Energy II: Acetyl CoA, Mitochondria, Oxygen
The last lecture spoke about conversion of glucose -> pyruvate and that this can take
place in the absence of O2, in muscles leading to the generation of lactate.
This is not an efficient way of generating ATP but serves a purpose in that it is quick
and only requires the appropriate enzymes and substrates.
This lecture talks about the other possible fate of pyruvate which is entering the TCA
(Krebs) cycle and ultimately generating ATP through oxidative phosphorylation. The
main advantage of this is that it produces a lot of ATP but the disadvantage is that it
requires O2.
Aerobic Respiration
Aerobic respiration occurs only in the presence of O2 and yields more energy in the
form of ATP and requires the citric acid cycle and oxidative phosphorylation. It takes
place in the mitochondria (example of compartmentalisation)
Mitochondrial structure is that it contains an outer mitochondrial membrane and an
inner mitochondrial membrane with the intermitochondrial space in between. On the
inside is the matrix (where TCA cycle occurs) and on inner mitochondrial membrane
is where oxidative phosphorylation occurs.
Citric Acid Cycle Overview
Prior to this glucose is converted to two (3C) pyruvate molecules. (from now one we’ll
be referring to one cycle of citric acid cycle so one of the 2 pyruvates).
The pyruvate then undergoes a reaction to become (2C) acetyl CoA, during this
reaction there is a loss of CO2 and an NADH is generated.
, ACoA then enters into the TCA cycle (which occurs in the mitochondrial matrix) and
reacts with (4C) oxaloacetate to become (6C) citrate.
The amount of oxaloacetate remains the same it is continually recycled
Citrate undergoes a series of reactions resulting in the loss of 2CO 2 becoming a 4C
molecule.
For every turn of the cycle you generate three NADH and one FADH 2
One GTP molecule is formed
ATP is NOT produced in the citric acid cycle
Fatty
acids
Proteins
So for each glucose:
6 NADH (within)+ 2 NADH (In producing ACoA)
2 FADH2
2 GTP
4 CO2 + 2CO2
The purpose of the TCA cycle is to generate the NADH and FADH2 to be used in the
ETC, thus providing most of the electrons for oxidative phosphorylation.
TCA also integrates carbohydrate, lipid and protein metabolism as these can enter as
ACoA (which is an important metabolic intermediate, so it acts as a feeding in point for
fatty acid and protein breakdown for energy generation).
The last lecture spoke about conversion of glucose -> pyruvate and that this can take
place in the absence of O2, in muscles leading to the generation of lactate.
This is not an efficient way of generating ATP but serves a purpose in that it is quick
and only requires the appropriate enzymes and substrates.
This lecture talks about the other possible fate of pyruvate which is entering the TCA
(Krebs) cycle and ultimately generating ATP through oxidative phosphorylation. The
main advantage of this is that it produces a lot of ATP but the disadvantage is that it
requires O2.
Aerobic Respiration
Aerobic respiration occurs only in the presence of O2 and yields more energy in the
form of ATP and requires the citric acid cycle and oxidative phosphorylation. It takes
place in the mitochondria (example of compartmentalisation)
Mitochondrial structure is that it contains an outer mitochondrial membrane and an
inner mitochondrial membrane with the intermitochondrial space in between. On the
inside is the matrix (where TCA cycle occurs) and on inner mitochondrial membrane
is where oxidative phosphorylation occurs.
Citric Acid Cycle Overview
Prior to this glucose is converted to two (3C) pyruvate molecules. (from now one we’ll
be referring to one cycle of citric acid cycle so one of the 2 pyruvates).
The pyruvate then undergoes a reaction to become (2C) acetyl CoA, during this
reaction there is a loss of CO2 and an NADH is generated.
, ACoA then enters into the TCA cycle (which occurs in the mitochondrial matrix) and
reacts with (4C) oxaloacetate to become (6C) citrate.
The amount of oxaloacetate remains the same it is continually recycled
Citrate undergoes a series of reactions resulting in the loss of 2CO 2 becoming a 4C
molecule.
For every turn of the cycle you generate three NADH and one FADH 2
One GTP molecule is formed
ATP is NOT produced in the citric acid cycle
Fatty
acids
Proteins
So for each glucose:
6 NADH (within)+ 2 NADH (In producing ACoA)
2 FADH2
2 GTP
4 CO2 + 2CO2
The purpose of the TCA cycle is to generate the NADH and FADH2 to be used in the
ETC, thus providing most of the electrons for oxidative phosphorylation.
TCA also integrates carbohydrate, lipid and protein metabolism as these can enter as
ACoA (which is an important metabolic intermediate, so it acts as a feeding in point for
fatty acid and protein breakdown for energy generation).
