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STRUCTURE AND REGULATION OF BIOCHEMICAL PATHWAYS (INHIBITION OF ENZYME…
STRUCTURE AND REGULATION OF BIOCHEMICAL PATHWAYS
METABOLISM:
The metabolism of an organism is the sum of all the chemical reactions that occur within its cells.
This includes the energy-transforming reactions of cells such as production of organic molecules. and the breakdown, recycling and extretatory processes.
Catabolic Reactions:
Catabolic reactions are reactions in which substrates are broken down and energy is released.
Catabolic reactions are exergonic because they release energy.
Anabolic Reactions:
Anabolic reactions are reactions that require an input of energy in order to produce larger molecules from smaller substrates.
anabolic reactions are endergonic because they require energy.
the energy is required to form bonds between molecules.
ENZYMES:
Biological catalysts that increase the rate of biochemical reactions in cells.
PROPERTIES OF ENZYMES:
composed of protein
Substrate specific:
catalyse chemical reactions involving one particular substrate molecule and not any other.
there are two theories to explain how enzymes react with their substrates.
LOCK AND KEY:
INDUCED FIT:
Optimal conditions:
enzymes have optimal conditions under which they work effectively and will catalyst a reaction so that the maximum product is produced per unit of time.
e.g. temperature
Sensitive:
sensitive to factors such as temperature and PH.
when these conditions are not optimal , the activity of enzymes is reduced.
extremes of such factors may lead to enzymes becoming denatured. When this happens the enzyme cannot recover its function because the shape of its active site has been permanently altered.
The rate of enzyme activity is dependent upon:
concentration of substrate - the higher the concentration of the substrate, the greater the rate of interaction between substrate molecules and enzymes, leading to increased rate of reaction.
concentration of enzyme - the more enzyme available to catalyze a reaction, the more rapidly the reaction will proceed until all enzyme molecules are fully engaged in the reaction.
temperature - the rate of enzyme catalyses reactions generally increase as the temperature increases. This is because the warmer particles become, the more rapidly they move, causing more collisions with the substrate.
Activation energy
:
the energy expended to initiate a reaction.
enzymes lower the activation energy, making it easier for the reaction to proceed.
INHIBITION OF ENZYME ACTIVITY
Reversible Inhibition:
the bonds formed between the inhibitor and enzyme are weak (eg. hydrogen bonds), so they are easily broken and the inhibitor reversed.
the reduction in enzyme activity can be partially overcome by increasing the concentration of substrate.
Irreversible inhibition:
the bonds formed between the inhibitor and enzyme are strong (eg. covalent bonds), so the binding is irreversible.
this means the inhibitor blocks the enzymes active site permanently, so the enzyme will no longer be able to take part in reactions.
Competitive Inhibition:
the inhibition of an enzyme due to a molecule that binds to the active site of the enzyme, preventing the substrate from binding.
Non-Competitive Inhibition:
The inhibition of an enzyme due to an inhibiting molecule binding to an allosteric site on the enzyme. This causes a conformational change in the active site of the enzyme that prevents the substrate from binding, or otherwise prevents a catalytic reaction from proceeding even if substrate is bound.
Feedback Inhibition:
occurs when a product produced late in a biochemical pathway acts as the inhibitor of an enzyme acting earlier in the pathway.
COENZYMES:
small organic molecules important to the normal functioning of enzymes.
eg. ATP, NADH, NADPH, Acetyl coenzyme A.
