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Biochemistry Year 1 > Enzymes > Flashcards

Enzymes Flashcards

1
Q

What is an important enzyme for exercise?

A

Nitric oxide synthase: NO drives relaxation of arterial smooth muscle

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2
Q

How does the induced fit model work?

A

Enzyme puts pressure on bonds in substrate, and a slight conformational change of activation site is needed

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3
Q

What are cofactors?

A

Enable the enzyme to catalyse reaction; can be bound tightly or loosely

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4
Q

What are types of cofactors?

A

Coenzymes, metals, and vitamin derivatives (e.g. B vitamins)

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5
Q

What is the difference between loose and tight cofactors?

A

Loose bind to enzyme before reaction and are released after the reaction; tight remain bound all the time (e.g. Haem in Hb)

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6
Q

How do enzymes allow catalysis?

A

Enzyme reduces Eact of reaction; enzyme stabilises transition state

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7
Q

What type of enzyme reaction is more common: reversible or irreversible?

A

Reversible

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8
Q

Which type of enzyme reaction is a non-equilibrium reaction?

A

Irreversible

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9
Q

Why are irreversible enzymatic reactions important?

A

Essential to regulation of cell

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10
Q

What are five groups of enzymes?

A

Transferases; hydrolases; oxidoreductases; kinases; phosphotases

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11
Q

How can enzymes be classified?

A

By the group they fall under, and/or the specific reaction they catalyse

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12
Q

What do transferases do?

A

Catalyse group transfer

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13
Q

What do hydrolases do?

A

Catalyse hydrolysis

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14
Q

What do oxidoreductases do?

A

Catalyse redox

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15
Q

What do kinases do?

A

Catalyse phosphate addition

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16
Q

What do phosphotases do?

A

Catalyse phosphate removal

17
Q

What is initial velocity?

A

V0; the highest rate of an enzyme catalysed reaction; occurs when substrate is at its greatest and product at lowest; occurs at initiation of reaction

18
Q

What is maximal velocity?

A

Vmax; maximum possible initial rate of reaction

19
Q

What is Michaelis Constant?

A

Km; concentration of substrate which allows enzye to work at half Vmax; is a measure of substrate-enzyme affinity

20
Q

What is the significance of a higher Km?

A

Has lower affinity, so larger substrate is need to get Km

21
Q

Why do cells normally have substrate concentration lower than Km?

A

Enzymes are working below saturation/ Vmax; enables enzymes to respond to changes easily, increasing or decreasing velocity as needed

22
Q

What happens to Vmax and Km when enzyme concentration is increased?

A

Increases Vmax as Vmax is dependent on amount of enzyme; does not affect K as concentration of substrate is not affected as enzyme is in extreme excess

23
Q

What happens to Vmax and Km when substrate concentration is increased?

A

No change

24
Q

How does temperature affect the rate of an enzymatic reaction?

A

Rate increases as temperature increases until denaturing; Q10 values quantify change in relation to temperature (typically is 2)

25
Q

What is competitive inhibition?

A

Competitive chemcial occupies active site and prevents ESC formation

26
Q

How can competitive inhibition be overcome?

A

Adding more substrate

27
Q

How does competitive inhibition affect Vmax and Km?

A

No change in Vmax, but increases Km

28
Q

What is non-competitive inhibition?

A

Binds to allosteric site of enzyme; interferes with ans stops enzyme function

29
Q

How does non-competitive inhbition affect Vmax and Km?

A

Vmax decreases, but no change in Km

30
Q

How can enzymes be regulated?

A

Covalent modification turns them on or off: addition and removal of molecules will change enzyme’s conformation, causing increase or decrease in activity

31
Q

What are common covalent modifications of enzymes?

A

Phosphorylation to a specific amino acid (~30%); acetylation; palmitoylation

Biochemistry Year 1 (23 decks)

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