Enzymes are biological catalysts that speed up chemical reactions without being used up or changed.
A substrate is a molecule that which an enzyme acts on
The functional part of an enzyme is called the active site
Describe the lock and key model of enzyme action: Enzymes have an active site of specific shape; the substrate that is a complemenatry shape binds to active site
The specific 3D shaped active site of an enzyme is determined by its sequence of amino acids (primary structure)
When a substrate binds to the active site we call the resulting structure an enzyme-substrate complex
A substrate does not have the same shape as the active site it has a complementary shape.
Enzymes are a type of biological molecule called proteins
Explain induced fit model in enzymes:
upon binding the active site of the enzyme molds around the substrate; active site becomes complementary
Increasing the temperature affects the rate of enzyme controlled reactions by:
increase in kineticenergy between molecules
molecule have more succesful collisions so more enzyme substrate complexes formed
rate of reaction increases
after optimum reached denaturation; loss of tertiary structure as break of bonds
active site altered so substrate can fit
decreasing temperature affects the rate of enzyme controlled reactions by:
decrease in kinetic energy between molecules
molecule have less succesful collisions so less enzyme substrate complexes formed
rate of reaction decreases
enzymes increase rate of reaction by lowering the activation energy of the reaction
Competitive inhibitors have similar shapes to the substrate, hence competing with the substrate for the available active site. Competitive inhibitors are not permanently bound to the enzyme active site
Non-competitive inhibitors are chemicals that bind to the enzyme and change its shape; eventually all enzymes will bind to non-competitive inhibitors.
How does the structure of enzymes relate to its function:
specific 3D tertiary structure
substrate complementary shape
substrate can bind to active site
How does competitve inhibitors affect the activity of enzymes?
Inhibitor has similar shape to subtrate
competes for active site
fewer enzyme substrate complexes formed but cannot react with the enzyme
How does incompetitve inhibitors affect the activity of enzymes:
Inhibitor differs to shape of substate
Bind to allosteric site
Alters active site so substrate can not bind and no substrate enzyme complexes formed
How does substrate concentration affect the activity of enzymes?
Substrate limiting factor
Enzyme active sites fully occupied
How does pH affect the activity of enzymes:
Ionic bonds holding tertiary structure break, active site denatures and substrate no longer binds to it charges of amino acid in active site affected: so fewer E-S complexes formed
Activation energy: minimum amount of energy required to bring particles into close contact; so that they will collide and react
Heterotrophs are organisms that obtain their nutrients by consuming other organisms
extracellular enzymes are enzymes that are released from the cells that make them
Intracellular enzymes are found in the cytoplasm or attached to cell membranes, their action takes place inside the cells
the enzyme lock and key hypothesis explains:
Enzyme specificity
The loss of activity when enzymes denature
Co factors are an additional non-protein molecule that is needed by some enzymes to help the reaction
Prosthetic groups are tightly bound cofactors
Coenzymes are cofactors that are bound and released easily
How does concentration affects to enzyme controlled reactions:
Proportional to rate of reaction until there are more substrates than enzymes present
Rate of reaction increases
Substrate binds to active site, but more enzymes are available
Rate increases if more substrate is added
Eventually, curve becomes constant (no increased rate)
Substrates occupy all active sites (all enzymes)
Adding more substrate won't yield more product, as no more active sites are available