Enzymes

Question 1

what is a chemical reaction?

Answer 1

a chemical reaction is a process that either forms or breaks the chemical bonds that hold atoms together. dehydration synthesis or hydrolysis.

Question 2

all chemical reactions either?

Answer 2

release energy or require an input of energy.

Question 3

what is a reaction that releases energy called?

Answer 3

its called an exergonic reaction. this means the reactants contain more energy than the products.

Question 4

what is a reaction that requires an input of energy called?

Answer 4

its called an endergonic reaction. this means that the products contain more energy than the reactants.

Question 5

every chemical reaction requires?

Answer 5

an initial investment of energy.

Question 6

for every reaction there is a specific?

Answer 6

activation energy that needs to be present: amount of initial energy that is required in order for the reactant molecules to contort so the bonds can break.

Question 7

where does the initial activation energy come from?

Answer 7

ea is often supplied in the form of heat that the reactants absorb from the environment. this heat causes the reactants to move more quickly so that they collide more often. the collisions also make the bonds more ready to break.

Question 8

once enough energy is absorbed so that the bonds can break…?

Answer 8

the ea has been met.

Question 9

what determines the rate of the reaction?

Answer 9

the activation energy

Question 10

for some chemical reactions the ea is low…?

Answer 10

low enough that they can proceed at room temperature in a short time.

Question 11

for some chemical reactions, the ea is high…?

Answer 11

high and at room temperature, the reaction may proceed at an unnoticeable rate.

Question 12

is the sucrose=glucose+fructose reaction fast or slow at room temperature?

Answer 12

it is very slow at room temperature.

Question 13

if reactions are to proceed at reasonable rates…?

Answer 13

one would have to increase the proportion of molecules that have enough energy. this can be done by? heating and decreasing the ea.

Question 14

heating? and problems?

Answer 14

heating can kill cells and would not be specific: all chemical reactions would speed up.

Question 15

decreasing the ea?

Answer 15

by decreasing the ea, one will ensure that a greater proportion of molecules will collide in order for the reaction to occur.

Question 16

the ea can be decreased how?

Answer 16

by the use of a catalyst. in biological systems a catalyst is called an enzyme. an enzyme is a protein.

Question 17

do enzymes change the reaction?

Answer 17

no, they do not change the reaction in any way, they just speed up the reaction.

Question 18

what is the effect of enzymes on reaction rate?

Answer 18

enzymes lower the ea: less collisions need to happen in order for the transition state to be reached.

Question 19

what is the substrate?

Answer 19

the substrate is the reactant an enzyme acts on.

Question 20

enzymes are?

Answer 20

• specific
• enzymes bind to its substrate forming an enzyme substrate complex

Question 21

what is the active site?

Answer 21

region on the enzyme where the substrate binds.

Question 22

what is an induced fit?

Answer 22

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

Question 23

how does the active site lower the ea barrier?

Answer 23

by orienting the substrates correctly to help the reaction occur, straining substrate bonds, providing a microenvironment that is favorable for the reaction to occur, may itself directly participate in the chemical reaction.

Question 24

an enzymes activity is affected?

Answer 24

by general environmental factors.

Question 25

each enzyme has?

Answer 25

an optimal temperature in which it functions and has an optimal pH in which it can function.

Question 26

what happens to an enzyme if the environmental conditions change?

Answer 26

protein becomes denatured and it is biologically inactive.

Question 27

what are cofactors?

Answer 27

many enzymes require cofactors for activity.
- they are not made of protein

Question 28

what are some inorganic cofactors?

Answer 28

metal atoms such as zinc, copper, iron.

Question 29

what are some organic cofactors?

Answer 29

organic cofactors are called coenzymes.
- most vitamins are coenzymes
- these cofactors may be bound permanently to the enzyme or may bind loosely and reversibly with the substrate.

Question 30

an enzymes activity can be?

Answer 30

inhibited.

Question 31

what are irreversible inhibitors?

Answer 31

inhibitors that bind to the enzyme via a covalent bond.
examples: toxins, poisons

Question 32

what is a reversible inhibitor?

Answer 32

inhibitors that bind to the enzyme via weak interactions.
- they can be competitive or noncompetitive.

Question 33

what is a competitive inhibitor?

Answer 33

competitive inhibitors bind to the active site of an enzyme, competing with the substrate.

CAN BE OVERCOME BY INCREASING SUBSTRATE CONCENTRATION.

Question 34

what is a noncompetitive inhibitor?

Answer 34

noncompetitive inhibitors bind to a site other than the active site.
- binding changes the conformation of the enzyme which interferes with the function of the active site.
- also called allosteric regulation.

CANT BE OVERCOME BY INCREASING SUBSTRATE CONCENTRATION.

Question 35

the inhibition of en enzyme activity is?

Answer 35

a normal process that happens in cells.
- used to control the enzymes involved in cellular metabolism.

Question 36

what is feedback inhibition?

Answer 36

the end product of a metabolic pathway shuts down the pathway by inhibiting an enzyme found in the beginning of the pathway.