cell respiration the process by which cells turn food molecules into cell energy

Cell Respiration

The process by which cells turn food molecules into

cell energy

The Complete breakdown of foods occurs in aerobic respiration

The general reaction of aerobic respiration is:

glucose + O2 CO2 + H2O + ATP + heat

• This reaction occurs in steps:– Glycolysis– Transition reaction– Krebs Cycle– Electron Transport Chain

Glycolysis

• Occurs in the cytoplasm• Splits a 6-carbon sugar into 2

x 3-C pyruvates• Reaction sequence:

Sugar (6C) 2 Pyruvates (3C)• Produces:

– 2 ATP molecules

– 2 NADH2

Transition reaction

• Processes pyruvate so that it can enter mitochondrion

• The reaction sequence:

2 pyruvate (3C) 2 acetyl (2C)• Produces:

– 2 NADH2

• 2 acetyl groups easily enter the mitochondrion of the cell

Transition between cytoplasm and mitochondrion

Krebs Cycle

• Occurs in the cytoplasm of the mitochondria (stroma)

• Cyclical series of reactions which breaks down acetyls releasing CO2

• Produces:– 2 ATP’s– 6 NADH2

– 2 FADH2

Up to this point, the entire molecule of glucose has been broken down to form 6 CO2’s

Yet, only 4 ATP’s have been formed during:

•Glycolysis

•Transition &

•Krebs CyclePotential energy of NADH2 and FADH2 can be released in Electron Transport Chain

Electron Transport Chain – harvests potential energy of NAD and FAD coenzymes

Occurs along inner membrane (cristae) of mitochondrion

Overall Energy Harvest of Aerobic Cell Respiration

Much more ATP than the 4 molecules

received through Gly, Trans, and

Krebs!!

We metabolize more than sugars!!

Can cells produce ATP without oxygen being present?

• Oxygen removes e-’s from the Electron Transport Chain to help make ATP

• If oxygen is not present, NADH2 must be oxidized to NAD+ to allow cells to make ATP

Animal cells engage in fermentation

• Fermentation allows NAD+ to be recycled

• Fermentation produces 2 ATP’s per molecule of glucose broken down

• Glucose is not completely broken down

Plant and fungal cellsengage in fermentation

• This process also allows NAD+ to be recycled

• Produces 2 ATP’s per molecule of glucose broken down

• Glucose is not completely broken down

Fermentations producemany foods and drinks!

• Dairy fermentations– Cheeses– Yogurts– Sour cream

• Fermented foods– Breads – Tofu and tempeh– Pickles, sauerkraut

• Fermented beverages– Wines, beers, ales