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Microbiology Exam 2 > Exam 2 > Flashcards

Exam 2 Flashcards

1
Q

What are biofilms?

A
  • common in nature
  • Most microbes grow attached to surfaces (sessile) rather than free floating (planktonic)
  • These attached microbes are members of complex, slime enclosed communities called a biofilm
  • Biofilms are ubiquitous in nature in water
  • Can be formed on any conditioned surface
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2
Q

How do biofilms form?

A
  • Microbes reversibly attach to conditioned surface and release a slimy matrix made up of various polymers, depending on the microbes
  • The polymers are collectively called extracellular polymeric substances (EPS) or extracellular matrix (ECM), and they include polysaccharides, proteins, glycoproteins, glycolipids, and DNA
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3
Q

What is heterogeneity in Biofilms?

A
  • A mature biofilm is a complex, dynamic community of microorganisms
  • Heterogeneity is differences in metabolic activity and locations of microbes
  • Interactions occur among the attached organisms
  • Exchanges take place metabolically, DNA uptake and communication
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4
Q

What do microbes do in biofilms?

A

The EPS and change in attached organisms’ physiology protect microbes from harmful agents

  • When formed on medical devices, such as implants, illness can result
  • Organism sloughing can contaminate water phase above biofilm such as in a drinking water system
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5
Q

What is Cell-Cell Communication Within the Microbial Populations?

A
  • bacterial cells in biofilms communicate in a density-dependent manner called quorum sensing
  • Produce small proteins that increase in level as microbes replicate and convert a microbe to a competent state
  • DNA uptake occurs, bacteriocins are released
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6
Q

What is quorum sensing?

A
  • N-acylhomoserine lactone (AHL) is an autoinducer molecule produced by many Gram-negative organisms
  • Diffuses across plasma membrane
  • Once inside the cell, induces expression of target genes regulating a variety of functions
  • Processes regulated by quorum sensing involve host-microbe interactions
  • symbiosis—Vibrio fischeri and bioluminescence in squid
  • Bonne Bassler
  • pathogenicity and increased virulence factor production
  • DNA uptake for antibiotic resistance genes
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7
Q

killing of all living organisms

A

Sterilization

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8
Q

killing or removal of pathogens from inanimate objects

A

Disinfection

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9
Q

killing or removal of pathogens from the surface of living tissues

A

Antisepsis

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10
Q

reducing the microbial population to safe levels

A

Sanitation

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11
Q

Pasteurization

A

Different time and temperature combinations can be used.

  • LTLT (low temperature/long time)
  • 63oC for 30 minutes
  • HTST (high temperature/short time)
  • 72oC for 15 seconds
  • UHT (Ultra-high temp) - 134oC for 2 seconds
  • Mainly used to sterilize milk
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12
Q

Steam autoclave

A

-121oC at 15 psi for 20 minutes

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13
Q

What do cold temps do?

A

-Low temperatures slow growth and preserve strains.
-Refrigeration temperatures (4oC - 8oC) are used for food preservation.
-Listeria monocytogenes
-For long-term storage of cultures
-Placing solutions in glycerol at -70oC
Lyophilization or freeze-drying

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14
Q

Filtration

A

-Micropore filters with pore sizes of 0.2 mm can remove microbial cells, but not viruses, from solutions.

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15
Q

Laminar flow biological safety cabinets

A

Laminar flow biological safety cabinets force air through filters, which remove > 99.9% of airborne particulate material 0.2 μm in size or larger

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16
Q

How can irradiation kill microbes?

A
  • Nonionizing Radiation: Ultraviolet light (UV)
  • 260 nm; has poor penetrating power; Used only for surface sterilization
  • Ionizing Radiation: Gamma rays, electron beams, and X-rays:
  • Has high penetrating power
  • Creates ion radicals targeting proteins and DNA
  • Used to irradiate foods and other heat-sensitive items
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17
Q

Chemical Agents: Disinfectants and Antiseptics

A

These include:
-Ethanol - 70%
-Iodine (Wescodyne and Betadine)
-Chlorine
-Ethylene oxide (a gas sterilant) - for heat and moisture sensitive materials
These damage proteins, lipids, and/or DNA
-Are used to reduce or eliminate microbial content from objects

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18
Q

Chemical Agents: Antibiotics

A
  • Antibiotics are compounds synthesized by one microbe that kill or inhibit the growth of other microbial species.
  • Prevents cell wall formation
  • Other antibiotics target:
  • Protein synthesis
  • Ribosomes
  • DNA replication
  • Cell membranes
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19
Q

Biological Agents: Biocontrol

A
  • Biocontrol is the use of one microbe to control the growth of another.
  • Probiotics contain certain microbes that, when ingested, aim to restore balance to intestinal flora
  • Lactobacillus
  • Phage therapy aims to treat infectious diseases with a virus targeted to the pathogen
  • A possible alternative to antibiotics in the face of rising antibiotic resistance
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20
Q

Nutrient Deprivation and Starvation

A
  • starvation is a stress that can elicit a “starvation response” in many microbes.
  • Enzymes are produced to increase the efficiency of nutrient gathering and to protect cell macromolecules from damage.
  • the response is usually triggered by the accumulation of small signal molecules such as cAMP or guanosine tetraphosphate, which globally transform gene expression.
  • These highly soluble, small molecules can quickly diffuse throughout the cell, promoting a fast response
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21
Q

Effects of Starvation

A
  • Some organisms growing on nutrient-limited agar can even form colonies with intricate geometrical shapes that help the population cope, in some unknown way, to food stress
  • When severely stressed by starvation, some members of a bacterial population appear to sacrifice themselves to save others
  • They do so by undergoing what is termed programmed cell death
  • The dying cells release nutrients that neighboring cells use to survive
  • One of the mechanisms for programmed cell death involves so-called toxin-antitoxin systems
  • For each TA pair, the toxin protein will kill the cell, but the antitoxin (sometimes a protein, sometimes a small RNA molecule) can inactivate the toxin
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22
Q

Cells treated with antimicrobials die at a _________ -______

A

logarithmic rate.

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23
Q

Metabolism is the total of all chemical reactions in the cell and is divided into two parts:

A

Catabolism: fueling reactions, energy-conserving reactions, provide ready source or reducing power (electrons), Generate precursors for biosynthesis

Anabolism: synthesis of complex organic molecules from simpler ones, requires energy from fueling reactions

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24
Q

Examples of simple molecules?

