BISC 1303 - Chapter 7: Cellular Respiration

Electrons have

potential energy

Oxidation

the loss of electrons, lower energy

Reduction

gain of electron, higher energy

Redox reactions

oxidations and reductions are coupled together, H+ may be transferred along with e-

Electron carrier

some organic molecules readily gain or lose electrons

E.G. NAD+ and NADH

Electron energy states

electrons can be at a high or low energy state

the further from the nucleus are at a higher level and have higher energy

Cellular Respiration

the complete breakdown and oxidation of glucose in order to generate ATP

C6H12O6 (glucose) + O2 (oxygen gas) → CO2 (carbon dioxide) + H2O (water) + energy (ATP)

happens in several stages:

Glycolysis (in cytoplasm, rest in mitochondria), Pyruvate Oxidation, Citric Acid/Krebs cycle and Oxidative Phosphorylation (electron transport chain)

Glycolysis

in Eukaryotes cells, this happens in the cytoplasm

10 enzyme metabolic pathway

glucose (6C) to pyruvate (3C) x2

ATP is spent in initial steps, but a net amount is generated

Pyruvate Oxidation

pyruvate broken down, oxidized attached to coenzyme (CoA)

releases CO2, generates NADH and results in acetyl-CoA

The Citric Acid Cycle (Krebs Cycle)

acetyl group (2C) transferred from CoA to oxaloacetate (4C) to form citrate (6C)

in several steps citrate is broken down and oxidized back into oxaloacetate

CO2 ×2 released

• ATP generated

• NADH generated

• FAD reduced to FADH2 (another e- carrier)

*a lot of the energy is in the NADH and FADH2

Electron Transport Chain (ETC)

NADH and FADH2 are oxidized back to NAD+ and FAD

their high energy electrons are passed through a series of other e- carriers

conceptual - lose energy with each transfer until they are transferred to O2 as low energy electrons, energy from e- used to pump H+ across the membrane (active transport), creates a “proton gradient”. the H+ cannot diffuse across the membrane

• the proton gradient has a lot of potential energy

ATP Synthase

a large multi-protein complex, spans the membrane and allows H+ to pass through, down their concentration gradient

this movement powers the rotation of a stalk, which generates ATP.

!!! this is where most of the ATP comes from in cellular respiration !!!

All the steps of cellular respiration put together…

each of these steps are put together to perform cellular respiration, proton gradient is required for this to work.

Catabolism of other carbohydrates

broke into monosaccharides, enter glycolysis

Catabolism of proteins

broke into amino acids, where they can then enter glycolysis, pyruvate oxidation, citric acid cycle

Catabolism of lipids/fatty acids

broken into 2-carbon units, enter citric acid cycle