2. cellular respiration Flashcards
what is respiration
Respiration is a series of metabolic pathways which bring about the release of energy from the breakdown of food molecules e.g. glucose. The energy released is used to regenerate the energy transfer molecule ATP.
Cellular respiration is central to metabolism and is linked to many other pathways.
what is a phosphorylation reaction
involves a phosphate group being added to a substrate.
ATP also has a role in carrying out phosphorylation reactions
describe the formation of ATP
The formation of ATP from ADP and Pi is a phosphorylation reaction since a phosphate group is added to ADP to form ATP
name the 3 sets of reactions in cellular respiration
1) glycolysis
2) citric acid cycle
3) electron transport chain
describe the first stage of respiration, glycolysis
is the breakdown of glucose to pyruvate in the cytoplasm.
ATP is required for the phosphorylation of glucose and intermediates during the energy investment phase of glycolysis. This leads to the generation of more ATP during the energy pay-off stage and results in a net gain of ATP.
what do dehydrogenase enzymes do
remove hydrogen ions and electrons from the intermediate substrate molecules.
These hydrogen ions and electrons immediately attach to co-enzyme molecules called NAD, forming NADH. These co-enzyme molecules are also known as hydrogen carriers.
where does the citric acid cycle take place
the citric acid cycle takes place in the matrix of the mitochondria
what is oxygen known as in the electron transport chain stage
the final hydrogen/electron-acceptor
how is water made during the final respiration stage
hydrogen ions and electrons are passes along the inner membrane transport chain so then they are free to join with the oxygen molecule to make water
describe fermentation
in the absence of oxygen, fermentation takes place in the cytoplasm
results in much less ATP (2ATP) being produced than in aerobic respiration (38ATP).
describe fermentation in animal cells
pyruvate is converted to lactate in a reversible reaction
describe fermentation in plant/yeast cells
ethanol and CO2 are produced in an irreversible reaction
what is the metabolic pathway for fermentation in plants and yeast
glucose —> pyruvate —> ethanol + carbon dioxide
what is the metabolic pathway for fermentation in animal cells.
glucose –> pyruvate <—> lactate (lactic acid)
describe the 6 stages of the citric acid cycle
-in aerobic conditions, pyruvate is broken down to an acetyl group (and carbon dioxide is released)
-acetyl combines with coenzyme A forming acetyl coenzyme A
-the acetyl group from acetyl coenzyme A combines with oxaloacetate to from citrate
-during a series of enzyme controlled steps, citrate is gradually converted back into oxaloacetate which results in the generation of ATP and release of carbon dioxide
-dehydrogenase enzymes removes hydrogen ions and electrons and pass them to the coenzyme NAD, forming NADH (in glycolosis and CCA)
-the hydrogen ions and electrons from NADH are passed to the elcectron transport chain on the inner mitochondria membrane