2. Respirasi heterotrof

Respirasi

Heterotrof

Heterotrof membutuhkan molekul organik sebagai makanan.

Energinya diperoleh dari ikatan kimia di dalam molekul makanan seperti karbohidrat, lemak dan protein.

AutotrofAutotrof merupakan organisme yang dapat menggunakan sumber energi dasar (sinar matahari) untuk membuat energi. Mis: tumbuhan dan beberapa mikroorganisme2 TypesPhotosynthetic autotrophsChemosynthetic autotrophs

ChemosynthesisChemosynthesis is a process used by prokaryotic organisms to use inorganic chemical reactions as a source of energy to make larger organic molecules.Chemosynthesis adalah proses yang digunakan oleh organisme prokariotik menggunakan reaksi kimia anorganik sebagai sumber energi untuk membuat molekul organik yang lebih besar.

Aerobic Vs. AnaerobicAerobic respiration requires oxygen.Anaerobic respiration does not require oxygen.

Aerobic RespirationAerobic cellular respiration is a specific series of enzyme controlled chemical reactions in which oxygen is involved in the breakdown of glucose into carbon-dioxide and water.The chemical-bond energy is released in the form of ATP.Sugar + Oxygen carbon dioxide + water + energy (ATP)

Summary:3 steps:1st glycolysis 2nd Krebs cycle3rd Electron Transport Chain (ETC)

A Road Map for Cellular RespirationCytosolMitochondrionHigh-energyelectronscarriedby NADHHigh-energyelectrons carriedmainly byNADHGlycolysisGlucose2PyruvicacidKrebsCycleElectronTransportFigure 6.7

GlycolysisStage 1: splitting glucose molecule (C6) into two PGALD (C3). 2 ATPs are used per glucose metabolism.

Stage 2: catalyzes the oxidation of PGALD to pyrvate. Generate s 4 ATPs per glucose metabolism.

glucose

Glycolysis

ATP

ADP

glucose-6-phosphate

Phosphoglucose Isomerase

fructose-6-phosphate

ATP

ADP

fructose-1,6-bisphosphate

Aldolase

glyceraldehyde-3-phosphate + dihydroxyacetone-phosphate

Triosephosphate

Isomerase

Glycolysis continued

Hexokinase

Phosphofructokinase

Glycolysis continued.Recall that there are 2 GAP per glucose.

glyceraldehyde-3-phosphate

NAD+ + Pi

NADH + H+

1,3-bisphosphoglycerate

ADP

ATP

3-phosphoglycerate

Phosphoglycerate Mutase

2-phosphoglycerate

H2O

phosphoenolpyruvate

ADP

ATP

pyruvate

Glyceraldehyde-3-phosphate

Dehydrogenase

Phosphoglycerate Kinase

Enolase

Pyruvate Kinase

1. Hexokinase catalyzes: Glucose + ATP glucose-6-P + ADP The reaction involves nucleophilic attack of the C6 hydroxyl O of glucose on P of the terminal phosphate of ATP. ATP binds to the enzyme as a complex with Mg++.

EMBED ChemDraw.Document.4.5

glucose glucose-6-phosphate

Hexokinase

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2. Phosphoglucose Isomerase catalyzes: glucose-6-P (aldose) fructose-6-P (ketose) The isomerization is an electron shift where 2 electron from C2 carbon reduce the C1 aldehyde of the glucose-6-phosphte molecule to an alcohol.


glucose-6-phosphate fructose-6-phosphate

Phosphoglucose Isomerase

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3. Phosphofructokinase catalyzes: fructose-6-P + ATP fructose-1,6-bisP + ADPThis highly spontaneous reaction has a mechanism similar to that of Hexokinase. The Phosphofructokinase reaction is the rate-limiting step of Glycolysis. .


