2.10 introduction to enzymes

Question 1

What is an enzyme catalyst? what is it like at the end of a reaction?

Answer 1

a chemical that speeds up the rate of a chemical reaction. It is chemically unchanged at the end of the reaction because they themselves are not consumed or used up during the course of the reaction.

Question 2

What effect do catalysts have on activation energy?

Answer 2

Reduces the activation energy

Question 3

What effect do catalysts have on transition state?

Answer 3

Lowers the energy of the transition state

Question 4

What is a substrate?

Answer 4

molecule upon which an enzyme acts

Question 5

How does a substrate interact with an enzyme?

Answer 5

The substrate binds to the enzyme by interacting with amino acids in the binding site

Question 6

What does the theory of induce fit state?

Answer 6

states that the binding of a substrate or some a molecules to an enzyme causes a change in the shape of the enzyme so as to enhance or inhibit its activity.

Question 7

What is a competitive inhibitor?

Answer 7

any molecule that can bind to the active site of an enzyme with sufficient affinity such that it can compete with the enzyme’s natural substrate and reduce enzyme activity as a result.

Question 8

What is the active site of an enzyme?

Answer 8

the region of an enzyme where substrate molecules bind and undergo a chemical reaction

Question 9

What is a non competitive inhibitor?

Answer 9

an inhibitor binding to an allosteric site resulting in decreased efficiency of the enzyme

Question 10

What is an allosteric site?

Answer 10

region of an enzyme that allows activator or inhibitor molecules to bind to the enzyme in order to activate or inhibit enzyme activity

site other than the active site

Question 11

what is cooperativity in enzymes?

Answer 11

a phenomenon in which the shape of one subunit of an enzyme is altered by the substrate or some other molecule so as to change the shape of a neighbouring subunit.

subunits of the enzyme of cooperating (working together) to change their shape

Question 12

what do allosteric regulation and cooperativity have in common?

Answer 12

both increase enzyme efficiency as the binding of a molecule induces change in all the enzyme subunits

Question 13

what is the difference between an allosteric site and an active site?

Answer 13

-allosteric site is a region of an enzyme that allows activator or inhibitor molecules to bind to the enzyme to either activate or inhibit enzyme activity

-an active site is a region of an enzyme where substrate molecules bind and catalyze the reaction resulting in the production of particular products

the difference is in terms of which molecules their sites can bind

Question 14

what is the allosteric site and cooperativity used for in terms of single and complex enzymes?

Answer 14

allosteric site is for both single enzymes and complex enzymes

cooperativity only works for enzyme complexes

Question 15

what is the difference between an allosteric site and an cooperativity in terms of substrate molecules?

Answer 15

an allosteric site has only non subtract molecules. cooperativity, occurring at the active site, has substrate molecules

Question 16

how is an enzyme denatured?

Answer 16

at a certain point, the speed of the reaction drops sharply. At this point, the thermal agitation (small component particles of a substance that is associated with heat) is severe enough to disrupt the bonds within the enzyme that stabilize the active conformation

Question 17

how does a decrease in temperature slow the rate of a reaction?

Answer 17

when a decrease in temperature occurs, the particles are not moving fast enough to collide with sufficient energy to break the bonds to release the energy needed to catalyze the reaction. therefore a decrease in temperature slows the rate of a reaction

Question 18

how is the optimal temperature of enzymes significant to the way particles move?

Answer 18

a temperature which allows the highest number of collisions without denaturation

Question 19

what is the optimal temperature of an enzyme?

Answer 19

human body temperature

Question 20

As with temperature, most enzymes also have an optimal pH (acidity and basic) in which they function best. Generally a pH of around 6-8 (close to neutral) is preferred. WHY?

Answer 20

Because the major addition or removal of H+ ions can disrupt the bonding necessary to maintain the 3D shape.

Question 21

why does the increase of substrate increased the rate at which a product is formed?

Answer 21

more substrate molecules will collide with enzyme active sites so more product will be formed

Question 22

the increase of substrate only occurs up to a maximum value whereby the enzyme becomes saturated with substrate. WHAT DOES THIS MEAN?

Answer 22

Once the enzyme is saturated with the substrate, an increase of substrate will have no effect on the rate of the reaction, because the enzyme is fully covered and will be working at its maximum limit.

Question 23

what does Km stand for?

Answer 23

the concentration of substrate with the reaction is half the maximum rate

Question 24

what does a low Km value mean?

Answer 24

the enzyme reaches a maximum catalytic rate at a low substrate concentration

Question 25

what does a low Km value indicate about how the enzyme binds to the substrate?

Answer 25

the enzyme binds the substrate tightly.

Question 26

what does a high km value mean?

Answer 26

enzyme catalyzed reaction reaches a maximum rate at a high concentration of substrate

Question 27

turnover number

Answer 27

the maximum number of substrate molecules converted to product per minute for each active site.

Question 28

what does a high km value indicate about the enzyme and the substrate?

Answer 28

the enzyme binds to the substrate very loosely

Question 29

how many substrates does it take to saturate the enzyme in a high km value and why?

Answer 29

it takes a lot of substrates to saturate the enzyme because the enzyme processes the substrate rapidly, it thus has a high turnover number

Question 30

how many substrates does it take to saturate the enzyme in a low km value and why?

Answer 30

it doesn’t take a lot of substrates to saturate the enzyme because the enzyme processes the substrate more slowly, it thus has a low turnover number

Question 31

activation energy

Answer 31

the amount of energy that must be put in for a reaction to begin

Question 32

why does an enzyme-catalyzed reaction increase with an increased concentration of enzyme?

Answer 32

the more enzymes involved in the reaction, the higher number of active sites to catalyze the reaction. the chemical reaction will speed up as long as the active sites are not fully saturated with substrate already

Question 33

why does the rate of an enzyme-catalyzed reaction increase with an increased concentration of enzyme up to a certain point ?

Answer 33

the chemical reaction will speed up as long as the active sites are not fully saturated with substrate already

Question 34

what is the relationship between optimal enzyme and substrate concentration?

Answer 34

they are inherently dependent on each other

Question 35

why are transition energy and activation energy proportional?

Answer 35

catalyst lower the energy of the transition state of a reaction/ since activation energy is the difference between the transition energy and the reactant energy, lowering the transition energy also lowers the activation energy.

Question 36

what is enzyme denaturation?

Answer 36

when the bonds within the enzyme, either hydrogen, van der waals, ionic of disulfide bridge bonds are disrupted

Question 37

whats is the exception to the optimal ph of enzymes?

Answer 37

pepsin also known as hydrochloric acids has a pH of 2 and works in the stomach

Question 38

what is the function of membrane bound compartments? what effect does it have outside the compartment?

Answer 38

separates substrates and enzymes that act upon them into the same compartment. this can increase substrate up to 10 times outside the compartment

Question 39

what are enzyme complexes?

Answer 39

the assembly of several enzymes into one molecules

Question 40

what is the function of enzyme complexes?

Answer 40

carry out a single or series of biochemical reactions that take place in the cells

1. increase substrate concentration

2.bring enzymes involved in the reaction into large enzyme complexes

3. large enzymes