Cellular Respiration

I. What is Cellular Respiration?  Cellular Respiration is the series of reactions by which organisms obtain energy by breaking down organic molecules into ATP energy. Cellular Respiration occurs in three main phases: Glycolysis, which is an anaerobic process (meaning it does not require O 2 ), Kreb’s Cycle, which is an aerobic process (meaning it does require O 2 ), and Electron Transport, which is an aerobic process (meaning it does require O 2 ).

I. What is Cellular Respiration?  C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + ATP Glucose Oxygen Carbon Water Energy Dioxide

II. Cellular Respiration Occurs in the Mitochondria

 A. Mitochondria are small compartments located inside plant and animal cells.  1) Outer Membrane – composed of a phospholipids bilayer; protects the mitochondria and controls what comes in and out  2) Cristae – the inner membrane is composed of a series of folds to increase the surface area inside the mitochondria  3) Matrix – the fluid component of the organelle; contains enzymes responsible for the citric acid cycles as well as other recyclable molecules that will be used in the process of Cellular Respiration

III. Phase One: Glycolysis

 A. Glycolysis is the process in which one molecule of glucose is broken in half, producing two molecules of pyruvic acid, a 3-carbon compound.  1) 4 ATP Produced – 2 ATP Used = Net Gain of 2 ATP  2) occurs in the cytoplasm of the cell  3) does NOT require O 2 (anaerobic)  4) also produces two molecules of NADH (energy)

IV. Phase Two: Kreb’s Cycle

 A. During the Krebs cycle, pyruvic acid is broken down into carbon dioxide in a series of energy-extracting reactions.  1) (1 ATP Produced per each turn of the cycle x 2 turns through the cycle) – 2 ATP used converting Pyruvic Acid to Acetyl-CoA = Net Gain of 0 ATP  2) occurs in the center cavity of the mitochondria  3) requires O 2 (aerobic)  4) 2 ATP are used converting the Pyruvic Acid from Glycolysis into a substance called Acetyl-CoA  5) enzymes break down the two smaller molecules produced during Glycolysis in CO 2

V. Phase Three: Electron Transport

 A. The Electron Transport Chain uses the high- energy electrons from the Kreb’s Cycle to convert ADP to ATP.  1) Net Gain of 34 ATP  2) occurs in the cristae of the mitochondria  3) requires O 2 (aerobic)  4) energy from hydrogen atoms produced during the first two stages of Cellular Respiration is transferred to ATP

V. Phase Three: Electron Transport  a) the hydrogen atoms carried by NADH are separated into their component parts  electrons (e-) and protons (H + )

V. Phase Three: Electron Transport  b) the electrons are passed to the chain of electron (e-) carrier molecules

V. Phase Three: Electron Transport  c) as the electrons (e-) move from one carrier to the next, they release energy

V. Phase Three: Electron Transport  d) some of this energy pumps the protons (H + ) across the inner membrane of the mitochondria and they accumulate in the outer compartment

V. Phase Three: Electron Transport  e) the concentration gradient produced results in diffusion of the protons (H + ) back into the inner compartment

V. Phase Three: Electron Transport  f) the protons pass through an enzyme complex located in the membrane which makes ATP from ADP and Phosphate

V. Phase Three: Electron Transport  g) the transferred electrons combine with protons (H + ) and molecular oxygen (O 2 ) to form water (H 2 O)