Exam #1 Flashcards

Question

Cellulose

Answer 1

Plant cellulose, which makes up the cell walls of most plants, is tough and mesh-like; cellulose fibrils are primary architectural elements. Bacterial cellulose has the same molecular formula as plant cellulose, but it has significantly different macromolecular properties and characteristics: it is more chemically pure higher water holding capacity greater tensile strength resulting from more polymerization ultrafine network architecture.

Answer 2

cellulose hydroxybutyric acid (manufacture of disposable diapers and plastics) ethanol (biofuel) hydrogen gas (possible biofuel) oil (possible biofuel) insect toxins (insecticides) antibiotics (treatment of disease) amino acids (dietary supplements)

Answer 3

Bacillus thuringiensis is closely related to B. cereus, a soil bacterium, and B. anthracis, cause of anthrax; the three organisms differ mainly in their plasmids. There are several dozen recognized subspecies of Bacillus thuringiensis. Upon sporulation, B. thuringiensis forms crystals of δ-endotoxins (called crystal proteins or Cry proteins), which are encoded by cry genes. The cry genes are located on a plasmid. B. thuringiensis serves as an important reservoir of Cry toxins for production of biological insecticides and insect-resistant genetically modified crops. When insects ingest toxin crystals, their alkaline digestive tracts denature the insoluble crystals, making them soluble, now able to be cut with proteases found in the insect gut, which frees the toxin. The Cry toxin then inserts into the insect gut cell membrane, forming a pore.

Answer 4

excellent model organisms metabolism, genetics similar to higher life-forms all cells composed of same elements synthesize structures in similar ways replicate DNA degrade foods via metabolic pathways

Answer 5

Emerging diseases pathogens can become resistant to antimicrobial medications (tuberculosis, malaria) increased travel and immigration many diseases eliminated from developed countries still exist in many parts of world (malaria, cholera, plague, yellow fever) changes in population weakened immune systems (elderly, HIV/AIDS) chronic diseases may be caused by bacteria -peptic ulcers caused by Helicobacter pylori

Answer 6

light is bent through lenses and enables a magnified view view size, shape and motility of prokaryotes and unicellular eukaryotes

Answer 7

controls the diameter of the light beam

Answer 8

focuses the light on the sample on your slide

Answer 9

Refraction is the bending of light as it passes from one medium to another. air <-> glass: different refractive index oil<-> glass: same refractive index More light passing through your sample gives you better resolution.

Answer 10

resolution: ability to clearly distinguish two objects that are close together together light microscope resolution:~ 0.3µm electron microscope resolution: ~0.3nm resolution is affected by: -quality and type of lens -wavelength of light -preparation of sample

Answer 11

I = 340/d where I is the magnifying power d is the diameter of the sphere expressed in mm. For example with a sphere of 1,7 mm of diameter you will obtain about a magnification of 200 X.

Answer 12

Bacterial cell walls maintain cell shape and rigidity and protect the cells from bursting due to osmotic pressure (turgor pressure). Bacterial cell walls are composed of peptidoglycan (but Archeal cell walls are not!).

Answer 13

Disruption of the cell wall of rod-shaped Bacillis species or Escherichia coli with lysozyme or penicillin results in formation of round, osmotically sensitive cells (SPHEROPLASTS) after microbe's cell wall digested, membrane tension causes cell to acquire spherical shape spheroplasts - osmotically fragile, lyse in hypotonic solution

Answer 14

FtsZ –forms part of ring in the middle of dividing cell required for constriction of cell membrane and cell envelope to yield two daughter cells. FtsZ can polymerise; bacterial homolog of Eukaryotic cytoskeletal component tubulin MreB - bacterial homolog of the Eukaryotic cytoskeletal component actin Crescentin is an intermediate-filament-like protein with an essential role in the curved-rod shape of Caulobacter crescentus

Answer 15

basic dyes (positive charge) attracted to negatively charged cellular components acidic dyes (negative charge) negative staining: cells repel, so dye colors background

