Enzymes Flashcards
What do enzymes do
Affect both structure & function: they catalyse reactions that affect metabolism at a cellular and whole organism level
Role of intracellular enzymes e.g. catalase
Produced inside cell
Catalase catalysed decomposition of hydrogen peroxide (which causes oxidative stress) into water & oxygen
Role of extracellular enzymes e.g. amylase & trypsin
Amylase - catalyses digestion of starch to maltose in saliva / small intensive lumen
Trypsin - pancreatic endopeptidase catalyses hydrolysis of peptide bonds in small intestine lumen
What are the two models of enzyme action
Induced fit model
Vs
Lock & Key hypothesis
Lock and key hypothesis steps
Induced fit model of enzyme activity
Factors that affect enzyme activity
Effects of pH
Temperature
Enzyme concentration
Substrate concentration
Effect on pH on enzyme activity
Diff enzymes = diff optimum pH conditions
pH changes affect the amino acids interactions in the chain
Making them unfold & altering the shape of the active site & the enzyme becomes denatured
Changes jn pH affect H bonds, ionic bonds & those between the amino acid variable R groups
All these bonds will act differently in diff concentrations of Hydrogen ions
This impacts the 3D shape therefore, change in reduction of RoR
Effect of temperature on enzyme activity
Higher temp = the molecules move faster & collide more often
Q10 - temp co-efficient: measures how much the rate of reaction increases with a 10°C rise in temperature
If the temp is too high… denatured! Bonds holding the proteins together vibrate until the bonds strain and then break
The breaking of these bonds, change in the tertiary structure of the protein
The enzyme = denatured, the active site has changed shape and is no longer complimentary to the substrate & the enzyme can no longer function as a catalyst
Enzyme concentration effect of enzyme activity
Effect of substrate concentration on enzyme activity
Effect of substrate concentration on enzyme activity
What are cofactors
Non protein compounds required for enzyme activity
-> coenzymes
-> inorganic cofactors
-> prosthetic groups
What are coenzymes
Organic Co-factors & don’t bind permanently & often transport molecules or electrons between enzymes
What are inorganic co-factors
E.g. Cl-
Often metal ions
These facilitate temporary binding between substrate & enzymes
What are prosthetic groups
Tightly bound cofactors act as a permanent part of enzymes binding site, e.g. Zn2+ for carbonic anhydrase
What are enzyme inhibitors
Substances that slow down or stop a reaction by affecting the binding of the substrate to the enzymes
These can be reversible or irreversible
What are irreversible inhibitors
E.g. heavy metal ions like mercury & silver
Cause disulphide bonds within the structure to break, causing the active site shape to change, thus affecting the protein activity
Reversible inhibitors ?
Bind to the active site through the hydrogen bonds and weak ionic interactions, therefore don’t bind permanent
What are the 2 types of reversible inhibitors
Competitive inhibitors
Non-competitive inhibitors
How do competitive inhibitors act / work / what are they
Similar in structure to the substrate molecule: they bind to the active site of the enzyme, decreasing its activity ad they compete with substances for the enzyme
Amount of product formed = same, but rate at which product formation occurs decreases
The higher the concentration of competitive inhibitor, the lower the reaction rate
Can be reversed by increasing substrate as this out competes them
How do non-competitive inhibitors work
- bind at another site on the enzyme = the allosteric site
- binding to this causes changes in the active site
Therefore preventing the binding of the substrate
Increasing substrate conc = no effect
Many drugs are inhibitors e.g. penicillin inhibits an enzyme
