3/19/2009. Ch. 5 Microbial metabolism. Metabolism basics (Fig. 5.1) Basic concepts of metabolic processes. Redox reactions (Fig. 5.

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Ch. 5 Microbial metabolism Breakdown of carbohydrates, lipids and proteins to produce cellular energy (catabolism) Redox (reduction/oxidation) reactions capture, store and use energy via electron

1) Metabolism is the sum of all biochemical reactions in the cell (pathways) Catabolic pathways break down nutrients to yield smaller molecules and capture stored energy Anabolic pathways synthesize

adients Nutrients are converted to 12 basic precursors by enzymes in basic pathways (e.g.

1 Ch. 5 Microbial metabolism Breakdown of carbohydrates, lipids and proteins to produce cellular energy (catabolism) Redox (reduction/oxidation) reactions capture, store and use energy via electron transfers among molecules Photosynthesis capturesandand stores energyfrom light Biosynthesis of macromolecules and their precursors (anabolic reactions) 1 Metabolism basics (Fig. 5.1) Metabolism is the sum of all biochemical reactions in the cell (pathways) Catabolic pathways break down nutrients to yield smaller molecules and capture stored energy Anabolic pathways synthesize larger molecules from smaller precursors and use energy 2 Basic concepts of metabolic processes Cells obtain nutrients from photosynthesis and/or transport from environment Nutrients are catabolized to release and capture stored energy in form of ATP or NADH or electrochemical (chemiosmotic) gradients Nutrients are converted to 12 basic precursors by enzymes in basic pathways (e.g., glycolysis, Krebs cycle and pentose phosphate cycle) Anabolic reactions convert precursor molecules (12) into building blocks, building blocks into macromolecules (polymerization) and macromolecules into cell structures to form a new cell. 3 Redox reactions (Fig. 5.2) Fundamentally all biochemical reactions involve the transfer of electrons Reduction is the gain of electrons; oxidation is loss of electrons and these are coupled A molecule that has been reduced becomes relatively more negative, an oxidized molecules becomes relatively more positive 4 Electron carriers NAD+/NADH, NADP+/NADPH and FAD/FADH 2 are all cellular electron carriers used by cells Electrons are transferred with protons (H transferred) Many metabolic pathways require these electron carriers 5 ATP production (Fig. 5.3) Substrate level phosphorylation involve transfer of high energy phosphate to ADP from another phosphorylated organic compound Oxidative phosphorylation uses energy from high energy electron transfers during respiration to make ATP from ADP and Pi Photophosphorylation uses energy from light to make electrons high energy 6 1

2 Enzymes (Figs. 5.4, 5.5) Enzymes are usually proteins that catalyze (speed up) biochemical reactions Enzymes often require cofactors Ribozymes are enzymes made of RNA instead of protein 7 8 Enzymatic reactions (Fig. 5.7) Substrate binds to active site of enzyme Enzyme catalyzes reaction Products leave active site 9 10 Enzymatic activity (Fig. 5.8) Thermal denaturation of proteins (Fig. 5.9) 11 Increasing heat causes H bonds to break Microbes live at all temps at which liquid H 2 O is found and the optimum folding/activity of proteins coincide with optimal growth temperature ph causes charges on proteins to change, so denaturation occurs via breaking of ionic bonds 12 2

Glycolysis catabolism of glucose (Fig. 5.

13 Glycolysis is a metabolic pathway in which glucose (6C sugar) is oxidized to pyruvic acid (2x3C), producing ATP and

NADH and FADH 2 enter electron transport system and form a H+ gradient H+ gradient used to make ATP 13 14 Products of

14 2 NADH and 4 ATP produced ATP production via substrate level phosphorylations Fermentation occurs if pyruvic acid

anaerobic and yields acid bi products Substrate level phosphorylation (Fig. 5.