Answer 16

simple staining - involves one dye differential staining - used to distinguish between different groups of bacteria Gram stain is a differential stain that distinguishes between Gram-positive bacteria and Gram-negative bacteria special stains (capsule, endospore, flagella) also useful

Answer 17

Gram stain reflects fundamental difference in cell wall structure separates most bacteria into two groups: Gram stain distinguishes between Gram-positive bacteria (purple) & Gram-negative bacteria (pink)

Answer 18

1. CRYSTAL VIOLET (PRIMARY STAIN) Cells stain purple 2. IODINE (MORDANT) Cells remain purple 3. ALCOHOL (DECOLORIZER) Gram positive:purple Gram negative: colorless 4. SAFRANIN (COUNTERSTAIN) Gram positive: purple Gram negative: pink

Answer 19

Mycobacterium genus: cell wall has mycolic acid – waxy fatty acid prevents uptake of dyes then resists decolorization. tuberculosis Mycobacterium tuberculosis: leprosy - chronic infectious disease caused by Mycobacterium leprae, an acid-fast, rod-shaped bacillus. Leprosy curable – treatment in early stages averts disability.

Answer 20

Plane refers to the orientation of the septum during division. If division occurs on one plane a chain is formed (strepto- Greek: twisted chain) Perpendicular division planes cause packets to form: tetrads and sarcinae Random division planes causes clusters to form (staphylo- Greek: grapelike cluster)

Answer 21

Origin of replication (OriC) is replicated oriC and newly synthesized DNA move to opposite ends of cell Plasma membrane and cell wall form septum (a partition separating two chambers) 2 identical daughter cells are formed

Answer 22

Surface area is the area around the cell membrane Volume is the space inside the cell The ratio is the surface area divided by the volume As radius of cell increases 1x to 3x, surface area increases from 1x to 9x volume increases from 1x to 27x As radius of cell increases 1x to 3x, surface area increases from 1x to 9x, volume increases from 1x to 27x The smaller the cell, the greater the surface-to-volume ratio. As the cell gets bigger, you have less surface area per unit of volume. .

Answer 23

cytoplasmic membrane phospholipid bilayer: essential part of cytoplasmic membrane - separates internal contents of cell from outside environment embedded integral membrane proteins - communication, transport cytoplasmic membrane lipids —>Bacterial, Eukaryotic cell membrane: fatty acids linked to glycerol by ester linkage Bacteria (and Eukaryotes): glycerol moiety is ester-linked to glycerol-3-phosphate backbone

Answer 24

Archeal cytoplasmic membrane: Hydrocarbons linked to glycerol by ether linkage Archaeal cell membranes are chemically different from all other living things, including a "backwards" glycerol molecule and isoprene derivatives in place of fatty acids. Archea: isoprenoid side chains are ether-linked to an glycerol-1-phosphate moiety b. monolayer-forming tetra-ether lipids: glycophospholipid from thermoacidophilic Thermoplasma acidophilum - heat resistant c. bilayer formed of archaeal diether lipids, found in order Halobacteriales

Answer 25

Within phospholipid bilayer some membrane proteins function as selective gates and/or sensors of environmental conditions plasma membrane: a selectively permeable barrier

Answer 26

electron transport chain uses energy from electrons to move protons out of cell creates electrochemical gradient across membrane energy called proton motive force harvested to drive cellular processes including ATP synthesis, some forms of transport, and motility protons outside hydroxide ions inside

Answer 27

ejection of protons creates electro-chemical gradient used to synthesize ATP, power transporters and flagella

Answer 28

a selectively permeable barrier – directed movement through selective gates Highly specific transport system - carriers transport a certain molecule type.

Answer 29

facilitated diffusion: form of passive transport movement down gradient; no energy required not typically useful in low-nutrient environments ***active transport: requires energy**** movement against gradient two main mechanisms: transporters use proton motive force transporters use ATP (ABC transporter) ATP Binding Cassette group translocation chemically alter compound phosphorylation common glucose

Answer 30

Green circles moving against their concentration gradient through a transport protein (requires energy) Yellow circles move down their concentration gradient (releases energy). The movement is coupled.

