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MCBM Exam 1 > Enzymes > Flashcards

Enzymes Flashcards

1
Q

What is a co-factor?

A

An additional non-peptide component of an enzyme

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2
Q

What is a co-enzyme?

A

A complex organic or metalloorganic co-factor

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3
Q

What are precursors to many enzymes?

A

Vitamins

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4
Q

What is a prosthetic group?

A

A covalently bound cofactor

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5
Q

What is a holoenzyme?

A

A complete, catalytically active enzyme

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6
Q

What is an apoenzyme?

A

Protein portion of holoenzyme

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7
Q

What does an oxidoreductase catalyze?

A

Transfer of electrons

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8
Q

What type of reaction does a transferase catalyze?

A

Group transfer reactions

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9
Q

What does a hydrolase catalyze?

A

Hydrolysis reactions

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10
Q

What reaction do lyases catalyze?

A

Addition or removal of groups to break or form double bonds

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11
Q

What type of reaction is catalyzed by an isomerase?

A

Transfer of groups within molecules to yield isomeric forms

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12
Q

What do ligases catalyze?

A

Formation of C-C, C-S, C-O and C-N bonds by condensation reactions coupled to ATP cleavage

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13
Q

What is the transition state?

A

The highest energy level of the reaction coordinate diagram

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14
Q

At the transition state, what is the probability of forming reactants vs. products?

A

Equal

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15
Q

What is activation energy?

A

Change in free energy from reactants to transition state

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16
Q

How do enzymes speed up a reaction?

A

By lowering the activation energy

17
Q

What determines the rate of a reaction at a given temperature?

A

Activation energy

18
Q

The higher the activation energy the ___ the reaction rate.

A

Slower

19
Q

Where on an enzyme does the substrate bind?

A

The active site

20
Q

How many amino acids are present at the active site?

A

10 or fewer

21
Q

What is the specific environment that an active site provides?

A
  • 3-D entity
  • Shape and components of active site are related to those of substrates
  • Usually either a cleft or crevice on the surface of the enzyme
  • Water is usually excluded
  • Usually a non-polar environment, so amino acid side chains can become highly active
22
Q

How do enzymes reduce the activation energy?

A
  • There is “loaned” energy from weak, non-covalent interactions between the substrate and the active site
  • Each interaction releases a small amount of energy that can be offset against activation energy
23
Q

What is the binding energy?

A

The sum of the energies released by the substrate-active site ineraction

24
Q

What is wrong with the lock and key hypothesis?

A

It creates an energy well, and more energy is needed to get to the transition state

25
Q

What are 3 common types of catalysis involving function groups?

A
  1. Acid base
  2. Covalent
  3. Metal ion
26
Q

What is catalysis?

A

The speeding up of a reaction by an enzyme - the active site can provide functional groups that interact transiently with the substrates

27
Q

What can serve as proton donors/acceptors in active sites?

A

Acidic side chains
Basic side chains
Hydroxyl amino acid side chains

28
Q

What is covalent catalysis?

A

When a transient covalent link is formed between the enzyme and substrate or intermediate

29
Q

What is metal ion catalysis?

A

Metal ions, either tightly bound to the enzyme or taken up with the substrate, create ionic interactions with the substrate and help orient and/or stabilized the charged transition state

30
Q

What is chymotrypsin?

A

A Serine protease that hydrolyses peptides on the carboxyl side of aromatic side chain residues

31
Q

Chymotrypsin is a good example of what?

A

Transition state stabilization

32
Q

By what means does chymotrypsin cleave peptides?

A

Using both covalent catalysis and general acid-base catalysis

33
Q

What are the two major stages of peptide cleavage by chymotrypsin?

A
  1. Acylation

2. Deacylation

34
Q

What occurs in acylation?

A
  • Peptide bond is cleaved
  • Peptide fragment from C-termal end is released
  • Ester linkage formed between peptidyl carbonyl carbon of the N-terminal peptide and serine 195 of the enzyme
35
Q

What occurs in deacylation?

A
  • Ester linkage is hydrolyzed
  • Peptide fragment is released
  • The enzyme is regenerated

MCBM Exam 1 (7 decks)

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