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MicroBiology > CH 11 microbial metabolism > Flashcards

CH 11 microbial metabolism Flashcards

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1
Q

CH 11

Metabolism

A
  • Catabolic rxns–break down complex molecules to simpler compounds, release E, supply e- (reducing power), provide materials for biosyn. (recycle)
  • anabolic rxns–build complex molecules from simpler compounds, uses E
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2
Q

CH 11

ATP: Energy Currency

A
  • ATP is formed as a result of catabolic rxns
  • ATP is used to drive anabolic rxns
  • Has high E phosphate bounds, transfers phosphate to other molecules (high group transfer potential)
  • Syn. by phosphorylation of ADP (AMP signals E defecit, produce more ATP)–substrate-level phosphorylation, oxidative phosphorylation (respiration), photophosphoylation (photosynthesis)
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3
Q

CH 11

Oxidation-Reduction rxns

A

Oxidation
Reduction

Coupled reactions

  • Reduction potential–measure of the tendency to lose e-, more negative more likely to lose e-, more + more likely to take e-
  • as e- move from donors to acceptors, E is released–syn. ATP, do work
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4
Q

CH 11

Electron Transport Chain

A
  • Glucose transfers e- to NAD+ to form NADH
  • NADH transfers e- to O2
  • e- pass though a series of electron carriers in ETC
  • each carrier has a slightly less negative red. pot. then previous
  • E is released and used to make ATP
  • ETC important in cellular E conservation
  • prokaryotes–found in plasma membrane and internal membranes
  • eukaryotes–found in mitochondrial cristae andchloroplast thylakoid membranes
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5
Q

CH 11

Electron carriers

A

NAD+/NADH, FAD/FADH2, Coenzyme Q, Cytochrome: Heme,

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6
Q

CH 11

NADH

A
  • the reduced form (carries electrons) of NAD + (nicotinaminde adenine dinucleotide). this is the most common electron carrier in cellular respiration
  • E as excited e- –stores high E e-, favorable e- donor, “reducing equivs”

-makes 3 ATP

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7
Q

CH 11

FADH2

A
  • flavin adenine dinucleotide; active carrier produced by citric acid cycle; donates electrons
  • E carrying, substrate for ox. phos. in mito.
  • coenzyme, e- carrier, transfers e- from Krebs cycle to ETC at a lower E level
  • makes 1.5 ATP
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8
Q

CH 11

Coenzyme Q

A
  • an electron carrier in the electron transport chain
  • also known as ubiquinone because it is a ubiquitous quinone
  • shuttles protons and electrons across the inner protein complexes of the mitochondrial membrane ETC
  • can transfer 1 or 2 e-, mobile within membrane
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9
Q

CH 11

Cytochrome Heme Proteins

A

Electron carrier, with iron alternating between Fe2+ and Fe3-

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10
Q

CH 11

Nutritional Types

A
  • Nutrients provide the basic materials for building biological molecules
  • source of E and e- for reducing molecules during biosyn.
  • microorgs. are categorized based on their C, E, and e- sources
  • nearly all pathogenic mircobes are chemoorganoheterotrophes
  • some microbes are able to alter their metabolism in response to environmental conditions
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11
Q

CH 11

Carbon Source

A
  • Autotrophs–use inorganic C, usually CO2, as sole source of C–Methanotrophs can use CH4
  • Heterotrophs–require an organic carbon source (sugar), cannot use CO2
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12
Q

CH 11

Energy Source

A
  • Phototroph–use light as E source

- Chemotroph–obtain E through the oxidation of organic/inorganic compounds

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13
Q

CH 11

Electron source

A
  • Lithotroph–uses inorganic substances as e- source (Fe+2–>Fe+3)
  • organotroph–uses organic compounds as an e- source
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14
Q

CH 11

photolithoautotrophs

A

-use CO2 and inorganic chemicals for C, light for E, inorganic e- donor

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15
Q

CH 11

chemolithoautotrph

A
  • fix CO2 as C source, organic chemicals as E source, e- donor from inorganic source
  • deep sea vent bacteria
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16
Q