Answer 31

Blue circles moving against their concentration gradient through a transport protein (requires energy) Yellow circles move down their concentration gradient (releases energy). The movement is coupled.

Answer 32

Many different antiporters support bacterial pH homeostasis, nutrient uptake, motility and ATP synthesis. Both Escherichia coli and Bacillus subtilis establish a proton motive force, (PMF). The PMF is used to energize solute transport, motility and ATP synthesis.

Answer 33

Use the energy of ATP binding and hydrolysis to transport substances across cell membranes. ABC transporters consist of trans-membrane domains which determine specificity of the transporter, and cytoplasmic ATP-binding domains. Can export and import substances across the cytoplasmic membrane. Importers also have a high-affinity binding protein that recognizes the substrate in the periplasm and delivers it to the transporter.

Answer 34

Cell membranes Cell wall peptidoglycan Outer structures: Capsule Flagella and bacterial motility Pili Internal structures Nucleoid Plasmids Ribosomes Storage granules Endospores

Answer 35

Only bacteria have a peptidoglycan cell wall

Answer 36

Lysozyme hydrolyses the glycosidic bonds that link NAM and NAG

Answer 37

Penicillin inhibits formation of crosslinks in peptidogycan wall binds enzyme: transpeptidase (penicillin binding protein) transpeptidase forms tetra-peptide crosslinks between adjacent glycan chains Penicillin becomes covalently linked to the enzyme’s active site - inhibits it, irreversibly

Answer 38

Penicillin will kill only cells that are actively synthesizing peptidoglycan (cells that are growing) because it interferes with peptidoglycan synthesis. Lysozyme breaks the bonds that join the subunits, thereby weakening the existing structure.

Answer 39

Gram-positive cells thick (20-80 nm) cell wall peptidoglycan layer outside plasma membrane Gram-positive cell walls contain teichoic acids negatively charged; give Gram-positive bacteria a negative exterior charge PAMP – recognition by immune system cells

Answer 40

LPS consists of: O side chain - vary sugar composition in response to antibodies lipid A portion (part of outer membrane lipid bilayer) LPS slows entry of antibiotics and other toxins Lipid A toxic (endotoxin) to humans - part of LPS molecule recognized by our host defenses. When large amounts accumulate (such as in a bloodstream infection), response by defense system itself can be deadly.

Answer 41

Archaea have several different types of cell wall. Some contain a structure reminiscent of peptidoglycan called pseudomurein. Other microbes will have a surface layer (S-layer) composed of repeating units of one or a few proteins, glycoproteins or sugar. These crystal lattices serve to protect the cell.

Answer 42

S-layers in Archaea: glycoprotein lattices : wall component composed of subunits with pillar-like, hydrophobic trans-membrane domains, or lipid-modified glycoprotein subunits. Some Archaea have a rigid wall layer (pseudomurein in methanogens) as intermediate layer between plasma membrane and S-layer. In Gram-positive bacteria S-layer proteins are bound to rigid peptidoglycan-containing layer via secondary cell wall polymers. In Gram-negative bacteria S-layer closely associated with lipopolysaccharide of outer membrane.

Answer 43

Bacteria with capsules attaching to intestinal cells(TEM) Bactria adhering to each other in a layer of slime (SEM) glycocalyx: extracellular polymer of glycoprotein (polysaccharide) protective outer layer not all bacteria have one if thick and sturdy, a capsule. if thin and diffuse, a slime layer

Answer 44

capsule considered virulence factor - enhance ability of pathogenic bacteria to evade phagocytosis attach to surfaces be protected from toxins, detergents, bacteriophages Example: Streptococcus pneumoniae capsule

Answer 45

glycosyltransferases assemble oligosaccharide repeats on cytoplasmic face of membrane Wzx flippase transports repeat units to external surface of membrane. repeat units polymerized by Wzy capsular polymerase to form high-molecular-weight capsular polysaccharides, which are then ligated to cell wall

