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94 Cards in this Set

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Bioenergetics

Quantitative study of the energy transformations in the living cell and the nature and function of the chemical processes underlying these transformations

Metabolism

An intricate network of multienzyme reactions/processes highly coordinated and regulated to meet the needs of the cell

Multi-step reaction pathway,


Enzyme-catalyzed steps,


Central reaction pathways/metabolites,


Few types of reactions,


Pathways are interrelated,


Regulatory mechanisms

General features of metabolism (6)

Catabolism

The breakdown of larger molecules into smaller ones; oxidative; releases energy

Anabolism

Synthesis of larger molecules from smaller ones; reductive; requires energy

Catabolism

Exergonic, converging

Anabolism

Energonic, diverging

Not enzymatically identical,


Both pathways occur in 3 major stages,


Both pathways are subject to regulation

3 features of catabolism and anabolism pathways

1. Interconversion of polymers and complex lipids with monomeric intermediates


2. Interconversion of monomeric sugars, amino acids, and lipids with still simpler organic compounds


3. Ultimate degradation to or synthesis from inorganic compounds, including CO2, H2O, and NH3

Three stages of catabolism and anabolism

To provide ATP for energy-dependent activities of the cell,


To provide reducing power (NADH, NADPH, etc.),


To provide building blocks

Strategy of metabolism (3)

First law of thermodynamics

Energy can neither be created nor destroyed but can only be transformed from one form to another

🔺H = Q - W


(Enthalpy = heat absorbed - work done)

Equation for first law of thermodynamics

Second law of thermodynamics

States that all processes, whether chemical or biological, tend to progress toward a situation of maximum entropy

Entropy (S)

Measure or indicator of the degree of disorder or randomness in a system

Equilibrium

Results when the randomness or disorder is at a maximum

Q = T🔺S


(Heat = temp x entropy)

Equation for second law of thermodynamics

Gibbs Free Energy

Unifies the 1st and 2nd law of thermodynamics

🔺G

Value of 🔺G when process is exergonic, favorable/spontaneous

🔺G > 0

Value of 🔺G when endergonic, not favorable

🔺G = 0

Value of 🔺G when at equilibrium

Kcal, joules

Unit of energy

Concentration of reactants and products

🔺G is dependent on this factor

Standard Free Energy Change, 🔺G^o

🔺G under standard conditions, that is, when reactants and products are kept at 1M concentrations

Nitrogenous base + sugar + phosphate group

Nucleotide

Type of molecule of ATP

-7300 cal/mol

🔺G^o of hydrolysis of ATP for each of the 2 terminal PO4 groups

Adenosine triphosphate

High-energy phosphate compounds

PEP,


1,3-biphosphoglycerate,


Phosphocreatine

Examples of very high energy phosphate compounds

Very high energy phosphate compounds

Have 🔺G^o of hydrolysis > -10,000 cal/mol

Low energy phosphate compounds

Have a 🔺G^o of hydrolysis

Glucose 6-P,


Glycerol 3-P,


AMP

Examples of low energy phosphate compounds

Electron transport chain

ETC

Respiratory chain

Other name of ETC

Inner mitochondrial membrane

Location of ETC

Electron transport chain

Final common pathway by which electrons derived from different fuels of the body flow to oxygen

5 separate enzyme complexes

Organization of ETC

Complexes I-IV

Contain part of ETC

Complex V

Catalyzes ATP synthesis

Coenzyme Q,


Cytochrome C

Relatively mobile electron carriers (examples)

1. Formation of NADH


2. NADH dehydrogenase


3. Coenzyme Q


4. Cytochromes


5. Cytochrome a + a3


6. Inhibitors

Reactions of the ETC (6)

Formation of NADH

NAD+ is reduced to NADH by dehydrogenases (removes 2 H atoms from their substrate)


Both e- but only 1 H+ are transferred to the NAD+ forming NADH + H+

NADH Dehydrogenase

H+ + H- carried by NADH are next transferred to NADH dehydrogenase

NADH Dehydrogenase

Enzyme complex embedded in inner mitochondrial membrane

FMN,


Several iron atoms paired with sulfur atoms

Contents of NADH dehydrogenase

FMN

Accepts 2H atoms, becoming FMNH2

Several iron atoms paired with sulfur atoms

Necessary for transfer of H atoms to coenzyme Q (ubiquinone)

