CHAPTER 8

Question 1

chemical reaction

Answer 1

occurs when atoms have enough energy to combine or change bonding partners

Question 2

metabolism

Answer 2

sum total of all chemical reactions occurring in a biological system at a given time; reactions involve energy changes

Question 3

energy

Answer 3

capacity to do work, or the capacity for change

Question 4

What are the types of energy?

Answer 4

CHEMICAL - stored in bonds
ELECTRICAL - separation of charges
HEAT - transfer due to temperature difference
LIGHT - electromagnetic radiation stored as photons
MECHANICAL - energy of motion

Question 5

potential energy

Answer 5

energy stored as chemical bonds, concentration gradient, or change imbalance

Question 6

kinetic energy

Answer 6

the energy of movement

Question 7

anabolic reactions

Answer 7

complex molecules are made from simple molecules; energy is required

Question 8

catabolic reactions

Answer 8

complex molecules are broken down into simpler ones; energy is released

Question 9

laws of thermodynamics

Answer 9

apply to all matter and all energy transformations in the universe; help us to understand how cells harvest and transform energy to sustain life

Question 10

What are the first two laws of thermodynamics?

Answer 10

1st - energy is neither created nor destroyed
2nd - when energy is converted from one from to another, some of that energy becomes unavailable to do work; disorder tends to increase because of energy transformations

Question 11

entropy (S)

Answer 11

a measure of the disorder in a system; it takes energy to impose order on a system; unless energy is applied to a system, it will be randomly arranged or disordered

Question 12

enthalpy (H)

Answer 12

total energy

Question 13

free energy (G)

Answer 13

usable energy that can do work; does not change in enzyme-substrate complex

Question 14

H = G + TS

Answer 14

unusable energy is represented by entropy (S) multiplied by the absolute temperature (T)

Question 15

exergonic

Answer 15

reactions that release free energy (-ΔG)

Question 16

endergonic

Answer 16

reactions that consume free energy (+ΔG)

Question 17

chemical equilibrium

Answer 17

balance between forward and reverse reactions, a state of no net change, ΔG = 0

Question 18

ATP (adenosine triphosphate)

Answer 18

captures and transfers free energy; can be hydrolyzed to ADP and Pi, releasing a lot of energy for endergonic reactions; can also phosphorylate (donate a phosphate group to) other molecules, which gain some energy; formation is endergonic and combined with hydrolysis they couple endergonic and exergonic reactions

Question 19

catalysts

Answer 19

increase rates of chemical reactions; not altered by the reactions

Question 20

enzymes (proteins)

Answer 20

biological catalysts that act as a framework in which reactions can take place; lower the energy barrier by bringing the reactants together; highly specific; its 3D shape determines its specificity; can increase reaction rates by 1 million to 10 to the 17 times (10^17)

Question 21

activation energy (Ea)

Answer 21

the amount of energy required to start the reaction; can come from heating the system

Question 22

transition state

Answer 22

reactive mode that activation energy puts the reactants in

Question 23

transition state intermediates

Answer 23

activation energy changes the reactants into unstable forms with higher free energy

Question 24

substrates

Answer 24

reactants; bind to the active site of the enzyme

Question 25

What are the six categories of enzymes?

Answer 25

• OXIDOREDUCTASES
• TRANSFERASES
• HYDROLASES
• LYASES
• ISOMERASES
• LIGASES

Question 26

enzyme-substrate complex (ES)

Answer 26

held together by hydrogen bonds, electrical attraction, or covalent bonds; the enzyme may change while bound to the substrate but returns to its original form

Question 27

riboenzymes

Answer 27

some RNA molecules that can act as biological catalysts
EXAMPLE: an RNA molecule catalyzes formation of peptide bonds between amino acids

Question 28

What are the three types of “partners” some enzymes require?

Answer 28

• PROSTHETIC GROUPS - non-amino acid groups bound to enzymes
• INORGANIC COFACTORS - ions permanently bound to enzyme
• COENZYMES - small carbon-containing molecules; not permanently bound

Question 29

enzyme inhibitors

Answer 29

molecules that bind to the enzyme and slow reaction rates; the ones that are naturally occurring regulate metabolism; the ones that are artificial can be used to treat disease, kill pests, or study how enzymes work

Question 30

irreversible inhibition

Answer 30

inhibitor covalently bonds to side chains in the active site and permanently inactivates the enzyme

Question 31

reversible inhibition

Answer 31

inhibitor bonds noncovalently to the active site and prevents substrate from binding

Question 32

competitive inhibitors

Answer 32

compete with the natural substrate for binding sites

Question 33

uncompetitive inhibitors

Answer 33

bind to the enzyme-substrate complex, preventing release of products

Question 34

noncompetitive inhibitors

Answer 34

bind to enzyme at a different site (not the active site); the enzyme changes shape and alters the active site (allostery)

Question 35

allosteric regulation

Answer 35

a non-substrate molecule binds enzyme at a site different from the active site, which changes enzyme shape
ACTIVE form - proper shape to bind substrate
INACTIVE form - cannot bind substrate

Question 36

allosteric enzymes

Answer 36

most are proteins with quaternary structure; active site is on the catalytic subunit; with inhibitors they bind to other polypeptides called regulatory subunits, at regulatory sites (allosteric sites); some have multiple subunits with active sites; reaction rate is very sensitive to substrate concentration (over a certain range); sensitive to low concentrations of inhibitors; important in regulating metabolic pathways

Question 37

non-allosteric enzymes

Answer 37

have one binding site which makes them have different reaction rates at low substrate concentrations

Question 38

What can affect an enzyme’s function?

Answer 38

• changes in PH
• changes in optimal TEMPERATURE