Respiration

Cellular respiration, the process in which nutrients are converted into

useful energy in a cell.

ATP- an energy carrier• ATP is Adenine

triphosphate• Think of it like

rechargeable batteries that are used to power the reactions in cells.

• When reactions that release energy happen in cells, ATP stores the energy

• When reactions need energy to make them happen, ATP supplies the power.

• The amount of ATP is a cell is small as it is constantly being used up.

• This means it constantly needs to be made.

• ATP is made in respiration.

• Most energy is stored in the 3rd bond.

• ATPase is the enzyme that converts ATP to ADP + P

The equation of respiration

Respiration occurs in the mitochondria

• Lots of mitochondria in a cell means lots of energy.

• Muscle cells etc. have lots of mitochondria.

Respiration occurs in two stages1.Glycolysis• This occurs in the

cytosol of the cytoplasm.

• Glyco means glucose lysis means splitting• 6 carbon glucose

molecules are broken down in to 3 carbon pyruvic acid molecules.

Glycolysis• 2 phosphate groups are

added to the glucose molecule. This requires energy.

• the 6C di-phosphate is broken down into 2x 3C pyruvate.

• Hydrogen is given off (carried by NAD+)

• ATP is made

Glycolysis

2.Respiration occurs in the matrix of the mitochondria (link reaction)

• Firstly pyruvate (pyruvic acid ) is converted in to Acetyl CoA ( a 2 carbon substance) By combining with CoA.

• CO2 is made• Hydrogen is made. It is

used later.

Secondly the Krebs cycle

• Each molecule of Acetyl CoA travels through a series of reactions.

• CO2 is given off.• ATP is made• Hydrogen is produced

and may be ‘carried’ in the form of NADH.

• CoA is recycled and used again.

Thirdly- the Electron transport chain (oxidative phosphorylation)• This occurs in the inner

membrane of the mitochondria (cristae)

• Oxygen is required (1 atom)

• The hydrogen made before is converted into water through a series of reactions.

• Lots of ATP is made

Summary

Summary again

Energy yields per glucose

• the potential maximum energy produced is38 ATP made up from

Glycolysis 2ATP Krebs cycle 2 ATP

Electron transport 34 ATPHowever each glucose probably makes less ATP as some electrons may get lost during the chemical reactions.

How is the rate of respiration controlled?

Feedback inhibition.• If there is too much ATP

or citrate then the process is inhibited. (stopped)

• if there is lots of AMP or ADP then the process is started.(stimulated)

Anaerobic respiration

• All organisms can metabolise glucose without using oxygen.

• Glycolysis occurs to make 2x pyruvate.

• In yeast and root cells alcoholic fermentation takes place

• In muscle cells lactic acid fermentation makes lactic acid

a closer look at alcoholic fermentation• CO2 is made • Hydrogen ions are

required.• At above 15%

ethanol the yeast is poisoned so it cannot continue indefinitely.

• Only 2ATP are made so most organisms cannot live this way

• Ethanol is CH3CH2OH

A closer look at lactic acid fermentation• The bodies last attempts

to make some energy to keep muscles going when you are exercising and you cannot get enough oxygen to the muscle cells.

• Lactic acid is toxic and makes muscles hurt.

• Lactic acid is broken down aerobically when O2 is available.

(oxygen payback)• Lactic acid is

CH3CHOHCOOH

The relationship between cellular respiration and photosynthesis