CH 11

photoorganoheterotrophs

A
  • E from light, sugar for C source, sugars for e-

- purple sulfur bacteria

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17
Q

CH 11

chemoorganoheterotroph

A

-sugars for C, E, and e- source

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18
Q

CH 11

Chemoorganotrophs

A
  • Use a wide variety of organic molecules as C/E/e- source–proteins, polysaccs, lipids
  • Broken down into subunits and converted to glucose or intermediate metabolite
  • allows the cell to maintain minimal machinery while being able to utilize many diff nutrients
  • sugars for C, E, and e- source
  • glycolysis, TCA, oxid. phos. and ETC, O2 as e- acceptor (aerboes)
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19
Q

CH 11

Glycolysis

A
  • Breaks down glucose to pyruvate
  • Embden-Meyerhof pahtway
  • Pentose-phosphate pahtway
  • entner-doudoroff pathway
  • reactions occur in cytosol and metabolite intermediates can be shuffled from one pathway to another
  • need to be able to summarize: starting points, products, critical/unique enzymes involved, ATP yields, metabolic roles of each pathway
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20
Q

CH 11

Embden-Meyerhof

A
  • Most common pathway
  • produces several precuroser molecules for biosyn pathways
  • divided into 6 C phase and 3 C phase
  • requires input of 2 ATP
  • each glucose produces–Net 2 ATP by sub. level phos., 2 molecules of pyruvate –>TCA, 2 molecules of NADH –> syn. ATP by oxid. phos.
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21
Q

CH 11

Pentose Phosphate Pathway

A
  • primary function is to generate NADPH–source of e- for reducing molecules during biosyn.
  • provides precursors for biosyn.–aromatic AA and NA
  • intermediates can enter EMP
  • Starts with G-6-P from EMP or group translocation
  • 2 key enzymes–transaldolase and transketolase
  • products cycle back through pathway until G-6-P completely broken down into CO2
  • Net yield from 3 G-6-P: 6 NADPH, 2 fructose-6-P, Glyceraldehyde-3-P–> pyruvate by EMP
22
Q

CH 11

NADH vs. NADPH

A
  • NADH–for ATP

- NADPH–for biosyn.

23
Q

CH 11

Entner-Doudoroff Pathway

A
  • Found in some soil bacteria and a few other gram neg.
  • one key enzyme is KDPG aldolase–converts 2-keto-3-deoxy-6-phosphoglucanate to pyruvate and glyceraldehyde-3-P
  • Glyceraldehye-3-P enters EMP to form pyruvate
  • Net yield: 1 ATP, 1 NADH, 1 NADPH per glucose
24
Q

CH 11

Tricarboxylic Acid Cycle

A
  • Oxidizes pyruvate to 3 CO2
  • also called Kreb’s cycle or TCA
  • First step uses a multienzyme complex (pyruvate dehydrogenase comples) to convert pyruvate to Acetyl CoA + NADH + CO2
  • Acetyl CoA enters the TCA and is borken down to CO2 through a series of redox rxns
  • net yield: 4 NADH, 1 FADH2, ! GTP
25
Q

CH 11

About the Tricarboxylic Acid Cycle

A
  • Considered a cycle bc one of starting products is regenerated in the process (oxaloacetate)
  • CoA (cofactor) is added at 2 points bc it provides a high E thiol linkage that makes next rxn energetically favorable
  • some microbes lack complete TCA, but contain most of the components
26
Q

CH 11

Electron Transport Chain

A

-electrons are transferred from NADH and FADH2 to O2 through a series of e- carriers-Eurkary. ETC in inner mito membrane–4 protein complexes connected by cyto. C and CoQ
(in plasma membrane of prokary.)
-for ever e- transfered, 10H+ tranfered out of cell (2 for complex 4)

