Respiration Flashcards
how much ATP is produced from aerobic respiration?
38 ATP
What are the stages of aerobic respiration?
glycolysis, link reaction, krebs cycle and electron transport chain
where does glycolysis occur?
in the cytosol
is oxygen required for glycolysis?
no oxygen is required
what happens to the glucose molecule in glycolysis?
glucose molecule is phosphorylated and is converted to hexose phosphate
what happens to the hexose phosphate in glycolysis?
It is split into triose phosphate
what happens to triose phosphate in glycolysis?
triose phosphate is dehydrogenated so 2 NADs are reduced to NADH. 4 ATP’s are produced by substrate level phosphorylation and pyruvate is produced
what happens to the pyruvate at the end of glycolysis?
if oxygen is available, it diffuses into the mitochondrial matrix for the link reaction
what does glycolysis produce?
2 ATP, 2 reduced NAD and 2 pyruvates
where does the link reaction occur?
in the mitochondrial matrix
how many times does the link reaction take place?
twice per glucose molecule, because there are two molecules of pyruvate
what happens to the pyruvate once it diffuses into the mitochondrial matrix?
it becomes dehydrogenated and the hydrogen released reduces NAD. the pyruvate is decarboxylated and produces acetyl
what happens to the acetyl during the link reaction?
the acetate combines with Co-enzyme A to form acetyl CoA
How many ATP’s are produced from the link reaction?
6 ATP
where does the krebs cycle take place?
in the mitochondrial matrix
what happens to the acetyl coA after entering the Krebs cycle?
acetate fragment from the acetyl coA combines with a 4C compound to produce a 6C compound – the co-enzyme A is regenerated in the process.
how is the 4C compound regenerated in the krebs cycle?
through a series of 6C and 5C intermediates. Two atoms of carbon are lost in two molecules of CO2 – the oxygen comes from water molecules. Because the process uses oxygen it is called oxidative decarboxylation.
what does the krebs cycle produce?
1 ATP, 3 reduced NAD, 1 reduced FAD and 2 carbon dioxide molecules
why is the process of the electron transport chain (ETC) necessary?
Because by the end of the Krebs cycle, much of the energy is still in the form of hydrogen atoms which are attached to the NAD’s and FAD’s
what will happen to the hydrogen atoms from reduced NAD/FAD after the Krebs Cycle?
they split into their protons and electrons; these electrons then pass along the ETC located within the inner membrane
how do protons enter the space between the inner and outer membrane?
by the proton pump mechanism
how do protons flow back into the matrix?
via the stalked particles due to their high conc. in the intermembranal space
what happens to the protons in the matrix?
they recombine with the electrons and the hydrogen atoms formed then recombine with oxygen to form water
how many molecules of ATP will NAD synthesise if it is the initial hydrogen acceptor compared to FAD?
NAD - 3 molecules of ATP
FAD - 2 molecules of ATP
what is the final electron acceptor at the end of the ETC?
oxygen
what happens in the absence of oxygen?
the reduced NADs and FADs cannot donate their hydrogen atoms at the ETC. If NAD is not oxidised, then the Link Reaction and Krebs Cycle does not occur - no oxidative phosphorylation. (ONLY GLYCOLYSIS OCCURS)
what are the two types of anaerobic respiration?
- fermentation (in higher plants and yeast to form alcohol)
- lactic acid formation (used in muscle cells, producing lactic acid)
What is the process of fermentation?
During glycolysis, the H+ released is passed onto the NAD+ carrier. Pyruvate is decarboxylated to produce ethanal.
- NADH/H+ passes the H to ethanal (final H acceptor) which is reduced to ethanol.
why does aerobic respiration take place in human muscle cells?
During vigorous exercise, the body cannot get sufficient oxygen to the muscle cells, so the cells produce ATP by glycolysis
How is lactic acid formed?
In Glycolysis, the NADH/H+ passes its hydrogen directly to pyruvate reducing it to lactate. This releases NAD+ to be reused in further glycolysis.
what becomes the final hydrogen acceptor in lactic acid formation?
pyruvate
What happens to lactic acid when oxygen becomes available?
- lactic acid is broken down in the liver
- most is converted to glycogen and stored for further energy release