Answer 46

MONOTRICHOUS: single flagellum at one end Example: Caulobacter crescentus Vibrio cholerae, Pseudomonas aeruginosa, Isiomarina loihiensis LOPHOTRICHOUS: flagella lined up at one end Example: Vibrio fischeri, Helicobacter pylori PERITRICHOUS: flagella are distributed all over the cell E. coli, Example: Salmonella typhimurium SPIROCHETES: specialized flagella inside periplasm causes corkscrew motion Example: Borerelia, Treponema and Leptospira bacterial flagella are powered by the proton motive force, but Archea use ATP for energy

Answer 47

A cell moves via a series of runs and tumbles. The cell moves randomly when there is no concentration gradient of attractant or repellent. When a cell senses it is moving toward an attractant, it tumbles (T) less frequently, resulting in longer runs (R).

Answer 48

flagellum bacterial propulsion- Driven by a transmembrane proton gradient, rotates both CCW and CW filament is helical and converts torque into thrust. The motor consists of stators or Mot complexes and a rotor or C ring, which also serves as the CCW⇄CW switch.

Answer 49

Archaeal flagellins possess a highly conserved hydrophobic N-terminal sequence that is similar to that of type IV pilins and clearly unlike that of bacterial flagellins. The Archaellum is a rotating Type IV pilus After the pre-archaellin has been processed, the motor complex assembles the filament. The motor complex is formed by the ring-forming scaffold protein FlaX The dimeric soluble domain of FlaF interacts with the S-layer.

Answer 50

pilli, fimbriae and adhesins

Answer 51

dynamic adhesive structures, major virulence determinants in several human pathogens pilus fiber composed of pilin subunits made by prepilin peptidase cleaved by prepilin peptidase PilD for proper pilus assembly and function pilin translocated across inner membrane where it forms dynamic multimeric filament secreted via pore-forming secretin PilQ to bacterial surface PilC - transmembrane protein on inner membrane ATPases (PilB and PilT) mediate pilus extension and retraction

Answer 52

DNA in the environment can be entangled by retracting type IV pili and introduced into the cell through the outer (OM) and inner membranes (IM). In the cytoplasm, the incoming DNA is integrated into the genome by homologous recombination

Answer 53

structure used by bacteria during conjugation (direct contact) transfer of genetic material between a donor and a recipient cell Plasmid DNA forms a mating bridge Pili works in attaching to naked DNA, other cells, and cellulose (to move around). Pili also retract and extend

Answer 54

cell-surface components on pili that facilitate adhesion to other surfaces

Answer 55

The nucleoid is a chromatin-dense area within the cytoplasm and contains the bacterial DNA, associated proteins and RNA that are responsible for controlling the bacteria's activity and reproduction

Answer 56

The bacterial chromosome is packed tightly Although there are no histones in prokaryotes, other bacterial proteins condense the bacterial chromosome within the cell.

Answer 57

Site of protein synthesis Prokaryotic ribosome: 70S ribosome composed of 30S and 50S subunits Eukaryotic ribosome: 80S - composed of 40S and 60S subunits

Answer 58

consist of RNA and protein differences between bacterial and eukaryotic ribosomes exploited to create antibiotics that specifically target bacterial ribosomes similarities and differences between DNA sequences that encode small subunit of ribosomal RNA are used to identify organisms and to create phylogenies 16S rRNA genes are sequenced and compared in Bacteria and Archea 18S rRNA genes are sequenced and compared in Eukaryotes.

Answer 59

accumulations of polymers synthesized from a nutrient a cell has in excess.

Answer 60

dormant cell type formed by species of Bacillus and Clostridium (anthrax, botulism, food poisoning) resist: high temperatures (including boiling), most disinfectants, low energy radiation, desication, UV light can survive many years until an environmental stimulus triggers germination germinating endospores exit dormant stage to become typical multiplying cell (vegetative cell).

