CATABOLIC PATHWAYS, FERMENTATION

22 Jan 02, 15 July 02, 13 July 07, 15July07

pp. 122-149, TFC 7^th: , Black: 120-136, Bauman 2^nd: 135-

Primary goal of catabolism of glucose is to generate ATP (p 127) to be used for anabolism, run the cell.

Transfer of electrons is source of energy: (overview on p 135)

Definition:        Fermentation   the catabolism of glucose in which the terminal H acceptor is organic

                          Respiration      the catabolism of glucose in which the terminal H acceptor is inorganic

Glycolysis (p 136) nets 2 ATPs ATP and 2 NADH per glucose molecule (p. 121), uses 2 NAD⁺

             pyruvate is end product

FERMENTATION regenerates NAD⁺ in the absence of an inorganic H acceptor (p 146)

Lactic Acid fermentation (homolactic fermentation (only lactic acid produced):

             yogurt, sauerkraut, pickles

Alcoholic fermentation (p 146)

Also see picture on top, p 148:

Other fermentation products:

        propionic acid formation    Propionibacterium         Swiss cheese

        acetic acid                           Acetobacter                    vinegar

        acetone                                Clostridium                    gas gangrene, industrial production of acetone

        methane                              Methanosarcina             fuel

        citric acid                            Aspergillus                    flavoring (soft drinks) 

RESPIRATION uses an inorganic H acceptor (oxygen, nitrogen, sulfur, etc)

Acetyl CoA is generated from pyruvate, feeds into Krebs cycle p. 140

Krebs cycle (p. 141)

        decarboxylation

        NADH

        FADH

        ATP

NADH and FADH feed their hydrogens into the electron transport system (142)

ATP is generated from the energy release by the oxidation of these hydrogens (p 143)

Alternative H acceptor molecules for respiration (anaerobic respiration, produces less ATP):

        N in NO₃^- yielding N₂ (denitrification)        Pseudomonas, Bacillus

        S in SO₄ yielding H₂S                                  Desulfovibrio

Total ATPs from single glucose with aerobic respiration: 38 

Other catabolic reactions:

        Protein to amino acids, deamination producing NH₃ (p 150)

fats to glycerol and fatty acids (saponification). Fatty acids can give off taste to butter and milk (butyric acid) (p 149)