2: Enzymes

Question 0

The term enzyme is from what Greek word that means leavened (yeast)

Answer 0

Enzmos

Question 1

Biologic polymers that catalyze the chemical reactions that make life.

Answer 1

Enzymes

Question 2

A handful of self-cleaving RNA molecules which are known as:

Answer 2

Ribozymes

Question 3

What are the vast majority of enzymes made of?

Answer 3

Proteins

Question 4

This is where catalysis occurs and what forces the substrate to resemble transition state.

Answer 4

Active site

Question 5

True or false: Enzymes are NOT hormones.

Answer 5

TRUE

Question 6

Give 3 characteristics of enzymes as catalyst.

Answer 6

1. Make rxn go faster (by at least 10 raised to the 6th)
2. Not be consumed in rxn
3. Not change the thermodynamics

Question 7

Physically distinct versions of enzymes that catalyze the same rxn, and provides back-up copy of essential enzyme.

Answer 7

Isozymes

Question 8

When we say part of an enzyme, this refers to substrate or active site?

Answer 8

Active site

Question 9

Reactant would pertain to:

Answer 9

Substrate

Question 10

The active site fits the substrate like a key fitting into its lock.

Answer 10

Lock and key model

Question 11

Alterations in the active site as enzymes & substrates bind.

Answer 11

Induced fit model

Question 12

Has active site & substrate.

Answer 12

Complementarity

Question 13

Job done with the least possible energy.

Answer 13

Efficiency

Question 14

The enzymes limited to specific locations.

Answer 14

Compartmentalization

Question 15

For each enzyme, only a few substrates and only one rxn is catalyzed.

Answer 15

Specificity

Question 16

Actions of enzyme are controlled by other substrates.

Answer 16

Regulated

Question 17

Give 2 reasons for compartmentalization.

Answer 17

Protection vs inhibitors

Promote favorable environment

Question 18

What are the substances required for enzyme function?

Answer 18

Prosthetic groups
Cofactors
Coenzymes

Question 19

Known as substrate shuttles.

Answer 19

Coenzymes

Question 20

With transient, dissociable attachment to enzyme.

Answer 20

Cofactors

Question 21

With tight & stable attachment to the enzyme.

Answer 21

Prosthetic groups

Question 22

A holoenzyme is composed of:

Answer 22

Enzyme + cofactor

Question 23

Composed of enzyme only.

Answer 23

Apoenzyme

Question 24

Name the 4 mechanisms for enhanced catalysis.

Answer 24

Catalysis by proximity Acid base catalysis Catalysis by strain Covalent catalysis

Question 25

Mechanism of catalysis due to ionizable aminoacyl side chains or prosthetic groups.

Answer 25

Acid-base catalysis

Question 26

Mechanism of catalysis by conformational change that weakens covalent bond.

Answer 26

Catalysis by strain

Question 27

When the enzyme is temporarily a reactant, and when cysteine, serine, histidine form transient covalent bond.

Answer 27

Covalent catalysis

Question 28

When there is creation of a region of high substrate conc once binding begins.

Answer 28

Catalysis by proximity

Question 29

The 'new school' enzyme naming is by the:

Answer 29

International Union of Biochemists

Question 30

What can be used for the enzymes first name in the 'old school'?

Answer 30

Substrate Source of enzyme A feature of its MOA

Question 31

The ________ name is based on the rxn catalyzed by enzyme followed by the suffix -ase

Answer 31

Second

Question 32

Enzyme classification: joining of two molecules coupled to hydrolysis of ATP

Answer 32

Ligases

Question 33

It transfers moieties such as glycosyl, methyl, phosphoryl groups.

Answer 33

Transferase

Question 34

It cleaves C-C, C-O, C-N & other bonds by atom elimination, leaving double bonds.

Answer 34

Lyases

Question 35

What catalyzes geometric or structural changes w/in molecule?

Answer 35

Isomerase

Question 36

Hydrolytic cleavage of C-C, C-O, C-N & other bonds.

