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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?

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
what do each of the following do? 1. oxidreducatases 2. transferases 3. hydrolases 4. lyases 5. isomerases 6. ligases
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
what is a proenzyme?
inactive form of enzyme -\> need to be activated before they come activated
27
proenzyme aka?
zymogen
28
how do you activate a zymogen / proenzyme?
proenzyme undergoes a proteolytic conversion
29
is activation of enzyme reversible?
no
30
what does trypsin do? what does trypsin prevent? (double check this is right)
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
where is chymotropsinogen: 1. made? 2. stored? 3. released? 4. made of how many a.a. residues? 5. activated? 6. role?
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
explain the two step activation process of the activation of chymotrypsinogen
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
when a substrate fits properly into an active site what is formed? write reaction
enzyme-substrate complex: E + S ⇌ ES ES -\> E + P overall reaction: E + S ⇌ ES -\> E + P
34
when a substrate fits properly into an active site what is formed? write reaction
enzyme-substrate complex: E + S ⇌ ES ES -\> E + P overall reaction: E + S ⇌ ES -\> E + P
35
what happens when enzyme past point of opt temp?
denature
36
why are enzymes disrupted at non-optimised pHs?
lose the appropriate functional charges and bonds on enzyme -\> LOSE THE TERTIARY STRUCTURE within enzyme.
37
why are enzymes disrupted at non-optimised pHs?
lose the appropriate functional charges and bonds on enzyme -\> LOSE THE TERTIARY STRUCTURE within enzyme.
38
explain how enzyme concentration effects enzyme kinetics
rate of reaction increases linearly with higher enzyme concentration if substrate concentration is constant
39
what happens to enzyme kinetics when substrate concentration is initially low then increases?
low conc: maximum activity occurs when enzyme is saturated relationship increases exponentially and levels off
40
what are inhibitors? give equation
molecules that cause a loss of enzyme activity E + S ⇌ ES -\> E + P E + I ⇌ EI. NO P FORMED
41
describe the different types of inhibitors
**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
what happens to reversible inhibitor when substrate concentration increases?
effect of reversible inhibitor reversed
43
example of non-comp. feedback inhibition?
**Isoleucine** (product) inhibits the enzyme that break downs **Threonine**. stops the pathway from being activated
44
what are isoenzymes?
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
what do isoenzymes allow?
They permit the **fine-tuning of metabolism** to meet the particular needs of a given tissue or developmental stage.
46
e.g. of isoenzyme?
lactate dehydrogenase (converts lactate to pyruvate)
47
explain how lactate dehydrogenase isoenzymes occur?
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
what can the release of enzymes in the blood be used as? give e.g.
diagnostic enzymes. e.g. cirrhosis (liver damage) can lead to elevated diagnostic enzymes.
49
what difference between enzyme and isoenzyme diagnosis?
enzymes can diagnose tissue damage specific isoenzymes can show which tissue damage has occured

FunMed Week 2 (10 decks)

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