27
Q

CH 11

Iron Sulfur Centers

A
  • Iron is NOT in a heme group.
  • The iron is linked to inorganic sulfur ions as part of the iron-sulfur center.
  • Centers contain either 2 Fe and 2 S or 4 Fe and 4 S and these are linked to the protein by cysteine residues.
  • Whether it be 2 Fe and 2 s, or 4 Fe and 4 S, the center can only accept or donate one electron
28
Q

CH 11

Bacterial ETC

A
  • within plasma membrane or internal membranes
  • e- carriers vary
  • extensively branched
  • e- can enter and exit the chain at several points
  • chain may be shorter–>release of less E
29
Q

CH 11

BD pathway v. BO pathway

A

-bacterial ETC
BD: low O2 concentration, 2H+ pumped
BO: greater O2 concentration, 4H+ pumped

30
Q

CH 11

Oxidative phosphorylation

A
  • syn. of ATP as the results of e- transport driven by the oxidation of a chemical E source
  • e- transport leads to movement of H+ across the membrane–matrix–> intermembrane space, cytoplasm–> periplasmic space (Creates proton motive force, fuels ATP synthase)
31
Q

CH 11

Proton Motive Force

A
  • charge/concentration gradient across memrane
  • used to do work when protons flow back into the cell–syn. of ATP from ADP and Pi, movement of flagella, transport of molecules across membrane
32
Q

CH 11

ATP synthase

A
  • enzyme that uses PMF to syn. ATP
  • located in plasma membrane of bacteria–cristae of eukary.

-flow of protons causes conformational changes in ATP synthase that allow binding of ADP and Pi, syn. of ATP, and release of ATP

33
Q

CH 11

Maximum ATP yield (chemoorganotrophs, eukary.)

A
  • substrate level phos. produced: 2ATP + 2GTP
  • Oxid. phos. produced: 10NADH (1NADH=2.5ATP) + 2FADH2 (1FADH2=1.5 ATO)
  • max total yield is 32 ATP
  • generally much lower in bacteria, esp. under low oxygen conditions
  • PMF used for other activities
  • intermediates removed from pathway
34
Q

CH 11

Anaerobic Respiration

A
  • Uses a molecule other than O2 as the terminal e- acceptor in the ETC
  • generally nitrate, sulfate, or CO2

-Produces less E, bc their reduction potential is less than O2

35
Q

CH 11

Denitrification

A
  • Process converting nitrate to N2 gas
  • Paracoccus denitrificans, Pseudomonas species, Bacillus species

-will perform aerobic respiration if O2 is available

(faculative anaerobes)

36
Q

CH 11

Methanogens (archaea)

A
  • obligate anaerobes

- reduce carbonate or CO2 to methane

37
Q

CH 11

Sulfur reducers

A
  • obligate anaerobes
  • Desulfovibrio an Desulfurmonas

-reduce sulfate to sulfide

38
Q

CH 11

Fermentation

A
  • Glycolysis
  • lack TCA cycle or ETC
  • ATP produced by SLP only
  • NADH produced by glycolysis reduces pyruvate or its derivative
  • acid fermentation or alcohol fermentation–mixed acid fermentation
39
Q

CH 11

Catabolism of Carbohydrates

A
  • microbes can utilize many diff carbs
  • polysaccs and disaccs are borken down to monosaccs
  • monosaccs enter glycolysis directly or are converted to G-6-P or F-6-P
  • must have right enzymes in order to convert diff carbs
40
Q

CH 11

Catabolism of Lipids

A

Triacylglycerols are hydrolyzed to glycerol and FA by lipases
-glycerol is converted to dihydroxyacetone phosphate and enters EMP

-FA are oxidized in the B-oxidation pathway to form acetyl-CoA, NADH, and FADH2 (make acetyl-CoA by cutting off 2 C’s at a time and adding CoA

41
Q

CH 11

Catabolism of Proteins

A
  • Proteins are hydrolyzed to AA that are then deaminated

- the organic acid is then converted to pyruvate, acetyl-CoA or an intermediate of the TCA cycle

