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FunMed Week 2 > Enzymes > Flashcards

Enzymes Flashcards

1
Q

which process do products of food undergo for to eventually produce ATP ?

A

citric cycle

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2
Q

what regulates metabolic pathways?

A

enzymes!

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3
Q

how do enzymes increase rates of biological reaction?

A

they lower the activation energy required for the reaction.

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4
Q

where does reaction occur in enzyme? how do you describe shape of substrate to this?

A

active site
complementary

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5
Q

when substrate goes into enzyme - what happens to the amino acid side chains?

A

the a.a. side chains of the enzyme and substrate align via H-bonds, salt bridges, hydrophobic interactions, VDWs

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6
Q

what are the hypotheses of enzyme action?

A
  1. Lock and Key H
  2. Induced Fit H
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7
Q

describe Lock and Key H

A

active site has RIGID shape
only substrates with matching shape can fit

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8
Q

describe Induced Fit H

A
  • the active site is flexible
  • the shapes of enzyme and active site and substrate to max. fit.
  • greater range of substrate specificity and can fit more than one enzyme
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9
Q

are all enzymes specific for their substrates?

A

no - theres a degree of specificity for substrates:

enzymes may recognise and catalyse:

  • single substrate
  • group of similar substrates
  • particular type of bond
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10
Q

what do enzymes sometimes need to for improved catalytic activity?

A

a co factor

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11
Q

what is an:

  1. apoenzyme
  2. holoenzyme?
A

apoenzyme: enzyme lacking a cofactor
holoenzyme: enyzme with a cofactor

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12
Q

how can you classify cofactors?

A

depending on how tightly they bind to an enzyme:

tightly bound cofactors act as activators or inhibitors of activity

loosely bound cofactors

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13
Q

what is the name for name tightly bound cofactors?

A

Prosthetic groups - usually inorganic ions

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14
Q

what is the enzymatic activity of enzymes that use loosely bound cofactors?

A

transfer electrons
form or break a covalent group
transfer a group

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15
Q

what is the name for name loosely bound cofactors?

A

coenzymes

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16
Q

are coenzymes proteins?

A

no ! - e.g. NADH

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17
Q

what reaction does NAD help to catalyse?

A

anaerobic glycolysis:

pyruvate -> lactate

or this reaction to occur, the enzyme lactate dehydrogenase requires NADH to be oxidised to NAD+

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18
Q

what does vitamin B3 deficiency lead to?
what is this disease characterised by?

A

Pellagra

scally sores on skin and tongue

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19
Q

what does vitamin B1 deficiency lead to?

which populations suffer this?

what is this disease characterised by?

what can this lead to?

A

Beriberi

  • in populations that eat polished white rice
  • alcoholics

CAN LEAD TO:
Wernicke-Korsakoff syndrome: brain damage

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20
Q

what does vitamin C deficiency lead to?

which populations suffer this?

what are they lacking?

A

scurvy

  • pregnant
  • drug users
  • homeless

a lack of collagen

21
Q

what is the vitamin that is a precursor for NAD+ coenzyme?

A

nicotinic acid

22
Q

what is the vitamin that is a precursor for tetrahydrofolate coenzyme?

A

folic acid

23
Q

how many % of genes encode for enyzmes?

A

25%

24
Q

what are the six categories that enzymes are split into?

A
  1. oxidreducatases
  2. transferases
  3. hydrolases
  4. lyases
  5. isomerases
  6. ligases
25
Q

what do each of the following do?

  1. oxidreducatases
  2. transferases
  3. hydrolases
  4. lyases
  5. isomerases
  6. ligases
A
  1. oxidreducatases - oxidation / reduction
  2. transferases - transfer groups of atoms (e.g. kinases)
  3. hydrolases - hydrolysis
  4. lyases - add / remove atoms to / from a double bond
  5. isomerases - rearrange atoms
  6. ligases - use ATP to combine molecules
26
Q

what is a proenzyme?

A

inactive form of enzyme -> need to be activated before they come activated

27
Q

proenzyme aka?

A

zymogen

28
Q

how do you activate a zymogen / proenzyme?

A

proenzyme undergoes a proteolytic conversion

29
Q

is activation of enzyme reversible?

