chapter 4 - enzymes Flashcards
what are enzymes?
enzymes catalyse reactions by lowering the activation energy for the reaction to occur
enzymes:
- metabolic reaction
- lower activation energy
- catalysts
- tertiary globular proteins
- > temp = denaturing (permanent)
- optimum temp = quickest reaction
the lock and key model
E+S -> ES complex -> EP complex -> E+P
the induced fit model
1) substrate binds to active site
2) induces enzyme to change shape and form an exact fit
3D flexibility
factors affecting rate if enzyme controlled reactions:
- temperature
- pH
- substrate concentration
- enzyme concentration
temperature
optimum = 37-40°c
• higher temp = higher collision frequencies (random)
• too hot = denatures
pH
changed in pH affect the ionic and hydrogen bonds in the tertiary structure of enzyme.
extreme pH = denature
alkali = solution base
substrate concentration
- low substrate concentration = low product concentration
* increase -> increase rate if reaction
enzyme concentration
- linear / directly proportional
* concentration of enzymes usually much lower than substrate
inhibitors
the presence of inhibitor molecules decreases the rate of enzyme reactions by binding with the enzyme (reversible OR irreversible)
competitive inhibitor
• this molecule competes with normal substrate for active site
(mostly reversible)
non-competitive inhibitor
• substrate cannot be converted into product
• inhibitor prevents the induced fit
• inhibitor binds with the allosteric site
(mostly permanent)
cofactors
- inorganic
- they form temporary binds with the enzyme but leave following the reaction
- assist in biochemical transformations
- non protein chemical compound or metallic ion
coenzyme
- large organic molecule
- they form temporary binds with the enzyme but leave following the reaction
- protein part
prosthetic group
- organic or inorganic
* permanently bound to the enzyme