Answer 61

attack essential molecular machines in bacteria, stopping or slowing their action, ultimately slowing growth or killing the cell. IN CELL WALL BETA-LACTAM ANTIBIOTICS such as penicillin and methicillin, contain an extremely reactive beta-lactam ring that attacks BPs (penicillin-binding proteins) that build the cell wall. VANCOMYCIN sequesters the building blocks of the cell wall so that they can no longer be crosslinked to form a tough protective layer. IN CYTOPLASM MACROLIDES and AMINOGLYCOSIDES attack ribosomes, blocking manufacture of new proteins. FUSIDIC ACID glues elongation factor G (EF-G) to ribosomes, stalling protein synthesis. RIFAMPICIN, QUINOLINES and ANTIFOLATES attack essential enzymes in bacteria.

Answer 62

Phagocytosis: pseudopodium is made when cell membrane pinches to trap a solid particle and a phagosome is made (food vacuole) Pinocytosis: membrane pinches to make a vesicle that traps extracellular fluid Receptor mediated endocytosis: receptors trap particles and a coated vesicle is made

Answer 63

Endosymbiont theory states that the ancestors of mitochondria as well as chloroplasts were bacteria residing within other cells in a mutually beneficial partnership. The intracellular bacterium in such a partnership is called an endosymbiont. As time went on, the endosymbiont lost key features sucha s a cell wall amd the ability to replicate independently. Mitochondria multiply by elongating and then dividing (binary fission). Plastids (bacteria) also became plants (eukaryotes)

Answer 64

the process by which a cell engulfs a solid particle to form an internal vesicle (phagosome) phagocytosis - specific form of endocytosis involving vesicular internalization of bacteria In immune system, a major mechanism used to remove pathogens.

Answer 65

oriC is the region where replication is initiated septum is the division site - division is initiated by assembly of the tubulin homologue FtsZ into a membrane‐tethered ring‐like structure 1. Origin of replication (OriC) is replicated 2. oriC and newly synthesized DNA move to opposite ends of cell 3. Plasma membrane and cell wall form septum (a partition separating two chambers) 4. 2 identical daughter cells are formed

Answer 66

a | The vegetative life cycle. In favorable conditions Bacillus subtilis elongates, replicates its chromosome and divides by binary fission. b | Bacillus subtilis can develop a highly resistant, dormant cell to survive harsh environmental conditions. When conditions improve the endospore germinates and B. subtilis re-enters vegetative life cycle.

Answer 67

exponential growth: population doubles each division generation time - time it takes for population to double varies among species environmental conditions growth can be calculated: Nt = N0 x 2n Nt = number of cells in population at time t N0 = initial number of cells n = number of generations at that point example: pathogen in potato salad at picnic in sun assume 10 cells with 20 minute generation time N0 = 10 cells in original population n = 12 (3 divisions per hour for 4 hours) Nt = N0 x 2n = 10 x 212 Nt = 10 x 4,096 Nt = 40,960 cells of pathogen in 4 hours!

Answer 68

rapid generation time with optimal conditions can yield huge populations quickly remember that generation time depends on species and growth conditions

Answer 69

pure culture is defined as a population of cells derived from a single cell pure culture obtained using aseptic technique minimizes potential contamination cells grown on culture medium contains nutrients dissolved in water broth (liquid) or solid gel

Answer 70

…need culture medium, container, aseptic conditions, method to separate individual cells with correct conditions, single cell will multiply form visible colony (~1 million cells easily visible) agar used to solidify not destroyed by high temperatures and can be sterilized liquifies above 95°C solidifies below 45°C few microbes can degrade growth in Petri dish allows air excludes contaminants culture medium in a Petri dish called a plate

Answer 71

mass of cells arising from a single cell by binary fission to produce clonal copies of that cell

Answer 72

-bacterial sample diluted on the plate by process called "streaking” -wire loop, sterilized by heating used to take sample, and make a streak on the agar dish -repeated second, third, and sometimes a fourth time result: individual bacterial cells isolated on plate, which then divide and grow into single "clonal" bacterial colonies Pure culture is defined as a population of cells derived from a single cell

