Chapter10

Question 1

What is a chemical reaction?

Answer 1

A process that either forms or breaks chemical bonds that hold atoms together

Question 2

What do all chemical reactions need/do?

Answer 2

They either require an input of energy or release energy

Question 3

What is an exergonic reaction

Answer 3

A reaction that releases energy , reactants contain more energy than the products

Question 4

What is a endergonic reaction?

Answer 4

A reaction that requires an input of energy , meaning the products contain more energy than the reactants

Question 5

What do all chemical reactions need?

Answer 5

An initial investment of energy

Question 6

What is activation energy ?

Answer 6

The amount of initial energy that is required in order for the reactant molecules to contort so bonds can break

Question 7

Where does Ea from come from?

Answer 7

-often supplied in the form of heat that reactants absorb from the envirnoment
-heat causes the reactants to move more quickly so they collide more
-collisions also make the bonds more ready to break
-once enough energy is absorbed so that bonds can break EA has been met

Question 8

What happens when Ea is low

Answer 8

Can proceed at room temp in a short time

Question 9

What happens when the EA is very high

Answer 9

At very high levels of EA and at room temp the reaction may proceed at a unnoticeable rate

Question 10

What would happen if tractions were to proceed at reasonable rates?

Answer 10

One reaction would have to increase the proportion of molecules that have enough energy to

Question 11

How can reactions increase the proportion of molecules that have enough energy

Answer 11

1)heating
The problem with heating
I) in living systems ,heat can kill cells
ii)would not be specific >all chemical reactions would speed up
2) decreasing the EA
By doing so one will ensure that a greater proportion of molecules will collide in order for the reaction to occur
iii) the EA can be decreased by the use of a catalyst

Question 12

What is a catalyst in a biological system?

Answer 12

An enzyme which is a protein

Question 13

Do enzymes change the reaction in any way?

Answer 13

Enzymes do not change the reaction they just speed up the reaction , they enable the reactant molecules to absorbs enough energy to reach the transition state even at mod temps

Question 14

What is the effect of enzymes on rate of reaction?

Answer 14

They lower the EA , less collisions need to occur for transition state to reach

Question 15

What is a substrate ?

Answer 15

The reactant an enzyme acts on

Question 16

How are enzymes and substrates related?

Answer 16

Enzymes bonds to the substrate forming an enzyme substrate complex

Question 17

What is the active site?

Answer 17

The region on the enzyme where the substrate binds

Question 18

What is an induced fit?

Answer 18

The shape of the enzyme changes slightly when the substrate enters and this is due to the interactions that happen between the chemical groups of the substrate and amino acids that make up the active site

Question 19

How does an enzyme lower the EA ?

Answer 19

-The active site can lower the barrier by orienting the substrates correctly to help the reaction occur
-straining substrate bonds
-Providing the micro environment that is favourable for reactions to occur
May participate directly in the chemical rxn

Question 20

How can an enzymes activity be affected ?

Answer 20

By the general environmental factors

Question 21

What do each enzymes need in order to function?

Answer 21

They have an optimal temperature where it functions
Has an optimal pH which it can function in

Question 22

What happens if an enzymes environment changes

Answer 22

The protein becomes denatured, biologically inactive

Question 23

What do many enzymes require ?

Answer 23

They require cofactors which are non protein chemical compounds that are required for an enzymes to act as a catalyst

Question 24

What are examples of inorganic cofactors

Answer 24

Metal atoms such as zinc, copper and iron , these bind allosterically to enzymes and changes the structure and chemical potential of active site

Question 25

What are organic cofactors?

Answer 25

They are called coenzymes such as vitamins
They may be bound permanently to the enzyme or may bind loosely and reversibly with the substrate

Question 26

What is irreversible inhibitors?

Answer 26

That bind to the enzyme via a covalent bond
Ie: toxins and poisons (nerve agent :sarin)

Question 27

What is reversible inhibitor ?

Answer 27

One that binds to the enzyme via weak interactions

Question 28

What are competitive inhibitors ?

Answer 28

Binds to the active site of an enzyme thereby competing with the substrate , can be overcome by increasing the substrate concentration, basically pretends to be the substrate

Question 29

What is a non competitive inhibitor?

Answer 29

Binds to a site that isn’t the active site , the binding changes the conformation of the enzyme which interferes with the function of the active site (allosteric regulation)

Question 30

Is the inhibition of enzymes normal ?

Answer 30

Yes the inhibition of enzyme activity is normal
An example is that its used to control the enzymes involved in cellular metabolism

Question 31

How can enzyme activity be controlled ?

Answer 31

By feedback inhibition , where the end product if a metabolic pathway shuts down the pathway by inhibiting an enzyme found at the beginning of a pathway