A

no

30
Q

what does trypsin do?

what does trypsin prevent?
(double check this is right)

A

trypsin is the common activator of all the pancreatic proenzymes into their active enzymes

prevents digestive enzymes from digesting the cells they are produced in

31
Q

where is chymotropsinogen:

  1. made?
  2. stored?
  3. released?
  4. made of how many a.a. residues?
  5. activated?
  6. role?
A

chymotropsinogen

  1. made: pancreas
  2. stored: membrane bound granules - acinar cells
  3. released: duodenum
  4. made of how many a.a. residues: 245
  5. activated: in the lumen
  6. role: cleaves peptide bonds containing aromatic a.a.
32
Q

explain the two step activation process of the activation of chymotrypsinogen

A
  1. trypsin cleaves chymotrypsinogen between a.a. 15 and 16 = two fragments: aa - 1-15, and 16-245
  2. a.a. 14 & 15 and a.a. 147 & 148 removed to generate active enzyme: alpha chymotrypsin
33
Q

when a substrate fits properly into an active site what is formed?
write reaction

A

enzyme-substrate complex:

E + S ⇌ ES

ES -> E + P

overall reaction:

E + S ⇌ ES -> E + P

34
Q

when a substrate fits properly into an active site what is formed?
write reaction

A

enzyme-substrate complex:

E + S ⇌ ES

ES -> E + P

overall reaction:

E + S ⇌ ES -> E + P

35
Q

what happens when enzyme past point of opt temp?

A

denature

36
Q

why are enzymes disrupted at non-optimised pHs?

A

lose the appropriate functional charges and bonds on enzyme -> LOSE THE TERTIARY STRUCTURE within enzyme.

37
Q

why are enzymes disrupted at non-optimised pHs?

A

lose the appropriate functional charges and bonds on enzyme -> LOSE THE TERTIARY STRUCTURE within enzyme.

38
Q

explain how enzyme concentration effects enzyme kinetics

A

rate of reaction increases linearly with higher enzyme concentration if substrate concentration is constant

39
Q

what happens to enzyme kinetics when substrate concentration is initially low then increases?

A

low conc: maximum activity occurs when enzyme is saturated

relationship increases exponentially and levels off

40
Q

what are inhibitors?
give equation

A

molecules that cause a loss of enzyme activity

E + S ⇌ ES -> E + P
E + I ⇌ EI. NO P FORMED

41
Q

describe the different types of inhibitors

A

1. competitive inhibitors:

competes with substrate for the active site

a) reversible competitive inhibitor: inhibitor displaced from active site and reaction can occur

b) irreversible competitive inhibitor: remains bound to active site

2. non-competitive inhibitors

substrate is broken into products, the products feedback and inhibit further breakdwon of the substrate

42
Q

what happens to reversible inhibitor when substrate concentration increases?

A

effect of reversible inhibitor reversed

43
Q

example of non-comp. feedback inhibition?

A

Isoleucine (product) inhibits the enzyme that break downs Threonine. stops the pathway from being activated

44
Q

what are isoenzymes?

A

enzyme that catalyse the same reaction in different tissues. have minor variations in the a.a. sequences of the subunits of the 4. structure

45
Q

what do isoenzymes allow?

A

They permit the fine-tuning of metabolism to meet the particular needs of a given tissue or developmental stage.

46
Q

e.g. of isoenzyme?

A

lactate dehydrogenase (converts lactate to pyruvate)

47
Q

explain how lactate dehydrogenase isoenzymes occur?

A

lactate dehydrogenase made up of 4 subunits. depending on how subunits combine, get a lactate dehydrogenase that has different kinetic properties and are found in different tissues.

e.g. lactate dehydrogenase H4 (4 subunits of H) found in Heart. c.f. in skeletal muscle: M4 (4 subunits of M)

48
Q

what can the release of enzymes in the blood be used as?
give e.g.

A

diagnostic enzymes.

e.g. cirrhosis (liver damage) can lead to elevated diagnostic enzymes.

49
Q

what difference between enzyme and isoenzyme diagnosis?

A

enzymes can diagnose tissue damage

specific isoenzymes can show which tissue damage has occured

FunMed Week 2 (10 decks)

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