ATP SYNTHESIS

ATP SYNTHESIS General

ATP Beta and gamma more energy Oxidative phosphorylation more imp. role in ATP formation than substrate

Mitochondria Structure

Outer Membrane Permeable

Inner membrane Cristae Impermeable Rich in proteins/enzymesETC and ATP synthase

Electron Transport System Four Protein Complexes

Complex I Enzyme NADH DEHYDROGENASE Energy DonorNADH Energy AcceptorCoQ (Complex III) Prosthetic GroupsFMN, Fe-S

Complex II Enzyme SUCCINATE DEHYDROGENASE Energy DonorFADH2 Energy Acceptor CoQ (Complex III) Prosthetic GroupsFAD, Fe-S

Complex III Complex IV

Donates Electron to Oxygen-H2O Formation of Electrochemical Potential

ETC complexes are electron transporters as well as H+ pumps Protons pumped from MatrixIntermembrane space

Complex I-III=4 Complex IIIII=0 Complex IIIIV=2 Complex IVO2=4

NADH VIA COMPLEX 1 =10 Protons=2.5 ATP FADH2 VIA COMPLEX 2=6 protons=1.5 ATP Establishes ELECTROCHEMCIAL POTENTIAL

Matrix negative compared to intermembrane space Provides driving force of ATP synthesis

ATP Synthase Fopore which protons return to matrix

Proton current causes roation of Fo and gamma subunit of F1 Conformational change in F1 leads to three steps

Binding of Pi and ADPalpha and beta pairs bind Synthesis of ATPeach ATP requires 4 protons Releasing Product

Oxidative Phosphorylation Oxidation

Coenzymes NADH or FADH2 oxidized via ETC-O2H2o Phosphorylation

ADP + PiATP Electrochemical potential is driving force

Transporters in the Mitochondrial Inner Membrane Adenosine Nucleotide Translocase (ANTIPORT)

ATP into Matrix ADP out

Phosphate Translocase (SYMPORT) Phosphate into Matrix H+ into matrix

Summary of Oxidative Phosphorylation

ATP Synthesisinterconversion of energyoxidation reductionelectrochemical gradient drives ATP synthesis

Reducing Equivalents Defined as 1 Hydrogen Atom (1 proton+ 1 electron) Carriers

NADNADH NADPNADPH FADFADH2 FMN

ETS, ATP SYNTHASE AND OXIDATIVE PHOSPHORYLATION Reducing Equivalents generated by FuelsProtein, Fats, CHO

Oxidation of food stored generates reducing equivalents and ATP synthesis Conversion to Acetyl CoA Oxidation of Acetyl CoA via TCA Generation of Reducing equivalents Synthesis of ATP

Acetyl CoA is common catabolism product Fatty Acid-palmitate3 Sugar2 Ketone Body-acetoacetate2 AA-alanine1 Ethanol1

Reducing Equivalent Shuttle Systems Carriers of Electrons and protons but not the NADH molecule to the matrix Malate/Aspartate Shuttle (LIVER)

1. NADH reduces oxaloacetate to malate Enzyme MALATE DEHYDROGENASE

2. Malate enters mitochondria MALATE/alpha-kg transporter

3. Malate re-oxidized to OAA in Mito matrix Produces NADH

4. NADH enters ETC2.5 ATPs 5. OAA transaminated to Aspartate

Enzyme ASPARTATE-GLUTAMATE TRANSPORTER 6. Aspartate Transported back to cytosol

ASPARTATE GLUTAMATE TRANSPORTER Glycerol-3 Phosphate Shuttle (BRAIN)

Dihydroxyacetone Phosphate (DHAP) reduced to glycerol-3-phosphate By NADH produced in glycolysis

G3P oxidized to DHAP in the inner mitochondrial membrane Enzyme G3P DEHYDROGENASE

Transfers electrons to FAD to form FADH2 FADH2 passes electrons to Complex III1.5 ATP when oxidized

Regulation of Oxidative Phosphorylation Role of ADP in Respiratory Control

Speed of oxygen reduction (decline in O2 concentration) represents speed of oxidative phosphorylation SubstratesPyruvate and malate enhance ADPenhances rapidly ADP/ATP and NAD/NADH ratios control oxidative phosphorylation

The rations of ADP/ATP and NAD/NADH are important regulatory factors of electron transport chain reaction, oxidative phosphorylation, and TCA cycle

Uncoupling Phosphorylation from Electron Transport Chain Disconnecting of ETC building of electrochemical potential and ATP

synthesis=Uncoupler Examples

DNP (dinitrophenol, a synthesized uncoupler) Phenolic Hydroxyl group that can be protonated/deprot in response to pH

Intermebrane space high Hydrogen Ion concentrationprotonated Protonated=lipophilic-rapidly diffuses into matrix

Matrixdeprotonated (-) Moves to the innermembrane space Counteracts the H+ pumps and disrupts electrochemical gradient

Presnece of uncoupler ETC will proceed Electrochemical potential will be disrupted

NO ATP synthesis Uncoupling Proteins (UCP)

UCP1newborns inner mito membrane brown adipose Mediates protons flowing from the intermembrane space to the matrix Electrochemical potential used for heat generation Cold+ UCP1 via norepi, B-adrenergic

ColdNEpiB-adrencAMPPKALipolysisFFAUCP-1

Tri-iodothyrine T3 affects expression of proteins involved in basal

metabolic rate and thermo genesis UCP-1 and UCP-3 Sarco/Endoplasmic Recticulum Ca-ATPase (SERCA1 and 2) Na/K ATPase

Inhibitors of ATP Synthase Oligomycin

Binds enzyme prevents H+ through proton channel Does not inhibit respiration directly but prevents dual stimulation by ADP An uncoupler can still stimulate oxygen consumption in the presence of

oligomyosin Conclusions from the Experiments (Oligomycin vs Uncoupler)

The energy that regulates the coupled system The uncoupler eliminates regulation by energy needs, and the ETS consumes O2

trying to restore the proton gradient The proton gradient also regulates the coupled system

Oligomycin shuts off ATP synthase, the H+ concentration gradient increases, slowing the rate of ETS, until uncoupler dissipates gradient and the ETC continues unchecked

The Coupling of Processes to body needs links metabolic pathways

Interlocking regulation of glycolysis, pyruvate oxidation, the citric acid cycle, and oxidative phosphorylation by relative concentrations of ATP, ADP, AMP and by NADH High ATP (Low ADP, AMP) produces low rates of

Glycolysis Pyruvate oxidation Acetate oxidate via TCA And oxidative phosphorylation

All four are stimulated by increases in rate of ATP utilization and ADP, AMP, Pi levels

Interlocking of glycolysis and TCA by citrateinhibits glycolysis Supplements the action of adenine nucleotide system

Increased levels of NADH and Acetyl coA also inhibit the oxidation of pyruvate to acetyl CoA and high NADH/NAD+ ratios inhibit the dehydrogenases of the TCA