Fig. 8-CO, p. 171

Eiwitten aminozuren CO2

Vetten glycerol, vetzuren ATPpolysacchariden monosacchariden H2O

Hoofdstuk Hoofdstuk IVIVDe Cellulaire RespiratieDe Cellulaire Respiratie

De synthese van ATP door afbraak van moleculenDe synthese van ATP door afbraak van moleculen

Aerobe respiratie: afbraak voedingsmoleculen tot COAerobe respiratie: afbraak voedingsmoleculen tot CO22 en en HH22O met produktie van ATP en O met produktie van ATP en met verbruik van met verbruik van zuurstofzuurstof (sommige prokaryoten, protisten, eukaryoten).(sommige prokaryoten, protisten, eukaryoten).

Anaerobe respiratie: idem maar Anaerobe respiratie: idem maar in afwezigheid van in afwezigheid van zuurstofzuurstof (sommige prokaryoten).(sommige prokaryoten).

Fermentatie: afbraak voedingsmoleculen Fermentatie: afbraak voedingsmoleculen zonder zonder elektronentransportketenelektronentransportketen met produktie van ATPmet produktie van ATP(sommige prokaryoten en fungi). (sommige prokaryoten en fungi).

p. 172

De aerobe respiratie

Glucose + 6 HGlucose + 6 H22O + 6 OO + 6 O22 →→→→→→→→ 6 CO6 CO22 + 12 H+ 12 H22O + O + EnergieEnergie

Fig. 8-1, p. 172

Vier stappen Vier stappen in de in de aaëërobe respiratierobe respiratie

1.1. GlycolyseGlycolyse: Glucose : Glucose →→→→→→→→ pyruvaat pyruvaat (ATP, NADH)(ATP, NADH)2.2. Vorming Vorming vanvan acetyl acetyl CoACoA + CO+ CO2 2 (NADH)(NADH)3.3. CitroenzuurcyclusCitroenzuurcyclus: CO: CO22, ATP, NADH en FADH, ATP, NADH en FADH22

4.4. ElektronentransportElektronentransport : NADH en FADH: NADH en FADH22 →→→→→→→→ ATPATP

Fig. 8-4a, p. 176

Energy investment phase and splitting of glucose

Two ATPs invested per glucose

GlucoseGlycolysis begins with preparation reaction in which glucose receives phosphate group from ATP molecule. ATP serves as source of both phosphate and energy needed to attach phosphate to glucose molecule. (Once ATP is spent, it becomes ADP and joins ADPpool of cell until turned into ATP again.) Phosphorylated glucose is known as glucose-6-phosphate. (Note phosphate attached to its carbon atom 6.) Phosphorylation of glucose makes it more chemically reactive.

ATP

ADP

Glucose-6-phosphate

Hexokinase

Phosphoglucoisomerase

1

Fig. 8-4a, p. 176

Glucose-6-phosphate undergoes another preparation reaction, rearrangement of its hydrogen and oxygen atoms. In this reaction glucose-6-phosphate is converted to its isomer, fructose-6-phosphate.

Next, another ATP donates phosphate to molecule, forming fructose-1,6-bisphosphate. So far, two ATP molecules have been invested in process without any being produced. Phosphate groups are now bound at carbons 1 and 6, and molecule is ready to be split.

Fructose-1,6-bisphosphate is then split into two 3-carbon sugars, glyceraldehyde-3- phosphate (G3P) and dihydroxyacetone phosphate.

Dihydroxyacetone phosphate is enzymatically converted to its isomer, glyceraldehyde-3-phosphate, for further metabolism in glycolysis.

Fructose-6-phosphate

PhosphofructokinaseATP

ADP

Fructose-1,6-bisphosphate

Aldolase

Isomerase

Dihydroxyacetonephosphate

Glyceraldehyde-3-phosphate (G3P)

2

3

4

5

Glucose + 2 ATP 2 glyceraldehyde 3-fosfaat + 2 ADP

Fig. 8-4b, p. 177

Energy capture phaseFour ATPs and two NADH produced per

glucose

Two glyceraldehyde-3-phosphate (G3P)from bottom of previous page

2 NAD+

2 NADH

Glyceraldehyde-3-phosphate dehydrogenase

Phosphoglycerokinase

Two 1,3-bisphosphoglycerate

2 ADP

2 ATP

Each glyceraldehyde-3-phosphate undergoes dehydrogenationwith NAD+ as hydrogen acceptor. Productof this very exergonic reaction is phosphoglycerate,which reacts with inorganic phosphate present incytosol to yield 1,3-bisphosphoglycerate.