A

Simple Molecules:

Amino Acids, Fatty Acids, Sugars, Nucleotides

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25
Q

Examples of complex molecules?

A

Complex Molecules:

Carbohydrates, Lipids, DNA, RNA, Proteins

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26
Q

Oxidation-Reduction (Redox) Reactions

A
  • Many metabolic processes involve oxidation-reduction reactions (electron transfers)
  • electron carriers are often used to transfer electrons from an electron donor to an electron acceptor
  • Transfer of electrons from a donor to an acceptor
  • Can result in energy release, which can be conserved and used to form ATP
  • the more electrons a molecule has, the more energy rich it is
    •One is electron donating (oxidizing reaction)
    •One is electron accepting reaction (reducing reaction)
    •Acceptor and donor are conjugate redox pair
    •Acceptor + e− donor
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27
Q

Electron Transport Chain (ETC)

A
  • Electron carriers organized into ETC
  • first electron carrier having the most negative E′0
  • potential energy stored in first redox couple is released and used to form ATP
  • First carrier is reduced and electrons moved to the next carrier and so on
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28
Q

What are Electron Carriers?

A
  • Located in plasma membranes and intracytoplasmic membranes of bacterial and archaeal cells
  • Located in internal membranes of mitochondria and chloroplasts in eukaryotic cells
  • Examples of electron carriers include NAD, NADP, FADH2 and ATP
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29
Q

Structure and Function of NAD

A

-Nicotinamide adenine dinucleotide carries 2-3x as much energy as ATP.
- NADH is the reduced form.
- NAD+ is the oxidized form
Overall, reduction of NAD+ accepts two hydrogen atoms and two electron to make NADH.

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30
Q

Additional Electron Carriers

A

-FAD: Flavin adenine dinucleotide; is another coenzyme that can transfer electrons.
- FADH2 (reduced form) versus FAD (oxidized form)
- Unlike NAD+, FAD is reduced by two electrons and two protons.
•FMN: flavin mononucleotide; riboflavin phosphate
•Coenzyme Q (CoQ): A quinone; Also called ubiquinone
-Cytochromes: Use iron to transfer electrons (iron is part of a heme group)
•Nonheme iron-sulfur proteins: For example, ferredoxin; Use iron to transport electrons (iron is not part of a heme group

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31
Q

Biochemical Pathways

A

•Pathways can be varied:

  • Linear; Cyclic; Branching
  • Pathways often overlap/ feed into each other
  • complex networks
  • Dynamic pathways can be used to monitor changes in metabolite levels (flux)
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32
Q

Enzyme Terminology

A
  • Protein catalysts: High specificity for the reaction catalyzed and the molecules acted on; substance that increases the rate of a reaction without being permanently altered
  • Substrates = reacting molecules
  • Products = substances formed by reaction
  • Some enzymes are composed solely of one or more proteins
  • Some enzymes are composed of two parts: one protein component and a nonprotein component
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33
Q

Structure of Enzymes

A
  • Apoenzyme: protein component of an enzyme
  • Cofactor: nonprotein component of an enzyme
  • Prosthetic group—firmly attached
  • Coenzyme—loosely attached, can act as carriers/shuttles
  • Holoenzyme = apoenzyme + cofactor
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34
Q

Classification of Enzymes

A

•Enzymes may be placed in one of six general classes and usually are named based on the substrate they act on and the reaction they catalyze
- look at table!

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35
Q

Enzymes are impacted by?

A

Substrate concentration, pH, Temperature

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36
Q

Enzyme Inhibition

A

Competitive inhibitor: Directly competes with binding of substrate to active site
- Noncompetitive inhibitor: Binds enzyme at site other than active site, changes enzyme’s shape so that it becomes less active

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37
Q

Metabolic Channeling

A
  • Differential localization of enzymes and metabolites
  • Compartmentation: Differential distribution of enzymes and metabolites among separate cell structures or organelles; Can generate marked variations in metabolite concentrations
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38
Q

Allosteric Regulation

A
  • Most regulatory enzymes
  • Activity altered by small molecule known as an allosteric effector
  • Binds noncovalently at regulatory site
  • Changes shape of enzyme and alters activity of catalytic site
  • Positive effector increases enzyme activity
  • Negative effector inhibits the enzyme
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39
Q

Covalent Modification of Enzymes

A
  • Reversible on and off switch
  • Addition or removal of a chemical group (phosphoryl, methyl, adenylyl)
  • Advantages of this method
  • Respond to more stimuli in varied/sophisticated ways
  • Regulation of enzymes that catalyze covalent modification adds second level of control
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40
Q

Feedback Inhibition

A
  • Also called end product inhibition
  • Inhibition of one or more critical enzymes in a pathway regulates entire pathway
  • Pacemaker enzyme: catalyzes the slowest or rate-limiting reaction in the pathway
  • Each end product regulates its own branch of the pathway
  • Each end product regulates the initial pacemaker enzyme Isoenzymes
  • Different enzymes that catalyze same reaction
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41
Q

______, _________, and __________ each store energy associated with an electron pair that carries reducing power

A

NADH, NADPH, and FADH2

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42
Q

Enzymes catalyze reactions by lowering the ____ required to reach the transition state. They couple energy transfer reactions to specific react- ions of biosynthesis and cell function.

A

ΔG

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43
Q

T/F: Catabolism provides energy for anabolism

A

True

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44
Q

Oxygen and other Electron Acceptors

A

Many microorganisms can grow in the presence of molecular oxygen (O2)

  • Some even use oxygen as a terminal electron acceptor (TEA) in the electron transport chain
  • This process is called aerobic respiration
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45
Q

Energy Carriers and Electron Transfer

A

Many of the cell’s energy transfer reactions involve energy carriers.

  • Molecules that gain or release small amounts of energy in reversible reactions
  • Examples: NADH, FADH2 and ATP§ Energy carriers can also transfer electrons.
  • NADH: Electron donor
  • NAD+: Electron acceptor
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46
Q

ATP as energy currency

A 
Adenosine triphosphate (ATP) contains a base, sugar, and three phosphates.
- ADP plus inorganic phosphate makes ATP.
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47
Q

ATP Carries Energy

A

ATP contains three phosphate molecules that yield energy upon hydrolysis.

