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Microbiology Lecture > chapter 11 > Flashcards

chapter 11 Flashcards

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1
Q

Fueling Reactions

A

Despite diversity of energy, electron, and carbon sources used by organisms, they all have the same basic needs
ATP as an energy currency
Reducing power to supply electrons for chemical reactions
Precursor metabolites for biosynthesis

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2
Q

Chemoorganotrophic Metabolism

A

the complete or incomplete oxidation of an organic compound (ie, Glucose) with the subsequent release of energy
Use of organic molecules as energy, carbon and electron source.
Three known chemoheterotrophic processes in nature
aerobic cellular respiration
anaerobic cellular respiration
fermentation

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3
Q

Cellular Respiration

A

A complete oxidation of glucose (or other organic molecule) all the way to 6 carbon dioxides (inorganic carbon - no organic molecule left) which uses an electron transport chain and an exogenous final electron acceptor of some type (oxygen or other molecule)
As electrons pass through the electron transport chain to the final electron acceptor, a proton motive force (PMF) is generated and used to synthesize ATP by means of ATPsynthases

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4
Q

aerobic cellular respiration

A

final electron acceptor is always oxygen

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5
Q

anaerobic cellular respiration

A

Final electron acceptor is never oxygen
final electron acceptor is a different exogenous acceptor such as
NO3-, SO42-, CO2, Fe3+, or SeO42-
organic acceptors may also be used

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6
Q

Fermentation

A

Incomplete oxidation of organic molecule where end products are organic acids or alchohols
Uses an endogenous electron acceptor
usually an intermediate of the pathway used to oxidize the organic energy source e.g., pyruvate
Does not involve the use of an electron transport chain nor the generation of a proton motive force
ATP synthesized only by substrate-level phosphorylation

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7
Q

catabolic pathways

A

Enzyme catalyzed reactions whereby the product of one reaction serves as the substrate for the next
Pathways also provide materials for biosynthesis
Amphibolic pathways

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8
Q

amphibolic pathways

A 
Function both as catabolic and anabolic pathways
Important ones
Embden-Meyerhof pathway
pentose phosphate pathway
tricarboxylic acid (TCA) cycle
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9
Q

aerobic cellular resp

A

Process that can completely catabolizes and oxidizes an organic energy source to CO2 using
glycolytic pathways (glycolysis) or other
TCA cycle or other
electron transport chain with oxygen as the final electron acceptor
Produces ATP, and high energy electron carriers (i.e., NADH

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10
Q

glycolysis

A

breakdown of 6 carbon glucose to two molecules of pyruvate (which have 3 carbons each); 4 ATP produced – 2 ATP consumed - 2 ATP net yield; 2 NAD-H produced (in cytoplasm in prokaryotes and eukaryotes)

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11
Q

formations of acetyl CoA

A

removal of 1 carbon dioxide from pyruvate to form 2 carbon acetyl group; 2 carbon acetyl group combines with coenzyme A; 2 NAD-H produced

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12
Q

citric acid cycle (kreb’s cycle0

A

2 carbon acetyl group completely oxidized to carbon dioxide; 2 GTP produced (converted to 2 ATP); 6 NAD-H produced; 2 FAD-H produced

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13
Q

etc- oxidative phosphorylations (chemiosmosis)

A

– energy contained in NAD-H and FAD-H released during electron transport; some of this energy then used to drive ATPases to make ATP during oxidative phosphorylation

= a series of e- carriers, operating together to transfer e- from NADH and FADH2 to a terminal e- acceptor, O2
E- flow from carriers with more negative reduction potentials (E0) to carriers with more positive E0

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14
Q

The Embden-Meyerhof Pathway

A

Occurs in cytoplasmic matrix of most eukaryotic microorganisms, plants, and animals, abd along inner cell membrane in prokaryotes
The most common pathway for glucose degradation to pyruvate in aerobic respiration, anaerobic respiration and fermentation
Function in presence or absence of O2

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15
Q

The Entner-Duodoroff Pathway

A

Used by soil bacteria and a few gram-negative bacteria
Replaces the first phase of the Embden-Meyerhof pathway

Yield per glucose molecule:
1 ATP
1 NADPH
1 NADH

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16
Q

The Pentose Phosphate Pathway

A 
Also called hexose monophosphate pathway
Can operate at same time as glycolytic pathway or Entner-Duodoroff pathway
Can operate aerobically or anaerobically
An amphibolic pathway
Used by many microorganisms
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17
Q

