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Biochemistry > Enzymes > Flashcards

Enzymes Flashcards

1
Q

Enzymes are proteins which act as…

A

Catalysts

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2
Q

Many drugs (and poisons) are…

A

Enzyme inhibitors 🛑

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3
Q

Penicillin binds to and inhibits the enzymes that make bacterial…

A

Cell Wall 🏰

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4
Q

Enzymes are ( non-specific / somewhat specific / highly specific )

A

Highly specific

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5
Q

Enzymes catalyse the making and breaking of ? in the cell

A

Covalent bonds

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6
Q

Enzymes allow reactions to take place more quickly and often at lower temperature and milder…

A

pH 👨🏻‍🔬

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7
Q

The regulation of biochemical reaction pathways is often controlled by…

A

Enzymes

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8
Q

The equation for Gibbs Free Energy is…

A

𝚫G = -RT(ln Keq)

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9
Q

Enzymes (increase / reduce / do not change ) activation energy

A

Reduce ⬇️

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10
Q

By binding the reactant an enzyme changes the reaction environment, which lowers activation energy by providing an alternative…

A

Transition state

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11
Q

Enzyme (do / do not / sometimes) affect Keq (equilibrium constant)

A

Do not 🙅‍♀️

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12
Q

Enzymes work on 3 principles

A
  • Proximity (bringing reactants closer together)
  • Orientation (arranging reactants favourably)
  • Strain / Distortion (applied to bonds)
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13
Q

Acid/base catalysis allows reactions to overcome low concentrations of…

A

H+/OH- (protons/ hydroxide ions)

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14
Q

In covalent catalysis, a temporary…

A

Covalent bond is formed between enzyme and substrate

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15
Q

The two models of the enzyme-substrate (ES) complex are…

A
  1. Lock and key 🔐

2. Induced fit

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16
Q

The four levels of enzyme specificity are…

A
  1. Absolute
  2. Bond specific
  3. Group specific
  4. Stereospecific (differentiates stereoisomers)
17
Q

There are 6 types of reactions which may involve enzymes…

A
  1. Redox
  2. T Transferases
  3. H Hydrolases
  4. L Lyases
  5. I Isomerases
  6. L Ligases (synthases)
18
Q

The turnover of an enzyme, or the number substrate molecules that can be converted to product by 1 enzyme in 1 second is quantified as… ⏳

A

Kcat

19
Q

Enzyme activity can be measured using…

A

Spectrophotometry

20
Q

To measure enzyme activity, we should measure the initial rates of reaction, as…

A

This is the only time when the substrate concentration is exactly known

21
Q

Equation for the rate (V) at a specified substrate concentration ( [s] )…

A

V = Vmax [s] / Km + [s] 🏎

22
Q

Km is the concentration of substrate needed to achieve…

A

1/2 Vmax 📈

23
Q

Km indicates the affinity of the enzyme for a substrate, i.e.

A

Stability of the enzyme-substrate complex (high stability, low Km & v.v.)

24
Q

Km is known as the Michaelis Constant and is calculated by fitting data using a non-linear least squares fitting programme. Why can’t Vmax be measured directly?

A

Because it occurs when the substrate concentration reaches infinity ( [s] = ∞ )

25
Q

Enzyme inhibitors can be either (2)…

A

Irreversible or irreversible

26
Q

The action of reversible enzyme inhibitors is either (3)…

A
  • Competitive
  • Non-competitive
  • Uncompetitive
27
Q

Competitive inhibitors tend to be structurally…

A

Similar to substrate molecules

28
Q

The effect of competitive enzyme inhibitors can be counteracted by…

A

Increasing substrate concentration 🔼

29
Q

The graph of substrate concentration on the X-axis, with V (velocity) on the Y-axis is known as the…

A

Michaelis-Menten plot 📈

30
Q

An example of an irreversible enzyme inhibitor is…

A

Penicillin

31
Q

What is used in combination with penicillin to inhibit B-Lactamase in penicillin-resistant bacteria (Augmentin)?

A

Potassium clavulanate

32
Q

Competitive inhibitors mimic the transition state…

A

But bind much more tightly than a substrate would 🤗

33
Q

Non-competitive inhibitors reduce Vmax because…

A

The enzyme is less efficient at catalysing the reaction

34
Q

Competitive inhibitors increase (Vmax / Km)

A

Km, Vmax is unchanged

35
Q

Which type of inhibitors are important for drug therapy? 💊

A

Competitive

36
Q

pH changes the 3D structure of the active site, or it may affect the charge of the group that binds the substrate. This means most enzymes work optimally over a narrow pH range. A notable exception to this is…

A

Papain (from pineapples), which shows little change in activity between pH 4 and pH 8 🍍

37
Q

An example of a non-competitive enzyme inhibitor is…

A

Roundup Weedkiller 🌿

38
Q

An example of a competitive enzyme inhibitor is…

A

Methotrexate (anticancer drug)

Biochemistry (21 decks)

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