fructose-6-phosphate fructose-1,6-bisphosphate

Phosphofructokinase

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4.Aldolase catalyzes: fructose-1,6-bisphosphate dihydroxyacetone-P + glyceraldehyde-3-PThe reaction is an aldol cleavage, the reverse of an aldol condensation. Note that C atoms are renumbered in products of Aldolase.


fructose-1,6-

bisphosphate

Aldolase

dihydroxyacetone glyceraldehyde-3-

phosphate phosphate

Triosephosphate Isomerase

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5. Triose Phosphate Isomerase (TIM) catalyzes: dihydroxyacetone-P glyceraldehyde-3-PThe dihidroxyacetone-P is isomerized to PGALD, thus this stage produce 2 molecules PGAL pe 1 glucose


fructose-1,6-

bisphosphate

Aldolase

dihydroxyacetone glyceraldehyde-3-

phosphate phosphate


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The ketose/aldose conversion involves acid/base catalysis, and is thought to proceed via an enediol intermediate, as with Phosphoglucose Isomerase. Active site Glu and His residues are thought to extract and donate protons during catalysis.


dihydroxyacetone enediol glyceraldehyde-

phosphate intermediate 3-phosphate


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6. Glyceraldehyde-3-phosphate Dehydrogenase catalyzes: glyceraldehyde-3-P + NAD+ + Pi 1,3-bisphosphoglycerate + NADH + H+


glyceraldehyde- 1,3-bisphospho-

3-phosphate glycerate


Dehydrogenase

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Exergonic oxidation of the aldehyde in glyceraldehyde- 3-phosphate, to a carboxylic acid, drives formation of an acyl phosphate, a "high energy" bond (~P). This is the only step in Glycolysis in which NAD+ is reduced to NADH.


glyceraldehyde- 1,3-bisphospho-

3-phosphate glycerate


Dehydrogenase

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7. Phosphoglycerate Kinase catalyzes: 1,3-bisphosphoglycerate + ADP 3-phosphoglycerate + ATPThis phosphate transfer is reversible (low DG), since one ~P bond is cleaved & another synthesized. The enzyme undergoes substrate-induced conformational change similar to that of Hexokinase.


1,3-bisphospho- 3-phosphoglycerate

glycerate

Phosphoglycerate Kinase

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8. Phosphoglycerate Mutase catalyzes: 3-phosphoglycerate 2-phosphoglyceratePhosphate is shifted from the OH on C3 to the OH on C2.


3-phosphoglycerate 2-phosphoglycerate

Phosphoglycerate Mutase

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9. Enolase catalyzes: 2-phosphoglycerate phosphoenolpyruvate + H2O


2-phosphoglycerate enolate intermediate phosphoenolpyruvate

Enolase

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10. Pyruvate Kinase catalyzes: phosphoenolpyruvate + ADP pyruvate + ATP


phosphoenolpyruvate pyruvate

Pyruvate Kinase

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Krebs Cycle

Makes ATPMakes NADH Makes FADH2

Conversion of pyruvate to Acetyl CoA2 per glucose (all of Krebs)Oxidative decarboxylationMakes NADH

Net From KrebsOxidative process3 NADHFADH2GTPX 2 per glucose6 NADH2 FADH22 GTPAll ultimately turned into ATP (oxidative phosphorylationlater)

Citrate Synthase Reaction (First)

Aconitase ReactionForms isocitrateGoes through alkene intermediate (cis-aconitate)elimination then additionHydroxyl moved and changed from tertiary to secondary(can be oxidized)13.3kJ

Isocitrate DehydrogenaseAll dehydrogenase reactions make NADH or FADH2 Oxidative decarboxylation-20.9kJEnergy from increased entropy in gas formation

-ketoglutarate dehydrogenaseSame as pyruvate dehydrogenase reactionFormation of thioester endergonic driven by loss of CO2 increases entropyexergonic-33.5kJ

