BACTERIAL METABOLISM

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Bacterial metabolism

Metabolism:

Metabolism Foods we eat consists of many types of compounds. Mostly Carbohydrates, Lipids and Proteins. All of them can serve as fuel for our bodies when run through their catabolic pathways. Even though there are different pathways to begin the breakdown of different compounds, all of them converge to one common catabolic pathway. The whole purpose of the catabolic pathway is to convert the chemical energy in foods to molecules of ATP.

Stages of Metabolism:

Stages of Metabolism Catabolic reactions are organized as - Stage 1: Digestion and hydrolysis breaks down large molecules to smaller ones that enter the bloodstream. Stage 2: Degradation break down molecules to two- and three-carbon compounds. Stage 3: Oxidation of small molecules in the citric acid cycle and electron transport provides ATP energy.

Metabolism:

Metabolism Catabolism  Energy Anabolism  Synthesis Energy released in catabolic reactions is trapped in 1) Phosphate bonds 2) Electrons

Metabolic pathways: Network of interconnected chemical reactions:

Metabolic pathways: Network of interconnected chemical reactions Circular pathway Branched pathway Linear pathway

Control of Metabolic Pathways:

Control of Metabolic Pathways Enzyme concentration (already covered) Enzyme modulators - Feedback- or end product inhibition - Hormones - Other signaling molecules Different enzymes for reversible reactions Enzyme isolation Energy availability (ratio of ADP to ATP)

Catabolic Pathways: ATP-Regeneration:

Catabolic Pathways: ATP -Regeneration Amount of ATP produced reflects on usefulness of metabolic pathways: Aerobic pathways Anaerobic pathways Different biomolecules enter pathway at different points

Glycolysis:

Glycolysis From 1 glucose (6 carbons) to 2 pyruvate (3 carbons) molecules Main catabolic pathway of cytoplasm Does not require O2  common for (an)aerobic catabolism Starts with phosphorylation of Glucose to Glucose 6-P (“Before doubling your money you first have to invest!”)

The Steps of Glycolysis:

The Steps of Glycolysis Net gain?

Pyruvate has 2 Possible Fates: :

Pyruvate has 2 Possible Fates: Anaerobic catabolism: Pyruvate Lactate Aerobic catabolism: Pyruvate Citric Acid Cycle

Citric Acid Cycle:

Citric Acid Cycle Other names ? Takes place in ? Energy Produced: 1 ATP 3 NADH 1 FADH2 Waste – 2 CO2 Electron transport System

Energy Yield of Krebs Cycle:

Energy Yield of Krebs Cycle NADH NADH NADH FADH 2

Final step: Electron Transport System :

Final step : Electron Transport System Chemiosmotic theory / oxidative phosphorylation Transfers energy from NADH and FADH2 to ATP (via e- donation and H+ transport) Mechanism: Energy released by movement of e- through transport system is stored temporarily in H+ gradient NADH produces a maximum of 2.5 ATP FADH2 produces a maximum of 1.5 ATP 1 ATP formed per 3H+ shuttled through ATP Synthase

Summary of CHO catabolism:

Summary of CHO catabolism Cellular Respiration Maximum potential yield for aerobic glucose metabolism: 30-32 ATP synthesized from ADP H 2 O is a byproduct

Important Consequences of Bacterial Metabolism:

Important Consequences of Bacterial Metabolism Beer, wine, and other alcoholic beverages. Bread (all of above are mostly products of the yeast Saccharomyces cerevisiae ). Products of lactic-acid bacteria (LAB) including sour milks, various cheeses, half-sour pickles, sauerkraut, etc. (e.g., of Lactococcus spp. & Lactobacillus spp.). Organic solvents including acetone (product of Clostridium acetobutylicum ) , butanol (ditto), and, of course, ethanol (product of S. cerevisiae ). Acetic acid (vinegar). Biochemical identification of bacterial species. Unique (e.g., not found in animals) targets for antimicrobial action. Disease (e.g., dental caries).

