Topic 4 Flashcards
Enzymes features
- biological catalysts- capable of speeding up biochemical reactions within cell
- proteins- has a specific 3D shape produced by specific order, number and type of amino acids
- polypeptide chains- consists of one or more polypeptide chains, folded and twisted to produce tertiary structure, or quaternary structure with enzymes
- active site- small pocket or cleft in enzyme, also called substrate binding site, essential for. enzyme to function
- specificity- one enzyme only catalyses one type of reaction
- complimentary- substrates have complimentary binding shape that fits active site
Enzyme specificity
Lock and Key Model
-substrate fits into active site of enzyme, like lock and key
-assumes active site is rigid and fixed
Induced fit model
-active site changes shape slightly to fit substrate
-active site has defined shape
cellular metabolism
sum of chemical reactions that occur in each living cell
types of chemical reactions
Anabolic and endergonic reactions
-chemical reactions in which atoms and molecules are bound together to make more complex molecules-anabolic reactions
-energy is required to form new chemical bonds-called endergonic reactions
Catabolic or exergonic reactions
-reactions that break down complex molecules into simpler molecules- catabolic reactions
-these reactions release energy-exergonic reactions
Activation Energy
- enzymes reduce activation energy- reducing amount of energy required to start reaction
- without enzymes, metabolism would be so slow , that it would not sustain life.
temperature affecting enzyme activity
- enzymes have optimum temperature range, optimum temperature being the temperature of environment they are found in
- as temperature increases, molecules become more excited, thus more kinetic energy so collide more often
- if too high, structure of protein is permanently changed, usually irreversible, with tertiary shape disrupted.
- if too low, enzyme activity is lower, due to lower kinetic energy, less chance of collisions between substrate and enzyme
factors affecting enzyme activity
- temperature
- pH
- substrate and enzyme concentration
- inhibiting work of enzymes
pH affecting enzyme activity
-enzymes have optimum pH range-denatured by extreme alkali and acidic environment
buffers
- minimize changes to H+ and OH+ in solution
- works by either donating H+ or accepting H+ from the solution to maintain a narrow range of pH
- carbonic acid and bicarbonate acts as a pH regulator
- if pH is left too high or too low, enzymes denature.
substrate/enzyme concentration affect on enzyme activity
- increase in substrate-results in more product being made- rate of reaction reaches a point of saturation due to
- increase in enzyme-increase yield of product in given time, until substrate is used up
- rate of reaction is proportional to enzyme concentration
irreversible inhibition
-occurs when compound covalently binds to one or more amino acids, altering structure of enzyme, affecting active site shape- permanently inhibits enzyme because inhibitor enzyme bond is so strong, cannot be reversed by addition of substrate
Reversible inhibition
- enzyme is not permanently inhibited or damaged
- inactivate enzymes with non-covalent interactions, that can be reversed, and can dissociate from enzyme
- can be competitive or non-competitive
Competitive inhibitors
- have similar shape to usual substrate for enzyme, compete with substrate for active site- bind temporarily with the active site.
- it gets in the way
- increase the substrate concentration, it can outcompete the inhibitor, so normal reaction can occur at reasonable rate.
non-competitive inhibitors
- don’t attach to active site, but attach to somewhere else on enzyme called allosteric site
- by attaching to allosteric site, the 3D structure of enzyme changes-thus changing active site’s shape
- due to no competition between substrate and inhibitor, increasing substrate concentration won’t help
End product inhibition
- presence of allosteric binding site on enzyme-enables regulation of metabolic pathways- process of end-product inhibition or the allosteric effect
- end product may act on enzyme in the chain, acting as an inhibitor to regulate its own production
why does allosteric effect occur
because end product molecules are able to bring about conformational changes within enzyme
-leads to disruption of active site, inability of substrate to bind to active site, or inability of products of reaction to be released
Cofactors
- composed of inorganic mineral ions
- bind tightly to the enzyme
- considered helper molecules/ions- essential in biochemical transformations
Coenzymes
- composed non-protein organic vitamins
- bind loosely and temporarily to enzyme
- do not form permanent part of enzymes structure
- assist in transfer of molecules
- act with enzymes to alter the rate of reactions