Succinyl CoA synthetaseHydrolysis of thioester Releases CoASHExergonicCoupled to synthesis of GTPEndergonicGTP very similar to ATP and interconverted later-2.9kJ

Succinate dehydrogenaseDehydrogenationUses FADNAD used to oxidize oxygen-containing groupsAldehydesalcoholsFAD used to oxidize C-C bonds0kJ

FumaraseAddition of water to a double bond-3.8kJ

Malate DehydrogenaseOxidation of secondary alcohol to ketoneMakes NADHRegenerates oxaloacetate for another round29.7 kJ

Net From KrebsOxidative process3 NADHFADH2GTPX 2 per glucose6 NADH2 FADH22 GTPAll ultimately turned into ATP (oxidative phosphorylationlater)

INHIBITOR OF TCA CYCLE1. FluoroacetateCondensation with CoA Fluoroacetyl-CoACondensation FluoroacetylCoA with Oxaloace- tate Fluorocitrate inhibit Akoni- tase enzyme accumulation of citrateFluoroacetate pesticide2. Malonate suksinat dehydrogenase enzyme3. Arsenite -ketoglutarate dehydrogenase enzyme

REGULATION OF TCA CYCLE

Electron Transport SystemThe electrons released from glycolysis and the Krebs cycle are carried to the electron-transport system (ETS) by NADH and FADH2.The electrons are transferred through a series of oxidation-reduction reactions until they are ultimately accepted by oxygen atoms forming oxygen ions.32 molecules of ATP are produced.

What is the electron transport chain?A chain of protein complexes embedded in the inner mitochondrial membrane. Transports electrons and pumps hydrogen ions into the intermembrane space to create a gradient.

Components of the electron transport chain (ETC)NADH dehydrogenaseUbiquinone (Q)Succinate dehydrogenase Cytochrome b-c1Cytochrome cCytochrome oxidase

Arranged in order of increasing electronegativity (weakest to strongest)

NADH produced from Krebs cycleNADH produced in the cytoplasm by glycolysis: CAN diffuse from outer mitochondrial membrane to intermembrane space. CANNOT diffuse from inner membrane to matrix.

NADH produced from glycolysisVSVSNADH produced from Krebs cycle: Already in the matrix.

What to do?Cytosolic NADH (NADH that are produced by glycolysis) pass electrons to shuttles

Glycerol-phosphate shuttle: Transfers electrons from cytosolic NADH to FAD to produce FADH2

Aspartate shuttle: Transfers electrons from cytosolic NADH to NAD+ to produce NADH

Complex I: NADH dehydrogenaseNADH dehydrogenase oxides NADH back to NAD+

The electrons are transferred to flavin mononucleotide (FMN) which reduces to FMNH2

The electrons are then passed to iron-sulphur proteins (FeS) located in NADH dehydrogenase

NADH + H+ NAD+ + 2H+ + 2e-

FMN + 2H+ + 2e- FMNH2

Complex I ContinuedElectrons are accepted by Fe3+ which is reduced to Fe2+

These two electrons are then given to ubiquinone (Q)The two hydrogen ions are pumped into the intermembrane space2Fe3+ + 2e- 2Fe2+ *One hydrogen ion is pumped per electron transferred

Ubiquinone (Q)A mobile electron carrier

Carries electrons to complex III, cytochrome b-c1

2Fe2+ gives 2e- to QQ is reduced to QH2 (ubiquinol) and 2Fe2+ is oxidized 2Fe3+

http://www.brookscole.com/chemistry_d/templates/student_resources/shared_resources/animations/oxidative/oxidativephosphorylation.htmlInteractiveAnimation:

Complex II: Succinate Dehydrogenase oxidation of succinate from Krebs cycle to fumarate

FADH2 then tries to oxidize back into FAD by passing its electrons to 2 Fe2+ 2Fe3+ + 2e- 2Fe2+ Succinate + FAD Fumarate + FADH2

These electrons from 2Fe2+ are then stolen by ubiquinone (Q), which carries them to complex III.

