CH 11 microbial metabolism Flashcards
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
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)
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
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
5
Q
CH 11
Electron carriers
A
NAD+/NADH, FAD/FADH2, Coenzyme Q, Cytochrome: Heme,
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
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
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
9
Q
CH 11
Cytochrome Heme Proteins
A
Electron carrier, with iron alternating between Fe2+ and Fe3-
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
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
12
Q
CH 11
Energy Source
A
- Phototroph–use light as E source
- Chemotroph–obtain E through the oxidation of organic/inorganic compounds
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
14
Q
CH 11
photolithoautotrophs
A
-use CO2 and inorganic chemicals for C, light for E, inorganic e- donor
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
16
Q
CH 11
photoorganoheterotrophs
A
- E from light, sugar for C source, sugars for e-
- purple sulfur bacteria
17
Q
CH 11
chemoorganoheterotroph
A
-sugars for C, E, and e- source
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)
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
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.
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
# CH 11
About the Tricarboxylic Acid Cycle
- 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
# CH 11
Electron Transport Chain
-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
# CH 11
Iron Sulfur Centers
* 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
# CH 11
Bacterial ETC
- 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
# CH 11
BD pathway v. BO pathway
-bacterial ETC
BD: low O2 concentration, 2H+ pumped
BO: greater O2 concentration, 4H+ pumped
30
# CH 11
Oxidative phosphorylation
- 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
# CH 11
Proton Motive Force
- 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
# CH 11
ATP synthase
- 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
# CH 11
Maximum ATP yield (chemoorganotrophs, eukary.)
- 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
# CH 11
Anaerobic Respiration
- 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
# CH 11
Denitrification
- Process converting nitrate to N2 gas
- Paracoccus denitrificans, Pseudomonas species, Bacillus species
-will perform aerobic respiration if O2 is available
(faculative anaerobes)
36
# CH 11
Methanogens (archaea)
- obligate anaerobes
| - reduce carbonate or CO2 to methane
37
# CH 11
Sulfur reducers
- obligate anaerobes
- Desulfovibrio an Desulfurmonas
-reduce sulfate to sulfide
38
# CH 11
Fermentation
- 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
# CH 11
Catabolism of Carbohydrates
- 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
# CH 11
Catabolism of Lipids
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
# CH 11
Catabolism of Proteins
- 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
# CH 11
Chemolithotrophs
- 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
# CH 11
Hydrogen-Oxidizing Bacteria
- 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
# CH 11
Nitrifying bacteria
- 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
# CH 11
Sulfur-Oxidizing bacteria
- 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
# CH 11
reverse electron flow
- 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
# CH 11
phototrophy
- 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
# CH 11
Oxygenic photosyn.
- 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
# CH 11
Photosystems
- 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
# CH 11
Anoxygenic photosynthesis
- 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
# CH 11
Rhodopsin-based phototrophy
- light E cause membrane protein archaeorhodopsin to transport protons across the membrane
- pmf is used to syn. ATP
-does not involve ETC
