4 metabolic pathways for cellular respiration
(Aerobic respiration)

2-Breakdown of
pyrvate.
Yield: 1 NADH for each pyruvate

3-Citric acid cycle
Yield: 1 ATP + 3 NADH + 1FADH2

4-Oxidative
phosphorylation (requires oxygen)

1-Glycolysis
Yield: 2 ATP

Energy investment

cleavage

Energy liberation


  • step 1-3
    -2 ATP hydrolyzed to create fructose-1,6 bisphosphate

  • steps 4-5
    -6 carbon molecules broken into two 3 carbon molecules of glyceraldehyde-3-phosphate.

-

  • steps 6-10
    -two glyceraldehyde-3-phosphate molecules broken down into two pyruvate molecules- produces 2 NADH and 4ATP

In eukaryotes, pyruvate is transported into the mitochondrial matrix.

Pyruvate is made in the cytosol by glycolysis. It travels through a channel in the outer membrane and an H+ inner membrane to reach the mitochondrial matrix.

CO2 and NADH is made.

During this process, the acetyl group is transferred to coenzyme A (CoA) and is later removed and enters the citric acid cycle.

Pyruvate is oxidized via pyruvate dehydrogenase to an acetyl group and

Metabolic cycle:

  • Some molecules enter while others leave.
  • Series of organic molecules regenerated in each cycle.

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1- Acetyl is removed from Acetyl CoA and attached to oxaloacetate to form citrate (aka citric acid).

2- Series of steps releases 2 CO2, 1 ATP, 3 NADH, and 1 FADH2.

3- Oxaloacetate is regenerated to start the cycle again.

Phosphorylation occurs by ATP synthase

Oxidative process involves electron transport chain.(ETC)
Produces a H+ electrochemical gradient.

Anaerobic Respiration and
Fermentation
(The two strategies used by cells in anaerobic conditions)

Produce ATP only via substrate-level phosphorylation.

Fermentation: is the breakdown of organic molecules without net oxidation.

  • Uses glycolysis to produce ATP.
  • Glycolysis uses up NAD+ and makes too much NADH under anaerobic conditions (dangerous situation).
    1- Muscle cells solve problem by reducing pyruvate into lactate.
    2- Yeast solve problem by making ethanol.

Use substance other than 02 as final electron acceptor in electron transport chain.

E.coli uses nitrate (NO3-) under anaerobic conditions.
Also makes ATP via chemiosmosis even under anaerobic conditions