  • ATP transfer energy in three different ways:
    1. Hydrolysis-releasing phosphate (Pi)
  1. Hydrolysis-releasing pyrophosphate (PPi)
  2. Phosphorylation of an organic molecule
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48
Q

Substrate-level phosphorylation

A
  • transfer of phosphate from high- energy molecule to ADP

- Require a kinase enzyme

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49
Q

Catabolism: The Microbial Buffet

A
  • Microbes catalyze many different kinds of substrates
  • Polysaccharides are broken down to pyruvate - glycolysis.
  • Pyruvate are fermented or further catabolized to CO2 and H2O via the TCA cycle.
  • Lipids and amino acids are catabolized to glycerol and acetate, as well as other metabolic intermediates.
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50
Q

Requirements for Carbon, Hydrogen, and Oxygen

A

Often satisfied together: Carbon source often provides H, O, and electrons

  • Heterotrophs: Use organic molecules as carbon sources which often also serve as energy source; Can use a variety of carbon sources
  • Autotrophs: Use carbon dioxide as their sole or principal carbon source; Must obtain energy from other sources
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51
Q

Nutritional Types of Organisms

A
  • Based on energy source:
  • Phototrophs use light
  • Chemotrophs obtain energy from oxidation of chemical compounds
  • Based on electron source:
  • Lithotrophs use reduced inorganic substances
  • Organotrophs obtain electrons from organic compounds
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52
Q

Chemoorganotrophic Fueling Processes

A
  • also called chemoheterotrophs
  • Processes used to catabolize energy source:
  • Aerobic respiration; Anaerobic respiration; fermentation
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53
Q

Most Respiration Involves Use of an ETC?

A
  • Aerobic respiration—final electron acceptor is oxygen
  • Anaerobic respiration—final electron acceptor is different oxidized molecule such as NO3−, SO42−, CO2, Fe3+, or SeO42−
  • 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
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54
Q

Chemoorganotrophic Fermentation

A
  • Uses an endogenous electron acceptor
  • Usually an intermediate of the pathway used to oxidize the organic energy source (for example, 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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55
Q

Chemoorganotrophic Energy Sources

A
  • Many different energy sources are funneled into common degradative pathways
  • Most pathways generate glucose or intermediates of the pathways used in glucose metabolism
  • Few pathways that each break down many nutrients greatly increase metabolic efficiency
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56
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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57
Q

Amphibolic Pathways

A
  • Include enzymes that function both catabolically and anabolically
  • For example, many enzymes of the Embden-Meyerhof pathway function catabolically during glycolysis but anabolically during gluconeogenesis
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58
Q

Breakdown of Glucose to Pyruvate pathways

A
  • Embden-Meyerhof pathway
  • Entner-Doudoroff pathway
  • Pentose phosphate pathway
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59
Q

Glycolysis/ Embden-Meyerhof Pathway

A
  • Occurs in cytoplasmic matrix of most microorganisms, plants, and animals
  • The most common pathway for glucose degradation to pyruvate in stage two of aerobic respiration
  • Function in presence or absence of O2
  • Two phases:
    Six-carbon phase
    Three-carbon phase
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60
Q

T/F: Enzymes necessary for glycolysis to occur are Highly Regulated–Transcription

A

True

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61
Q

Glycolysis (EMP)

A

Essential Catabolism of Glucose

  • Plants animals and microbes
  • It occurs in the cytoplasm of the cell
  • It functions in the presence or absence of O2
  • It involves ten distinct reactions that are divided into two stages
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62
Q

Stage 1- Energy Investment

A

Glucose is “activated” by 2 phosphorylations

  • Two ATPs are expended - Investment: 2 ATP
  • Fructose-1,6-bisphosphate is cleaved into two 3-carbon- isomers:
  • Dihydroxyacetone phosphate (DHAP)
  • Glyceraldehyde-3-phosphate (G3P)
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63
Q

Stage 2 - Energy Yield

A
  • Each glyceraldehyde-3-phosphate molecule is ultimately converted to pyruvate.
  • 2 Pyruvate
  • Redox reactions produce two molecules of nicotinamide adenine dinucleotide (NADH)
  • 2NADH
  • Four ATP molecules are produced by substrate-level phosphorylation
  • Net ATP = (total - invested) = 2 ATP
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64
Q

Embden-Meyerhof Pathway Specifics

A
  • Addition of phosphates “primes the pump”

- Oxidation step—generates NADH, high-energy molecules used to synthesize ATP by substrate-level phosphorylation

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65
Q

Summary: Glycolysis

A

Primary pathway to convert ONE glucose to TWO pyruvate

  • pathway generates:
  • Net gain of 2 ATP, 2 pyruvate
  • 2 ATP expended to break glucose
  • 4 ATP harvested
  • 2 NADH ———– will generate more ATP later
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66
Q

Glucose Utilization

A
  • Microbes reduce pyruvate to different end products
    Glycolysis/ Embden-Meyerhof Pathway
    • 2 ATP and 2NADH Entner-Dourdoroff (ED) Pathway
    • 1 ATP, 1 NADH, 1 NADPH
    Pentose Phosphate Pathway (PPP) • Sugars (3-7 Cs), 2 NADPH
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67
Q

Entner-Doudoroff Pathway Specifics

A
  • Used by some Gram-negative bacteria, especially those found in soil
  • Replaces the 6-carbon phase of the Embden-Meyerhof pathway
  • Yield per glucose molecule:
  • 1ATP
  • 1 NADPH
  • 1NADH
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68
Q

Pentose Phosphate Pathway

A
  • Also called hexose monophosphate pathway
  • Can operate at same time as Embden-Meyerhof pathway or Entner-Doudoroff pathway
  • Can operate aerobically or anaerobically An amphibolic pathway:
  • Glucose-6-P + 12NADP+ + 7H2O — 6CO2 + 12NADPH + 12H+ Pi
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69
Q

Why do cells create Pyruvate?

A
  1. Fermentation
    - Recycling of NADH to NAD+
    - Produce acid and/or alcohol
  2. TCA cycle for additional metabolites and more NADH and FADH2
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70
Q

Glycolysis pathway

A

2 ATP and 2 NADH

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71
Q

ED pathway

A

1 ATP, 1 NADH, and 1 NADPH

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72
Q

Pentose phosphate pathway:

A

2 NADPH

73
Q

There are three main types of catabolic pathways:

A
  • Fermentation
  • Respiration
  • Photoheterotrophy
74
Q

What do microbes do with pyruvate?