42
Q

CH 11

Chemolithotrophs

A
  • obtain e- for ETCs from the oxidation of inorganic molecules, not from NADH produced by the oxidation of glucose
  • need e- for building new molecules too-molecules to donate in ETC have lower reduction potentials than NAD+/NADH, so e- start later in the ETC chain, meaning less E is released and less protons can be pumped

-mostly aerobic, so terminal e- aceptor is O2, but donors can come in lower on the chain

43
Q

CH 11

Hydrogen-Oxidizing Bacteria

A
  • Use hydrogen gas as e- donor
  • H2/2H+ has a very neg. reduction potential
  • can donate electron to ETC or to NAD+
  • alcaligenes, pseduomonas, hydrogenobacter
44
Q

CH 11

Nitrifying bacteria

A
  • nitrification–oxidize ammonia to nitrate, sewage treatment
  • nitrosomas: converts ammonia to nitrate
  • Nitrobacter: converts nitrite to nitrate
  • unuseable for of N to a useable for for humans
45
Q

CH 11

Sulfur-Oxidizing bacteria

A
  • Sulfur-oxidizing bacteria oxidize sulfur, hydrogen sulfide, thiosulfate, etc. to sulfuric acid–ecological impact (intestines–ouch!)
  • Beggiatoa, Thiobacillus, Thiomagarita

-acid limits growth of other bacteria, so no competition and can grow freely

46
Q

CH 11

reverse electron flow

A
  • both sulfur-oxidizing and nitrifying bacteria use reverse e- flow to generate NADH
  • e- can move up or down the ETC depending on cells need for NADH or ATP
  • reverse ETC requires E, gives you reducing power so can build molecules
  • e- move down the ETC and produce ATP
  • when NADH is needed, e- move up the ETC to reduce NAD+ to NADH
  • driven by the pmf
47
Q

CH 11

phototrophy

A
  • use light E to syn. ATP and reducing power
  • use the ATP and reducing power for CO2 fixation

-3 types of photorophy–oxygenic photosyn., anoxygenic photosyn., rhodopsin-based phototrophy (very diff from other two types)

48
Q

CH 11

Oxygenic photosyn.

A
  • Oxygen released
  • cholorphyll, carotenoids, and phycobiliproteins used to trap light E
  • assembled into complex networks called light harvesting antennas
  • located in the plasma membrane in bacteria
  • located in the cholorplast of eukaryotes
  • Two complexes: PSI and PSII, work in tandem
  • light E causes release of e- from PSI to e-carriers–cycle back to PSI–>ATP, reduce NADP+–>NADPH
49
Q

CH 11

Photosystems

A
  • light E causes the release of e- from PSII–pass through e-carriers to replace e- lost by PSI, generates ATP
  • water donates e- to PSII–release of Oxygen
  • ATP syn. occurs as a result of pmf
  • PSII–e- from water or excited by light, excites PSII, goes to ETC, creates pmf, makes ATP; e- can go to PSI

–PSI-e- from PSII or excited by light, cycles back to PSI to make ATP through ETC, or go to NADP+ to make NADPH, noncyclic

50
Q

CH 11

Anoxygenic photosynthesis

A
  • phototrophic green bacteria, phototrophic purple bacteria, heliobacteria
  • strict anaerobes– use a molecule other than water as an e- source, so oxygen is not produced
  • bacteriochlorophylls are the light harvesting pigments, carotenoids
  • have only one PS, cyclic e- flow–generates pmf for ATP syn, does not produce NAD(P)H
  • syn. of NAD(P)H–oxidation of H gas, reverse e- flow, pull e- from ETC at higher E state
51
Q

CH 11

Rhodopsin-based phototrophy

A
  • light E cause membrane protein archaeorhodopsin to transport protons across the membrane
  • pmf is used to syn. ATP

-does not involve ETC

MicroBiology (18 decks)

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