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