Answer 36

Hydrolase

Question 37

What catalyzes redox rxns?

Answer 37

Oxidoreductase

Question 38

Deals w/ quantitative measurement of rates of enzyme-catalyzed rxns.

Answer 38

Enzyme kinetics

Question 39

True or false: Enzyme kinetics plays a central role in drug discovery.

Answer 39

TRUE

Question 40

It predicts whether a rxn will proceed spontaneously or is favorable & energy available to do work.

Answer 40

Gibbs free energy

Question 41

True or false: The natural & favorable tendency for processes is to proceed from an area of low energy to an area of high energy.

Answer 41

FALSE (should be from high to low)

Question 42

The reaction when there is net loss of energy, and is it spontaneous or not?

Answer 42

Exergonic rxn, YES

Question 43

Endergonic rxn pertains to the net ______ of energy.

Answer 43

Gain

Question 44

True or false: Endergonic rxn is a spontaneous rxn.

Answer 44

FALSE

Question 45

Characteristics of a standard free energy charge:

Answer 45

(Reac) & (prod): 1 molar Temp: 25 degress Celcius/298 K Pressure: 1 atmosphere

Question 46

Law used for coupling rxn:

Answer 46

Hess law (energy of consecutive rxns are additive)

Question 47

A rxn w/ a positive net G may still yield an overall negative free energy change if it is coupled to another rxn w/ ____________. This is an implication of what?

Answer 47

large negative net G, Hess law

Question 48

If the net energy is equal to 0:

Answer 48

Equilibrium

Question 49

What are the effects of enzymes on Gibbs free energy?

Answer 49

Lower free energy of activation Do not change the energy of reactants & products Do not change equilibrium rxn

Question 50

What are the factors affecting "collision"?

Answer 50

Substrate concentration Temperature pH Inhibitors

Question 51

For 2 molecules to react this theory is applies:

Answer 51

Kinetic theory/Collide theory (possess enough energy to overcome energy barrier to reach transition state)

Question 52

Increase substrate concentration will have what effect on reaction rate?

Answer 52

Increase

Question 53

Relates reaction rate to substrate concentration:

Answer 53

Michaelis-menten equation

Question 54

What kind of curve shows Michaelis-menten kinetics & shows saturability?

Answer 54

Hyperbolic curve

Question 55

How fast the reaction is:

Answer 55

Initial velocity

Question 56

When there is low substrate affinity the Michaelis constant is

Answer 56

High

Question 57

Michaelis constant (Km) is ________ proportional to substrate affinity.

Answer 57

Inversely

Question 58

The maximal number of substrate molecules converted to product per unit time:

Answer 58

Maximum velocity

Question 59

First order kinetics with rate directly proportional to [s]?

Answer 59

Below Km

Question 60

It is the reciprocal of the Michaelis-Menten equation:

Answer 60

Lineweaver-Burke plot

Question 61

Kinetics above Km in which rate is not affected by [s]:

Answer 61

Zero order kinetics

Question 62

Used to determine the mechanism of action of enzyme inhibitors and to calculate Km and Vmax:

Answer 62

Lineweaver-burke plot

Question 63

The equation used for multimeric enzymes:

Answer 63

Hill equation

Question 64

What is the curve in the Hill equation?

Answer 64

Sigmoidal curve

Question 65

The increase in substrate will also increase enzyme activity. This is called:

Answer 65

Cooperativity

Question 66

What are the factors affecting reaction rate?

Answer 66

Temperature | pH

Question 67

If there is an increase of inhibitors, reaction rate will inc or dec?

Answer 67

Decrease

Question 68

Any substance that diminishes the velocity of an enzyme catalyzed rxn:

Answer 68

Enzyme inhibitor

Question 69

Give the types of inhibitors:

Answer 69

Competitive vs noncompetitive | Reversible vs irreversible

Question 70

The Km in competitive inhibition will inc or dec?

Answer 70

Increase

Question 71

Inhibitors bind to a different site from the active site:

Answer 71

Noncompetitive