A
  1. Fermentation: recycling of NADH to NAD+ Produce acid and/or alcohol
  2. TCA cycle to create additional precursor (biosynthesis) metabolites and more NADH and FADH2
75
Q

The Tricarboxylic Acid Cycle

A

In prokaryotes, it occurs in the cytoplasm - In eukaryotes, in the mitochondria

  • Glucose catabolism connects with the TCA cycle through pyruvate breakdown to acetyl-CoA and CO2
  • Acetyl-CoA enters the TCA cycle by condensing with the 4-C oxaloacetate to form citrate
76
Q

Pyruvate to Acetyl-CoA

A

Conversion of pyruvate to acetyl-CoA is catalyzed by a very large multisubunit enzyme called the Pyruvate Dehydrogenase Complex (PDC)

77
Q

Pyruvate Dehydrogenase Complex

A
  • Key player in directing glucose catabolism into respiration
  • Defects in PDC in human mitochondria can cause issues in organs with high metabolic rates
  • Myocardial infarction
  • Heart Failure
  • Neurodegeneration
  • Inhibited by increased Acetyl-CoA
    • Converted to Acetate
78
Q

Summary: Pyruvate to TCA Cycle

A

For each Pyruvate oxidized:

  • Pyruvate Dehydrogenase Complex (PDC)
  • 1 CO2, 1 NADH
  • Kreb’s Cycle/TCA Cycle
  • 2 CO2 are produced by decarboxylation
  • 3 NADH and 1 FADH2 are produced
  • 1 ATP is produced by substrate-level phosphorylation.
  • Some cells make GTP instead of ATP (it still is only 1 molecule produced!)
  • However, GTP and ATP are equivalent in stored energy.
79
Q

TCA

A
  • Originally evolved to aid in Amino Acid Production
  • 2-oxoglutarate to Glutamate to Glutamine
  • Oxaloacetate to Aspartate to Nucleotides
  • Amphibolic Pathway
  • Treponema pallidum (Syphillis) abandoned TCA through reductive evolution and rely on host amino acids for survival
80
Q

Electron Carriers

A 
NADH=  3 ATP X 2 Glycolysis+8 TCA= 30ATP
FADH2 = 2 ATP X 2 TCA= 4ATP
2 ATP Glycolysis + 2 ATP TCA
Electron Carriers
Theoretical Yield = 38 ATP
E. coli produces 20 ATP per glucose; extreme variation of the number of ATP produced by bacteria ....
**Oxygen and Carbon source availability
81
Q

Glyoxylate Bypass/Shunt

A
  • When glucose is absent, cells can catabolize acetate or fatty acids using a a process called Glyoxylate Shunt/ Glyoxylate Bypass
  • Includes two enzymes that divert Isocitrate to Glyoxylate
  • Incorporate a second Acetyl-CoA to form Malate
  • The Glyoxylate Bypass cuts loss of CO2
  • Produces 2 NADH , 1 FADH2
82
Q

Mycobacterium tuberculosis

A
  • In 1998 - 6.7 million cases with 2.4 deaths Most lethal infection in the world
    Latent TB in over 2 million people
    • Grow within macrophages; can persist for long periods
    Provide lipids via Glyoxylate Bypass
    -Diverts Carbon to build sugars/amino acids
    Glyoxylate Bypass essential to the pathogenicity of M. tuberculosis
83
Q

ETC is in __________ in eukaryotes, and ________ of prokaryotes

A

Mitochondria, plasma membrane

84
Q

In bacterial ETC,

A

Microbes transfer energy

85
Q

Where does ALL the NADH and FADH2 go?

A
  • Each Glucose consumed: (10 NADH + 2 FADH2)
  • Glycolysis: 2 NADH
  • Transition step (Pyruvate to Acetyl-CoA): 2 NADH
  • TCA: 6 NADH; 2 FADH2
86
Q

Electron Transport Chains

A

The mitochondrial electron transport chain (ETC) = 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

87
Q

What are redox pairs in the ETC?

A
  • Each carrier is reduced and then reoxidized
  • Carriers are constantly recycled
  • the difference in reduction potentials electron carriers, NADH and O2 is large, resulting in release of great deal of energy
88
Q

Bacterial and Archaeal ETCs differ from Eukaryotic ETCs, how?

A
  • Located in plasma membrane
  • Some resemble mitochondrial ETC, but many are different:
  • Different electron carriers
  • Different terminal oxidases
  • May be branched
  • May be shorter—fewer protons and therefore less energy
89
Q

ETC: Big Picture

A
  • Microbes transfer energy by moving electrons
  • Electrons move from reduced molecules to energy
    carriers
  • From energy carriers to membrane protein carriers, and then
  • Finally to oxygen or oxidized minerals
  • ETS generate “proton motive force (PMF)”
  • The PMF will be used to make ATP
90
Q

Major classes of metabolism that use an ETS include…?

A
  • Organotrophy (organic electron donors)
  • Lithotrophy (inorganic electron donors)
  • Phototrophy (light excites electrons)
  • Many prokaryotes use more than one type of metabolism.
  • Rhodopseudomonas palustris, use all three e- sources
91
Q

The Respiratory ETS

A
  • ETS occurs in the bacterial cell membrane
  • Microbes use many electron acceptors.
  • Aerobic: Oxygen (O2)
  • Anaerobic: metals, oxidized ions of nitrogen or sulfur.
  • Salmonella Typhimurium infecting the gut epithelium
  • Use toxic compound tetrathionate (S4O62-) as a terminal electron acceptor.
92
Q

Paracoccus denitrificans ETC Used During Aerobic Respiration

A
  • NADH delivers
  • e- transfers across to systems
  • protons pumped out of the membrane
93
Q

Electron Transport Chain of E. coli

A
  • Different array of cytochromes used than in mitochondrial chain
  • Branched pathway
  • Upper branch— stationary phase and low aeration
  • Lower branch— log phase and high aeration; more O2; more ATP
94
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

95
Q

Oxidoreductase Protein Complexes

A

A respiratory electron transport system includes at least three functional components:

  1. Oxidoreductase (or dehydrogenase)
  2. A mobile electron carrier
  3. A terminal oxidase
96
Q

E. coli electron transport system

A
  1. The substrate dehydrogenase receives a pair of electrons, such as from NADH
  2. It donates the electrons ultimately to a mobile electron carrier, such as quinone (Q)
    - Quinone picks up 2 H+ from solution and is thus reduced to quinol (QH2)
  3. The oxidation of NADH and reduction of Q is coupled to pumping 4H+ across the membrane
  4. A terminal oxidase complex, typically includes a cytochrome, receives the two electrons from quinol (QH2)
    - 2H+ are translocated outside the membrane
    - In addition, 2H+ are pumped across the membrane, when the electrons are passed through the terminal oxidase complex.
  5. The terminal oxidase complex transfers the electrons to a terminal electron acceptor such as O2
    - E. coli ETS can pump up to ~ 8-10 H+ for each NADH molecule, and ~ 6 H+ for each FADH2 molecule
    - Generates an electrochemical gradient of protons, called a proton motive force
97
Q

Chemiosmotic Hypothesis

A
  • The most widely accepted hypothesis to explain oxidative phosphorylation
  • Protons move outward from the mitochondrial matrix as e- are transported down the chain
  • Proton expulsion during e- transport results in the formation of a concentration gradient of protons and a charge gradient
  • The combined chemical and electrical potential difference make up the proton motive force (PMF)
98
Q

Mitochondrial Respiration

A

Mitochondrial ETS differ from that of E. coli in these respects:

  1. Possess an intermediate cytochrome oxidase complex for transfer of electrons.
  2. Mitochondrial ETS pumps 12 H+ per NADH, 2 more than E. coli
99
Q

The Proton Motive Force

A

The transfer of H+ through a proton pump generates a proton motive force.

  • It drives the conversion of ADP to ATP through ATP synthase.
  • This process is known as the chemiosmotic theory.
  • 1978 - Peter Mitchell wins Nobel Prize
100
Q

The F1Fo ATP Synthase

A
  • The F1Fo ATP synthase is a highly conserved protein complex, made of two parts:
  • Fo: embedded in the membrane
  • Pumps protons - F1: protrudes in the cytoplasm- Generates ATP
101
Q

ATP synthase

A
  • Harvest energy from proton motive force to synthesize ATP
  • 10 protons pumped out per NADH
  • 1 NADH produces 3 molecules of ATP
  • 6 protons pumped out per FADH
  • 1 FADH2 produces 2 molecules of ATP
  • look at pictures on slide
102
Q

ATP Yield During Aerobic Respiration

A
  • Maximum ATP yield can be calculated
  • includes phosphorus to oxygen (P/O) ratios of NADH and FADH2
  • ATP produced by substrate-level phosphorylation
  • The maximum total yield of ATP during aerobic respiration by eukaryotes is 32
103
Q

Theoretical vs. Actual Yield of ATP

A
  • Amount of ATP produced during aerobic respiration varies depending on growth conditions and nature of ETC
  • Under anaerobic conditions, glycolysis only yields 2 ATP molecules
  • Factors affecting ATP yield::
  • Bacterial ETCs are shorter and have lower P/O ratios
  • ATP production may vary with environmental conditions
  • PMF in bacteria and archaea is used for other purposes than ATP production (flagella rotation)
  • Precursor metabolite may be used for biosynthesis
104
Q

Summary: total ATP from 1 Glucose

A

Substrate phosphorylation: 4 ATP generated; Net 2 from glycolysis; 2 ATP from TCA

  • Oxidative phosphorylation: 34 ATP generated; 6 ATP from glycolysis; re-oxidation of 2 NADH § 6 from transition step; re-oxidation of 2 NADH § 22 from TCA cycle; re-oxidation of NADH and FADH2
  • Total yield from 1 Glucose: 4 + 34 = 38 (theoretical maximum)
  • Eukaryotic cells have theoretical maximum of 36; 2 ATP spent crossing mitochondrial membrane
105
Q

T/F: An ETS includes at least three functional components

A

T: Substrate dehydrogenase, mobile electron carrier, and terminal oxidase

106
Q

T.F: Three protons drive each F1Fo cycle, synthesizing one molecule of ATP.

A

True

107
Q

T/F 12 H+/NADH for eukaryotes and 10 H+/NADH for bacteria

A

True

108
Q

1 NADH = ____ ATP

1 FADH2 = ______ ATP

A

3, 2

109
Q

T/F: Anaerobic respiration is unique to prokaryotes.

A

True

110
Q

Anaerobic respiration electron carriers

A
  • Since it is unique to prokaryotes, they use alternative electron acceptors
  • Some bacteria use nitrate
  • Nitrate reduced to nitrite (NO3-→NO2-)
  • Some use Sulfur compounds
  • Sulfate reduced to sulfite (SO42-→SO32-)
111
Q

Nitrate Reduction Test

A
  • test for nitrate breakdown
  • inoculate with material
  • add reagent
  • clear- red- reduced!
  • stays clear- add Zn2+- red change here it - now
112
Q

Sulfate reducing bacteria

A
  • H2S byproduct

- pumped out fewer H+, so less ATP

113
Q

Anaerobic Respiration

A
  • Uses electron carriers other than O2
  • Generally yields less energy because E0 of electron acceptor is less positive than E0 of O2
  • Dissimilatory nitrate reduction:
  • Use of nitrate as terminal electron acceptor, making it unavailable to cell for assimilation or uptake
  • Denitrification
  • Reduction of nitrate to nitrogen gas
  • In soil, causes loss of soil fertility
114
Q

ETC Used During Anaerobic Respiration

A
  • complex
  • branched chain
  • different e- carriers
  • nitrate reduced
  • nitrite– nitric oxide
  • NO– nitric oxide— N2
115
Q

F1 ____?

F0 _____?

