72 ❯ STEP 4. Review the Knowledge You Need to Score High
❯ Rapid Review
Try to rapidly review the material presented below.
There are two main categories of respiration: aerobic and anaerobic.
Aerobic respiration:glycolysis→Krebs cycle →oxidative phosphorylation →36 ATP per
glucose molecule
Anaerobic respiration (fermentation): glycolysis →regenerate NAD+→2 ATP per glucose
molecule
Glycolysis:conversion of 1 glucose molecule into 2 pyruvate, 2 ATP, and 2 NADH;
occurs in the cytoplasm, and in both aerobic andanaerobic respiration; musthave NAD+
to proceed.
Total energy production to this point →2 ATP +2NADH
Krebs cycle:conversion of 1 pyruvate molecule into 4 NADH, 1 FADH 2 , 1 ATP, H 2 O, and
CO 2 ; occurs twicefor each glucose to yield 8 NADH, 2 FADH 2 , and 2 ATP; occurs in
mitochondria.
Total energy production per glucose molecule to this point →4 ATP +10 NADH
+2 FADH 2
Oxidative phosphorylation:production of large amounts of ATP from NADH and FADH 2.- Occurs in the mitochondria; requires presence of oxygen to proceed.
- NADH and FADH 2 pass their electrons down the electron transport chain to produce
ATP. - Each NADH can produce up to 3 ATP; each FADH 2 up to 2 ATP.
•1⁄2 O 2 is the final acceptor in the electron transport chain. - Movement of electrons down the chain leads to movement of H+out of matrix.
- Ox-phos regenerates NAD+so that glycolysis and the Krebs cycle can continue!
Chemiosmosis:coupling of the movement of electrons down the ETC with the formation
of ATP using the driving force provided by the proton gradient; occurs in bothcell respi-
rationandphotosynthesis to produce ATP.
ATP synthase:enzyme responsible for using protons to actually produce ATP from ADP.
Total energy production per glucose molecule to this point →38 ATP (use 2 in process)
→36 ATP total
Fermentation(general): process that regenerates NAD+so glycolysis can begin again. - Occurs in the absence of oxygen.
- Begins with glycolysis: 2 ATP, 2 pyruvate, and 2 NADH are produced from 1 glucose
molecule. - Because there is no oxygen to accept the electron energy on the chain, there is a shortage
of NAD+, which prevents glycolysis from continuing.
Fermentation(alcohol): occurs in fungi, yeast, and bacteria; causes conversion of pyruvate
to ethanol.
Fermentation(lactic acid): occurs in human and animal muscle cells; causes conversion of
pyruvate→lactate; causes cramping sensation when oxygen runs low in muscle cells.