Lecture 12: Respiration and Fermentation
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How does bacterial respiration work? How is this different to fermentation?
• Molecule X outside the cell enters and is oxidized = energy release • Molecule Y outside the cell enters and is reduced = energy release FERMENTATION 1. Molecule X outside the cell enters and is oxidized = energy release 2. THERE IS NO Y 3. Molecule X needs to be converted to something else that can THEN be reduced
What are the three glucose metabolic pathways? What is their end products?
• Glycolysis • Pentose phosphate pathway • Entner-Doudoroff pathway “Pyruvate” - NADPH used specifically for anabolic reactions
What is the result of the PPP
• 2x NADPH (for synthesis) • glycolysis intermediates (Glyceraldehyde 3-phosphate • Ribose 5-phosphate (biosynthetic intermediate for nucleotides) • Anabolic pathway compared to glycolysis a. 2 NADPH b. 1 ATP c. 1 NADH
How is ATP generated in fermentation
• No outside electron acceptors involved; no membrane or e- transport system req.; no ATP synthase needed • “Metabolism where E is derived from partial oxidation of an organic compound using organic intermediates as electron donors and acceptors • ALL ATP PRODUCED BY SUBSTRATE LEVEL PHOSPHORYLATION a. transfer of a Pi back onto an ADP
How do different bacteria carry out fermentation?
• Lactic acid bacteria: Gram-positive bacteria that ferment sugars (glucose) with lactic acid as major producta. lactobacilli - relatively acid tolerant (grow at pH4), so change the environment to something they can survive but other organisms cant. NON-PATHOGENIC, ACID KILLS OTHERS b. Streptococcus
How does yeast generate energy?
ETHANOL FERMENTATION • Low [glucose], high [oxygen] = “pasteur effect” - fermentation suppressed • High [glucose], low [oxygen] = “crabtree effect” - aerobic respiration suppressed 2 pyruvate -> 2 acetaldehyde -> 2 ethanol ETHANOL PRODUCTION SERVES TO KILL OTHER COMPETING BACTERIA
What do bacteria do when there is no oxygen?
• Metal respiration • Denitrification • sulphate respiration • fumarate respiration • sulphur respiration • methanogenesis
What do bacteria do when there is no oxygen?
• Metal respiration • Denitrification • sulphate respiration • fumarate respiration • sulphur respiration • methanogenesis
How does the nitrogen cycle work?
• NH4+ (organic nitrogen) • nitrification (NH2OH) • NO2- (nitrate) • Denitrification (NO-> N2O) • Fixation (N2-> NH4+) (organic)
What are the different nitrogen cycle pathways?
• Nitrification (aerobic) a. Nitrate to nitrite b. Nitrite to NO3- • Denitrification (anaerobic)