Enzymes

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Questions and Answers

What are the properties of catalysts?

Catalysts are mostly proteins and they are:-

Efficient- work at body temperature in aqueous solution, near neutral pH. It can increase the rate of reaction by a factor of up to 1020.
Specific- each enzyme has a limited range of substrates, some can distinguish stereoisomers
Potent- each enzyme molecule can convert many substrate molecules into product per second

What is the mechanism of enzyme action?

Enzymes speed up the rate at which a reaction reaches equilibrium 1) Bind and stabilize the transition state 2) Reduce activation energy by providing an alternative reaction pathway

What are isozymes?

Isoforms of enzymes - catalyze the same reaction but have different properties and structure

What are protein kinases?

Protein kinases are molecules that facilitate phosphorylation reaction. Signup and view all the answers

What are cofactors?

Metal ions required for enzymatic activity Signup and view all the answers

What are coenzymes?

Organic molecules required for enzymatic activity Signup and view all the answers

What are prosthetic groups?

Tightly bound coenzymes Signup and view all the answers

What is an apoenzyme?

enzyme without cofactor Signup and view all the answers

What is a holoenzyme?

Enzyme with cofactor Signup and view all the answers

What does the substrate- enzyme complex involve?

The substrate binds to an active site which is a cleft or crevice. It contains amino acids essential for catalytic activity and amino acids for highly specific interactions. Signup and view all the answers

What is the lock and key model?

Active site of unbound enzyme is complementary to the shape of the substrate Signup and view all the answers

What is the induced fit model?

Binding of a substrate induces a conformational change in the enzyme and it results in a complementary fit Signup and view all the answers

What effect does temperature and pH have on enzyme activity?

<ol> <li>Each enzyme will have an optimum - at either side of the optimum, enzyme activity will decrease</li> <li>Active site can be altered by extreme temperature/pH</li> </ol> Signup and view all the answers