Forming Acetyl CoA-Oxidation of Pyruvate

A

In aerobic respiration, the 3 carbon pyruvate molecule is next converted to the two carbon acetyl group by the removal of a carbon dioxide; the acetyl group then combines with coenzyme A to make acetyl-CoA; 1 NAD-H is also made per pyruvate
The acetyl group then enters the Citric Acid Cycle (CAC);here it is completely oxidized to CO2

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18
Q

Tricarboxylic Acid Cycle

A

Also called citric acid cycle and Kreb’s cycle
Common in aerobic bacteria, free-living protozoa, most algae, and fungi
A major role is as a source of carbon skeletons for use in biosynthesis and energy metabolism

2 molecules of CO2
3 molecules of NADH
one FADH2
one GTP

19
Q

Paracoccus denitrificans

A

Facultative, soil bacterium
Extremely versatile metabolically
Under oxic conditions, uses aerobic respiration
similar electron carriers and transport mechanism as mitochondria
protons transported to periplasmic space rather than inner mitochondrial membrane
can use one carbon molecules instead of glucose

20
Q

oxidative phosphorylation

A

Process by which ATP is synthesized as the result of electron transport driven by the oxidation of a chemical energy source (organic or inorganic)

21
Q

ATP yield during aerobic respiration

A

Maximum ATP yield can be calculated
includes P/O ratios of NADH and FADH2
ATP produced by substrate level phosphorylation
The theoretical maximum total yield of ATP during aerobic respiration is 38
the actual number closer to 30 than 38

The theoretical maximum total yield of ATP during aerobic respiration is 36 in a eukaryote and 38 in a prokaryote
Actual yield in each is much lower
About 30 in eukaryotes (proton leakage) and 16-28 in prokaryotes (see next slide

22
Q

Methanogenesis

A

Methanogens use CO2 as a final electron acceptor and reduce it to CH4 (methane) in a series of reactions
Source of electrons is organic compound or inorganic compound

23
Q

Carbohydrates

A

Monosaccharides
converted to other sugars that enter glycolytic pathway
Disaccharides and polysaccharides
cleaved by hydrolases or phosphorylases

24
Q

lipid catabolism

A

Triglycerides
common energy sources
hydrolyzed to glycerol and fatty acids by lipases
glycerol degraded via glycolytic pathway
fatty acids often oxidized via β-oxidation pathway

25
Q

protein and amino acid catabolism

A

Protease: hydrolyzes protein to amino acids
Deamination: removal of amino group from amino acid
resulting organic acids converted to pyruvate, acetyl-CoA, or TCA cycle intermediate
can be oxidized via TCA cycle
can be used for biosynthesis
can occur through transamination

26
Q

Chemolithotrophs

A

organisms that obtain energy and electrons from the oxidation of reduced inorganic compounds
Many sources of reduced inorganic molecules exist in the environment
The oxidation of different reduced inorganic compounds yields varying amounts of energy

27
Q

92- hydrogen oxidation

A

Hydrogen oxidizing bacteria (hydrogen oxidizers)
Oxidize H2 to release energy and electrons
H2 oxidizing Bacteria and Archaea are known
Found deep in earth; deep under sea
Catalyzed by hydrogenase – separates electrons and protons
Electron transport chain often has oxygen as the final electron acceptor
Often facultative
Organic molecules made from CO2 by Calvin Cycle
But, in the presence of organic compounds such as glucose, synthesis of Calvin cycle and hydrogenase enzymes is repressed

28
Q

Sulfur oxidizing bacteria

A

Sulfur or sulfur oxidizing bacteria
Many reduced sulfur compounds are used as electron donors
H2S, S0, S2O3- are commonly used; end products are more oxidized forms of sulfur (SO42- is the most oxidized)
One product of sulfur oxidation is H+, which results in a lowering of the pH of its surroundings
Usually aerobic (use O2 as final electron acceptor), but some organisms can use nitrate as an electron acceptor
Play role in sulfur cycle

29
Q

nitrogen oxidation-nitrification

A

NH3, NH4, and NO2- are oxidized by nitrifying bacteria during the process of nitrification
Two groups of bacteria work in concert to fully oxidize ammonia to nitrate
Genera: Nitrosomonas (NH3 > NO2) & Nitrobacter (NO2>NO3)
Only small energy yields from this reaction
Growth of nitrifying bacteria is very slow

