Respiration

Respiration

Aerobic respiration is the controlled release of energy from food using oxygen. 

-This reaction is controlled by enzymes.

Formula:

C₆H₁₂O₆   +   6O₂       ➔        6CO₂ + 6H₂O + Energy (ATP)

Glucose + Oxygen      ➔       Carbon dioxide + water + energy 

Aerobic respiration occurs in 2 stages

Stage 1: Glycolysis

• Takes place in the cytosol (the cytoplasm without the organelles)

• Does not require oxygen- anaerobic stage

• It only releases small amounts of energy

• Is the same for both aerobic and anaerobic respiration

A 6 carbon carbohydrate (Glucose) is converted to two 3-molecules with the release of a small amount of energy.

Stage 2:

• This stage requires and uses oxygen- aerobic

• It releases a large amount of energy

• It occurs in the mitochondria 

This stage the 3 carbon molecule made in stage one is broken down into carbon dioxide and water.

                  Anaerobic Respiration/ Fermentation

Anaerobic respiration is the controlled release of energy from food without using oxygen.

Is also known as fermentation.

Only a small amount of energy is released. This happens during Stage 1 (Glycolysis). The further breakdown of pyruvic acid does not release any more energy.

There are 2 examples of anaerobic respiration:

1. Lactic acid Fermentation 2. Alcohol Fermentation

Detailed Study of Aerobic Respiration 

This is a two stage process.

Stage 1:  

Glycolysis Location: Cytosol (cytoplasm without any organelles)

This is an anaerobic process. 

Glucose (a 6 Carbon molecule) is broken down into Pyruvic acid ( a 3 Carbon molecule) with the production of 2 ATP molecules and a NADH molecule.

Stage 2:

  Aerobic Stage Location: Mitochondria

1. If oxygen is present Pyruvic acid will enter the mitochondria.

2. Here it will lose a carbon dioxide molecule and form acetyl Coenzyme A (2 carbon molecule)

3. Pyruvic acid also loses two high energy electrons and a proton which are used to make NADH.

4. NADH will enter an electron transport system.

Krebs Cycle 

1. The Acetyl coA will enter a chain of reactions called Krebs cycle. 

2. Acetyl CoA is broken down to C0₂ and protons (H⁺) and electrons (e^-).

3. These electrons are used to make:

-ADP+P + energy form ATP.

-NAD+ 2e+ H form NADH

Electron Transport System - 

1. This occurs in the inner membrane of the mitochondria (infoldings allow for increased surface area)

2. The NADH molecule which was produced in Krebs Cycle is now broken down in the electron transport chain. 

3. NADH is broken down into NAD + 2e + H. 

4. The high energy electrons are passed from Electron transport molecule to electron transport molecule losing energy. Some of this energy is used to form ATP from ADP + P and some is lost as heat.

5. At the end of the system the low energy electron combines with oxygen and protons (H) to form water. 

Importance of the Electron Transport System 

• Produces ATP.

• Cannot work in the absence of oxygen as it is needed at the end to remove the low energy electrons and make water.

Differences between Aerobic and Anaerobic :