AP Bio Kalsang Choekgi
I. Cell Respiration: means by which cells extract energy stored in food and transfer that energy to molecules of ATP.
II. Two types of cell respiration
A. Aerobic respiration (with Oxygen)
a) Occurs in the cytoplasm and produces ATP without the need of oxygen.
b) Ten step process
(1) breaks down 1 molecule of glucose into 2 3-carbon molecules of pyruvate
(2) 2 NAD+ are reduced to 2 NADH
(3) Phosphate groups are added to each 3-carbon sugar
(4) ADP -> ATP through a direct enzymatic transfer of a phosphate to ADP
(5) 2 ATP and 2 pyruvates are produced.
2. Krebs Cycle
a) Takes place in the matrix of the mitochondria and requires only the pyruvate from glycolysis.
b) The Process
(1) The Pyruvate from the glycolysis is combines with CoA to form acetyl co-A (which enters the cycle), also turned into CO2.
(2) NAD+ -> NADH because a molecule is released as CO2. Thus, energy is needed to break off the molecule and so NAD+ captures that energy and changes.
(3) The CoA combines with a 4-carbon molecule to create 6-carbon molecule.
(4) NAD+ NADH and the 6-carbon molecule turns into a 5-carbon molecule when one molecule turns into CO2
(5) NAD+ NADH
(6) another molecule is released as CO2 changes the 5-carbon molecule to a 4-carbon molecule.
(7) That 4-carbon molecule is then processed through the cycle again after NAD+ NADH and FAD2+ NADH2
c) The cycle produces 1 ATP per turn by substrate-level phosphorylation.
3. Electron transport chain
a) Proton pump in the mitochondria.
(1) two reactions, one exergonic and one endergonic
b) Uses energy released from the exergonic flow to pump protons against a gradient from the matrix to the outer compartment
(1) establishes a proton gradient in the mitochondrion.
c) ETC is basically a collection of molecules embedded in the cristae membrane of the mitochondria.
d) The Process
(1) NADH NAD+ after it donates e- to the ETC
(2) 2 H+ protons pumped across the membrane
(3) The electrons pass from one protein to the next.
(a) energy is released at each transfer
(4) H+ protons are moved across the concentration gradient.
(5) The electrons combine with O2 to form water
(6) H+ concentration gradient is formed across the membrane which is used to fuel the production of ATP.
4. Oxidative phosphorylation
a) Most of the energy is produced during oxidative phosphorylation.
(1) Phosphorylation of ADP to ATP by the oxidation of the carrier molecules NADH and FADH2.
(a) This energy mechanism is called chemiosmosis
(i) Uses portential energy stored in the form of proton (H+) gradient to phosphorylate ADP and produce ATP.
B. Anaerobic respiration
1. Consists of glycolysis + lactic acid fermentation.
2. Pyruvate from glycolysis is reduced to form lactate (lactic acid).
a) In the process, NADH is oxidized back to NAD+