Enzymes as Biological Catalysts

Question 1

d: enzyme

Answer 1

any protein that acts as a catalyst, increasing the rate at which a chemical reaction reaches equilibrium

Question 2

do enzymes affect the equilibrium position of a reaction?

Answer 2

NO

Question 3

Apart from proteins, what else can be a catalyst and give examples

Answer 3

some types of RNA eg ribozymes

Question 4

What is optimal conditions for enzymes in the body? (3)

Answer 4

body temp
in solution
neutral pH

Question 5

are enzymes specific, how?

Answer 5

distinguish stereoisomers

Question 6

why can an enzyme be described as potent?

Answer 6

each enzyme molecule can convert many substrate molecules into product per second

Question 7

d: transition state

Answer 7

is the reaction intermediate species which has the greatest free energy

Question 8

How do enzymes reduce the activation energy?

Answer 8

energy by providing alternative reaction pathways

Question 9

What is Glycogen Storage disease?

Answer 9

Enzyme deficiency that results in failure of

glycogen to enter transition state

Question 10

What is the cause of glycogen storage disease?

Answer 10

:Defective glycogen synthesis/breakdown in muscle, liver & kidney

Question 11

Symptoms of Glycogen storage disease

Answer 11

Hypoglycaemia
Hepatomegaly (liver swelling)
skin and mouth ulcers
bacterial and fungal infection
bowel inflammation and irritability

Question 12

treatment of glycogen storage disease

Answer 12

Slow release glucose meal (eg corn-starch)
Feed little & often = “mimic” glycogen
conversion to glucose

Question 13

what does the catalytic activity of enzymes depend on?

Answer 13

on presence of small molecules, called cofactors or coenzymes.

Question 14

what are cofactors?

Answer 14

is a non-protein chemical compound or metallic ion

Question 15

what is a coenzyme?

Answer 15

organic molecules that change charge or structure during the course of the reaction, but are regenerated

Question 16

what are tightly bound coenzymes called?

Answer 16

prosthetic group

Question 17

Enzyme without cofactor is called ____.

Answer 17

apoenzyme

Question 18

Enzyme with cofactor is called _______.

Answer 18

holoenzyme

Question 19

complete the equation

apoenzyme + cofactor =

Answer 19

holoenzyme

Question 20

give eg of cofactor and how it is used

Answer 20

metal ion -zinc
involved in redox reactions
stabilise transition states

Question 21

give eg of coenzyme and how it is used

Answer 21

many are derived from vitamins
many involved in redox reactions
NAD+, FAD
others involved in group transfer processes

Question 22

what does CoA (= Coenzyme A) transfer?

Answer 22

acetyl groups

Question 23

What does ATP (coenzyme) transfer?

Answer 23

phosphate groups

Question 24

d: energy barrier

Answer 24

stops reaction occurring under normal conditions

Question 25

what do the symptoms of vitamin deficiencies reflect?

Answer 25

the loss of specific enzyme activities

Question 26

what is a common coenzyme for redox reactions?

Answer 26

Nicotinamide adenine dinucleotide (NAD+)

Question 27

how does a substrate bind to an enzyme?

Answer 27

via an active site

Question 28

what does the active site contain?

Answer 28

AA essential for catalytic activity | AA for highly specific interactions

Question 29

d: lock and key model

Answer 29

Active site of unbound enzyme is complementary to the shape of the substrate

Question 30

d: induced fit model

Answer 30

Binding of substrate induces a conformational change in enzyme, results in complementary fit

Question 31

give an example of an induced fit model

Answer 31

hexokinase

Question 32

Give the names of the 3 active sites where hydrolysis of peptides occur and what do they contain

Answer 32

chymotrypsin trypsin elastase reactive serine residue

Question 33

what happens at chymotrypsin site?

Answer 33

hydrophobic pocket binds aromatic amino acids

Question 34

what happens at trypsin site?

Answer 34

negatively charged Asp interacts with positively charged Lys or Arg

Question 35

what happens at elastase site?

Answer 35

active site partially blocked, only amino acids with small or no side chains can bind

Question 36

d: isozymes

Answer 36

each of two or more enzymes with identical function but different structure

Question 37

give an example of isozyme

Answer 37

Lactate Dehydrogenase

Question 38

how are isozymes useful for diagnostic purposes

Answer 38

Relative amounts of isozymes in blood and tissue can be measured

Question 39

if you found the brain type of CK enzyme in blood what would this suggest?

Answer 39

stroke or tumour

Question 40

if you found the heart type of CK enzyme in blood what would this suggest?

Answer 40

heart attack

Question 41

how is enzyme activity regulated?

Answer 41

via phosphorylation

Question 42

give an example of reversible covalent modification

Answer 42

phosphorylation of proteins

Question 43

d: phosphorylation

Answer 43

introduce a phosphate group into (a molecule or compound)

Question 44

what can phosphorylation do to an enzyme?

Answer 44

convert it into active or inactive form

Question 45

how are phosphorylation reactions carried out?

Answer 45

by protein kinases

Question 46

d: zymogen

Answer 46

an inactive substance which is converted into an enzyme when activated by another enzyme.

Question 47

egs of irreversible covalent modification enzymes

Answer 47

trypsinogen | chymotrysinogen

Question 48

egs of irreversible proteolytic enzymes

Answer 48

blood coagulation enzymes | digestive enzymes

Question 49

list 5 general characteristics which are universal to all enzymes

Answer 49

are proteins specific can be regenerated affected by temp , pH and amount

Question 50

why must cofactors be recycled? What does this cause?

Answer 50

not enough cofactors to molecules | anaerobic respiration