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Flashcards in Enzymology Deck (30)
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1
Q

What are enzymes

A

a molecular catalyst in a biological system. Most but not all are proteins

2
Q

Properties of enzymes:

A
  1. Have immense catalytic power
  2. Highly specific
  3. Usually catalyze only single chemical reaction or a set of closely related chemical reactions.
3
Q

Components of a protein enzyme:

A
  1. 1 or more polypeptide chains.
  2. Cofactor: an additional non peptide component of an enzyme
  3. Coenzyme: a complex organic or metalloorganic cofactor
  4. Prosthetic group: covalently bound cofactor
  5. Holoenzyme: a complete, catalytically active enzyme
  6. Apoenzyme: protein portion of holoenzyme.
4
Q

Many vitamins are precursors of

A

coenzymes

5
Q

What is the transition state

A

the configuration (of atoms, bonds, electrons) along the reaction coordinate corresponding to the highest energy

6
Q

At the transition state, there is an ____probability of forming reactants or products

A

equal

7
Q

Change in free energy from reactants to transition state is called the

A

activation energy

8
Q

Rate constant of a reaction (k) is ____ and ___ proportional to the activation energy

A

inversely and exponentially

9
Q

Activation energy determines the rate of a reaction at a given:

A

temperature

10
Q

The higher the AE =

A

slower rate

11
Q

The lower the AE=

A

faster rate

12
Q

Enzymes ____activation energy

A

lower

13
Q

What is the active site of an enzyme

A

the location on enzyme where substrate(s) bind. Provides specific environment for reactions

14
Q

Active site features:

A
  1. 10 or fewer aa
  2. water usually excluded from site
  3. Non polar envmt, so aa side chains become highly active
15
Q

How is activation energy reduced

A

Loaned energy from weak, non covalent interactions between the substrate and active site. Each interaction releases a small amount of energy that can be offset against activation energy. The sum of these energies released by substrate active site interaction is called the binding energy

16
Q

Activation energy -binding energy =

A

catalyzed activation energy

17
Q

What is the lock and key hypothesis

A

Proposed that shape of substrate and active site must match in order for substrate to fit side

18
Q

T/F There is a problem if weak interactions between enzymes and substrates are optimized in the enzyme substrate complex

A

T

19
Q

What is the induced fit hypothesis

A

Once substrate bound, structure of enzyme shifts so active site assumes closer fit

20
Q

Weak interactions between enzyme and substrate are optimized in the

A

transition state

21
Q

poorer fit –> lower binding energy–> higher activation energy–> ____reaction rate

A

slower

22
Q

Thrombin is a proteolytic enzyme and only cleaves between ____ and ____

A

argenine and glycine

23
Q

What is catalysis

A

The active site can provide functional groups that interact transiently with the substrates

24
Q

3 common types of catalysis involving functional groups are

A
  1. acid base
  2. covalent
  3. metal ion
25
Q

Positively charged intermediates:

A

remove proton (base)

26
Q

Negatively charged intermediates:

A

add proton (acid)

27
Q

Specific acid/base catalysis:

A

acid or base from water

28
Q

General acid/base catalysis:

A

proton donor/acceptor

29
Q

What is covalent catalysis

A

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

30
Q

What is metal ion catalysis

A

Metal ions can be tightly bound to enzyme or taken up with substrate. Ionic interactions between metal ion and substrate help orient substrate and/or stabilize charged transition state.