Coenzyme Q

Can accept H atoms both from FMNH2 (NADH dehydrogenase) and FADH2 (succinate dehydrogenase and acyl CoA dehydrogenase)

Cytochromes

e- are passed down the chain from coenzyme Q to cyt b, c, and a+a3

Cytochromes

Contains a heme group made of a porphyrin ring containing an atom of iron

Cytochrome iron

Reversibly converted from its ferric to its ferrous form

Cyt a+a3

Cytochrome oxidase


Contains bound copper atoms required for complex reaction

Cyt a+a3

At this site, the transported e-, molecular oxygen and free protons are brought together to produce water

Inhibitors of electron transport

Prevent the passage of e- by binding to a component of the chain

Amytal and rotenone,


Antimycin,


CN- and CO-

Examples of inhibitors of electron transport

Amytal and rotenone

Inhibits NADH dehydrogenase

Antimycin

Inhibits cyt b-c complex

CN- and CO-

Inhibits cyt oxidase

Cyanide Poisoning

CN- acts as final e- acceptor; mitochondrial respiration and energy production cease; cell death occurs rapidly

Hypoxic injury

Happens when a tissue is deprived of its oxygen supply as a result of e- transport inhibition; dec ATP; inc anaerobic glycolysis; inc lactic acid; dec pH; damage lysosomal membranes; digestion of cellular components

Complex I,


NADHQ reductaze

Other names of NADH dehydrogenase

FMN,


Fe-S

Prosthetic groups of NADH dehydrogenase

NADH

E- donor of NADH dehydrogenase

CoQ

E- acceptor of NADH dehydrogenase

Rotenone,


Riboflavin deficiency

Inactivated NADH dehydrogenase

Coenzyme Q,


Ubiquinone

Other names of CoQ

CoQ

Prosthetic groups of CoQ

NADH dehydrogenase

Electron donor of CoQ

b-c1 complex

E- acceptor of CoQ

Generation of free radicals,


Doxorubicin

Inactivates CoQ

Complex III,


Ubiquinone-cytochrome c oxidoreductase

Other names of cytochrome b-c1 complex

Fe-S,


Heme b562,


Heme b566,


Heme c1

Prosthetic groups of cytochrome b-c1 complex

CoQ

E- donor of cytochrome b-c1 complex

Cytochrome c

E- acceptor of cytochrome b-c1 complex

Antimycin,


Demerol,


Fe deficiency

Inactivates cytochrome b-c1 complex

Heme c

Prosthetic group of cytochrome c

Heme c

Prosthetic group of cytochrome c

Cytochrome oxidase

E- acceptor of cytochrome c

Fe deficiency

Inactivates cytochrome c

Complex IV,


Cytochrome aa3

Other names of cytochrome oxidase

Heme a,


Heme a3,


CuA,


CuB

Prosthetic groups of cytochrome oxidase

Cytochrome c

E- donor of cytochrome oxidase

O2

E- acceptor of cytochrome oxidase

Cyanide,


Carbon monoxide,


Ischemia,


Fe and Cu deficiency

Inactivates cytochrome oxidase

Complex II

Other name for succinate dehydrogenase

FAD, Fe-S

Prosthetic groups of succinate dehydrogenase

Succinate

E- donor of succinate dehydrogenase

CoQ

E- acceptor of succinate dehydrogenase

Malonate

Inactivate succinate dehydrogenase

Standard Reduction Potential, Eo

Characterized tendency of a redox pair to lose e-

Mitchell Hypothesis

Also known as chemiosmotic hypothesis (oxidative phosphorylation)

Mitchell Hypothesis

Explains how the free energy generated by the transport of e- via ETC is used to produce ATP from ADP and Pi

Electron transport

Accdg to chemiosmotic hypothesis, this is coupled to transport of protons across the inner mitochondrial membrane from the matrix to the intermembrane space

Chemiosmotic hypothesis

Creates an electrical gradient and pH gradient which produces energy sufficient to drive ATP synthesis

ATP synthetase (complex V)

Synthesizes ATP using the energy of the proton gradient generated by ETC; converts ADP and Pi to ATP and H2O

Chemiosmotic hypothesis

Proposes that after protons have been transferred to the cytosolic side of the inner mitochondrial membrane, they can reenter the matrix by passing through a channel in the ATP synthetase molecule resulting in the synthesis of ATP from ADP and Pi and at the same time, dissipating the pH and electrical gradients