3 Glycolysis catabolism of glucose (Fig. 5.13) Fig Glycolysis is a metabolic pathway in which glucose (6C sugar) is oxidized to pyruvic acid (2x3C), producing ATP and NADH For aerobes, pyruvic acid further broken down via Krebs cycle to yield more NADH, FADH 2 and ATP Electrons from NADH and FADH 2 enter electron transport system and form a H+ gradient H+ gradient used to make ATP Products of glycolysis (Fig NADH and 4 ATP produced ATP production via substrate level phosphorylations Fermentation occurs if pyruvic acid does not enter the Krebs cycle and if electrons from glucose metabolism don t go down ETS Fermentation typically anaerobic and yields acid bi products Substrate level phosphorylation (Fig. 5.15) These reactions are part of glycolysis ATP only produced via this mechanism during fermentation Sufficient levels of ATP are made to allow growth of microbes Pentose phosphate pathway (Fig. 5.16) Pentose phosphate pathway (Fig. 5.16) Used in conjunction with glycolysis by most microbes Generates NADPH and precursors for making building blocks (amino acids, nucleotide sugars) Generates starting material for photosynthesis, ribulose 5 phosphate

20 19 Most of the ATP produced in microbes is produced by an electron

As electrons flow, energy is used to pump H+s out of cell Many different

21) Fermentation (Fig. 5.22 and Table 5.

especially cytochromes As concentration of H+ builds, they are forced back

acceptor, the most ATP is produced 21 Fermentation yields of ATP small

4 Krebs (aka TCA) cycle (Fig. 5.19) Respiration the electron transport system Fig Most of the ATP produced in microbes is produced by an electron transport system The system is a series of membrane bound electron carriers As electrons flow, energy is used to pump H+s out of cell Many different ETSs occur in microbes 20 ATP production during respiration (Fig. 5.21) Fermentation (Fig and Table 5.3) H+ s are pumped out as electrons pass through various carriers, especially cytochromes As concentration of H+ builds, they are forced back through membrane bound ATP synthases, making ATP When O 2 is final electron acceptor, the most ATP is produced 21 Fermentation yields of ATP small relative to respiration Fermentation of sugars quickly ikl uses up NAD+, which needs to be regenerated to keep up ATP production 22 Regenerating NAD+ Some fermentation products (Fig. 5.23) Fig

Photosynthesis overview 2 parts of photosynthesis, one lightdependent (photophosphorylation) and the other

generate ATP in a process similar to respiration The ATP from the light dependent reactions is used to

Photosystems and chlorophylls (Figs. 5.26 and 5.

molecules embedded in sea of light harvesting pigments Light energy collected and transferred to chls to

28b) ATP is generated from proton motive force generated as electrons move through ETS The final e

5 Photosynthesis overview 2 parts of photosynthesis, one lightdependent (photophosphorylation) and the other not (CO 2 fixation, Calvin Benson cycle) Photophosphorylation uses light to generate high energy e s that generate ATP in a process similar to respiration The ATP from the light dependent reactions is used to drive the reduction of CO 2 to form 6C sugars from 5C sugars CO 2 fixation also requires NADPH 25 Photosystems and chlorophylls (Figs and 5.27) Photosystems are found on special membranes called thylakoids Photosystems contain chlorophyll molecules embedded in sea of light harvesting pigments Light energy collected and transferred to chls to acctivate electrons High energy e s transferred from chls through ETS tp produce H+ grad and then ATP 26 Cyclic photophosphorylation (Fig. 5.28a) Non cyclic photophosphorylation (Fig. 5.28b) ATP is generated from proton motive force generated as electrons move through ETS The final e acceptor is the initial donor in a cycle The NADPH needed for CO 2 fixation must come from somewhere else 27 2 light dependent steps are needed to elevate low energy e s from H 2 O to high enough level to generate PMF and generate ATP + NADPH O 2 is the biproduct when H 2 O is e donor 28 Table 5.5 Calvin cycle (Fig. 5.29)

6 Calvin Benson cycle Uses RuBisCo to generate 2 x 3C molecules per each CO 2 molecule added to the 5C, ribulose bisphosphate Cycle requires 3ATP and 2 NADPH for each CO 2 fixed (and reduced) Energy from the ATP and NADH is stored and can later be recovered from the sugars produced G3P feeds directly into glycolysis

7/5/2014. Microbial. Metabolism. Basic Chemical Reactions Underlying. Metabolism. Metabolism: Overview

7/5/2014. Microbial. Metabolism. Basic Chemical Reactions Underlying. Metabolism. Metabolism: Overview PowerPoint Lecture Presentations prepared by Mindy Miller-Kittrell, North Carolina State University Basic Chemical Reactions Underlying Metabolism Metabolism C H A P T E R 5 Microbial Metabolism Collection