ATP outputs in aerobic respiration

[Bad Student]

Yo Schooby

Are the two NADH molecules produced during glycolysis the source of the 2 extra ATP molecules produced in the electron transport chain?

[ealam2]

Can someone please kindly explain cellular respiration step by step in each process? (I haven't done much pre-reading as of now which I will soon.)

And photosynthesis if possible? Thanks!

[Yacoubb]

Cellular Respiration is the biochemical process by which living organisms break down chemical energy, glucose, either obtained through photosynthesis/chemosynthesis in autotrophs, or obtained by diet in heterotrophs. By breaking down this chemical energy, it is converted into a form of energy that is usable by living organisms; that is, Adenosine Tri-phosphate (ATP).

There are two types of cellular respiration:
(1) Aerobic Cellular Respiration ~ energy yield of 36-38 ATP molecules/glucose molecule
(2) Anaerobic Cellular Respiration ~ energy yield of 2 ATP molecules/glucose molecule

The difference between aerobic cellular respiration and anaerobic cellular respiration is that while aerobic cellular respiration has an oxidative reaction stage (using oxygen), anaerobic cellular respiration takes place in the absence of glucose.

Stage One: Glycolysis
Location: Cytosol (intracellular aqueous environment).
The glucose molecule is broken down into 2 pyruvate molecules (or pyruvic acid). When the glucose molecule is broken down, 4 ATP energy molecules are formed per glucose molecule. However, there is a net output of 2 ATP energy molecules that can be used for expenditure by the organisms for the endergonic functions above. The other 2 ATP molecules are involved in the active transport of pyruvate molecules into the mitochondria across the mitochondrial membrane. This only happens if oxygen is present. However, in the absence of oxygen (anaerobic cellular respiration), the pyruvate is converted to lactic acid in animals and ethanol in plants/yeast. The build-up of lactic acid in the muscles is responsible for muscle fatigue.

So, this is where anaerobic respiration ends. 2 ATP molecules are produced, and as you can see, it is not very efficient, and is only resorted to in periods of strenous activity when oxygen is absent. The next two stages of aerobic respiration take place in the mitochondria; this is why prokaryotes, that lack mitochondria, can only respire anaerobically, and thus has a very low energy yield, of only 2 ATP molecules/glucose molecule.

Aerobic Cellular Respiration Stages:
(1) Glycolysis - takes place in the cytosol, net output energy of 2 ATP molecules/glucose molecule
(2) Kreb's Citric Acid Cycle - 2 ATP molecules/glucose molecule ~ takes place in matrix of mitochondria.
(3) Electron Transport Chain  - 32-34 molecules/glucose molecule ~ takes place in cristae of the mitochondria.

As you can see, aerobic cellular respiration does take longer than anaerobic respiration, however, it is more efficient in the yield of energy.

Energy is required by living organism in order to sustain life. This simple acronym, MRS GRE, is a great way to remember:

Movement
Respiration
Secretion of waste
Growth and repair
Reproduction
Energy expenditure

[Bad Student]

I was taught a slightly different version of MRS GREN in year 9.

Movement
Respiration
Sensitivity

Growth
Reproduction
Excretion
Nutrition

[Stick]

OK, I know what the outputs are for ATP now. Thanks everyone.

Also, prokaryote cells can do aerobic respiration, Yacoubb. My teacher told us that it occurs in the cytosol and the plasma membrane using special chemicals.

[Yacoubb]

OK, I know what the outputs are for ATP now. Thanks everyone.

Also, prokaryote cells can do aerobic respiration, Yacoubb. My teacher told us that it occurs in the cytosol and the plasma membrane using special chemicals.

Ooh okay, thanks for that. Could you elaborate on it? Interesting to know that!

[Ancora_Imparo]

Put simply, the cell membrane in prokaryotes does a similar job to the mitochondria in eukaryotes. All the components needed for aerobic respiration are located in the cell membrane. Eg: ATP synthase enzyme is embedded in the cell membrane.

[Yacoubb]

Put simply, the cell membrane in prokaryotes does a similar job to the mitochondria in eukaryotes. All the components needed for aerobic respiration are located in the cell membrane. Eg: ATP synthase enzyme is embedded in the cell membrane.

So just to confirm, the presence of ATP synthase, in addition to other molecules found in the plasma membrane, make aerobic cellular respiration possible in prokaryotic organisms that obviously lack mitochondria.

[Ancora_Imparo]

So just to confirm, the presence of ATP synthase, in addition to other molecules found in the plasma membrane, make aerobic cellular respiration possible in prokaryotic organisms that obviously lack mitochondria.

Correct.

I don't think you need to know this amount of detail for Units 3/4 however. Just keep the fact that certain prokaryotes, mainly aerobic bacteria, can undergo aerobic cellular respiration in the back of your mind. As you said, it is quite interesting.

[Shenz0r]

Whoa guys - you really are going into an insane amount of depth here (and I'm not sure if it's needed - interesting to know, but VCAA doesn't expect you to)

For the exam you pretty much just need to know the inputs and outputs of each stage of cellular respiration (so glycolysis, Kreb's Cycle, and Electron Transport) and the general gist of what happens in each stage.

[psyxwar]

Wait, what exactly is the difference between oxidative phosphorylation and electron transport? Are they both the same thing?

[Smiley_]

hi
is this is my textbook defintion for \
aerobic respiration
Cellular respiration in which oxygen is
consumed by oxidation (e.g. of glucose) and carbon dioxide
is produced. In most organisms this is the usual way in
which cells obtain most of their energy.

is this a good definition also
which other way can cells obtain energy is anaerobic respiration ?

[Ancora_Imparo]

Wait, what exactly is the difference between oxidative phosphorylation and electron transport? Are they both the same thing?

Again, you don't need to even know what oxidative phosphorylation is, but you can think of it as being the same as electron transport. In short, the electron transport chain allows for the oxidative phosphorylation of ADP to ATP via the oxidation of electron carriers.

[Ancora_Imparo]

hi
is this is my textbook defintion for \
aerobic respiration
Cellular respiration in which oxygen is
consumed by oxidation (e.g. of glucose) and carbon dioxide
is produced. In most organisms this is the usual way in
which cells obtain most of their energy.

Personally, I would also add that water and 36/38 ATP are produced. If the question was worth 3 or more marks, you could also mention that the steps involved are glycolysis, which occurs in the cytosol, as well as the Kreb's Cycle and electron transport chain, which occur in the mitochondria.

[Yacoubb]

Personally, I would also add that water and 36/38 ATP are produced. You could also mention that the steps involved are glycolysis, which occurs in the cytosol, as well as the Kreb's Cycle and electron transport chain, which occur in the mitochondria.

Aerobic Cellular Respiration is the exergonic process by which living organisms use oxidation to break down glucose into 36-38 ATP molecules per glucose molecule.

^ I think that the definition above is an appropriate one because it encapsulates the fact that it is an exergonic process, occurs in the presence of oxygen, it breaks down glucose to form ATP, and the ATP energy yield per molecule of glucose.