Cellular Respiration

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Cellular Respiration• The process by which glucose is converted is into

carbon dioxide, water, and ENERGY

+ O2 CO2 + H2O + Energy

Comparing Combustion to Respiration

Review of Terminology

Oxidation - loss of electrons- gain of oxygen- loss of hydrogen

Reduction - gain of electrons- loss of oxygen- gain of hydroven

Review of Terminology

Oxidation - loss of electrons- gain of oxygen- loss of hydrogen- ON more positive

Reduction - gain of electrons- loss of oxygen- gain of hydrogen- ON less positive

REDOXreaction

Review of Terminology

aerobic- with O2

anaerobic - without O2

Stage One - Glycolysis

Anaerobic

1 mol glucose 2 mol pyruvate

C6H12O6 + 2NAD+ 2 C3H3O3 - + 2NADH + 4H+ + energy

Stage One - Glycolysis

Anaerobic

1 mol glucose 2 mol pyruvate

C6H12O6 + 2NAD+ 2 C3H3O3 - + 2NADH + 4H+ + energy

oxidation

reduction

NAD+ and NADH

Glycolysis

Stage Two – Aerobic or Anaerobic Respiration

• Aerobic or Anaerobic respiration follows depending on whether O2 is available or not.

Pyruvate

O2CO2 + H2O aerobic respiration

No O2

No O2lactic acidanaerobic respiration

Ethanolanaerobic respiration

Aerobic Respiration

Redox Reaction:

2 C3H3O3 - + 2NADH + 4H+ + 6O2 6CO2 + 6H2O + 2NAD+

pyruvate

Overall Reaction Adding together the rxns for Stage One and Stage Two gives the

overall reaction ….Stage OneC6H12O6 + 2NAD+ 2 C3H3O3 - + 2NADH + 4H+ + energy

Stage Two2 C3H3O3 - + 2NADH + 4H+ + 6O2 6CO2 + 6H2O + 2NAD+

C6H12O6 + 6 O2 6 CO2 + 6 H2O ∆ H = -2816 kJ/mol equivalent to 36 ATP

The Half Reactions

The overall redox rxn for aerobic respiration is made up the following two half rxns:

oxidation half reaction (C gets oxidized) C6H12O6 + 6 H2O 6CO2 + 24H+ + 24 e

reduction half reaction (O gets reduced) 6O2 + 24H+ + 24 e 12H2O

C6H12O6 + 6 O2 6 CO2 + 6 H2O

Aerobic Pathway for Pyruvate

The Role of Fe and CuFe and Cu in cytochromes are involved in moving the electrons

produced in the oxidation step to the reduction step • this occurs in the Electron Transport Chain • coupled to the oxidation step is a reduction involving Fe or Cu:

Fe3+ + e Fe2+ or Cu2+ + e Cu+

• coupled to the reduction step is an oxidation involving Fe or Cu:

Fe2+ Fe3+ + e or Cu+ Cu2+ + e

Energy Output

Goal – release the energy from glucose to fuel cell processes

- ATP is an energy storage molecule like a battery

- The conversion of ATP ADP releases stored energy (30.5 kJ/mol)

Energy Output

Exothermic

Endothermic

Energy Tally

Anaerobic Respiration• occurs during strenuous exercise when enough O2 is not

available for aerobic respiration

• lactic acid is produced which causes muscle cramping

• the overall redox reaction is: C3H3O3 - + NADH + H+ C3H5O3

- + NAD+ + energy as 2 ATPPyruvate Lactate The two half rxns that make up this redox rxn are:

Anaerobic Respiration• occurs during strenuous exercise when enough O2 is not available

for aerobic respiration

• lactic acid is produced which causes muscle cramping

• the overall redox reaction is: C3H3O3 - + NADH + H+ C3H5O3

- + NAD+ + energy as 2 ATPPyruvate Lactate oxidation half reaction NADH + H+ NAD+ + 2 e + 2 H+

reduction half reaction C3H3O3 - + 2 e + 2H+ C3H5O3

-

Anaerobic Respiration

Eventually O2 will again be available and the lactic acid will get oxidized to make CO2 and H2O by this overall redox reaction:

C3H6O3 + 3 O2 3 CO2 + 3 H2O + energy

Lactic acidconjugate acid for lactate ion

Fermentation• a form of anaerobic respiration that occurs in yeast • pyruvate is converted in ethanol 2 C3H3O3 - + 2NADH + 4H+ 2 CH3CH2OH + 2CO2 + 2NAD+

• adding the glycolyis reaction and this reaction gives the

overall fermentation reaction: C6H12O6 2 CH3CH2OH + 2 CO2

Two Anaerobic Pathways

Summary of the Aerobic and Anaerobic Pathways

Transport Processes in Cellular Respiration

1) Electron Transport Chain

• cellular respiration involves redox reactions • the Electron Transport Chain involves the movement of e’s in these

redox reactions • at the same time ADP gets released as ATP (energy out) • Cytochromes are Fe and Cu containing protein molecules that can

shuttle around e’s (see aerobic respiration above)

A Cytochrome Molecule

Transport Processes in Cellular Respiration

2) O2 Transport in the Blood• Haemoglobin is an oxygen transport protein• it consists of 4 heme groups:

Haemoglobin

• O2 gets moved through the blood by forming a dative bond with the iron in the heme group

• CO and CN- preferentially form dative bonds with the Fe in the heme group blocking the site from oxygen carbon monoxide poisoning or cyanide poisoning

Videos

• How NAD works• Glycolysis• ATP