Exam 3: Lecture 18

Question 0

Sir Archibald Edward Garrod

Answer 0

• First to make connection between disease and fundamental errors in biochem reactions
• Coined term “inborn errors of metabolism”
• Enzymes must be link, mutations can cause altering biochem reactions

Question 1

Definition of enzyme

Answer 1

• A protein that speeds up a chemical reaction in a living organism
• acts as a catalyst for specific chemical reactions, converting substrates to products

Question 2

_______ cleave peptide bonds at specific sites

Answer 2

•Proteases

Question 3

Active Site

Answer 3

• Usually void of water

* controls the proper shape, pH, and polarity for substrate binding and chemical reactivity

Question 4

Transition state

Answer 4

•Unstable and highest level of free energy

Question 5

Small molecules that contribute to the chemical reaction of the enzyme are?

Answer 5

• Cofactors
• many different roles in catalysis
• enzymes that use the same cofactor share similar mechanisms of catalysis

Question 6

Apoenzyme

Answer 6

•Enzyme without its cofactor

Question 7

Haloenzyme

Answer 7

•Cofactor bound and catalytically active

Question 8

Types of Cofactors

Answer 8

• Metals: + charges, stable coordination of active site groups, contribute to chemical reactivity.
• Coenzymes: small organic molecules often derived from vitamins

Question 9

Coenzymes that are tightly bound are called?

Answer 9

•Prosthetic groups

Question 10

Scurvy

Answer 10

• Cofactor deficiencies: Vit C cofactor for lysyl hydroxylase-involved in collagen assembly
• Spongy gums, hemorrhaging of skin and mucous membranes

Question 11

Ariboflavinosis

Answer 11

• Cofactor deficiency: Riboflavin (B2) required fro FAD synthesis
• Reduced glutathione reductase activity (cleans up reactive oxygen species)-requires FAD

Lesions in corner of mouth and on lips, UV sensitive

Question 12

Active site of alcohol dehydrogenase

Answer 12

• NAD+ is reduced to NADH in the conversion of ethanol to acetaldehyde
• The cofactos NAD+ and Zinc are in a specific arrangement for this catalysis

Question 13

What are the 6 classes of enzymes and their type of reaction?

Answer 13

• Oxidoreductases: oxidation-reduction
• Transferases: group transfer
• Hydrolases: Hydrolysis reaction (transfer of functional groups to water)
• Lyases: Addition or removal of groups to form double bonds
• Isomerases: Isomerization (intramolecular group transfer)
• Ligases: Ligation of two substrates at the expense of ATP hydrolysis

Question 14

Oxidoreductases

Answer 14

• Enzyme that catalyzes the transfer of electron from one molecule to another
• Reductant = hydrogen or e- donor
• Oxidant = hydrogen or e- acceptor

Question 15

Alcohol Dehydrogenases (ADH)

Answer 15

• oxidorgenase that converts alcohols to aldyhydes or ketones with the reduction of NAD+ to NADH
• Alcohol = oxidized
• NAD+ = reduced

Question 16

Transferases

Answer 16

• Donor molecules required (source of methyl groups for ATP)
• Kinases Receptors: phosphorylate proteins and themselves
• usually at tyrosine (TKRs), serine, and threonine residues

Question 17

Hydrolases

Answer 17

• Hydrolysis of covalent bonds

* transfer function groups to water

Question 18

What hydrolases cleave double sugars to single?

Answer 18

• Disaccharidases

* Defect in lactase = lactose intolerance

Question 19

Lyases

Answer 19

• Addition or removal of double bonds

* Aldolase: catalyzes second step of glycolysis

Question 20

Isomerases

Answer 20

• intramolecular group transfer

* produce is an isomer of the substrate

Question 21

Triose phyosphate isomerase

Answer 21

• intramolecular oxidation-reduction reaction
• Glu 165 acts as a base/oxidant
• His 95 acts as acid/reductant

Question 22

Ligases

Answer 22

• enzymes that catalyzes the covalent linkage of two substrates
• usually at the expense of ATP hydrolysis

Question 23

DNA Ligase

Answer 23

• forms two covalent phosphodiester bonds between 3’ hydroxy ends of one nucleotide with the 5’ phosphate end of another
• uses ATP