enzymes

Question 1

catalysts

Answer 1

enhance rate of reaction by a factor of millions relative to an uncatalysed reaction. not permanently altered

Question 2

where does the substrate bind to the enzyme?

Answer 2

the active site

Question 3

are enzymes specific?

Answer 3

enzymes are highly specific. they discriminate between substrates with similar structures

Question 4

how do enzymes accelerate reaction rates?

Answer 4

by decreasing the activation energy

Question 5

what are catalytic groups?

Answer 5

amino acid side chains that line the active site actively participate in the catalytic process

Question 6

is the active site big?

Answer 6

no its a small site on the protein. most of amino acids in an enzyme are not in contact with substrate

Question 7

what is the active site formed by?

Answer 7

amino acids that come from different parts of the linear amino acid sequence

Question 8

what weak attractions bind the substrate to the active site?

Answer 8

ionic, H-bonds , hydrophobic

Question 9

induced fit model

Answer 9

enzyme conformation changes to accomodate the substrate

Question 10

what changes the structure of the active site?

Answer 10

non-covalent interactions between enzyme and substrate

Question 11

does proximity and orientation of S to catalytic groups matter?

Answer 11

YES

Question 12

hydrolysis of sucrose by the enzyme sucrase

Answer 12

sucrase is a digestive enzyme that catalyses the hydrolysis of sucrose to fructose and glucose. The glycosidic bond is broken by hydrolysis

Question 13

example of a natural antibacterial agent

Answer 13

lysozyme

Question 14

what does lysozyme do?

Answer 14

breaks the glycosidic bond between sugar D and E. enzyme is breaking up cell wall of bacteria so it is destroyed and all contents are released.

Question 15

what factors affect the rate at which enzymatic reactions proceed?

Answer 15

temperature, pH , enzyme concentration, substrate concentration , the presence of inhibitors or activators

Question 16

effect of temp on enzyme-catalysed reactions

Answer 16

enzymes are sensitive to temp
optimum temp- operates at max efficiency
optimum temp close to normal temp of organism it comes from

Question 17

optimum pH of pepsin

Answer 17

2

Question 18

optimum pH of trypsin

Answer 18

8

Question 19

what is denaturation?

Answer 19

loss of a proteins native structure

Question 20

can a denatured protein work?

Answer 20

no it is biologically inactive

Question 21

what structure does an enzyme loose if it is denatured ?

Answer 21

secondary and tertiary

Question 22

enzyme inhibitors

Answer 22

enzyme reaction rates can be inhibited or decreased by enzyme inhibitors

Question 23

example of an inhibitor?

Answer 23

Rifampicin: binds to RNA pol in bacteria- prevents initiation of transcription

Question 24

competitive inhibitors

Answer 24

bind to the active site of an enzyme, competing with the substrate - structurally similar to S

Question 25

non-competitive inhibitors

Answer 25

bind to another part of an enzyme, causing the enzyme to change shape and even if the S can bind the active site is less effective

Question 26

what happens in feedback inhibition

Answer 26

the end product of a metabolic pathway is the enzyme inhibitor and shuts down the pathway

Question 27

what does feedback inhibition prevent

Answer 27

prevents a cell from wasting chemical resources by synthesising more product than is needed

Question 28

covalent modification

Answer 28

reversible interconversion between active site and inactive forms

Question 29

what does phosphorylation of a protein by a protein kinase do

Answer 29

can either increase or decrease the proteins activity

Question 30

what are proenzymes or zymogens ?

Answer 30

several enzymes stored as inactive precursors, activated by irreversible cleavage of 1 or a few peptide bonds

Question 31

what is prothrombin?

Answer 31

a blood-clotting enzyme

Question 32

what triggers the conversion of prothrombin to thrombin ?

Answer 32

injury to a blood vessel

Question 33

what does thrombin convert

Answer 33

fibrinogen to fibrin

Question 34

enzymes catalytic groups are always beside each other in the linear polypeptide chain

Answer 34

false

Question 35

ES are stabilised by covalent interactions

Answer 35

false

Question 36

the structure of an enzyme is changed following a catalytic reaction

Answer 36

false

Question 37

the active site if an enzyme and the substrate fit exactly together

Answer 37

false