A

Turns

Produces ATP

116
Q

Fermentation

A
  • No ATP because of no ETC
  • most fermenters produces acids
  • e- from NADH/NADPH donated to pyruvate
  • energy stored in ATP
  • during glycolysis- substrate level
  • O2– not needed!
  • NADH– NAD+
  • Still need PMF- reverse ATP synthase to pump H+ out of cell
  • Recycle NADH– NAD+ needed to get rid of e-
    Completion of Glucose Catabolism
  • Electrons from NADH (NADPH) are donated to pyruvate
  • Byproducts including alcohols, carboxylates as well as Hydrogen and CO2
  • Energy Stored in ATP
    -Most fermentations do not generate ATP beyond that produced by glycolysis
  • Microbes compensate by consuming large quantities of substrate and
  • Excreting large quantities of byproducts.
117
Q

4 Fermentation Pathways

A
  • Homolactic fermentation: Produces 2 molecules of lactic acid
  • Ethanolic fermentation: Produces two molecules of ethanol and two CO2
  • Heterolactic fermentation: Produces 1 molecule of lactic acid, 1 ethanol, and 1 CO2
  • Mixed-acid fermentation: Produces acetate, formate, lactate, and succinate, as well as ethanol, H2, and CO2
118
Q

Phenol Broth Test and Sorbitol-MacConkey Agar

A
  • used to identify the microbe causing a disease and prescribe an effective antibiotic, hospitals use rapid and inexpensive biochemical tests
  • Starts red— yellow if acid produced/more acidic
  • Agar: White colonies fail to ferment sorbitol, unlike red colonies; can cause illness
119
Q

Methyl Red (MR) and Voges-Proskauer (VP)

A
  • It is a simple broth that contains peptone, buffers, and glucose
  • Methyl red differs from Phenol red in that it is yellow at pH 6.2 and above and red at pH 4.4 and below
  • Positive Result will be RED
  • MR: turn RED if the organism uses the mixed acid fermentation pathway to make acids
  • VP: tests for organisms that use butylene glycol pathway and produce acetoin
  • Positive - Deep red
  • Negative - copper color
120
Q

Fermentation

A
  • Oxidation of NADH produced by glycolysis
  • Pyruvate or derivative used as endogenous electron acceptor
  • Substrate only partially catabolized
  • Oxygen not needed
  • Oxidative phosphorylation does not occur
  • The only ATP created is formed by substrate-level phosphorylation
121
Q

Catabolism of Other Carbohydrates

A
  • Many different carbohydrates can serve as energy source

- Carbohydrates can be supplied externally or internally (from internal reserves)

122
Q

Carbohydrates

A
  • Monosaccharides: Converted to other sugars that enter glycolytic pathway
  • Disaccharides and polysaccharides: Cleaved by hydrolases or phosphorylases
123
Q

Lipid Catabolism

A
  • Triglycerides are common energy sources
  • Hydrolyzed to glycerol and fatty acids by lipases
  • Glycerol degradedvia glycolytic pathway
  • Fatty acids often oxidized via β- oxidation pathway
124
Q

Fatty Acid β Oxidation

A
  • created of e- carriers: more energy

- FA broken down

125
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 occur through transamination
126
Q

Chemolithotrophy

A
  • Carried out by certain bacteria and archaea- released from inorganic molecule energy source
  • Transferred to terminal e- acceptor by ETC
  • ATP synthesized by ETC and oxidative phosphorylation
127
Q

Energy Sources

A
  • Bacterial and archaeal species have specific electron donor/acceptor preferences
  • Much less energy is available from oxidation of inorganic molecules than glucose due to more positive redox potentials
128
Q

3 Major Groups of Chemolithotrophs

A
  • Have significant ecological impact
  • Several bacteria and archaea oxidize hydrogen
  • Nitrifying bacteria oxidize ammonia to nitrate
  • Sulfur-oxidizing microbes
  • Hydrogen sulfide (H2S), sulfur (S0), thiosulfate (S2O32−)
  • ATP can be synthesized by both oxidative phosphorylation and substrate-level phosphorylation
129
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
  • F1: Knob outward, proton potential (-)
130
Q

Photosynthesis

A
  • Energy from light trapped and converted to chemical energy
  • A two-part process
  • Light reactions: light energy is trapped and converted to chemical energy
  • Dark reactions: energy produced in the light reactions is used to reduce CO2 and synthesize cell constituents
131
Q

Light Reactions in Oxygenic Photosynthesis

A
  • Photosynthetic eukaryotes and cyanobacteria
  • Oxygen is generated and released into the environment
  • Most important pigments are chlorophylls
132
Q

Chlorophyll

A
  • Major light-absorbing pigments

- Different chlorophylls have different absorption peaks

133
Q

The Light Reaction in Oxygenic Photosynthesis— Accessory Pigments

A
  • Accessory pigments (for example, carotenoids and phycobiliproteins)
  • Transfer light energy to chlorophylls
  • Absorb different wavelengths of light than chlorophylls
134
Q

Phototrophy = Light Dependent Reactions

A
  • Photoreceptors absorb light
  • Excites an e- to a higher orbital level and subsequent return to ground state
  • High # of photoreceptors found in membrane
  • Photoexcited electrons used to power cell growth
  • e- are transferred through ETS to pump protons
  • The absorption and relaxation of the light absorbing molecule is coupled to energy storage
  • Proton Gradient
135
Q

Overview

A
  • Reaction Center delivers e- through carriers to ETS

e- produces NADH and NADPH

  • Electrochemical gradient created across photosynthetic membrane
  • ATP created through photophosphorylation
136
Q

How do they manage to trap sunlight?

A
  • Purple bacteria and Cyanobacteria’s membranes are folded in oval pockets (thylakoids) to increase the opportunity to trap photons of energy
  • The F1 knob of ATP synthase appears to face “outward” in photo synthetic organelles
  • proton potential is more negative in the cytoplasm, thus drawing protons through the ATP synthase to generate ATP.
137
Q

Phototrophy

A
  • Antenna system
  • Complex of chlorophylls that capture photons and transfer the energy among photopigments
  • Light harvesting pigments: Bacteriochlorophyll (G, P, R), carotenoids (O, R, Y), chlorophylls (G) phycocyanins (B), phycoerythrins (R) • Capable of trapping light outside of the visible spectrum of light
  • Transfer energy to Reaction Center
  • Reaction Center Complex:
  • Photosystem I and II
  • Light harvesting complexes absorb light energy
  • Photon energy separates an electron from chlorophyll (e- is replaced by H2S (PSI) or from ETS (PSII))
138
Q

Cyanobacteria

A
  • Oxygen producing bacteria that appear green due to presence of chlorophyll
  • Phototrophic Autotroph
  • Variety of sizes
  • “Light Reactions” of Photosynthesis
  • Photoexcitation leads to splitting of H2O and release of e-
  • e- are transferred to ETS which creates a proton potential that will power ATP Synthase to create ATP
  • *Purple Sulfur Bacteria split H2S to acquire e-**
139
Q

