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biochemistry > Enzymes as Biological Catalysts > Flashcards

Enzymes as Biological Catalysts Flashcards

1
Q

d: enzyme

A

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

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2
Q

do enzymes affect the equilibrium position of a reaction?

A

NO

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3
Q

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

A

some types of RNA eg ribozymes

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4
Q

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

A

body temp
in solution
neutral pH

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5
Q

are enzymes specific, how?

A

distinguish stereoisomers

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6
Q

why can an enzyme be described as potent?

A

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

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7
Q

d: transition state

A

is the reaction intermediate species which has the greatest free energy

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8
Q

How do enzymes reduce the activation energy?

A

energy by providing alternative reaction pathways

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9
Q

What is Glycogen Storage disease?

A

Enzyme deficiency that results in failure of

glycogen to enter transition state

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10
Q

What is the cause of glycogen storage disease?

A

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

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11
Q

Symptoms of Glycogen storage disease

A 
Hypoglycaemia
Hepatomegaly (liver swelling)
skin and mouth ulcers
bacterial and fungal infection
bowel inflammation and irritability
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12
Q

treatment of glycogen storage disease

A

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

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13
Q

what does the catalytic activity of enzymes depend on?

A

on presence of small molecules, called cofactors or coenzymes.

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14
Q

what are cofactors?

A

is a non-protein chemical compound or metallic ion

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15
Q

what is a coenzyme?

A

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

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16
Q

what are tightly bound coenzymes called?

A

prosthetic group

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17
Q

Enzyme without cofactor is called ____.

A

apoenzyme

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18
Q

Enzyme with cofactor is called _______.

A

holoenzyme

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19
Q

complete the equation

apoenzyme + cofactor =

A

holoenzyme

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20
Q

give eg of cofactor and how it is used

A

metal ion -zinc
involved in redox reactions
stabilise transition states

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21
Q

give eg of coenzyme and how it is used

A

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

22
Q

what does CoA (= Coenzyme A) transfer?

A

acetyl groups

23
Q

What does ATP (coenzyme) transfer?

A

phosphate groups

24
Q

d: energy barrier

A

stops reaction occurring under normal conditions

25
Q

what do the symptoms of vitamin deficiencies reflect?

A

the loss of specific enzyme activities

26
Q

what is a common coenzyme for redox reactions?

A

Nicotinamide adenine dinucleotide (NAD+)

27
Q

how does a substrate bind to an enzyme?

A

via an active site

28
Q

what does the active site contain?

A

AA essential for catalytic activity

AA for highly specific interactions

29
Q

d: lock and key model

A

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

30
Q

d: induced fit model

A

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

31
Q

give an example of an induced fit model

A

hexokinase

32
Q

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

A

chymotrypsin
trypsin
elastase
reactive serine residue

33
Q

what happens at chymotrypsin site?

A

hydrophobic pocket binds aromatic amino acids

34
Q

what happens at trypsin site?

A

negatively charged Asp interacts with positively charged Lys or Arg

35
Q

what happens at elastase site?

A

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

36
Q

d: isozymes

A

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

37
Q

give an example of isozyme

A

Lactate Dehydrogenase

38
Q

how are isozymes useful for diagnostic purposes

A

Relative amounts of isozymes in blood and tissue can be measured

39
Q

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

A

stroke or tumour

40
Q

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

A

heart attack

41
Q

how is enzyme activity regulated?

A

via phosphorylation

42
Q

give an example of reversible covalent modification

A

phosphorylation of proteins

43
Q

d: phosphorylation

A

introduce a phosphate group into (a molecule or compound)

44
Q

what can phosphorylation do to an enzyme?

A

convert it into active or inactive form

45
Q

how are phosphorylation reactions carried out?

A

by protein kinases

46
Q

d: zymogen

A

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

47
Q

egs of irreversible covalent modification enzymes

A

trypsinogen

chymotrysinogen

48
Q

egs of irreversible proteolytic enzymes

A

blood coagulation enzymes

digestive enzymes

49
Q

list 5 general characteristics which are universal to all enzymes

A

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

50
Q

why must cofactors be recycled? What does this cause?

A

not enough cofactors to molecules

anaerobic respiration

biochemistry (5 decks)

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