Cell Respiration

1
Cell Respiration

• The process by which cells turn food molecules
  into
• cell energy

2
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

3
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

4
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

5
Transition between cytoplasm and mitochondrion
6
Krebs Cycle

• Occurs in the cytoplasm of the mitochondria
  (stroma)
• Cyclical series of reactions which breaks down
  acetyls releasing CO2
• Produces
• 2 ATPs
• 6 NADH2
• 2 FADH2

7
Up to this point, the entire molecule of glucose
has been broken down to form 6 CO2s

• Yet, only 4 ATPs have been formed during
• Glycolysis
• Transition
• Krebs Cycle

Potential energy of NADH2 and FADH2 can be
released in Electron Transport Chain
8
Electron Transport Chain harvests potential
energy of NAD and FAD coenzymes
Occurs along inner membrane (cristae) of
mitochondrion
9
Overall Energy Harvest of Aerobic Cell Respiration
Much more ATP than the 4 molecules received
through Gly, Trans, and Krebs!!
10
We metabolize more than sugars!!
11
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

12
Animal cells engage in fermentation

• Fermentation allows NAD to be recycled
• Fermentation produces 2 ATPs per molecule of
  glucose broken down
• Glucose is not completely broken down

13
Plant and fungal cellsengage in fermentation

• This process also allows NAD to be recycled
• Produces 2 ATPs per molecule of glucose broken
  down
• Glucose is not completely broken down

14
Fermentations producemany foods and drinks!

• Dairy fermentations
• Cheeses
• Yogurts
• Sour cream
• Fermented foods
• Breads
• Tofu and tempeh
• Pickles, sauerkraut
• Fermented beverages
• Wines, beers, ales