*OBJ - Enzymes & their classifications

Question 1

Explain why enzymes are called biological catalysts

Answer 1

• Enzymes provide the necessary environment for chemical reactions to progress at a reasonably faster rate - Remained unchanged - Dependent on pH, temp, concentrations, polarity, etc - But in human body pH = 7.4, temp = 37C and aqueous environment -> So need enzymes! - Different steps but same substrates & ending products

Question 2

Distinguish between an uncatalyzed and a catalyzed reaction mechanistically

Answer 2

Uncatalyzed= slower or needed higher activation energy/different conditions Catalyzed = different steps but same product

Question 3

Describe the structural and functional significance of an enzyme active site

Answer 3

Active site: region where substrate fits into, binds and the chemistry happens (some require cofactors/coenzymes) Mediated by enzyme side chains

Question 4

Define the terms EP and ES in an enzyme catalyzed reaction

Answer 4

Enzyme -Substrate complex Enzyme-Product complex

Question 5

Distinguish between substrate binding and substrate catalysis, and describe how both functions can be accomplished by the active site

Answer 5

a

Question 6

Define cofactors and coenzymes; describe their roles in the active site of an enzyme

Answer 6

Apo enzyme - need a cofactor/enzyme Holoenzyme - enzyme with the cofactor/enzyme as a unit Cofactor: 1+ inorganic ions (1/3 of enzymes require metal ions for catalytic activity - Fe, Cu, Zn, Mn, Co) Coenzyme: organic of metallo-organic molecules that are carrier of specific functional groups (shuttles) **Both take part in substrate binding and/or in catalysis

Question 7

Identify the active groups of the activation-transfer coenzymes (such as thiamine pyrophosphate, pyridoxal phosphate, coenzyme A, biotin) and oxidation-reduction coenzymes such as NAD+

Answer 7

Go over the mechanism of this table

& for Biotin

Question 8

Summarize the different roles that metal ions can play in enzyme catalyzed reactions

Answer 8

Cofactor in substrate binding, catalysis, coordinated atom

Question 9

List the six major classes of enzymatic reactions and identify the types of chemical reactions catalyzed by each of them

Answer 9

a