6-3 Aerobic Respiration

How much ATP is produced in anaerobic respiration?

2 ATP

Pyruvic acid, the end product of anaerobic respiration has almost as much energy as does glucose…

Aerobic respiration continued…

In order for pyruvic acid to be broken down, yielding further energy, 2 things are required:

1) Oxygen (O2)

2) Mitochondria

Breaking pyruvic acid…

Once pyruvic acid enters the mitochondrion, it is broken into a 2 carbon molecule, which bonds to an enzyme called coenzyme A (CoA) to form acetyl CoA.

Each molecule of pyruvic acid yields 1 CO2, and 1 NADH

Pyruvic Acid

NAD+

NADH CO2

CoA

Krebs here I come!!!

Once the acetyl-CoA is formed, it enters into what is called the Kreb’s Cycle, or Citric Acid Cycle.

What is a cycle?A repeating series of events…

Except for the acetyl-CoA, everything else in the cycle is reused.

Krebs again…

For every “turn” of the Kreb’s cycle:

• 1 acetyl-CoA is required

• 2 molecules of CO2 are made

• 3 molecules of NADH are made

• 1 molecule of FADH2 is made

Interesting tidbits…

For every turn of the Kreb’s cycle, only 1 ATP is produced!!!

Anyone recall how much ATP comes out of aerobic respiration?

36ATP!!!Where does the rest of the energy come from?

Working on the chain…

Well, we haven’t seen much ATP made yet, but what has been happening?

REDUCTION OF NAD+ & FAD!!!

We’ve got 10 NADH at this point and 2 FADH2! That’s a lot of stored energy.

Where does it go?

The energy stored in NADH and FADH2 is released in a series of steps called the electron transport chain.

The ETC is simply a series of step in which electrons are passed from carrier to carrier, until finally O2 accepts the last 2 electrons.

Ahhh, big words…

As electrons are passed, energy is passed as well…

Some of that energy is used to convert ADP to ATP by means of a H+ pump (don’t worry about this!).

The last step…

Again, O2 is the final electron acceptor. It combines with 4 H, to form… WATER!!!

All in all, we gain 2 ATP from glycolysis, 2 ATP from the Kreb’s, and 32 from the ETC for a total of 36 ATP gained!!!

Net Reactions:

The overall process we have talked about can be summarized as:

C6H12O6 + 6 H2O + 6 O2

6 CO2+ 12 H2O + 36 ATP

Recap:

Why do aerobic respiration instead of anaerobic?

Aerobic respiration yields 18 times more energy!!! (36:2)

Man vs. Machine

Another interesting tidbit:

Roughly 45% of the available energy of a glucose molecule is stored as ATP following aerobic respiration.

In comparison only 20% of the energy of gasoline is used by cars.

What happens if we don’t have oxygen?

Why do we need oxygen?

Aerobic respiration can’t occur without it.

Without oxygen, the Kreb’s cycle will stop, leaving a buildup of pyruvic acid…

The fate of pyruvic acid.

Without oxygen, what are 2 things that could happen to pyruvic acid?

Alcoholic or lactic fermentation!

What happens to us?

Lactic acid fermentation!

Oxygen Debt

Anytime your muscles get starved for oxygen, and lactic acid fermentation begins, you experience oxygen debt.

Oxygen debt is the amount of oxygen your body requires to get rid of lactic acid.

Atkins Heaven

We’ve talked about glucose as the main source of energy for ATP, but proteins and fats may be used as well.

Fat produces twice as much energy as glucose does, but you must be twice as active to burn a gram of fat…

The end…

Proteins may be used as an energy source as well, though there is much controversy as to whether this is good for the body or not…

Ramifications?