Cellular respiration

Equation for cellular respiration

C6H12O6 + 6O2 → 6H2O + 6CO2 + ATP (energy)

Where does glycolysis occur?

In the cytoplasm

Steps of glycolysis

Glucose is phosphorylated twice by two ATP molecules to form fructose 1-6 biphosphate and 2 ADP.

Then, glucose is split in half into 2 molecules of G3P

The G3P molecule is oxidized by NAD+ → NADH, then a random phosphate group is added to form NADH and an intermediate molecule

This intermediate molecule is then dephosphorylated by 2ADP → 2ATP and pyruvate.

This is all happening with 2 molecules of G3P , so in the end you get: 4 ATP, 2 pyruvate, and 2 NADH. But net gain of ATP is 2 since we invested 2 in the beginning.

Where does the link reaction occur

In the mitochondrial matrix

What occurs during the link reaction

The pyruvate molecule is oxidized and decarboxylated with acetyl groups added to it to form Acetyl CoA, reducing NAD+ → and producing NADH and 2 molecules of CO2

Where does the krebs cycle occur

In the mitochondrial matrix

What occurs during the krebs cycle

Acetyl CoA (2C) + oxaloacetate (4C) → citric acid (6C)

Citric acid is then oxidized and decarboxylated, reducing NAD+ → NADH and releasing one CO2 molecule, producing a 5C molecule

This 5C molecule is then oxidized and decarboxylated, reducing NAD+ → NADH and releasing one CO2 molecule, producing a 4C molecule

This 4C molecule is then turned into a new 4C molecule, and the energy from this reaction binds ADP + Pi → ATP

This new 4C molecule is oxidized, reducing FADH → FADH2 and producing a diff 4C molecule

This diff 4C molecule is oxidized again, reducing NAD+ → NADH, producing oxaloacetate !! Cyclical nature as the end product is also what started the reaction.

Produces 4CO2, 6 NADH, 2 FADH2, 2 ATP, and oxaloacetate.

Where does the electron transport chain occur

In the inner membrane of the mitochondria

What occurs during the electron transport chain

NADH and FADH2 split (oxidize) and drop off their e- and H+ at the ETC

The H+ accumulate in the matrix and the e- are taken by the ETC

The e- goes through the first protein complex to the third to the fourth, and as it moves it loses energy, which is taken by the protein complexes to pump H+ into the intermembrane space

Now there is large amount of H+ in a small space, so the concentration of H+ in the intermembrane space is very high compared to the matrix, thus the H+ want to diffuse and go to the matrix

They can only do this by flowing through ATP synthase since the rest of the membrane is impermeable to H+, so as H+ flows through ATP synthase, the enzyme spins and rotates and uses this mechanical energy to make ADP + Pi → ATP

A lot of ATP is formed.

Oxygen is the final electron acceptor. The only reason the ETC works is because the e- are being pulled to something - oxygen. Oxygen has a very high affinity, so the e- are very attracted. Oxygen accepts e- and h+ (4e- + 4H+ + O2 → H2O) forming water as a waste product

Here, a lot of ATP is formed, H2O, and NAD+ and FADH too

What occurs during anaerobic respiration in humans

Glucose is phosphorylated twice by two ATP molecules to form fructose 1-6 biphosphate and 2 ADP.

Then, glucose is split in half into 2 molecules of G3P

The G3P molecule is oxidized by NAD+ → NADH, then a random phosphate group is added to form NADH and an intermediate molecule

This intermediate molecule is then dephosphorylated by 2ADP → 2ATP and pyruvate.

Pyruvate is then reduced to lactate and NADH is oxidized to NAD+ so glycolysis can occur again

What occurs during anaerobic respiration in yeast/fermentation

Glucose is phosphorylated twice by two ATP molecules to form fructose 1-6 biphosphate and 2 ADP.

Then, glucose is split in half into 2 molecules of G3P

The G3P molecule is oxidized by NAD+ → NADH, then a random phosphate group is added to form NADH and an intermediate molecule

This intermediate molecule is then dephosphorylated by 2 ADP → 2 ATP and pyruvate.

Pyruvate is then decarboxylated to ethanal and CO2

Ethanal is then reduced to Ethanol and NADH is oxidized to NAD+ so this can occur again