the ionic and hydrogen bonds breaking the tertiary structure and denaturing the enzyme

effect of substrate concentration on enzyme activity

• doesn’t increase enzyme activity

• provides excess substrate molecule

• active site become saturated when all are in use

• graph plateaus

effect of enzyme concentration on enzyme activity :

• decreases when substrate molecules are limited and not available to bind the active sites

• increased concentration doesn’t effect reaction rate

how to calculate rate of reaction on a graph?

• draw a tangent

• calculate gradient of tangent

inorganic cofactor :

• small inorganic molecule

• e.g. chloride ions needed for amylase

organic cofactors (coenzymes) :

• catalyse the reaction allowing substrate to bind to the active site

• temporarily binds to enzyme

• can be recycled by different enzymes

prosthetic groups :

• binds to in active protein to activate the protein and provide an active site for substrate

• e.g. zinc permanently binds to carbon anhydrase

competitive inhibitors :

• has a similar shape to substrate and competes with substrate for the active site

• blocks active site with no reaction

non competitive inhibitors :

• binds to another site called the allosteric site

• causes active site to alter the 3d tertiary structure meaning the substrate no longer fits

reversible inhibition :

• weak hydrogen or ionic bonds

• inhibitor can be removed with excess substrate concentration

• e.g.competitive inhibition

non reversible inhibition :

• strong covalent bonds

• inhibitor cannot be removed easily

• e.g. non competitive inhibition

end product inhibition :

• where the product of an enzyme reaction binds to another enzyme and inhibits its activity

• form of negative feedback