Chlorophylls Absorb Light

A
  • Chromophore: Light absorbing e- carrier
  • Chlorophyll absorbs red/blue and reflects green
  • Cyanobacteria
  • Rhodobacter aka Purple-Sulfur bacteria• Absorbs far red to UV range due to Bacteriochlorophyll
  • Absorbs light “missed” by cyanobacteria and algae
  • Photolysis of H2S
140
Q

3 Different ETS Systems

A
  • Anaerobic Photosystem I: Receives e- with H+ from H2S, HS-, H2 or reduced iron, Chlorobia sp
  • Anaerobic Photosystem II: Returns e- from ETS to bacteriochlorophyll
  • Oxygenic Z pathway: Two pairs of e- received from water to generate O2, Cyanobacteria and Chloroplasts
    • Electron Transport System
  • Each photoexcited e- enters ETS; PSI: e- transferred to NADP+, PSII from ETS
  • H2O photolysis- e- flow from PSII to PSI releasing O2 from H2O
  • Oxygenic Photosynthesis
    **H2S and thiosulfate serve as e- donors during Anoxygenic photosynthesis
  • Oxygen byproduct is not made • Energy Carriers
    PSI e- make NADPH, PSII e- activate H+ pumps to drive ATP Synthesis
  • Oxygenic Z pathway- makes both NADPH and ATP Both are used to FIX Carbon
141
Q

Winogradsky Column

A

Classic demonstration of the metabolic diversity of prokaryotes.

  • All life on earth can be categorized in terms of the organism’s carbon and energy source:
  • Energy can be obtained from: light reactions (phototrophs) or from chemical oxidations of organic or inorganic substances (chemotrophs); the carbon for cellular synthesis can be obtained from CO2 (autotrophs) or from preformed organic compounds (heterotrophs).
  • Only in the domain bacteria - and among the bacteria within a single Winogradsky column - do we find all four basic life strategies.
  • Classic demonstration of how microorganisms occupy highly specific microsites according to their environmental tolerances and their carbon and energy requirements.
  • And, finally, the column enables us to see how mineral elements are cycled in natural environments
  • Cyanobacteria on top of column
142
Q

Anabolism Uses Energy From Catabolism

A
  • Energy from catabolism is used for biosynthetic pathways
  • Using a carbon source and inorganic molecules,
    organisms synthesize new organelles and cells
  • Antibiotics inhibit anabolic pathways
  • A great deal of energy is needed for anabolism
143
Q

Principles Governing Biosynthesis

A

Macromolecules are synthesized from limited number of simple structural units (monomers)

  • Saves genetic storage capacity, biosynthetic raw material, and energy
  • Many enzymes do double duty
  • Many enzymes used for both catabolic and anabolic processes; saves materials and energy
  • Catabolic and anabolic pathways are not identical as some enzymes function in only one direction
  • Anabolism consumes energy
  • Anabolic and catabolic reactions are physically separated
  • Located in separate compartments
  • Allows pathways to operate simultaneously but independently
  • Catabolic and anabolic pathways use different cofactors
  • Catabolism produces NADH
  • NADPH used as electron donor for anabolism
  • Large assemblies (for example, ribosomes) form spontaneously from macromolecules by self-assembly
144
Q

Precursor Metabolites

A

Generation of precursor metabolites is critical step in anabolism

  • Carbon skeletons are used as starting substrates for biosynthetic pathways
  • Examples are intermediates of the central metabolic pathways
  • Most are used for the biosynthesis of amino acids and nucleotides
145
Q

The Fixation of CO2 by Autotrophs

A
  • Calvin-Benson (Calvin) cycle
  • Reductive TCA cycle
  • Reductive acetyl-CoA pathway
  • 3-hydroxypropionate/4-hydroxybutyrate pathway
  • Dicarboxylate/4-hydroxybutyrate cycle
146
Q

Calvin-Benson Cycle—Which Organisms, and Where?

A
  • Used by most autotrophs to fix CO2
  • Also called the reductive pentose phosphate cycle
  • in eukaryotes, occurs in stroma of chloroplasts
  • In cyanobacteria, some nitrifying bacteria, and thiobacilli, may occur in carboxysomes
  • Inclusion bodies that may be the site of CO2 fixation
  • Consists of 3 phases:
  • The Carbon Fixation phase
  • The Reduction phase
  • The Regeneration phase
  • Three ATPs and two NADPHs are used during the incorporation of one CO2
147
Q

The Carboxylation Phase

A
  • Catalyzed by the enzyme ribulose 1,5-bisphosphate carboxylase/oxygenase (RuBisCO)
  • Rubisco is thought to be the most plentiful enzyme on earth
  • Rubisco catalyzes addition of CO2 to ribulose 1,5-bisphosphate (RuBP), forming 2 molecules of 3-phosphoglycerate (PGA)
148
Q

The Reduction and Regeneration Phases

A
  • 3-phosphoglycerate reduced to glyceraldehyde 3-phosphate (G3P)
  • RuBP reformed
  • Carbohydrates (for example, fructose and glucose) are produced
149
Q

Other CO2-Fixation Pathways: The Reductive TCA Cycle

A
  • Used by some chemolithoautotrophs

- Runs in reverse direction of the oxidative TCA cycle

150
Q

Gluconeogenesis

A
  • Synthesis of Glucose from noncarbohydrate precursors
  • Shares 6 enzymes with the Embden-Meyerhof pathway
  • Four reactions catalyzed by enzymes specific for gluconeogenesis:
  • Two enzymes are involved in converting pyruvate to phosphoenolpyruvate
  • One enzyme is involved in formation of fructose 6-phosphate from fructose 1,6-bisphosphate
  • One enzyme removes the phosphate from glucose 6-phosphate to generate glucose
151
Q

Synthesis of Monosaccharides/Polysaccharides

A
  • several sugars are synthesized while attached to a nucleoside diphosphate such as uridine diphosphate glucose (UDPG)
  • Synthesis of starch and glycogen also involves nucleoside diphosphate sugars
152
Q

Peptidoglycan Synthesis

A
  • Complex process involving Uridine Diphosphate (UDP) derivatives (NAM and NAG
  • Bactoprenol phosphate used to transport NAG-NAM-pentapeptide units across the cell membrane
  • Cross links are formed by transpeptidation

-NAM/NAG synthesized in cytosol and carried by UDP derivatives to membrane
- NAM/Nag joined together
- attached to bactoprenol to carry across to membrane
- once across, join NAM and HAG to growing polypeptide chain
- bactoprenol- lose p to transfer back across
read slides!

