Enzymes

Question 1

An ______________ is a protein or in some cases a RNA catalysts that acts upon a substrate (S).

Answer 1

Enzyme (E)

Question 2

The ___________ is the region of the enzyme where a substrate binds and catalysis occurs.

Answer 2

Active site

Question 3

In order to function properly, many enzymes contain ________ such as Mg²⁺, Zn²⁺, Fe²⁺ or ________ such as biotin, NAD+, FAD+, coenzyme A.

Answer 3

Cofactors

Coenzymes

Question 4

Cofactors are generally ________ and coenzymes are generally ________.

Answer 4

Inorganic

Organic

Question 5

When an enzyme is bound to it cofactor, it is called a ______________.

Answer 5

Holoenzyme

Question 6

When the enzyme lacks its cofactor, it is called a _____________.

Answer 6

Apoenzyme

Question 7

Enzymes specifcally bind a substrate or several similar substrates via _____________________________.

Answer 7

Non-covalent interactions

Question 8

An enzyme is said to be _______________________ to the substrate with regards to shape, charge distribution, stereochemistry, etc.

Answer 8

Structurally complementary

Question 9

There are two models for enzyme-substrate interactions. What are they?

Answer 9

Lock and key hypothesis

Induced fit hypothesis

Question 10

In the ____________________ hypothesis, proposed by FIscher in 1894, the enzyme is a ______ and the substrate is a _______. Only the correctly sized _____ (substrate) can fit into the ________________ (active site) of the _______ (enzyme)

Answer 10

Lock and key

Lock

Key

Key

Key hole

Lock

Question 11

In the lock and key hypothesis, the enzyme is ______________ complementary to the substrate.

Answer 11

Perfectly complementary

Question 12

In the _____________________ hypothesis proposed by Koshland in 1958, the enzyme undergoes a conformational change upon binding with the substrate. The active site is ____________.

Answer 12

Induced fit

Flexible

Question 13

What makes enzymes different from other catalysts?

Answer 13

1. They are soluble in water
2. They can operate under mild temperatures and pHs
3. They are very specific for their substrates
4. They engage in no side reactions
5. They produce only one enantiomer as product
6. They have great catalytic power

Question 14

Enzymes catalyze reactions up to _________ times the original rate

Answer 14

10^16/17

Question 15

What do all catalysts do?

Answer 15

Lower the activation energy (Ea = ∆G^‡)

Question 16

How is the activation energy of a reaction related to the speed of a reaction?

Answer 16

High Ea = Slow rate

Low Ea = High rate

Question 17

What is the Arrhenius equation?

Answer 17

It describes the relationship between ∆G^‡ and k, the rate of the reaction

Question 18

The relationship between ∆G‡ and k is _________ and ______________ related.

Answer 18

Inversely

Exponentially

Question 19

The rate or k of a reaction decreases with lower ∆G‡ because the Arrhenius equation shows that k is inversely and exponentially related to ∆G‡.

Question 20

A catalyst does NOT make a reaction more or less spontaneous, it only affects the _______ of the reaction.

Answer 20

Rate

Question 21

A catalyst does not affect the thermodynamics of a reaction, only the _________ of a reaction.

Answer 21

Kinetics

Question 22

Be familiar with an energy diagram for a reaction.

Answer 22