Introduction To Enzymes In Physiology Flashcards
What is an enzyme?
- Biological catalysts
- Provide reaction surface (active site)
- Weaken bonds in the reactants ( may provide acid base catalysis)
- Doesn’t change position of equilibrium
Should there be a positive or negative 🔺G and what is the equation to calculate it?
- Negative
- 🔺G = free energy of initial state - free energy of final state
What is the lock and key hypothesis?
- Active site has a rigid shape
- Fit between substrate and enzyme is exact
- E-S complex formed
- Products are different shapes from substrate and are released
What is the Induced Fit Hypothesis?
- Active site is flexible and can change conformation
- Shape of enzyme, active site and substrate adjust to maximise fit
- Greater range of substrate specificity
How does changing pH affect enzymes?
-Alters the ionisation state of amino acid side chains
- Alters ionic bonding, structural stability, shape & functionality of enzyme
- Overall 3D structure
How does changing temperature affect enzyme activity?
- Most active at optimum temperatures
- Show little activity at low temps
- Activity is lost at high temps as denaturalising occurs
What are Cofactors?
-Non protein prosthetic group (metal ions or inorganic group)
- Cofactors bind to enzyme and maintain correct config of active site
What are Coenzymes?
- Organic molecule bound to the enzyme by weak interactions
- Transfer electrons or small groups between substrates
What are the different classifications of enzymes?
- Oxidoreductases
- Transferases
- Hydrolases
- Lyases
- Isomerases
-Ligases/synthases
What are Oxidoreductases?
- Catalyse transfer of electrons from donors to acceptors
- Catalyse oxidation-reduction pathways
- E.g Dehydrogenases accept and donate electrons as hydride ions or hydrogen atoms
What are Transferases?
- Catalyse transfer of a specific functional group between molecules
- E.g Kinases, Aminotransferases, Glycosyltransferases,
Acyltransferases
What are Kinases and Aminotransferases?
- Kinases: transfer phosphate groups usually ATP to another molecule
- Aminotransferases: transfer amino groups, important in amino acid metabolism
What are Glycosyltransferases and Acyltransferases?
- Glycosyltransferases: transfer carbohydrate residues
- Acyltransferases: transfer fatty acyl groups
What are Hydrolases and describe examples?
- Catalyse cleavage of bonds by the addition of water molecules
- Phosphatases : Hydrolyse phosphoric ester bonds
- Lipases : hydrolyse ester bonds in lipids
- Peptidases : Hydrolyse peptide bonds to form 2 products
What are Lyases?
- Catalyse the addition of water, ammonia or CO2 to double bonds
- Cleave bonds by means other than hydrolysis or oxidation
-Decarboxylases : Remove CO2 - Dehydrases : Remove H2O
- Deaminases : Remove NH3