Answer 73

prokaryotes grown on agar plates or in tubes or flasks of broth closed systems nutrients not renewed; wastes not removed termed batch cultures yields characteristic growth curve

Answer 74

number of cells does not increase begin synthesizing enzymes required for growth delay depends on conditions

Answer 75

cells divide at constant rate generation time can be measured during active division most sensitive to antibiotics production of primary metabolites

Answer 76

variable length, depends on species and environment nutrient levels too low to sustain growth total numbers remain constant some die, release contents; others grow secondary metabolite production occurs - nutrients depleted and wastes accumulate

Answer 77

Primary metabolites are directly involved in the normal growth, development, and reproduction of the microoganism. Secondary metabolites (late log/stationary phase) are not involved in normal growth, but are organic compounds that may have a more ecological or relational function. Streptomycin (Streptomyces sp.) and penicillin (fungi) are examples of important secondary metabolites.

Answer 78

total number of viable cells decreases cells die at constant rate exponential, but usually much slower than cell growth

Answer 79

some fraction may survive adapted to tolerate worsened conditions

Answer 80

colonies and liquid cultures share similarities important differences based on location -position of single cell determines its environment -edge of colony has O2, nutrients center of colony has depleted O2, nutrients -accumulation of potentially toxic wastes including acids colony may range from exponential growth at edges to death phase in center

Answer 81

open system required to maintain continuous growth -termed continuous culture -nutrients added, wastes removed continuously chemostats can maintain continuous growth continually drips fresh medium into culture in chamber equivalent volume removed -contains cells, wastes, spent medium nutrient content and speed of addition can be controlled -achieve constant growth rate and cell density

Answer 82

Nutrients added, wastes removed continuously Nutrient content and speed of addition can be controlled Achieves constant growth rate and cell density steady state is reached ~ 3.7 hours after start up in this example. steady state equilibrium - point where cells will not grow any faster in the system. control factors: pH level, temperature, dissolved oxygen level, dilution rate, and agitation speed.

Answer 83

in nature, organisms grow as members of mixed communities and biofilms nutrients usually in short supply direct analysis of DNA from environmental samples provides more information than culture prokaryotes regularly grow in close association, many different species together their interaction can be cooperative metabolic waste of one can serve as nutrient for other or, their interaction can be competitive some bacteria synthesize toxins to inhibit competitors

Answer 84

Because of logarithmic growth, small differences in generation times quickly produce very large differences in total numbers of cells The ability of a microbe to compete successfully for a habitat is often related to the rate at which it multiplies Antagonism also helps determine community makeup

Answer 85

bacteriocins kill closely related strains: They are ribosomally synthesized antimicrobial peptides produced by bacterial species to inhibit the growth of other closely related bacteria. The producer strain also encodes an immunity protein to protect itself from its own bacteriocin.1

Answer 86

microorganisms historically studied in laboratory but dynamic, complex conditions in nature have profound effect on microbial growth, behavior cells sense changes, adjust to surroundings, synthesize compounds useful for growth bacteria in low-nutrient environments common in nature; include lakes, rivers, streams microorganisms that can grow in dilute aqueous solutions are widespread; most grow in biofilms polysaccharide-encased communities extract trace nutrients absorbed by water from air or absorbed onto the biofilm Biofilms cause slipperiness of rocks, in sink drains, scum in toilet bowls, dental plaque

Answer 87

biofilms have characteristic architecture channels through which nutrients and wastes pass *cells communicate by synthesizing chemical signals biofilms have important implications dental plaque leads to tooth decay, gum disease most infections (ear infections, cystic fibrosis) industrial concerns: accumulations in pipes, drains biofilm structure shields microbes growing within may be hundreds of times more resistant to disinfectants biofilms can also be helpful bioremediation, wastewater treatment

