respiration Flashcards
whats the difference between anaerobic and aerobic respiration
aerobic requires oxygen and produces carbon dioxide water and much ATP
anaerbic respiration takes place in the absense of oxygen and produces lactate in animals and ethanol and CO2 in plantsand fungi and little atp
what are the four stages of respiration - briefly describe them
glycolysis - splitting of 6 carbon molecule into a 3 carbon molecule
link reaction-thr 3 carbon molecule enters a series of reactions which lead to the formation of a two carbon acetylcoenzyme
krebs -the introduction of acetylcoenzyme into a cycle of oxidation reduction reactions which yield some ATP and a large quantity of reduced NAD and FAD.
oxidative phosphoryation -the use of electrons associated with reduced NAD and FAD released from krebs cycle to synthesise ATP witth water as a by product
Describe what occurs in glycolysis
glycogen in liver converted into glucose
firstly glucose molecule is phosphorylated into glucose phosphate ,before glucose is split into two its made more reactive by addition of two phosphates , these come from the hydrolysis of two ATP molecules to ADP.this provides energy to activate glucose and lower activation energy for enzyme controlled reaction to follow
phosphorylated molcule split into two 3 carbon molecules (triose phsophate )
Oxidation of triose phosphate molecule as as hydrogen is removed and transfeered to NADto form reduced NAD
Enzyme controlled reaction convert each triose phophate into 3 carbon called pyruvate “ ATP molecules are regenerated by addition of phosphate to ADP
whats the yield from glycolysis of one glucose molecule
two molecules of ATP ( 4 put , 2 of them were used to start so net gain of 2)
two molecules of reduced NAD
two molecules of pyruvate
where does the link reaction take place
matrix of mitochondria
pyruvate enters the mitochondrial matrix via active transport
what occurs during the link reaction
Carbon dioxide is removed from pyruvate (decarboxylation) and diffuses out of the mitochondria and out of the cell
Hydrogen is removed from pyruvate (dehydrogenation/oxidation) – accepted by NAD, producing reduced NAD
This converts pyruvate into a 2C molecule which immediately combines with coenzyme A to form the 2C compound acetyl coA
describe what occurs during the krebs cycle
the two carbon acetyl coenzyme from links combines with a 4 carbon to form a 6 carbon molecule
in a series of reactions the four carbon molcule undergoes dehydrogenation and decarboxylation to form a four carbon molecule and a single molecule of ATP is produed as a result of substrate level phosphorylation.
the four carbon molecule can now join with another coenzyme to begin the cycle again.
what are the products of krebs for every pyruvate molecule
reuced NAD and FAD which have the potential to produce ATP by oxidative phosphorylation
whats the significance of krebs cycle
it breaks down larger molecules into smaller molecule pyruvate is broken down into CO2
it produces hydrogen ions that are carried by NAD to the electron transfer chain and providde energy for oxidative phosphorylation
it regenerates the four carbon molecule with acytelcoenzyme which would otherwise accumulate
its a source of intermediate compounds used by cellsin the manufacture other important substances such as fatty acids
what do metabollically active cell contain (mitochondria )
have more densly packed cristae which provide a greater surface area of membrane incooperating enzymes
oxidative phosphorylation the synthesis of ATP describe the processs
why is oxygen important in the final stage of phosphorylation
the importance of oxygen is to act as the final electron acceptor of the hydrogen atoms produced in glycolysis and krebs cycle without the removals of of hydrogen ions at the end of the chain .Without its role in removing hydrogen ions at the end of the chain hydrogen ions and electrons would back up along the chain and
why does anaerbic respiration occur
If oxygen is not available, the link reaction and Krebs cycle stop and oxidative phosphorylation cannot occur as there is no final electron acceptor. Glycolysis can still continue as long as the pyruvate can be removed and the reduced NAD can be converted back to NAD. This does not produce as much energy, the net yield is 2 ATP per glucose molecule.
anaerbic respiration in animals
In animals this is done by converting pyruvate to lactate (lactate fermentation) in the cytoplasm. Reduced NAD from glycolysis transfers H to pyruvate to form lactate and NAD so glycolysis can continue. The lactate built up in muscles diffuses into the blood and is carried in solution as lactic acid in the blood plasma to the liver, where liver cells convert it back to pyruvate. This requires oxygen, this is the oxygen debt.
pyruvate + reduced NAD > oxidised NAD +lactate
what happens when oxygen is availabe again
When oxygen is available again after exercise and oxygen uptake is greater than normal, some of the pyruvate in the liver cells is oxidised through the link reaction, Krebs cycle and electron transport chain. Some pyruvate is reconverted to glucose in the liver cells and this is released into the blood or converted into glycogen to be stored.
