Ch. 8 An Introduction to Metabolism

Question 1

what is a catabolic pathway?

Answer 1

breaking down of complex things into simpler things: hydrolysis, energy releasing, is exergonic

Question 2

what is an anabolic pathway?

Answer 2

building up: dehydration synthesis, energy is needed = endergonic

Question 3

what is the 1st law of thermodynamics?

Answer 3

-there is a finite amount of energy in the universe, and it cannot be created or destroyed, only changed forms

Question 4

what is the 2nd law of thermodynamics?

Answer 4

the entropy of the universe increases with every energy transfer = organisms must absorb energy to stay organized

Question 5

what is kinetic energy?

Answer 5

energy of motion - such as molecules moving

Question 6

what is potential energy?

Answer 6

energy of position or state - such as a reaction giving off energy

Question 7

what is an open system?

Answer 7

a system that allows both heat and matter to leave it

Question 8

what is a closed system?

Answer 8

a system that allows heat, but not matter, to leave it

Question 9

what is free energy?

Answer 9

the portion of a system’s energy that can perform work = G
larger G = more work can be done
-unstable systems have more G than stable ones

Question 10

what can the body do with spontaneous free energy?

Answer 10

1. transport - ex - Na/K pump
2. mechanical work - ex - muscle movement
3. chemical work - ex - building polymers

Question 11

how does ATP perform work?

Answer 11

when atp undergoes hydrolysis, it releases a LOT of free energy, which is coupled to reactions that are endergonic [need an input of energy]

Question 12

what are the three components of ATP?

Answer 12

adenosine [nucleic acid] attached to a ribose sugar, with 3 phosphate groups on the end
-the bond in the last 2 phosphate has a LOT of potential energy stored

Question 13

what are the functions of enzymes in biological systems?

Answer 13

to reduce the amount of energy required for a reaction by lowering the activation energy

Question 14

what are the characteristics of enzymes? [6]

Answer 14

1. they reduce activation energy
2. they have ACTIVE SITES which are very specific, only work w/ certain molecules
3. the enzyme is unchanged at the end of the reaction
4. enzyme reactions are mostly reversible, depends on [S] and [P]
5. if there is unlimited substrate, increasing [enzyme] will increase rate of reaction
6. if there is a fixed amount of enzyme, increasing [substrate] will increase rate of reaction until all active sites are filled

Question 15

what is activation energy?

Answer 15

the amount of energy that must be put into a reaction for it to commence

Question 16

what is free energy change?

Answer 16

the amount of energy released in the conversion of reactants to products

Question 17

what is a transition state?

Answer 17

the part of a reaction with the highest potential energy

Question 18

what factors can affect the function of enzymes?

Answer 18

temperature - too high and the enzyme is denatured, too low and the molecules move too slowly for a reaction to occur

pH - extremes on either end lead to loss of shape and function

Question 19

what are enzyme cofactors?

Answer 19

inorganic molecules that help enzymes - Fe2+, Cu2+, Zn2+

Question 20

what are coenzymes?

Answer 20

organic molecules that help enzymes, many involved in ATP-making reactions:
Vitamin B3 = niacin = NADH
Riboflavin = FMN and FAD
Pantothenate = Acetyl CoA

Question 21

what is competitive inhibition of enzymes?

Answer 21

-a molecule binds to the active site and prevents substrate binding
-often the product of a metabolic pathway

Question 22

what is a non-competitive inhibitor of enzymes?

Answer 22

a molecule that binds to the enzyme at someplace other than the active site
-ex heavy metals

Question 23

what is allosteric regulation?

Answer 23

when another molecule binds to a site other than the active site - occurs on enzymes with active/inactive forms

Question 24

what is an allosteric activator?

Answer 24

a molecule that stabilizes the active form of an enzyme

Question 25

what is an allosteric inhibitor?

Answer 25

a molecule that stabilizes the inactive form of an enzyme

Question 26

what is feedback inhibition?

Answer 26

when the first enzymes in a metabolic pathway are inhibited by the product of the pathway
-> avoids unnecessary production of the end product