Answer 88

bacterial cells living within a biofilm: growth of aerobic organisms can deplete O2, create microzones where obligate anaerobes can grow fermenters can produce organic acids that may be metabolized by other organisms; various growth factors can also be transferred between organisms microbes unexpected in a macroenvironment might thrive in the microenvironment Living organisms interact with each other in symbiotic relationships: commensalism, mutualism, parasitism

Answer 89

Prokaryotes inhabit nearly all environments some live in comfortable habitats favored by humans some live in harsh environments termed extremophiles; most are Archaea Major conditions that influence growth: temperature atmosphere pH water availability

Answer 90

optimum growth usually close to upper end of range psychrophiles: –5° to 15°C found in Arctic and Antarctic psychrotrophs: 15° to 30°C important in food spoilage mesophiles: 25° to 45°C pathogens 35° to 40°C thermophiles: 45° to 70°C common in hot springs hyperthermophiles: 70° to 110°C usually members of Archaea found in hydrothermal vents

Answer 91

proteins of thermophiles resist denaturing thermostability comes from amino acid sequence number and position of bonds which determine structure temperature and food preservation refrigeration (~4°C) slows spoilage by limiting growth of fast-growing mesophiles psychrophiles, psychrotrophs can still grow, but slowly freezing preserves food; not effective at killing microbes temperature and disease temperature of different parts of human body differs some microbes cause disease in certain parts Hansen’s disease (leprosy) in coolest regions (ears, hands, feet, fingers) due to preference of M. leprae

Answer 92

Grows only when O2 is available Requires O2 for respiration Produces superoxide dismutase and catalase

Answer 93

Grows best when O2 is available, but also grows without it. Uses O2 for respiration, if available. Produces superoxide dismutase and catalase

Answer 94

Cannot grow when O2 is present Does not use O2 Does not produces superoxide dismutase and catalase

Answer 95

Grows only if small amounts of O, are available. Requires O, for respiration. Produces some superoxide dismutase and catalase.

Answer 96

Grows equally well with or without O2 Does not use O2. Produces superoxide dismutase but not catalase.

Answer 97

Oxygen, aerobic respiration, electron transfer chain, oxygen as final electron receptor (series of redox reactions - gets reduced to water)

Answer 98

reactive oxygen species using O2 in aerobic respiration produces harmful reactive oxygen species (ROS) as by-products includes superoxide (O2–) and hydrogen peroxide damaging to cellular components cells must have mechanisms to protect obligate anaerobes typically do not almost all organisms growing in presence of oxygen produce enzyme: superoxide dismutase - inactivates superoxide by converting to O2 and H2O2 almost all also produce catalase – converts H2O2 🡪 O2 + H2O exception is aerotolerant anaerobes; makes for useful test production of catalase distinguishes Staphylococcus species (catalase +) from Streptococcus species (catalase -)

Answer 99

bacteria survive a range of pH; have optimum most maintain constant internal pH, typically near neutral -pump out protons if in acidic environment -bring in protons if in alkaline environment most microbes are neutrophiles range of pH 5 to 8; optimum near pH 7 food can be preserved by increasing acidity H. pylori grows in stomach; produces urease to split urea into CO2 and ammonia to decrease acidity of surroundings acidophiles grow optimally at pH below 5.5 Picrophilus oshimae has optimum pH of less than 1! alkaliphiles grow optimally at pH above 8.5

Answer 100

environmental changes often alter communities organisms adapted to live in one environment likely not well suited to a different one growth, metabolism of organisms changes nutrients become depleted, wastes accumulate can bring about succession of bacterial species succession in raw milk is example… Production of acid causes souring and encourages growth of yeasts and molds. Eventually, bacteria digest the proteins, causing putrefaction.

