chapter five: microbial metabolism

Transcription

1 chapter five: microbial metabolism Revised 9/22/2016

2 oxidation-reduction redox reaction: coupled reactions e- donor oxidized donor Ox Red ADP + P i ATP Ox Red reduced A chemical A

3 redox reactions aerobic respiration oxygenic photosynthesis

4 nutritional classification: metabolic strategy carbon source organic/inorganic heterotroph autotroph electron source organic/inorganic energy source light/chemical organic photoautotroph chemoautotroph energy source light/chemical electron source organic/inorganic electron source organic/inorganic photoorgano heterotroph Non-Sulfur Purple Bacteria chemoorgano heterotroph electron acceptor organic/inorganic inorganic photolitho autotroph sulfur oxidizers chemolitho autotroph iron oxidizers respiration oxygen other inorganic fermentation butanediol mixed acid lactic acid alcohol aerobic respiration e- acceptor oxygen/other anaerobic respiration oxygenic photosynthesis Cyanobacteria (plants too) anoxygenic photosynthesis PSB, GSB, GNSB

5 acquiring ATP: substrate level phosphorylation

6 acquiring ATP: oxidative phosphorylation & chemiosmosis

7 heterotrophy: respiration The ETC process The ETC overview Factors affecting the ETC Switching to fermentation electron path (oxidation)

8 heterotrophy: respiration & fermentation C 6 H 12 O 6 NAD + inorganic e- acceptor ETC reduced e- acceptor CO 2 NADH ADP + P lots of ATP 2 H + C 6 H 12 O 6 NAD + organic pyruvate ferm lactic acid ethanol & CO 2 mixed acids butanediol pyruvate NADH substrate P few ATP

9 heterotrophy: respiration & fermentation respiration 1. inorganic e - acceptor 2. does NOT mean O 2 3. organic mole. CO 2 fermentation 1. organic e - acceptor 2. organic organic mole. 3. incomplete H stripping, The Kreb s Cycle The Kreb s Cycle in detail lower ATP yield

10 Chapter Five Learning Objectives 1. Define oxidation and reduction. Why are these recations always coupled and described as redox reactions? 2. What do redox reactions look like in biological systems. 3. Identify the redox partners in aerobic and anaerobic respiration and oxygenic and anoxygenic photosynthesis. 4. How is ATP generated in both substrate level and oxidative phosphorylation? 5. Why is it so important that the electron transport chain is housed in a lipid bilayer membrane? Why is a terminal electron acceptor so important? 6. What happens in a microorganism if the terminal electron acceptor of the ETC is not available? What molecules build up? What is done with these molecules? 7. Discuss the major differences between respiration and fermentation. What are the four basic kinds of fermentation?

11 chemo-: conversion of chemical E ATP iron oxidation sulfur oxidation autotrophy: chemosynthesis 2Fe 2+ 2Fe 3+ H 2 S SO 4 2- NAD + 2 H + ADP + P NAD + 2 H + ETC ADP + P ETC NADH ATP NADH ATP -synthesis: carbon fixation (CO 2 organic molecule) carbon fixation heterotrophy carbon fixation heterotrophy

12 chemosynthesis: iron oxidation: Thiobacillus ferrooxidans 2Fe 2+ 2Fe 3+ NAD + 2 H + ADP + P ETC NADH ATP carbon fixation heterotrophy

13 chemosynthesis: sulfur oxidation: Sulfolobus acidocaldarius H 2 S SO 4 2- NAD + 2 H + ETC ADP + P NADH ATP carbon fixation heterotrophy

14 autotrophy: photosynthesis photo: light E chemical E light-dependent (light) reactions ATP & NAD(P)H reducing power H 2 S/H 2 O S o /O 2 (bacterio) chlorophyll oxidized (B)chlorophyll NAD(P) ADP + P ETC NAD(P)H ATP carbon fixation heterotrophy synthesis: light-independent (dark) reactions carbon fixation: piling e - onto CO 2

15 autotrophy: oxygenic photosynthesis H 2 O O 2 Chl oxidized Chl NADP ADP + P ETC NADPH ATP carbon fixation heterotrophy

16 autotrophy: anoxygenic photosynthesis H 2 S S o Bchl oxidized Bchl NAD ADP + P ETC NADH ATP carbon fixation heterotrophy

17 photosynthetic electron flow & chemiosmosis cyclic photosynthesis in the purple sulfur bacteria non-cyclic photosynthesis in the cyanobacteria Comparing Eukaryotic & Prokaryotic photosynthesis

18 microbial CO 2 fixation

19 photosynthesis compared Eukaryotes Prokaryotes Algae, Plants Cyanobacteria Green Bacteria Purple Bacteria electron donor H 2 O H 2 O or H 2 S sulfur compounds sulfur compounds O 2 production environment oxygenic aerobic oxygenic anoxygenic aerobic anaerobic CO 2 fixation Calvin-Benson Calvin-Benson anoxygenic anaerobic Reverse Citric Acid (Reverse Kreb s) Hydroxypropionate anoxygenic anaerobic Calvin-Benson

20 amphibolism & ATP

21

22 metabolic diversity: the non-sulfur purple bacteria chemoheterotrophic growth aerobic respiration fermentation photoautotrophic growth anaerobic, anoxygenic photosynthesis H 2 for e - & CO 2 for C photoheterotrophic growth anaerobic, anoxygenic photosynthesis C 6 H 6 O 4 (succinate) for both

23 metabolism & media

24 chapter 5 learning objectives 1. How is ATP generated in chemosynthesis, photosynthesis and respiration? How is the process different for each and how is it the same? 2. Discuss the redox partners of sulfur and iron oxidizing bacteria. 3. How do non-cyclic and cyclic photosynthesis differ? How does each produce ATP and NADPH/NADH, what is each used for? 4. How is carbon fixed during chemosynthesis and photosynthesis? How is the process similar and how is it different? 5. How do amphibolism, catabolism and anabolism relate to growth and repair in cells?