2.2 Cellular Respiration Flashcards
what are the 3 stages aerobic respiration can be split into?
- glycolysis
- citric acid cycle
- electron transport chain
describe ‘stage 1 of aerobic respiration — glycolysis’
- takes place in the cytoplasm of the cell
- does not require oxygen
Glycolysis is the breakdown of glucose into two pyruvate molecules.
The production of pyruvate from glucose involves the production of several intermediate molecules. Phosphorylation of glucose and these intermediates requires ATP molecules in an energy investment stage.
More ATP molecules are then regenerated than were used in the production of other intermediates (during the energy investment stage). This breakdown of glucose into pyruvate therefore results in a net gain of ATP molecules.
Dehydrogenase enzymes remove hydrogen ions and electrons from intermediates of this cycle, which are passed to the coenzyme NAD (forming NADH). The hydrogen ions and electrons are passed to the electron transport chain on the inner mitochondrial membrane.
If oxygen is available, pyruvate molecules progress into the citric acid cycle. If oxygen is not available then pyruvate undergoes fermentation in the cytoplasm of the cell.
what are the roles of the dehydrogenases and NAD in respiration?
dehydrogenase — remove hydrogens and electrons from intermediates during glycolysis and the citric acid cycle and pass them to the coenzyme NAD
NAD — forms NADH (by the removal of hydrogen and electrons) and is transferred to the electron transport chain (stage 3)
describe ‘stage 2 of aerobic respiration — citric acid cycle’
- takes place in the matrix of the mitochondria
- requires oxygen
In aerobic conditions, pyruvate is broken down to form an acetyl group. This combines with Coenzyme A to form Acetyl Coenzyme A.
The acetyl group then enters a cycle of reactions called the citric acid cycle.
The acetyl group combines with oxaloacetate to form citrate. A cycle of reactions occur eventually resulting in the regeneration of oxaloacetate which will combine with another acetyl group and so the cycle repeats.
During the cycle, 2 molecules of carbon dioxide are released, hydrogen and electrons are removed and combine with NAD and enough energy is produced to regenerate a molecule of ATP.
describe ‘stage 3 of aerobic respiration — electron transport chain’
- takes place in the cristae of the mitochondrion
- requires oxygen
An electron transport chain is a series of carrier proteins attached to the inner membrane of the mitochondria. There are many of these chains attached to the membrane.
The electrons brought by the NADH flow along the electron transport chain releasing energy.
The energy is used to actively transport hydrogen ions across the membrane, from the matrix of the mitochondrion (low concentration of hydrogen ions) into the interior-membrane space (high concentration of hydrogen ions).
As the hydrogen ions flow back through membrane proteins, ATP synthase, they rotate and synthesise ATP.
The hydrogen ions and electrons combine with oxygen to form water.
summarise stage 1 of aerobic respiration (glycolysis)
- occurs in the cytoplasm
- no oxygen is required
- substrates = glucose and ATP
- coenzyme involved = NAD
- products = pyruvate, hydrogen, electrons and ATP
summarise stage 2 of aerobic respiration (citric acid cycle)
- occurs in the matrix of the mitochondrion
- oxygen is required
- substrate = pyruvate
- coenzymes involved= enzymes A and NAD
- products = carbon dioxide, hydrogen, electrons and ATP
summarise stage 3 of aerobic respiration (electron transport chain)
- occurs in the cristae of the mitochondrion
- oxygen is required
- substrates = hydrogen, electrons, water and oxygen
- coenzyme involved = NAD
- products = water and ATP
describe ‘fermentation in muscle cells’
- occurs in the cytoplasm
- substrate = glucose
- coenzyme involved = NAD
- products = lactate, ATP, hydrogen ions and electrons
describe ‘fermentation in yeast/plant cells’
- occurs in the cytoplasm
- substrate = glucose
- coenzyme involved = NAD
- products = ethanol, carbon dioxide, ATP, hydrogen ions and electrons
what is ATP used for?
to transfer energy from respiration to he cellular processes which require it
name 4 cellular processes that require energy
- muscle cell contraction
- protein synthesis
- DNA replication
- active transport
- cell division