One of phosphates of 1,3-bisphosphoglycerate reactswith ADP to form ATP. This transfer of phosphate fromphosphorylated intermediate to ATP is referred to assubstrate-level phosphorylation.

Two 3-phosphoglycerate

Phosphoglyceromutase

6

7

Fig. 8-4b, p. 177

Two 2-phosphoglycerate

Enolase

Pyruvate kinase

Two pyruvate

2 H2O

Two phosphoenolpyruvate2 ADP

2 ATP

3-phosphoglycerate is rearranged to 2-phosphoglycerateby enzymatic shift of position of phosphate group.This is a preparation reaction.

Next, molecule of water is removed, which results information of double bond. The product, phosphoenolpyruvate (PEP), has phosphate group attached by an unstable bond (wavy line).

Each of two PEP molecules transfers its phosphate groupto ADP to yield ATP and pyruvate. This is substrate-levelphosphorylation reaction.

8

9

10

2 glyceraldehyde 3-fosfaat + 2 NAD+ + 4 ADP 2 pyruvaat + 2 NADH + 4 ATP

2 pyruvaat + 2 NAD+ + 2 CoA 2 acetyl CoA + 2 NADH + 2 CO2

Vitamine Vitamine B5B5

Per glucose Per glucose zijn er twee zijn er twee KrebsKrebs--cyclicycli nodignodig: : dit leidt dit leidt tot 4 COtot 4 CO22, 6 NADH, 2 FADH, 6 NADH, 2 FADH22 en 2 ATPen 2 ATP

Per glucosePer glucosebijbij acetylacetyl CoA vormingCoA vorming : 2 CO: 2 CO22 en 2 en 2 NADHNADH

Per Per glycolyseglycolyse((dusdus per glucose): 2 ATP en 2 NADHper glucose): 2 ATP en 2 NADH

Volledige cyclusVolledige cyclus, per glucose:, per glucose:

4 4 ATPATP’’ ss, 10 , 10 NADHNADH ’’ ss, 2 FADH, 2 FADH22’’ s en 6 COs en 6 CO22’’ ss

Oxidatieve fosforylatie

p. 182Symphocarpus foetidus

Chemische verbranding Chemische verbranding van glucose van glucose →→→→→→→→ 2870 2870 kJoulekJoule/mol/mol

VrijeVrije energieenergievan de van de fosfaatbindingfosfaatbinding in ATP in ATP →→→→→→→→ 31,8 31,8 kJoulekJoule/mol/mol

36 ATP 36 ATP →→→→→→→→ 1146 1146 kJoulekJoule/mol/mol

1146/2870 1146/2870 →→→→→→→→ 40% 40% rendement rendement (+(+warmtewarmte))

Deaminatie Deaminatie van van aminozurenaminozurenAlanineAlanine →→→→→→→→ pyruvaatpyruvaatGlutaminezuur Glutaminezuur →→→→→→→→ αααααααα--ketoglutaarzuurketoglutaarzuurAsparaginezuur Asparaginezuur →→→→→→→→ oxaloacetaatoxaloacetaat

Ook regulatie Ook regulatie van:van:

HexokinaseHexokinase: : inhibitie inhibitie door glucosedoor glucose--6 6 fosfaatfosfaat

Pyruvaat kinasePyruvaat kinase: : inhibitie inhibitie door ATPdoor ATP

Pyruvaat dehydrogenasePyruvaat dehydrogenase

Drie enzymen Drie enzymen van de van de citroenzuurcitroenzuur--cycluscyclus

ADPADP

AnaAnaëërobe respiratie robe respiratie en en fermentatiefermentatie

AnaAnaëërobe respiratierobe respiratie: : alternatieve elektronenacceptorenalternatieve elektronenacceptorenSOSO44

22--, NO, NO33--, Fe, Fe3+3+, CO, CO22 →→→→→→→→ HH22S, NOS, NO22

--, N, N22, Fe, Fe2+2+, CH, CH44

FermentatieFermentatie: : anaanaëëroob proces zonder elektronentransportroob proces zonder elektronentransportRegeneratieRegeneratievan NADvan NAD++ door door reductie reductie van van organische organische moleculenmoleculen

Red-eared Slider (Trachemys scripta elegans).

Credit: © Cleve Hickman Jr./Visuals Unlimited 304559