Ch 10 Introduction To Metabolism

Front 1

features common to all types of metabolism

Back 1

• life obeys the laws of thermodynamics
• ATP is the most common energy conservation molecule in the cell
• oxidation-reduction (redox) reactions play a critical role in energy conservation
• the chemical reactions that occur in cells are organized into pathways
• each reaction of a pathway is catalyzed by an enzyme or a ribozyme
• the functioning of biochemical pathways is regulated

Front 2

3 types of work carried out by cells

Back 2

1. chemical
2. transport
3. mechanical

Front 3

1st law of thermodynamics

Back 3

energy can be neither created nor destroyed

Front 4

2nd law of thermodynamics

Back 4

Concept that events in the universe tend to proceed "downhill" ; from state of higher energy to state of lower energy. This is an increase in entropy or disorder.

Front 5

exergonic reaction

Back 5

• -∆G +∆S (increasing entropy)
• spontaneous reaction
• favorable reaction
• proceeds in the forward direction
• oxidation

Front 6

endergonic reaction

Back 6

• +∆G -∆S (decreasing entropy)
• requires energy
• unfavorable reaction
• proceeds in the reverse direction
• reduction

Front 7

ATP

Back 7

• adenosine triphosphate
• a nucleoside triphosphate
• pyrimidine right (adenine) + ribose + 3 Phosphates
• used in energy transfer
• link between exergonic and endergonic reactions
• high phosphate transfer potential

Front 8

NTPs

Back 8

used in metabolis

Front 9

GTP

Back 9

used in protein synthesis

Front 10

CTP

Back 10

used in lipid synthesis

Front 11

UTP

Back 11

used in peptidoglycan and polysaccharide synthesis

Front 12

glucose 6-phosphate

Back 12

an example of a low-energy phosphorylated compound

Front 13

oxidation

Back 13

catabolic reaction

-∆G +∆S (increasing entropy)

favorable / exergonic

Front 14

reduction

Back 14

anabolic reaction

+∆G -∆S (decreasing entropy)

unfavorable / endergonic

Front 15

standard reduction potential (E0)

Back 15

measure of the tendency of the donor of the half reaction (redox) to lose an electron

electrons move from -E0 > +E0 molecules

Front 16

free energy change is defined at standard conditions including:

Back 16

concentration

pH

temperature

Front 17

Electron Transport Chains (ETC)

Back 17

• generally associated with membranes
• electron flow from -electron carrier > +electron carrier
• during respiratory processes exogenous O2 serves as a terminal electron acceptor

Front 18

exogenous

Back 18

produced outside the body

Front 19

electron carriers

Back 19

NADH & NADPH: nicotinamide ring - 2e- + 1 H

FAD & FMN: complex ring system - 2e- + 2 H

CoQ & quinone: 2e- + 2 H

cytochromes: use Fe to transport 1 e- at a time

Front 20

biochemical pathways

Back 20

produce metabolites in biological systems

Front 21

metabolite flux

Back 21

rate of turnover of a metabolite; the rate at which a metabolite is formed and then used

measure of pathway activity used to understand metabolic networks

Front 22

enzymes and ribozymes

Back 22

• protein catalysts and RNA catalysts respectively
• great specificity
• increase the rate of reaction without being altered itself
• lower activation energy

Front 23

holoenzyme

Back 23

an apoenzyme (protein) + cofactor complex

Front 24

prosthetic group

Back 24

a cofactor that is firmly attached to an apoenzyme

Front 25

coenzyme

Back 25

a cofactor that is loosely attached to an apoenzyme

Front 26

activation energy

Back 26

the amount of energy required to reach a transition state

enzymes lower the activation energy required to reach the transition state

Front 27

denaturation

Back 27

if the temperature rises too much above the optimum, an enzymes structure will be disrupted and its activity lost

Front 28

competitive inhibitor

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directly competes with the substrate an an enzymes catalytic site and prevents the enzyme from forming product

Front 29

noncompetitive inhibitor

Back 29

affect enzyme activity by binding to the enzyme at some location other than the active site

Front 30

3 methods of regulating metabolism

Back 30

1. metabolic channeling
2. regulation of gene expression
3. post translational regulation of enzyme activity

Front 31

metabolic channeling

Back 31

influences pathway activity by localizing metabolites and enzymes into different parts of a cell

Front 32

regulation of gene expression

Back 32

regulates the synthesis of a particular enzyme by altering transcription and translation rates to control the amount of enzyme present of the cell

Front 33

posttranslational regulation

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direct stimulation or inhibition of the activity of critical enzymes can rapidly alter pathway activity. Methods include:

• allosteric regulation (reversible)
• covalent modification of enzymes (reversible)
• feedback inhibition (reversible)

Front 34

reversible covalent modificaiton

Back 34

switch regulatory enzymes on a off by addition or removal of a chemical group:

• phosphoryl
• methyl
• adenylyl

Front 35

feedback inhibition

Back 35

the end product of a pathway inhibits earlier processes in a pathway; results in changes in product concentration

Front 36

isoenzymes

Back 36

different forms of an enzyme that catalyze the same reaction

often used to regulate branched pathways