30
Q

Reverse electron flow by chemolithotrophs

A

Calvin cycle requires NAD(P)H as e- source for fixing CO2
many energy sources used by chemolithotrophs have E0 more positive than NAD+(P)/NAD(P)H
use reverse electron flow to generate NAD(P)H

31
Q

Photoautotrophic metabolism

A

Photoautotrophs use energy from the sun and electrons from an inorganic molecule
Photoautotrophs synthesize organic molecules from CO2 by a series or reactions called the Calvin Cycle during the overall process of photosynthesis
Overall, two important things happen during photosynthesis:
Light energy is converted to chemical bond energy in the organic molecules synthesized
CO2 is reduced to organic C6H12O6 (carbon fixation); this brings carbon into ecosystems
The reactions of photosynthesis are divided into two phases:
The Light reactions happen during the day; ATP and NADP-H (reducing power) are made
The Dark reactions (aka, light-independent) usually happen at night; this is when CO2 is reduced to organic C6H12O6

32
Q

Photosynthetic Pigments

A

Photosynthetic pigments capture light energy
Pigments absorb some wavelengths of light and reflect others
The color you perceive is the reflected wavelength
Organisms must produce some form of chlorophyll (or bacteriochlorophyll) to be photosynthetic
Chlorophyll is a porphyrin
Number of different types of chlorophyll exist
Different chlorophylls have different absorption spectra
Chlorophyll pigments are located within special membranes
In eukaryotes, called thylakoids
In prokaryotes, pigments are integrated into cytoplasmic membrane or in internal structures called chlorosomes

33
Q

Chlorophylls

A

major light-absorbing pigments

different chlorophylls have different absorption peaks

34
Q

Accessory pigments

A

transfer light energy to chlorophylls
e.g., carotenoids and phycobiliproteins
accessory pigments absorb different wavelengths of light than chlorophylls

35
Q

Antenna pigments

A

highly organized arrays of chlorophylls and accessory pigments
captured light energy and transfer it to a special reaction-center chlorophyll
directly involved in photosynthetic electron transport

36
Q

photosystems

A

groups of pigments and some enzymes involved in capturing light energy
Anoxygenic photosynthesis has 1 photosystem; oxygenic photosynthesis has 2 photosystems

37
Q

Reaction centers

A

participate directly in the conversion of light energy to ATP
Certain atoms in reaction center have one or more electrons raised from the ground state to an excited state; this is a conversion of light energy to a type of electrical energy (movement of electrons)
Electrons then travel down electron transport systems

38
Q

antenna pigments

A

funnel light energy to reaction centers

39
Q

chlorosomes

A 
function as massive antenna complexes
Found in green sulfur bacteria
40
Q

light reactions

A

The light reactions occur only when light is shining. During these reactions, ATP and NADP-H (reducing power) are made. It takes 18 ATP and 12 NADP-H + 6 CO2 to make 1 molecule of glucose.
In anoxygenic photosynthesis, electrons to reduce NADP+ to NADP-H come from an inorganic source other than H2O (ie, H2S, S)
In oxygenic photosynthesis, electrons to reduce NADP+ to NADP-H come from water. Water is split by light into electrons, protons and O2 in a process called photolysis.
In both anoxygenic and oxygenic photosynthesis, ATP is made by ATPases during electron transport. Because the source of energy to make ATP is light we call this photophosphorylation

41
Q

anoxygenic photosynthesis

A

Anoxygenic photosynthesis occurs in at least three phyla of Bacteria (phototrophic green bacteria, phototrophic purple bacteria, and heliobacteria)
Electron transport reactions occur in the reaction center of anoxygenic phototrophs; there is only 1 photosystem
Reducing power for CO2 fixation comes from reductants present in the environment (i.e., H2S, Fe2+, or NO2-)
Requires reverse electron flow to energize electrons to reduce NADP+ to NADP-H

42
Q

oxygenic photosynthesis

A

Oxygenic phototrophs use light energy to generate ATP and NADPH in two photosystems:
The two light reactions are called photosystem I and photosystem II
Photosystem I make NADP-H; Photosystem II makes ATP
Z scheme” of photosynthesis
Photosystem II transfers energy to photosystem I
ATP can also be produced by cyclic photophosphorylation

43
Q

carbon fixation

A

The reduction of carbon dioxide to organic carbon most commonly happens in a series of reactions called the Calvin cycle.
This is the most common means of carbon fixation for both phototrophs and chemolithotrophs
This process is discussed in Ch. 12

Microbiology Lecture (11 decks)

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