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RespirationRespirationA level Biology

Watford Girls Grammar school

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When oxygen is available, aerobic respiration can take placeAerobic respiration has 4 stages:

Glycolysis

The link reaction

The Krebs cycleOxidative phosphorylation

When there is no oxygen available,

anaerobic respiration takes place

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GlucoseGlucose

Glucose is the substrate

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GlucoseGlucoseATP

Glucose is phosphorylated

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GlucoseGlucoseATP

Glucose 6 PGlucose 6 P

Forming G6P

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GlucoseGlucoseATP


ATP

G6P is phosphorylated

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GlucoseGlucoseATP


ATP

Fructose 1,6 PFructose 1,6 P

Forming

F1,6P

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GlucoseGlucoseATP


ATP


33--C sugarC sugar 33--C sugarC sugar

F1

,6P splits to formtwo 3 carbon sugars

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GlucoseGlucoseATP


ATP



PyruvatePyruvate PyruvatePyruvate

These are converted topyruvate

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GlucoseGlucoseATP


ATP




2ATP 2ATP

Giving out 2 ATP

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GlucoseGlucoseATP


ATP




2ATP 2ATP

2H 2H

and 2H

+

each

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GlucoseGlucoseATP


ATP




2ATP 2ATP

2H 2H

N

et yield then is:2ATP

2x (2H+)

Glycolysis occurs in

the cytoplasm.

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Pyruvate is converted to acetyl coenzyme A

PyruvatePyruvate

Acetyl coenzyme AAcetyl coenzyme A

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Giving out 2H

+

PyruvatePyruvate


2H

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and CO2

PyruvatePyruvate


2H CO2

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This occurs inside the mitochondria.

PyruvatePyruvate


2H CO2

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Net yield then is:

2x 2H+

2 CO2 PyruvatePyruvate


2H CO2

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In the matrix of the mitochondrion:


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Acetyl CoA combines with a 4C acid


Four carbon acidFour carbon acid

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forming the 6 carbon compound citrate:


Citrate (6C)Citrate (6C)Four carbon acidFour carbon acid

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The citrate is decarboxylated to a 5C acid:



Five carbon acidFive carbon acid

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releasing CO2


CO2



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and 2H+


2H

CO2



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The 5C acid is decarboxylated - reforming the 4C acid:


2H

CO2



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Releasing another CO2


2H

CO2


Five carbon acidFive carbon acidCO2

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three 2H+


2H

CO2



2H

2H2H

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and an ATP


2H

CO2



2H

2H2H

ATP

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Net yield:

2ATP

4CO28x 2H+Acetyl coenzyme AAcetyl coenzyme A

2H

CO2



2H

2H2H

ATP

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The 2H+ reduces NAD to NADH+ + H+

2H

NADNAD

FADFAD

carriercarrier

carriercarrier

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The 2H+ reduces NAD to NADH+ + H+

2H

NADHNADH

HH

FADFAD

carriercarrier

carriercarrier

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FAD is then reduced

2H

NADNAD

FADHFADH

HH

carriercarrier

carriercarrier

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generating ATP

2H

ATP

NADNAD

FADHFADH

HH

carriercarrier

carriercarrier

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Two more carriers are reduced

2H

ATP

NADNAD

FADFAD

carriercarrier

carriercarrier

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generating more ATP.

2H

ATP

NADNAD

FADFAD

carriercarrier

carriercarrier

ATP

ATP

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The 2H+ is then passed onto O2

2H

2H

O2

ATP

NADNAD

FADFAD

carriercarrier

carriercarrier

ATP

ATP

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Which forms water.

2H

H2O

2H

O2

ATP

NADNAD

FADFAD

carriercarrier

carriercarrier

ATP

ATP

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This occurs across the inner membrane of the mitochondria

ATP synthesised using the stalked particles.

2H

H2O

2H

O2

ATP

NADNAD

FADFAD

carriercarrier

carriercarrier

ATP

ATP

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Some of the 2H+ reduces FAD

2H

H2O

2H

O2

NADNAD

FADFAD

carriercarrier

carriercarrier

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So only produces 2ATP.

2H

H2O

2H

O2

NADNAD

FADFAD

carriercarrier

carriercarrier

ATP

ATP

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Glycolysis

6 H2O

2(2H+)

6 O2

2 ATPGlucoseGlucose

Link reaction

Krebs cycle

2 CO2

4 CO2

2(2H+)

2(2H+)

2 ATP

4 ATP

6 ATP

4 ATP

18 ATP6(2H+)

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In the absence of

oxygen anaerobicrespiration takes place

GlucoseGlucose

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Glucose is

phosphorylated to two3-C sugars

2ATP


GlucoseGlucose

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These are then

converted to pyruvate,generating ATP & 2H+

2(2H+)

2 ATP


2ATP


2 ATP

2(2H+)

GlucoseGlucose

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In yeast the pyruvate is

decarboxylated toethanal:

2(2H+)

2 ATP

CO2


2ATP


CO2

2 ATP

2(2H+)

GlucoseGlucose

EthanalEthanal EthanalEthanal

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Net production is:

2ATP2CO22 ethanol

2(2H+)

2 ATP

CO2


2ATP


CO2

2 ATP

2(2H+)

EthanolEthanol EthanolEthanol

GlucoseGlucose

EthanalEthanal EthanalEthanal

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In animals, the

pyruvate is convertedto lactate:

2(2H+)

2 ATP


2ATP


2 ATP

2(2H+)

LactateLactate LactateLactate

GlucoseGlucose

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using the 2H+ again:

2(2H+)

2 ATP


2ATP


2 ATP

2(2H+)


GlucoseGlucose

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Net production is:

2ATP2 lactate

2(2H+)

2 ATP


2ATP


2 ATP

2(2H+)


GlucoseGlucose

16557710 respiration

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