153
Q

Bactoprenol—A Critical Molecule for Peptidoglycan Synthesis

A

Bactoprenol is connected to N-acetylmuramic acid (NAM) by pyrophosphate

154
Q

Vancomycin vs bacitracin

A

Vancomycin: inhibits peptidoglycan synthesis and prevents linking of molecules; Blocks transpeptidation
Bacitracin: stops p from leaving

155
Q

Assimilatory Nitrate Reduction

A
  • Used by bacteria to reduce nitrate to ammonia and then incorporate it into an organic form
  • Nitrate reduction to nitrite catalyzed by nitrate reductase
  • Reduction of nitrite to ammonia catalyzed by nitrite reductase
156
Q

Nitrogen Fixation

A
  • Reduction of atmospheric nitrogen to ammonia
  • Catalyzed by nitrogenase
  • Found only in a few bacteria and archaea
157
Q

Mechanism of Nitrogenase Activity

A
  • Occurs in 3 steps to reduce N2 to 2 molecules of NH3
  • Requires large ATP expenditure!!
  • Once reduced, NH3 can be incorporated into organic compounds
158
Q

Sulfur Assimilation

A
  • Sulfur needed for:
  • Synthesis of amino acids cysteine and methionine
  • Synthesis of several coenzymes (for example, coenzyme A and biotin)
  • Sulfur obtained from:
  • Cysteine and methionine—obtained from either external sources or intracellular amino acid reserves
  • Sulfate
159
Q

Use of Sulfate as a Sulfur Source

A
  • Sulfate = inorganic sulfur source
  • used by fungi
  • Assimilatory sulfate reduction
  • sulfate reduced to SO32− and then to H2S, then used to synthesize cysteine
  • Cysteine can then be used to form sulfur- containing organic compounds
  • different than dissimilatory sulfate reduction, where sulfate acts as electron acceptor for anaerobic respiration
160
Q

Amino Acid Biosynthetic Pathways

A
  • Used in the synthesis of multiple amino acids

- A single precursor metabolite can give rise to several amino acids

161
Q

Anaplerotic Reactions

A
  • TCA cycle intermediates are used in many amino acid biosynthetic pathways
  • Replenishment of these intermediates is provided by anaplerotic reactions
  • Allow TCA cycle to function during periods of active biosynthesis • For example, anaplerotic CO2 fixation
  • For example, glyoxylate cycle
162
Q

Anaplerotic CO2 Fixation

A

Phosphoenolpyruvate (PEP) carboxylase
• Phosphoenolpyruvate + CO2 ® oxaloacetate + Pi
• Pyruvate carboxylase
• Pyruvate + CO2 + ATP + H2O– oxaloacetate + ADP + Pi

163
Q

Glyoxalate Cycle/Bypass**

A
  • Other anaplerotic reactions are part of the glyoxalate cycle, a modified TCA cycle
  • isocitrate lygase–glycoxlate
  • malate synthesis
  • fill in the blank
164
Q

How Are Purines, Pyrimidines, and Nucleotides Synthesized?

A
  • Most microbes can synthesize their own purines and pyrimidines
  • Purines
  • Cyclic nitrogenous bases consisting of 2 joined rings
  • Adenine and guanine
  • Pyrimidines
  • Cyclic nitrogenous bases consisting of single ring
  • Uracil, cytosine, and thymine-
  • Nucleoside = nitrogenase base-pentose sugar
  • Nucleotide = nucleoside-phosphate
165
Q

Phosphorus Assimilation

A
  • Phosphorus found in nucleic acids as well as proteins, phospholipids, ATP, and some coenzymes
  • Most common phosphorus sources are inorganic phosphate and organic molecules containing a phosphoryl group
  • Inorganic phosphate (Pi) incorporated through the formation of ATP by:
  • Photophosphorylation
  • Oxidative phosphorylation
  • Substrate-level phosphorylation
166
Q

Lipid Synthesis

A
  • Major required component in cell membranes
  • Most bacterial and eukaryal lipids contain fatty acids or their derivatives
  • Fatty acids
  • Synthesized then added to other molecules to form other lipids such as triacylglycerols and phospholipids
167
Q

Fatty Acid Synthesis

A

Synthesized from acetyl-CoA, malonyl-CoA, and NADPH by fatty acid synthase complex
• During synthesis, the intermediates are attached to the acyl carrier protein
• Double bonds can be added in two different ways

168
Q

Phospholipids

A
  • Major components of eukaryotic and bacterial cell membranes
    • Synthesized from phosphatidic acid by forming CDP- diacylglycerol, then adding an amino acid
  • DHAP transformed into G3P to triglycerol
  • precursor molecules for phopholipids
169
Q

Lipopolysaccharides

A 
Lipid A: endotoxin
O Antigen: immune response
 LPS molecules are an important component of the Gram-negative bacterial cell wall structure
• Combines lipid and carbohydrate anabolic pathways
• Lipid A-core branch
• Oligosaccharide core
• O-antigen branch
-  Fatty acid synthesis + UDP ---- LPS
170
Q

Lipopolysaccharide Insertion Into Cell Wall

A

Current model suggests multiple proteins, called Lpt proteins, “walk” newly-made LPS across the cell wall

  • LPS outer membrane
  • periplasmic space- between inner/outer membrane
171
Q

Photo

A

light as energy!

172
Q

Chemo

A

energy! from chemicals

173
Q

Litho

A

electrons from inorganic matter

174
Q

Organo

A

electrons from organic matter

175
Q

Hetero

A

reduced organic molecules

176
Q

Auto

A

CO2 as source of energy

177
Q

Energy sources like phototrophs, chemolithotrophs or chemoorganotrophs provide ____?

A

ATP

178
Q

Carbon sources like autotrophs and heterotrophs provide _______?

A

Precursor metabolites

179
Q

Electron sources like organotrophs and lithotrophs provide ____?

A

Reducing power through electrons

Microbiology Exam 2 (1 decks)

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