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Foods provide us with calories but they are not the form of energy used by cells. Food is broken down by enzymes in the digestive system to form glucose. Celllular Respiration in the mitochondria forms ATP from these sugars.

The Chemistry of Respiration energy and mitochondria clip

Adenosine triphosphate The energy released during respiration is not used directly by cells. Instead it is used to make a molecule called ATP which stores the energy until it is needed. ATP = Adenosine triphosphate

What does ATP do? ATP supplies energy for all the processes that need it. For example: movement chemical reactions growth. slow twitch/fast twitch investigation

Structure of ATP adenosine Pi

Formation of ATP ATP is made when another molecule called adenosine diphosphate (ADP) is bonded to a third inorganic phosphate (Pi) using the energy released from glucose.

adenosine + Pi adenosine Pi Enzymes Energy from respiration Energy Rich bond formed

Summarised as: ADP + Pi ATP The whole process is under the control of enzymes

The role of ATP ATP stores the energy in the third bond of the molecule The energy is released when that bond is broken to release the third inorganic phosphate (Pi) .

adenosine Pi ATP Enzymes Pi adenosine + ADP Energy released to do work

Summary ATP energy (out) cellular respiration cell activities ATP ADP + Pi energy (out) (in) cellular respiration cell activities The whole process is an enzyme controlled reaction.

Aerobic respiration = respiration with oxygen.

glucose + OXYGEN carbon dioxide + water + ATP C6H12O6 + O2 ――> CO2 + H2O + ATP

Aerobic respiration happens in 2 stages: Stage 1 – Glycolysis glyco lysis glucose splitting This stage occurs in the cytoplasm.

Glycolysis does not require oxygen In glycolysis, a glucose molecule is broken down into pyruvic acid. This process requires 2 ATP to start the reaction. glucose series of enzyme controlled reactions energy released to make 4 ATP (-2ATP+4ATP=2ATP) Net gain of 2ATP pyruvic acid Glycolysis does not require oxygen

Stage 2 – Breakdown of pyruvic acid The pyruvic acid made in glycolysis (stage1) still contains a lot of energy. It moves into the mitochondria to continue the process. It can only be broken down to release the rest of the energy in the presence of oxygen.

pyruvic acid energy released to make large quantity of ATP (~36 molecules) series of reactions, called The Kreb Cycle &Electron Transport Chain carbon dioxide + water

ATP production – summary glucose 2 ADP + 2 P = 2 ATP pyruvic acid 34 ADP + 34 P = 34 ATP carbon dioxide + water

Summary of ATP production Stage 1 and 2 release all the chemical energy in one molecule of glucose to make a total of 36 ATP molecules. 2 molecules ATP from glucose  pyruvic acid 34 molecules ATP from pyruvic acid  carbon- dioxide + water Total 36 molecules ATP

Anaerobic Respiration (in animals) anaerobic = in the absence of oxygen

In low oxygen conditions or during heavy exercise, when not enough oxygen can be supplied, muscle cells swap to anaerobic respiration

in absence of oxygen pyruvic acid is turned into lactic acid. glucose glycolysis still happens as it does not require oxygen 2 ADP + 2 P 2 ATP pyruvic acid in absence of oxygen pyruvic acid is turned into lactic acid. lactic acid

A build up of lactic acid produces muscle fatigue A build up of lactic acid produces muscle fatigue. Muscle fatigue makes muscles ache and contract less powerfully. A recovery period is needed. During this time more oxygen is taken in to convert the lactic acid back into pyruvic acid again. The volume of oxygen needed is called the oxygen debt.

Summary oxygen debt e.g. during hard exercise oxygen debt glucose pyruvic acid oxygen debt e.g. during hard exercise oxygen debt repaid during recovery time lactic acid

Anaerobic Respiration in plants The same process occurs in plants and yeast in low oxygen conditions, e.g. muddy, flooded soils.

ethanol + carbon dioxide glucose pyruvic acid 2 ADP + 2 P 2 ATP glycolysis still happens, producing 2 ATP molecules This time in absence of oxygen, pyruvic acid is turned into carbon dioxide and ethanol This is irreversible ethanol + carbon dioxide

Comparison of aerobic and anaerobic respiration in animals in plants and yeast Oxygen required? yes no Glycolysis occurs ATP yield 36ATP 2ATP Glucose completely broke down? End products Carbon dioxide and water Lactic acid Ethanol and carbon dioxide