CELLULAR RESPIRATIONPlant cells harvest energy from the sun, and store it as glucose. That glucose must be transformed into energy the cell can use, specifically ATP. This takes place in the mitochondria of cells.

There are two ways that a cell can harvest energy from the food (glucose) it takes in:

Anaerobic Cell Respiration (Fermentation) – glucose metabolism in the absence of oxygen that produces 2ATP molecules and either ethanol or lactic acid. Involves 2 stages:GlycolysisFermentation

Aerobic Cellular Respiration – glucose metabolism with oxygen that produces 36 ATP molecules, CO2 and H2O. Involves 4 stages:GlycolysisPyruvate oxidationKrebs cycleElectron transport and chemiosmosis

STAGE ONE – Glycolysis glucose is broken down through a series of steps to produce 2 – 3carbon molecules of pyruvate and net 2 ATP.

STAGE TWO – Fermentation (without O2)

in the ABSENCE of oxygen, NADH generated from glycolysis passes its H atoms to either acetaldehyde to produce ethanol or to pyruvate to produce lactic acid.

Products of fermentation include:– wine– beer– soy sauce– bread– carbonated beverages– cheese

Lactic acid production causes:– muscle cramps– soreness– stiffness– fatigue

These are all signs of oxygen debt in the muscles.

During Fermentation, NAD+ is restored. This gives cells the opportunity to continue with cellular respiration if oxygen becomes available.

Stage 2 – Pyruvate oxidation (with O2)

CO2 is removed from pyruvate, NAD+ is reduced to NADH, and co-enzyme A is attached to the remaining 2 carbon molecule to form acetyl Co-A.

STAGE THREE – Krebs cycle

a series of reactions that transfers energy from organic molecules to ATP, NADH, and FADH2 and removes carbon as CO2.

STAGE FOUR – Electron Transport Chain

and Chemiosmosis

NADH and FADH2 carry hydrogen atoms and electrons to a series of compounds in the mitochondria that pump H+ ions into the intermembrane space. As H+ ions move through channels down the concentration gradient, ATP is produced. Oxygen is the final electron acceptor in the ETC. Without it, electrons cannot move through the chain and no energy is made.

Chemiosmosis

Overview of Cellular Respiration

The Products of Cellular Respiration

What do we get?

Stage CO2

producedNADH produced

FADH2 produced

ATP consumed

ATP produced

Net ATP produced

Glycolysis 2 2 44 (NADH)

6

Pyruvate oxidation

2 2 6 ( NADH) 6

Kreb’s Cycle

4 6 2 24 (FADH)

18 (NADH)

24

TOTAL 6 10 2 38 36