Unlike complex I, complex II doesnt have enough free energy for active transport of the hydrogen ions (protons) from FADH2 across the intermembrane . This is why oxidation of FADH2 only yields 2 ATP molecules instead of 3 ATP molecules like NADH.Complex II Continued...Q + 2Fe2+ 2Fe3+ + QH2

Complex III: cytochrome b-c1Contains cytochrome b, cytochrome c1, and FeS proteins.QH2 passes two electrons to cytochrome b causing Fe3+ to reduce to Fe2+Same way from cyt b to FeS protein and then to cyt c1

Cytochrome C (c) Im a protein and like Q...

I am also a water soluble mobile electron carrier. I transport electrons one at a time from complex III to complex IV.

Complex IV: Cytochrome Oxidase (The End of the Line)This is the end of the line for electrons from NADH or succinate.Oxygen (breathed in) is reduced and when combined with these electrons, they form...WATER

THIS REACTION IS EXPLOSIVE! Its highly exergonic, releasing large amounts of energy.

O2 (g) + 2H+ + 2e- H2O (l)

Electrochemical gradient

A concentration gradient created by pumping ions into a space surrounded by a membrane that is impermeable to the ions.Two components: electrical and chemicalProton-motive force (PMF) moves protons through an ATPase complex on account of the free energy stored in the form of an electrochemical gradient of protons across a biological membrane.

Chemiosmosis

Peter Mitchell Nobel Prize in Chemistry in 1978A process for synthesizing ATP using the energy of an electrochemical gradient and the ATP synthase enzyme. osmosisAfter chemiosmosis, ATP molecules are transported through both mitochondrial membranes.

Connections!

Electrons from NADH and FADH2 were passed down the ETCAs the electrons move down, energy released moves protons to create electrochemical gradientProtons move through proton channels, and release energy to synthesize ATP from ADP and PiThe many processes of ATP synthesis are all continuous

FermentationFermentation describes anaerobic pathways that oxidize glucose to produce ATP.An organic molecule is the ultimate electron acceptor as opposed to oxygen.Fermentation often begins with glycolysis to produce pyruvic acid.

Anaerobic Cellular RespirationAnaerobic respiration does not require oxygen as the final electron acceptor.Some organisms do not have the necessary enzymes to carry out the Krebs cycle and ETS.Many prokaryotic organisms fall into this category.Yeast is a eukaryotic organism that performs anaerobic respiration.

glycolysisAnaerobic RespirationAlcoholic fermentationBacteria, Yeast 2 ATPLactic acid fermentationMuscle cells 2 ATPAerobic RespirationCytoplasmFirst step in anaerobic respiration is also glycolysisDiagramC6H12O6 glucose

Alcoholic FermentationAlcoholic fermentation is the anaerobic pathway followed by yeast cells when oxygen is not presentPyruvic acid is converted to ethanol and carbon-dioxide.4 ATPS are generated from this process, but glycolysis costs 2 ATPs yielding a net gain of 2 ATPs.

Alcoholic fermentationoccurs in bacteria and yeast Process used in the baking and brewing industryyeast produces CO2 gas during fermentation to make dough rise and give bread its holes

ALCOHOL FERMENTATION

Lactic Acid FermentationIn Lactic acid fermentation, the pyruvic acid from glycolysis is converted to lactic acid.The entire process yields a net gain of 2 ATP molecules per glucose molecule.The lactic acid waste products from these types of anaerobic bacteria are used to make fermented dairy products such as yogurt, sour cream, and cheese.

Lactic acid fermentationoccurs in muscle cells Lactic acid is produced in the muscles during rapid exercise when the body cannot supply enough oxygen to the tissuescauses burning sensation in muscles

glucose lactic acid + carbon dioxide + 2 ATP

LACTIC ACID FERMENTATION

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2. Respirasi heterotrof

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