Chapter 7 - cellular respiration and fermentation

Cellular respiration equation?

C6H12O6 + O2 = CO2 + Energy (ATP)

Cellular respiration

Exergonic

Glucose oxidation

Consuming food to break it down into energy (ATP)

Redox reaction

Glucose in cellular respiration gets oxidized and oxygen gets reduced

4 steps of Glucose oxidation

1. Glycolysis, 2. Pyruvate oxidation, 3. Citric acid, 4. Oxidative phosphorylation

Glycolysis

Occurs in the cytosol, breaks one glucose molecule into two oyruvates

Pyruvate oxidation

Occurs in the mitochondrion

The citric acid

Takes place in the mitochondrion, completes the breakdown of glucose into CO2

Oxidative phosphorylation

NADH (along with FADH2) is used to create ATP (also in the mitochondrion)

Oxidation

Removes electrons from donor molecules leaving them oxidized

Reduction

Add electrons to acceptor molecules, leaving them reduced

Electron carries

Mobile electron carries bind to and shuttle high-energy electrons

ATP

Energy currency of the cell

Phosphorylation

ADP + P = ATP, endergonic

Dephosphorylation

ATP = ADP + P, exergonic

Glycolysis

most common pathway for breakdown of glucose is glycolysis

What happens in glycolysis

Glycolysis does not use oxygen, 2 glucose molecule generated

What is being produced in glycolysis

1 glucose molecule generates:

• 2ATP

• 2NADH

• 2 Pyruvate

Phase 1 of glycolysis: Requires energy input

2 ATP molecules are used to split glucose into 2 x G3P

Phase 2 of glycolysis: generates energy

• 2 x G3P is converted to 2x Pyruvate

• Generates: 2 × 2ATP, 2 × 1NADH

Pyruvate oxidation

Pyruvate converted into acetyl CoA while producing NADH and releasing CO2

Citric acid cycle or Krebs cycle

1 acetyl - CoA generates:

• 2 CO2

• 1 FADH2

• 1 ATP

• 3 NADH

Oxidative phosphorylation

Consists of 2 processes:

1. Electron transport chain

2. Chemiosmosis

Electron transport chain

Mainly produces ATP

Chemiosmosis

involves diffusion across a membrane

Main structure involved in Chemiosmosis

ATP synthase, proton flow causes part of the synapse to rotate against the other, each rotation causes ATP to be generated

How many ATP produced in total in glucose oxidation

32

How many ATP produced by Oxidative phosphorylation

28

How many ATP produced by cellular respiration

22

Fermentation

Occurs when the cells are unable to undergo respiration due to lack of oxygen

Fermentation reduces/ produces what

• recycled NADH to NAD+ so it’s available for glycolysis

• Produces 2 ATP

1. Lactic acid fermentation

Regenerates NAD+ by reducing Pyruvate to form lactate

2. Alcohol fermentation

Cells that employ alcohol fermentation are used commercially, obligate anaerobes vs facultative anaerobes

Cellular respiration vs Fermentation

For cellular respiration - Pyruvate processing starts when final electron acceptor in ETC is present

For Fermentation - Pyruvate reduction starts if final electron acceptor in ETC is NOT present