Flashcards with Answers on Micro Bio – Microbiology
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Overview of Microbial Metabolism
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oCells reproduce typically when doubled in size |
Enzymes
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o Temperature and pressure inside cell too low and necessitates a catalyst o Cofactors § Complex organic molecules (coenzmyes) or simple ions · Mg++ · Ca++ · Fe++ · Cu++ · Zn++ § Many derived from vitamins · NAD from niacin (Vit B12) § Role · Accept atoms or electrons · Donate atoms or electrons · Electron carriers · Ion attraction in binding substrates o Factors affecting activity § Temperature § pH § Enzyme and substrate concentrations § Inhibitors Protein portion of enzyme in inactive form is called apoenzyme and nonprotein componet (cofactor) = whole active enzyme (holoenzyme) |
Dehydrogenation Reactions |
o Oxidation-reduction reactions where 1 or 2 hydrogen atoms transferred to electron carrier like NAD+ § Oxidized substrate loses two H atoms, reducing NAD+ to NADH + H+
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Bioenergetic Fundamentals
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o Carbohydrates are primary energy source § Energy rich § Easily broken down § Other sources used o Chemical degradation of Glucose § C6H12O6 + 6 O2 à 6 H2O + 6CO2 + 686 kcal/mol o Cells oxidize glucose through metabolic pathways and trap and store energy o Three basic mechanisms § Substrate level phosphorylation § Oxidative phosphorylation § Photophosphorylation |
Substrate Level Phosphorylation |
o Energy trapped in high energy phosphate bond on substrate and then transferred to ATP o Example – Phosphoenylpyruvate o PEP + ADP à Pyruvate + ATP |
Oxidative Phosphorylation
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o Oxidation energy captured in electrons bound to electron carriers o Carriers transfer electrons through electron transport chain à proton gradient formed o Electrochemical proton gradient à ATP synthesis (chemiosmosis) o Oxygen final electron acceptor à water |
Photophosphorylation |
o Energy in light absorbed by exciting chlorophyll electrons o Electrons passed through electron transport chain which forms ATP and NADPH o Water replaces lost electrons forming oxygen o ATP and NADPH à glucose synthesis |
Carbohydrate catabolism
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o Glucose most common substrate for energy production o Microbes catabolize by § Respiration § Fermentation o Depends on metabolic capabilities and whether electron acceptor like oxygen is present o Respiration used if § Microbes have ETC and § Inorganic electron acceptor present such as O o Fermentation used if § Inorganic electron acceptor not present or § Microbes have no ETC o Initial step of both pathways glycolysis (Embden Meyerhof pathway) § Glucose à pyruvate o Pyruvate’s fate different in fermentation and respiration |
Glycolysis
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o 10 enzymatic steps to degrade glucose o glucose + 2 NAD + 2 ADP + 2 Pi à 2 pyruvate + 2 ATP + 2 NADH o Other carbs first converted to glucose, then use glycolysis o Alternatives § Some microbes degrade glucose by · Hexose Monophosphate Shunt · Enter-Doudoroff Pathway |
Respiration |
o Occurs in 3 stages (eukaryotes happens in mitochondria) § Pyruvate à acetyl-CoA · 5 steps · 3 different enzymes · 5 cofactors o Thiamine pyrophosphate o Lipoic acid o CoA o FAD o NAD § Acetyl-CoA à Krebs à CO2 and electrons on carriers · 2 Pyruvate à 6 CO2 + 8 NADH + 2 FADH2 + 2 ATP
· § ETC à ATP from chemiosmosis · Aerobic respiration: Oxygen (final electron acceptor) + electrons à water · Anaerobic respiration: inorganic molecules NO3, SO4, CO2 final electron acceptor · Membrane bound structures that accept electrons and transfer them to inorganic acceptor o Eukaryotes – inner mitochondrial wall o Prokaryotes – cytoplasmic membrane · Forms proton gradient o Eletrochemical potential called proton motive force |
Chemiosmosis
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§ Proton gradient à protons go through protein channels in ATP synthase à ADP and Pi form ATP § 34 ATP per glucose |
Summary of Aerobic Respiration
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§1 glucose ·Glycolysis à2 ATP ·Krebs cycle à2 ATP ·Chemiosmosis à34 ATP ·Total à38 ATP §Captures 40% of energy, rest heat |
· Fermentations |
o Release energy from sugar o Don’t require oxygen or ETC o Use organic molecule as final electron acceptor o Inefficient § 1 or 2 ATP per glucose due to incomplete breakdown o Two stages § Glycolysis § Pyruvate into another stable organic end product like ethanol or fatty acid o NADH must be recycled back to NAD through fermentation since there is no ETC o End products § Species always forms same end product, but products vary by species · CO2 · Propionic acid · Lactic acid · Ethanol · Acetone · Isopropanol · Acetic acid § Identification trait o Ethanol § Yeast à alcohol, bread o Lactic acid § Lactobacilli and streptococci (important in dental carries formation) à yogurt and cheddar § Muscles cramp with lactic acid when no oxygen
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Clinical correlation – Dental carries
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o Tooth composed of 95% hydroxyapatite o Dissolves at 5.5 o Plaque convert sugar to acids o Streptococci make lactic acid o 10% glucose for 1 min à pH rapidly below 5.5 within 2 min and for 22 min § Erosion reversible if infrequent
Critical pH=5.5. Tooth enamel in insoluable at neutral pH and begins to dissolve at 5.5 |
Other fermentations |
o Other products § Amino acids § Purines § Pyrimidines o Most smell bad § Carbs à fatty acids § Amino acids à amines like putracine and cadaverine and sulfur compounds o Anaerobic fermentation produces smelly (bad breath) and harmful acids § Proprionibacteria acnes on skin causes body odor § Ones in mouth can smell bad |
Other catabolic pathways |
o Other sources of energy § Proteins, Carbs, Lipids o Must be broken down to amino acids, fatty acids, nucleotides, etc outside cell to cross membrane o Microbes effect breakdown by extracellular enzymes (proteases, lipases, nucleases) that hydrolyze macromolecules § Components transferred across membrane into Glycolysis and Krebs § Secretions are virulence factors due to damage cause to host tissues · Proteases hydrolyze proteins on eukaryotic cell surfaces like adhesins and receptors · Phospholipases can hydrolyze phospholipids of membranes · Lipase and phosphatases from intracellular pathogens can interrupt intracellular pathways |
Photosynthesis
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o Basis of all life and food chains o Produces oxygen |
| Oxidation reduction rxns. |
| Cells break down reduced organic compounds and extract their stored energy primilary by carry out oxidation-reduction rxn. Oxidatioin is removal of electrons and reduction is addition |
