enzymes<3

Question 1

classification of enzymes

Answer 1

1. oxidoreductase
2. transferase
3. hydrolase
4. liyase
5. isomerase
6. ligase

Question 2

what does oxidoreductase do

Answer 2

catalyse oxidation and reduction reactions

Question 3

what does transferase do?

Answer 3

catalyse group transfer reactons- often require a coenzyme

Question 4

what does lyase do?

Answer 4

catalyse lysis of substrate

Question 5

what does isomerase do?

Answer 5

catalyse structural changes in a single molecule

Question 6

what does ligase do?

Answer 6

catalyse ligation, joining of two substrates requires ATP

Question 7

describe oxidoreductase and give example

Answer 7

lactate dehydrogenase,
get NAD+ production
NAD+ is a coenzyme

Question 8

describe transferase and give example

Answer 8

catalyse group transfer reaction, often require coenzyme
portion of substrate binds covalently
includes kinase and alanine transaminases

Question 9

describe LYASES and give example

Answer 9

catalyse lysis of substrates
to cut
example = pyruvate decarboxylase

Question 10

describe isomerase

Answer 10

catalyse structural changes in a single molecule
one substrate and one product
catalyse inter conversion of L-alanine to D-alanine

Question 11

describe ligases

Answer 11

catalyse ligation -> joining of two
requires ATP
example L-glutamine to L-glutamate. catalysed by glutamate synthesase

Question 12

what is a first order reaction

Answer 12

a reaction whose rate is directly proportional to the conservation of only one reactant

Question 13

ES complexes are formed when binding occurs between the two via a —— bond in the —— ——-

Answer 13

covalent bond in the active site

Question 14

interactions between substrate and protein are ———-

Answer 14

transient

Question 15

a simple enzymatic reaction occurs in two steps

Answer 15

1. formation of complex

2. dissociation of enzyme and product

Question 16

what is a michellis mention equation used for

Answer 16

determine efficiency and specify of such reactions.

Question 17

how to plot a michellis mention and what does this allow us to do

Answer 17

plot initial velocity VS substrate concention allows us to calculate Km

Question 18

what is Km

Answer 18

mechellis menton constant

Question 19

shape of curve is typically …

Answer 19

hyperbollic

Question 20

how to calculate Km

Answer 20

Vmax/2 =Km

Question 21

the lower the value of Km, the tighter or looser substrate binding

Answer 21

tighter

Question 22

what is Km used to determine

Answer 22

used to distinguish between different enzymes

Question 23

what does Km measure

Answer 23

stability of ES complex

Question 24

what is an enzyme inhibitor

Answer 24

a compound that binds to an enzyme and interferes with its activity

Question 25

key features of reversible enzyme inhibitor

Answer 25

small - bind reversibly
natural enzyme inhibitors usually in metabolism
equilibrium defined by inhibition constant K

Question 26

key features of irreversible enzyme inibition

Answer 26

form stable covalent bond

usually caused by ALKYLATION or ACYLATION of side chains of an amino acid residue

Question 27

what is the effect of competetative inhibition (I binds to E only)

Answer 27

Raises Km

Vmax unchanged

Question 28

what is the effect of uncompetitive inhibition (I binds to ES only)

Answer 28

lowers Vmax and Km

ratio of Vmax;Km remains unchanged

Question 29

what is the effect of non competitive inhibition (I binds to E or ES)

Answer 29

lowers Vmax

Km remains unchanged

Question 30

key features of polar amino acid residue

Answer 30

active site lined with hydrophobic residue
polar amino acids undergo chemical change during catalyst
most act indirectly

Question 31

key features of acid based catalyst

Answer 31

increase rate of reaction achieved by catalytic transfer of a proton.
rely on Aa side chains that donate and accept protons
histidine ideal for group proton transfer

Question 32

key features of covalent catalyst

Answer 32

substrate bound covalently to the enzyme to form reactive intermediates
reacting side chains either neuclophile or electrophile