The Hexose Monophosphate (HM) Pathway (also known as oxidative pentose, OM, or pentose phosphate pathway) :

The Hexose Monophosphate (HM) Pathway (also known as oxidative pentose, OM, or pentose phosphate pathway) It provides all the key intermediates not provided by the EM pathway.

The Entner-Doudoroff Pathway:

The Entner-Doudoroff Pathway It may be considered an alternate hexose monophsphate pathway. It provides a minimum of five of the critical biosynthetic intermediates: glucose-6-P triose phosphate 3-phosphoglycerate phosphoenol pyruvate (PEP) pyruvate

The Entner-Doudoroff Pathway:

The Entner-Doudoroff Pathway It begins the same as the HM pathway up to phosphogluconic acid. Then, instead of being converted to pentose and carbon dioxide, it is dehydrated yielding 2-keto-3, dehydro, 6 phosphogluconic acid. pyruvate Glyceraldehyde-3-P The top half of the molecule of glucose

The Entner-Doudoroff Pathway:

The Entner-Doudoroff Pathway Both the EM and the ED pathway convert a glucose molecule to two molecules of pyruvate. pyruvate Glyceraldehyde-3-P The top half of the molecule of glucose In the EM pathway, pyruvate arises by the intermediate formation of glyceraldehyde-3-P. In the ED pathway, from the top half of the molecule of glucose.

THE BASICS OF PHOTOSYNTHESIS:

Almost all plants are photosynthetic autotrophs, as are some bacteria and protists THE BASICS OF PHOTOSYNTHESIS Autotrophs generate their own organic matter through photosynthesis Sunlight energy is transformed to energy stored in the form of chemical bonds (a) Mosses, ferns, and flowering plants (b) Kelp (c) Euglena (d) Cyanobacteria

WHY ARE PLANTS GREEN? :

WHY ARE PLANTS GREEN? Plant Cells have Green Chloroplasts The thylakoid membrane of the chloroplast is impregnated with photosynthetic pigments (i.e., chlorophylls, carotenoids).

AN OVERVIEW OF PHOTOSYNTHESIS:

AN OVERVIEW OF PHOTOSYNTHESIS Photosynthesis is the process by which autotrophic organisms use light energy to make sugar and oxygen gas from carbon dioxide and water

AN OVERVIEW OF PHOTOSYNTHESIS:

AN OVERVIEW OF PHOTOSYNTHESIS Chloroplast ADP + P NADP  Light reactions Calvin cycle Light The light reactions convert solar energy to chemical energy Produce ATP & NADPH The Calvin cycle makes sugar from carbon dioxide ATP generated by the light reactions provides the energy for sugar synthesis The NADPH produced by the light reactions provides the electrons for the reduction of carbon dioxide to glucose

Light Reactions:

Light Reactions Two electron pathways operate in the thylakoid membrane: the noncyclic pathway and the cyclic pathway. Both pathways produce ATP; only the noncyclic pathway also produces NADPH. ATP production during photosynthesis is called photophosphorylation ; therefore these pathways are also known as cyclic and noncyclic photophosphorylation .

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Takes place in thylakoid membrane Uses two photosystems, PS-I and PS-II (consists of pigment complexes) PS II captures light energy Causes an electron to be ejected from the reaction center (chlorophyll a ) Electron travels down electron transport chain to PS I Replaced with an electron from water causes H + to concentrate in thylakoid chambers causes ATP production PS I captures light energy (electrons and H) Transferred permanently to a molecule of NADP + Causes NADPH production Light Reactions: The Noncyclic Electron Pathway

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Light Reactions: Noncyclic Electron Pathway

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Uses only photosystem I (PS-I) Begins when PS I complex absorbs solar energy Electron ejected from reaction center Travels down electron transport chain Causes H + to concentrate in thylakoid chambers Which causes ATP production Electron returns to PS-I (cyclic) Pathway only results in ATP production Light Reactions: The Cyclic Electron Pathway

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Light Reactions: Cyclic Electron Pathway

