Enzymes

Question 1

What is the effect of enzymes on chemical reactions?

Answer 1

Biological catalysts that increase the rate of reaction by lowering activation energy.

Question 2

How do enzymes lower activation energy?

Answer 2

Facilitate formation of the transition states.

Question 3

Give the key features of enzymes (6) :

Answer 3

• very specific (they can work on many enzymes
• unchanged after a reaction (active site is the same at the beginning as it is in the end )
• do not effect equilibrium
• increase the rate of reaction
• proteins
• may need cofactors

Question 4

What is the active site?

Answer 4

Where the substrate binds and where the reaction occurs

Question 5

What is the make up of the active site?

Answer 5

• very small, only made up of a small amount of amino acids

- the active site is made by amino acids from different parts of the sequence

Question 6

What is the structure of the active site?

Answer 6

They are clefts / crevices

They have a complimentary shape to the substrate

Question 7

What are the two hypothesis for binding of enzymes?

Answer 7

Induced fit

Lock and key

Question 8

Explain the LK hypothesis

Answer 8

The active site has a complimentary shape to the substrate

100% complimentary

Question 9

Explain the IF hypothesis

Answer 9

The active site is not completely complimentary to the substrate but the active site forms a complimentary shape post binding.

Question 10

How do substrates bind to active sites?

Answer 10

Lots of NON covalent bonding via interactions with amino acid residue

• VDW
• hydrogen bonds

Sometimes they can be convalent

Question 11

Why does the substrate use that form of bonding to the active site

Answer 11

Non covalent so it can be weak so the substrate can easily be released.

Question 12

How they work:

Answer 12

The enzymes holds the substrate In the right configuration in a transition state and forms the ES complex
We put energy in then and the substrate has been broken down
(Holds substrate in right configuration to make enzyme work)

Question 13

How do we measure progression of enzyme reactions?

Answer 13

We look at the appearence of product over time

Question 14

What is the time where we know the concentration of the substrate

Answer 14

T0

Question 15

What effects enzyme activity?

Answer 15

• temperature
• pH
• substrate conc
• enzyme activity

Question 16

How does SC effect reaction rate?

Answer 16

More available substrates for empty active sites

Expressed in Michaelis Mensen

Question 17

What is the michaelis menten

Answer 17

The rate of the reaction is related to the conc of the substrate and this can be expressed by the equation.

Question 18

What is v max

Answer 18

Maximal rate when all the enzyme active sites are saturated with substrate

Question 19

What is Km

Answer 19

Substrate concentration that gives half maximal velocity

Question 20

What is the significance of the Km?

Answer 20

Measures the affinity of an enzyme for the substrate

Question 21

what does a low Km signify

Answer 21

High affinity for substrate

Question 22

What does a high Km mean?

Answer 22

Low affinity for substrate

Question 23

What are the units for V max values

Answer 23

1 unit = amount of enzyme that converts 1 micro mol of product per min under standard conditions

Question 24

What is the significance of V max values?

Answer 24

V max is a rate

The rate of enzyme catalysed reaction is proportional to the concentration of enzyme

Question 25

What is the best way to estimate kM and V max

Answer 25

The michaelis menten is rearranged to form a line weaver burk plot. It is a linear display

Question 26

On a LBP how do you calculate V max

Answer 26

Intercept = 1/ v max | Rearrange

Question 27

What does the gradient represent on a LBP

Answer 27

Rate, as it is km/ v max

Question 28

How to work out the Km on a LBP

Answer 28

X intercept = -1 / kM | It is a reciprocal value so take that into account

Question 29

What is an enzyme inhibitor?

Answer 29

Molecules that slow down or prevent an enzyme reaction

Question 30

What are two general different pathways for inhibition

Answer 30

1. Irreversible- forming convalent bonds with the enzyme | 2. Reversible- non convalent.

Question 31

What are the to different forms on reversible inhibition

Answer 31

Competitive and non competitive

Question 32

Where does C inhibition bind and what does it effect

Answer 32

Binds at active site and only effects Km and not V max

Question 33

Where do NC inhibitors bind and what do they effect

Answer 33

Binds at at the allosteric site | Effects V max but not Km

Question 34

Mechanism of C inhibition

Answer 34

The inhibitor is a similar shape to the substrate, and can bind to the active site. Reducing the number of active sites available, increasing the amount of time it takes to reach v max Often have different groups that interact in the same way

Question 35

How to combat C inhibition

Answer 35

Add more substrate and the inhibitor will eventually be overpowered

Question 36

Mechanism of NC inhibition

Answer 36

Binds at at the allosteric site changing the shape of the active site of the enzyme This decreases the turnover number of the enzyme

Question 37

Does binding outside active site always lead to inhibition?

Answer 37

No, sometimes it causes activation

Question 38

NC inhibition on line weaver burk

Answer 38

ADD PHOTO

Question 39

C inhibition graph

Answer 39

Pic