Question

What is the chemical equation for cellular respiration?

Answer 1

The overall (unbalanced) chemical equation for cellular respiration is:

`"C"_6"H"_12"O"_6 + "O"_2 → "CO"_2 + "H"_2"O" + "energy"`

Explanation:

The balanced equation is

`"C"_6"H"_12"O"_6 + "6O"_2 → "6CO"_2 + "6H"_2"O" + "energy"`

The equation expressed in words would be:

`"glucose + oxygen → carbon dioxide + water + energy"`

The equation is formulated by combining the three following processes into one equation:

1. Glycolysis — the breakdown of the form of a glucose molecule into two three-carbon molecules i.e. pyruvate (pyruvic acid).

2. The Tricarboxylic Acid Cycle or Krebs Cycle — the three-carbon pieces are pulled apart bit by bit to release the energy stored in those covalent bonds. This is where most of the `"CO"_2` is formed.

3. The Electron Transport Chain and Oxidative Phosphorylation — this sequence requires the `"O"_2` and produces most of the energy. This energy comes in the form of `"ATP"`, or adenine triphosphate.

Answer 2

`C_6H_12O_6` + 6`O_2` -> 6`CO_2` + 6`H_2O` + ATP

Explanation:

It is important to know that the equation listed above is a summary equation. The process of cellular respiration involves many different steps (reactions) to break down glucose using oxygen to produce carbon dioxide, water and energy in the form of ATP.

The 6 carbon atoms present in a glucose molecule make it possible to form 6 carbon dioxide molecules.

The 12 hydrogen atoms in the glucose make it possible for form 6 water molecules.

To balance the oxygen atoms for the reactant side, you need to count 6 atoms from the glucose. In order to form the 6 molecules of carbon dioxide and 6 molecules of water you will have a total of 18 oxygen atoms on the product side (6 * 2) + (6 * 1) = 18. In order to get 18 oxygen atoms on the reactant side you need an additional 12 oxygen atoms from oxygen `O_2` to balance the numbers.

The process of cellular respiration will produce 36 ATP molecules in Eukaryotes (plant/animal etc.) for every one glucose molecule. The process will produce 38 ATP molecules for every one glucose in Prokaryotes (bacteria).

The reason why eukaryotes produce the smaller amount of ATP is that they need to use energy to move the pyruvate (from glycolysis) needed for the Krebs cycle into the mitochondria.

This video gives a quick review of respiration and discusses a lab which tests how temperature can alter the rate of respiration in yeast. The process takes place more quickly in warm conditions because of greater movement of particles.

This video gives a more detailed discussion of the topic of cellular respiration.

Hope this helps!