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Science for Medicine A > Enzymes > Flashcards

Enzymes Flashcards

1
Q

Enzymes properties and functions

A 
Globular
Biological catalyst
Can be regulated
Increase rates of spontaneous reactions
Lower activation energy
Accelerate movement towards reaction equilibrium
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2
Q

Ribozymes

A

catalytic RNA molecules with no protein component

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3
Q

Cofactor

A

Non-protein component needed for activity

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4
Q

Coenzyme

A

organic molecule produced by vitamins and is involved in the reaction

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5
Q

Prosthetic Group

A

Cofactor covalently bound to enzyme or very tightly associated

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6
Q

Apoenzyme

A

Component of enzyme that contains cofactor

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7
Q

Holoenzyme

A

Whole enzyme

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8
Q

Active site

A

Part of the enzyme in which the substrate binds and is acted upon

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9
Q

Transition state

A

moment that chemical bonds are formed and broken

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10
Q

How is the Michaelis Menton constant calculated

A

from the hyperbolic reaction curve as half vmax= substrate concentration at half vmax

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11
Q

[S]

A

Substrate concentration

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12
Q

V0

A

Initial reaction velocity

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13
Q

Vmax

A

Maximum reaction velocity

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14
Q

Km

A

Affinity

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15
Q

Large Km

A

less stable E-S complex

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16
Q

Smaller Km

A

More stable E-S complex

17
Q

Glucokinase

A

High Km, High Vmax

18
Q

Hexokinase

A

Low Km, Low Vmax

19
Q

Double displacement

A

Amino group being transferred from an amino acid

20
Q

Allosteric

A

enzyme that contains many active sites and subunits

Reversible attachment

21
Q

uncompetitive inhibitor

A

Stops enzyme carrying out reaction once substrate has bound to the enzyme
enhances the binding of substrate (so reducing Km), but the resultant enzyme-inhibitor-substrate complex only undergoes reaction to form the product slowly, so that Vmax is also reduced

22
Q

Non-competitive inhibitor

A

Binds before and changes shape of enzyme preventing the reaction taking place
Vmax is reduced
Km remains unchnaged

23
Q

2 models of allosteric enzyme kinetics

A

Concerted Model

Sequential Model

24
Q

Concerted Model

A

Each subunit consist in 2 different confirmation
Allosteric activators stabilise the open conformation
Allosteric inhibitors will stabilise the closed confirmation

25
Q

Sequential Model

A

No flipping between conformational states

Binding of first substrate causes a conformational change that allows the second substrate to bind more easily

26
Q

Covalent modification

A

Enzymes can be regulated by phosphorylation

27
Q

Enzymes that catalyse the phosphorylation of enzymes

A

Protein kinases

Protein phosphatases

28
Q

Multiple phosphorylation sites

A

allow very fine control of enzyme function, enzyme never in off state

29
Q

Proteolytic Cleavage

A

Enzymes can exist as inactive precursor proteins that are cleaved to give active enzymes such as insulin

30
Q

Irreversible inhibitors

A

Cyanide binds to Fe3+ in cytochrom C oxidase and starves the cells of ATP and disrupts terminal respiration

31
Q

Competitive inhibitors

A

Increase in Km, Vmax unchanged

32
Q

AZT

A

Nucleotide analogue
Competitive inhibition of reverse transcriptase
Mimics the ordinary DNA pre-cursor

33
Q

Feedback Inhibition

A

A build up of end product can slow down the whole pathway

34
Q

Isoenzyme

A

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

35
Q

Competetive Inhibitor

A

Increase Km by interfering with the binding of the substrate, but they do not affect Vmax because the inhibitor does not change the catalysis in ES because it cannot bind to ES

36
Q

Haem Group

A

The Fe2+ ion lies in the middle of a complex nitrogen and carbon containing (porphyrin) ring structure

Science for Medicine A (31 decks)

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