Respiration

Respiration

Respiration is a biological process that releases energy for various functions e.g. active transport, movement, and secretion, from substrates. Sugars are also ot the only molecules that can be used as respiratory substrate (lipids hydrolysed to fattu acids and glycerol) and amino acids (hydrolysed to amio acids)

Key Words

• Aerobic respiration - release of energy from substrates that occurs in the presence of oxygen.
• ATP - universal energy currency
• Phosphorylation - the addition of an inorganic phosphate group to a molecule. the reverse is dephosphorylation
• Oxidation - loss of electrons (often with H+ ions)
• Reduction - gain of electrons
• Dehydrogenation - hydrogen is removed
• Decarboxylation - carboxyl group is removed

 There are two types of phosphorylation involved in respiration: substrate level phosphorylation and oxidative phosphorylation.

Glycolysis

The first stage of respiration, doesn't require oxygen so can also be involved in anaerobic respiration.                                                 

Substrate-level phosphorylation occurs to make the glucose 6C unstable. It becomes glucose bi-phosphate (6C) and 2ATP is dephosphorylated to 2ADP+Pi (adenosine diphosphate and inorganic phosphate). Electrons are used to split glucose bi-phosphate into 2 triose phosphate (TP, 3C).  Phosphorylation occurs as 4ADP+Pi becomes 4ATP and 2 hydrogen are removed to bind to NAD carriers. Becomes 2 pyruvate molecules (3C).  If involved in anaerobic respiration (without oxygen), pyruvate doesnt progress to Link Reaction but accepts the electrons from reduced NAD to produce ethanol (plants - fermemtation)/lactate (animals) in a reversible reaction Products: 

• 2 pyruvate
• a net gain of 2ATP as despite 4ATP…