respiration

the formation of ATP from the break down of glucose takes place during the process of cellular respiration

aerobic respiration anaerobic respiration

require oxygen and produces carbon dioxide, water and much ATP

this takes place in the absence of oxygen and produces lactate (in animals) or ethanol and carbon dioxide (in plants and fungi ) but only a little ATP in both cases

• glycolysis • link reaction • krebs cycle • oxidative phosphorylation

the splitting of the 6 carbon glucose molecule into two 3- carbon pyruvate

3 carbon pryvate molecules enter into a series of reactions which lead to the formation of acetylcoenzyme A a 2- carbon molecule

the intro of acetylcoenzyme A into a cycle of oxidation reduction reaction that yield some ATP and a large quantity of reduced NAD and FAD

the use of the electrons, associated with reduced NAD and FAD, released from the krebs cycle to sythesise ATP with produced as a by- product

glycolysis is the initial stage of both aerobic and anaerobic respiration

glycolysis occurs in the cytoplasm of all living cells and is the process which a hexose sugar - usually glucose- is split into two molecules of 3 - carbon molecule pyravate

pyravate

• phosphorylation of glucose to glucose phosphate • splitting of the phosphorylated glucose • oxidation of triose phosphate • the production of ATP

before it can be split into two, glucose must first be made reactive by the addition of two phosphate molecules (phosphorylation) The phosphate molecules come from the hydrolysis of two ATP molecules to ADP. This provides energy to activate glucose and lowers the activation energy for the enzyme controlled reaction that follows

each glucose molecule is split into two 3- carbon molecules known as triose phosphate

hydrogen is removed from each of the triose phosphate molecules and transferred to a hydrogen - carrier molecule known as NAD to form reduced NAD

enzyme - controlled reaction convert each triose phosphate into another 3 - carbon molecule called pyravate In the process, two molecules of ATP are regenerated from ADP

2 molecules of ATP (four molecules of ATP are produced by two were used up in the initial phosphorylation of glucose and so the net increase is tow molecules) 2 molecueles of reduced NAD 2 molecules of pyravate

they have the potential to provide energy to produce more ATP

glycolysis provides indirect evidence for evolution Enzymes for the glycolysis pathway are found in the cytoplasm of cells and so glycolysis does not require any organelle or membrane for it to take place

no oxygen is needed so it can take place whether or not it is present

in the absence of O2, the pyruvate produced by glycolysis can be converted into either lactate/ethanol during anaerobic respiration This is necessary in order to re-oxidise NAD so that glycolysis can be continue

the pyravate molecules produced during glycolysis process has potential energy that can only be released in a process called the krebs cycle before they can enter the krebs cycle they must be oxidised in a process known as the link reaction

before they can enter the krebs cycle, these pyruvate molecules must first be oxidised in a procedure known as the link reaction