CELLULAR RESPIRATION

• It stores and transfers energy between chemical reactions in the cell, allowing the cell to carry outits functions such as:nerve impulses, producing DNA.
  
• RESPIRATION converts the chemical energy in carbohydrates, lipids and protiens into chemical energy in ATP.
  
• Respiration is a series of many chemical reactions some in which release energy.

GLUCOSE + OXYGEN = CARBON DIOXIDE + WATER + ENERGY

THERE ARE FOUR STEPS TO RESPIRATION:

1. GLYCOLYSIS - This occurs in the cytoplasm.
It begins with glucose and ends in pyruvate.
Anerobic respiration only takes place here as oxygen is not required.

2. THE LINK REACTION - This occurs in the matrix of the MITOCHONDRIA.
It links glycolysis with the krebs cycle.

3. THE KREBS CYCLE - The enzymes for the krebs cycle are in the matrix of the
MITOCHONDRIA. ACETYLCOENZYME A.

4. THE ELECTRON TRANSPORT CHAIN- This takes place on the inner surface of the
inner membrane of the mitochondria.

This takes place in the absence of oxygen, and in times of high energy requirments, as the mucsles quickly use up ATP and cannot make or deliever it quick enough.

Only 2 ATP can be produced in anerobic respiration.

GLUCOSE = ATP + PYRUVATE = LACTATE

OXYGEN DEBT
This is respiring anerobically producing lactate that need to be converted by adding oxygen. Oxygen consumption remains high after excersize to 'pay off the debt' built up in anareobic respiration.

All ANEROBIC REPIRATION takes place in the CYTOPLASM, as the mitochondria cannot carry out any reactions without oxygen.

The breakdown of PYRUVTE to LACTATE removes HYDROGEN from REDUCED NAD so NAD is reformed. Allowing GLYCOLYSIS to continue.

GLUCOSE, is a CARBOHYDRATE as is perfect for respiration.

If glucose is not available cells can use LIPIDS.

LIPIDS need to be digested into FATTY ACIDS + GLYCEROL, they are now small enough to get into the cells. The cells have to use some ATP energy to convert the fatty acids and glycerol into other molecules that can enter the repiration reactions.

GLYCEROL enters at GLYCOLYSIS and is converted to PYRUVATE.
FATTY ACIDS are converted into ACETYL COENZYME A and enter the KREBS CYCLE.

If neither glucose or lipids are available the body will use PROTIENS.

The body must digest protiens into smaller molecules called AMINO ACIDS. these are now small enough to get into the cells. The AMINO ACIDS enter the respiration pricess at different stages of the KREBS CYCLE, depending on the TYPE of AMINO ACID.