Degredative pathways to release ATP energy for cell functions (catabolic)

Evolution of Catabolic pathways Anaerobic Fermentation – evolved in primitive bacteria still used by some unicellular organisms

Anaerobic Fermentation Steps: Glycolysis then regeneration of NAD+ (Glycolysis breaks glucose in ½) A) 2 ATP added to glucose B) unstable intermediate forms C) NAD+ picks up H from glucose D) Intermediate splits into 2 pyruvates E) 4 ATP generated (net gain of 2 ATP) F) NADH drops hydrogen off on pyruvates G) CO2 and alcohol by products form

Net gain of 2ATP is enough energy for a unicellular organism…. but not for a multicellular organism

Advent of non-cyclic photosynthesis Caused free O2 to build up in the ocean

Build up of O 2 in atmosphere Obligate Anaerobes: die in presence of O2 Present day obligate anaerobes regulated to anaerobic environments. Form endospores against the O2 laden air. Example disease causing bacteria: Botulism (Clostridium botulinum), Tetnus (Clostridium tetani)

Other lines evolved anti-oxidants/defense against the oxidative properties of O2 can survive the presence of free oxygen Some organisms found ways to use the O2 to generate more energy per glucose : aerobic cellular respiration Some organisms can use aerobic respiration when O2 is present then switch to anaerobic fermentation when in anaerobic conditions = facultative aerobes (yeast)

Aerobic Respiration Evolved a way to use e- on NAD+ in electron transport chain to get more ATP /glucose. Anaerobic fermentation => 2 ATP gain Aerobic respiration => 32 ATP gain Some bacteria became obligate aerobes Animals plants fungi…..

Aerobic Respiration 4 Parts Step 1..Glycolysis Step 2.. Acetyl-CoA formation Step 3…Krebs Cycle (citric acid cycle) Step 4… Electron transport and oxidative phosphorylation

Aerobic Glycolysis Glucose split in cytoplasm (before entering mito.) 2ATP added to Glucose Unstable intermediate forms then splits NAD+ reduced into NADH 4 ATP made Net gain = 2 ATP per glucose

1) Substrate level phosphorylation creates unstable intermediate 2) Intermediate splits then forms 2 PGAL

3) NAD+ is reduced 4) NADH carries e- and H+ to mitochondria 5) Each PGAL has enough energy to make 2 ATP 6) 2 pyruvates (pyruvic acids) move to mito

Acetyl-CoA formation The pyruvate enters the mitochondrial matrix (in prokaryotes stays in cytoplasm) One C is removed and converted to CO2 One NAD+ is reduced to NADH Coenzyme A binds to the remaining 2 C forming Acetyl-CoA

Krebs cycle : Citric Acid Cycle Acetyl Co-A drops off 2 C onto oxaloacetate to form citrate CoA is thereby regenerated and returns to pick up more C from pyruvate 3NAD + and 1FAD reduced to form NADH and FADH 2 To do this, a series of intermediates have all their Hydrogens removed Remaining C and O released as 2CO2 1 ATP is produced Oxaloacetate is reformed Cycle runs one time for each pyruvate

Electron Transport Chain e- brought to ET chain by NADH & FADH 2 NADH and FADH 2 come from Glycolysis & Kreb’s e- passed down chain of proteins in a series of oxidation/reduction reactions Protein pumps use energy from e- to pump H + H + build up in intermembrane space creating electrochemical gradient (lots of Potential E) e- at end of chain picked up by O 2

Chemiosmosis = energy coupling mechanism converts potential energy of chemical gradient into chemical energy (ATP)

Oxidative phosphorylation Producing ATP using the energy of oxidation reactions in the e- transport chain Generates 26 – 28 ATP per glucose

Electrons from Glycolysis Passed through mito membrane by transport proteins to NAD+ or FAD on inside of mito Slightly less ATP is formed if FAD pick up e-

Lack of Oxygen in mitochondria Oxygen = final electron acceptor in aerobic resp If no O2 oxidizes the last protein in e- transport chain, chain stops Oxidative phosphorylation stops NADH &FADH2 build up, NAD+ & FAD run out Kreb cycle stops NADH from glycolysis can’t drop of e- at mito

Lactic Acid Fermentation-animals NADH drops off electrons onto pyruvate pyruvate is converted to Lactic acid

Other Macromolecules as fuel Only Glucose runs entire aerobic resp pathway Carbs converted to glucose before being used When carbs run out Fats used Triglycerides break into …… fatty acids & glycerol Glycerol converted to PGAL & enters…. Glycolysis Fatty acids are converted into acetyl-CoA enters Kreb’s

Proteins broken into …. amino acids Amino acids break into a) NH3 (nitrogenous waste) converted to urea b) carbon backbone converted to pyruvate or Acteyl Co-A