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Thylakoid space acts as a reservoir for hydrogen ions (H + ) Each time water is oxidized, two H + remain in the thylakoid space Electrons yield energy Used to pump H + across thylakoid membrane Move H + from stroma into the thylakoid space Flow of H + back across thylakoid membrane Energizes ATP synthase Enzymatically produces ATP from ADP + P This method of producing ATP is called chemiosmosis. ATP Production

Calvin Cycle Reactions: Carbon Dioxide Fixation:

36 Calvin Cycle Reactions: Carbon Dioxide Fixation CO 2 is attached to 5-carbon RuBP molecule Result in a 6-carbon molecule This splits into two 3-carbon molecules (3PG) Reaction accelerated by RuBP Carboxylase (Rubisco) CO 2 now “fixed” because it is part of a carbohydrate

Calvin Cycle Reactions: Carbon Dioxide Reduction:

37 Calvin Cycle Reactions: Carbon Dioxide Reduction 3PG reduced to BPG BPG then reduced to G3P Utilizes NADPH and some ATP produced in light reactions

Calvin Cycle Reactions: Regeneration of RuBP:

38 Calvin Cycle Reactions: Regeneration of RuBP RuBP used in CO 2 fixation must be replaced Every three turns of Calvin Cycle, Five G3P (a 3-carbon molecule) used To remake three RuBP (a 5-carbon molecule)

The Calvin Cycle: Fixation of CO2:

39 The Calvin Cycle: Fixation of CO 2

Importance of Calvin Cycle:

40 Importance of Calvin Cycle G3P (glyceraldehyde-3-phosphate) can be converted to many other molecules The hydrocarbon skeleton of G3P can form Fatty acids and glycerol to make plant oils Glucose phosphate (simple sugar) Fructose (which with glucose = sucrose) Starch and cellulose Amino acids

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In C 3 plants , the Calvin cycle fixes CO 2 directly; the first molecule following CO 2 fixation is 3PG. In hot weather, stomata close to save water; CO 2 concentration decreases in leaves; O 2 increases. O 2 combines with RuBP instead of CO 2 This is called photorespiration since oxygen is taken up and CO 2 is produced; this produces less 3PG. Most plants are C 3 plants

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In a C 3 plant, mesophyll cells contain well‑formed chloroplasts , arranged in parallel layers. In C 4 plants, bundle sheath cells as well as the mesophyll cells contain chloroplasts. In C 4 leaf, mesophyll cells are arranged concentrically around the bundle sheath cells. C 4 Photosynthesis

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Remember C 3 plants use RuBP carboxylase to fix CO 2 to RuBP in mesophyll; the first detected molecule is 3PG. C 4 plants use the enzyme PEP carboxylase (PEPCase) to fix CO 2 to PEP (phosphoenolpyruvate, a C 3 molecule); the end product is oxaloacetate (a C 4 molecule). In C 4 plants, CO 2 is taken up in mesophyll cells and malate, a reduced form of oxaloacetate, is pumped into the bundle‑sheath cells; here CO 2 enters Calvin cycle. In hot, dry climates, net photosynthetic rate of C 4 plants (e.g., corn) is 2–3 times that of C 3 plants. Photorespiration does not occur in C 4 leaves because PEP does not combine with O 2 ; even when stomata are closed, CO 2 is delivered to the Calvin cycle in bundle sheath cells. C 4 plants have advantage over C 3 plants in hot and dry weather because photorespiration does not occur; e.g., bluegrass (C 3 ) dominates lawns in early summer, whereas crabgrass (C 4 ) takes over in the hot midsummer. C 4 Photosynthesis

Bacterial photosynthesis:

Bacterial photosynthesis It is similar to green plants in cyanobacteria , and accessory pigments is phycobilins. In purple photosynthetic bacteria have only a single photosystem reaction center. Electron donor is hydrogen sulfide and electron acceptor is NAD + .

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It's not that easy bein' green… but it is essential for life on earth! THANK YOU