Week 2 (enzymes) Flashcards
What does a catalyst do?
Increase the rate of a reaction without being consumed by the reaction.
It does this by lowering the activation energy.
Give examples of enzymes in biology
There are lots of digestive enzymes that break down food and release nutrients needed for the body.
E.g., lipase, amylase, peptidase
Give examples of enzymes in industry
Rennet is a mix of enzymes used in cheesemaking. Pepsin breaks down the protein, chymosin curdles milk and lipases breaks down fats.
Invertase breaks down hard sugars into soft sugars and is used to make soft-centred chocolates.
Give an example of enzymes in agriculture
Phytases are added to animal feed to make minerals more bioavailable.
What are enzymes?
Usually proteins
Biological catalysts
Why are enzymes necessary?
Many biological reactions are chemically unfavourable so need enzymes.
Uncatalysed reactions in biology tend to be quite slow.
Enzymes are usually much better (specific and efficient) than catalysts in chemistry.
If human enzymes don’t work properly it can lead to disease.
Other than their amino acids what may enzymes also require to function?
Cofactors
Coenzymes
Some enzymes will only need either a cofactor or coenzyme whilst other enzymes will require both.
What are ribosozymes?
RNA enzymes
RNA molecules can have complex tertiary structure and so can be catalytically active.
Name two common cofactor metal ions
Iron
Zinc
What are cofactors?
An inorganic ion or a coenzyme required for enzyme activity.
They are often found in enzymes that catalyse redox reactions.
They also affect bonding, and can have a structural role.
What are coenzymes?
An organic cofactor require for the action of certain enzymes.
More complex organic cofactors.
They are often derived from vitamins and often act as transient carriers for functional groups.
What are prosthetic groups?
A metal ion or organic compound (other than an amino acid) covalently bound to a protein and essential to its activity.
They bind tightly or covalently to a protein, and act as structural elements.
What is an apoenzyme?
The protein portion of an enzyme that is inactive.
It is exclusive of any organic or inorganic cofactors or prosthetic groups that might be required for catalytic activity.
What is a holoenzyme?
A catalytically active enzyme, including all necessary subunits, prosthetic groups and cofactors.
Where does an enzyme-catalysed reaction take place?
Active site
What happens at the active site?
A substrate molecule binds in the active site and is acted upon by the enzyme.
Describe the active site
The surface of the active site is lined with amino acid residues that allow the substrate to bind and catalyse its chemical transformation.
What is chymotrypsin?
It is a protease that catalyses the hydrolysis of peptides bonds.
It is specific for peptide bonds next to aromatic amino acids.
What do and don’t enzymes affect?
Enzymes affect the rate of reaction but do not affect its equilibrium.
What leads to a change in Gibbs free energy of the system?
The progression of a reaction; conversion of substrates into products.