Chapter 11

Question 1

what is a chemical reaction?

Answer 1

a process that either forms or breaks chemical bonds that hold atoms together.

Question 2

dehydration synthesis vs hydrolysis?

Answer 2

in dehydration synthesis, two molecules combine to form a larger molecule with the removal of water.
in hydrolysis, larger molecule is broken down into smaller ones with the addition of water.

Question 3

all chemical reactions either?

Answer 3

release energy or require an input of energy.

Question 4

what is an exergonic reaction?

Answer 4

a reaction that releases energy. this means that the reactants contain more energy than the products.

Question 5

what is an endergonic reaction?

Answer 5

a reaction that requires an input of energy. this means that the products contain more energy than the reactants.

Question 6

EVERY chemical reaction requires what?

Answer 6

an initial investment of energy.

Question 7

for every reaction, there is a specific activation energy EA that needs to be present. this refers to?

Answer 7

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

Question 8

EA is often supplied in the form of?

Answer 8

heat that reactants absorb from the environment, this heat causes the reactants to move more quickly, so they collide more often.
- collisions make the bonds break easily
- once enough energy is absorbed so the bonds can break, EA has been met

Question 9

for some chemical reactions, the EA is low enough that? or high enough?

Answer 9

they can proceed at room temperature in a short time.
for others, the EA is very high, and at room temperature, the reaction may proceed at an unnoticeable rate.

Question 10

sucrose = glucose + fructose reaction? fast or slow at room temp?

Answer 10

its very slow at room temperature

Question 11

to increase the proportion of molecules with enough energy, it means?

Answer 11

1. heating: raising the temperature increases collisions. BUT, the problem is heat can kill cells, and not all chemical reactions would speed up.
2. decreasing the EA: decreasing EA ensures that a greater proportion of molecules will collide in order for the reaction to occur.
   - EA can be decreased by the use of a catalyst, in biological systems a catalyst is called an enzyme, it is a protein.

Question 12

enzymes dont change the reaction in any way, they?

Answer 12

just speed up the reaction: enable reactant to absorb enough energy to reach their transition state.

Question 13

what is the effect of enzymes on reaction rate?

Answer 13

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

Question 14

what is the substrate?

Answer 14

reactant an enzyme acts on. enzyme is specific based on active site shape.

Question 15

what is the enzyme?

Answer 15

protein that binds to the substrate forming an enzyme substrate complex.

Question 16

what is the active site?

Answer 16

region on the enzyme where the substrate binds.

Question 17

induced fit enzyme?

Answer 17

the shape of an enzyme changes slightly when the substrate enters: due to the chemical groups of the substrate and the amino acids that make up the active site.

Question 18

the active site can lower EA by?

Answer 18

• orienting the substrates correctly to help the reaction occur
• straining substrate bonds
• providing an environment that is favorable for the reaction to occur

Question 19

an enzymes activity is affected by?

Answer 19

general environmental factors

Question 20

each enzyme has an?

Answer 20

optimal temperature in which it functions, optimal pH in which it can function

Question 21

what may happen to an enzyme if environmental conditions change?

Answer 21

protein becomes denatured
and becomes biologically inactive

Question 22

many enzymes require?

Answer 22

cofactors for activity: not made of protein

Question 23

what are some inorganic cofactors?

Answer 23

metal atoms such as zinc, copper, iron

Question 24

what are some organic cofactors?

Answer 24

called coenzymes: most vitamins are coenzymes.
- may be bound permanently to the enzyme or bind loosely with the substrate.

Question 25

enzyme activity can be inhibited: irreversible inhibitor?

Answer 25

inhibitors that bind to the enzyme via a covalent bond
example: toxins, poison, sarin

Question 26

reversible inhibitor?

Answer 26

one that binds to the enzyme via weak interactions:
competitive inhibitor
noncompetitive inhibitor

Question 27

what is competitive inhibitor?

Answer 27

bind to the active site of the enzyme thereby competing with the substrate

Question 28

what is noncompetitive inhibitor?

Answer 28

bind to a site other than the active site: interferes with the function of the active site

Question 29

the inhibition of enzyme activity is a normal process that happens in cells example?

Answer 29

used to control the enzymes involved in cellular metabolism.

Question 30

what is feedback inhibition?

Answer 30

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