Answer 101

all microorganisms require water for growth dissolved salts, sugars make water unavailable to cell If solute concentration is higher outside of cell, water diffuses out (osmosis) some microbes withstand or even require high salt halotolerant: withstand up to 10% (Staphylococcus) halophiles: require high salt concentrations marine bacteria ~3% extreme halophiles ≥ 9% (Dead Sea, Utah’s salt flats)

Answer 102

prokaryotes have remarkable metabolic diversity require nutrients to synthesize cell components lipid membranes, cell walls, proteins, nucleic acids made from subunits: phospholipids, sugars, amino acids, nucleotides major elements like carbon, hydrogen, oxygen, nitrogen, sulfur, phosphorus, potassium, magnesium, calcium, and iron make up cell components carbon source distinguishes different groups: ->heterotrophs use organic molecules as carbon source ->autotrophs use inorganic carbon: CO2 (carbon fixation) nitrogen required for amino acids, nucleic acids many use ammonia (some convert nitrate to ammonia) nitrogen fixation important iron, phosphorus often limiting trace elements usually available (cobalt, zinc, copper, molybdenum, manganese)

Answer 103

Bacterial iron sources include host proteins (transferrin, lactoferrin, heme, siderophores) These iron sources are transported into a Gram-negative cell via outer membrane receptors, periplasmic binding proteins (PBP), ATP-binding cassette (ABC) transporters

Answer 104

some microbes can’t synthesize certain molecules fastidious: have complicated nutritional requirements amino acids, vitamins, purines, pyrimidines only grow if these growth factors are available reflects biosynthetic capabilities -E. coli synthesizes all cellular components from glucose, has wide metabolic capabilities -Neisseria unable to synthesize many, requires numerous growth factors

Answer 105

energy sources: sunlight, chemical compounds phototrophs obtain energy from sunlight plants, algae, photosynthetic bacteria chemotrophs extract energy from chemical compounds mammalian cells, fungi, many types of prokaryotes sugars, amino acids, fatty acids common sources chemolithotrophs use inorganic chemicals such as hydrogen sulfide (H2S), hydrogen gas (H2)

Answer 106

Energy source: sunlight Carbon source: CO2

Answer 107

Energy source: sunlight Carbon source: organic compounds

Answer 108

Energy source: Inorganic chemicals (Ha, NH3, NO,", Fe?*, HyS) Carbon source: CO2

Answer 109

Energy source: Organic compounds (sugars, amino acids, etc.) Carbon source: Organic compounds

Answer 110

complex media contain a variety of ingredients exact composition highly variable often a digest of proteins chemically defined media composed of exact amounts of pure chemicals used for specific research experiments usually buffered

Answer 111

special types of culture media useful for isolating and identifying a specific species selective media inhibit growth of certain species differential media contain substance that microbes change in identifiable way

Answer 112

aerobic most obligate aerobes and facultative anaerobes can be incubated in air (~20% O2) -broth cultures shaken to provide maximum aeration many medically important bacteria (Neisseria, Haemophilus) grow best with increased CO2 some are capnophiles, meaning require increased CO2 one method is to incubate in candle jar microaerophilic require lower O2 concentrations than achieved by candle jar can incubate in gas-tight container with chemical packet chemical reaction reduces O2 to 5–15%

Answer 113

anaerobic: obligate anaerobes sensitive to O2 anaerobic containers useful if microbe can tolerate brief O2 exposures; can also use semisolid culture medium containing reducing agent (sodium thioglycolate) reduces O2 to water anaerobic chamber provides more stringent approach

Answer 114

enrichment cultures used to isolate organism that constitutes small fraction of mixed population provide conditions promoting growth of particular species specific carbon source

Answer 115

direct cell counts: total numbers (living plus dead) direct microscope count cell-counting instruments (Coulter counter, flow cytometer) viable cell counts: cells capable of multiplying can use selective, differential media for particular species plate counts: single cell gives rise to colony plate out dilution series: 30–300 colonies ideal plate counts determine colony-forming units (CFUs)

Answer 116

a colony-forming unit (CFU) is a unit used to estimate the number of viable bacteria (or fungal) cells in a sample. viable – has the ability to multiply via binary fission under the controlled conditions. ... DOESN’T INCLUDE CELLS IN SUPENSION THAT ARE DEAD, UNABLE TO FORM COLONIES ON PLATE. concentration of bacteria in a liquid suspension is expressed as cells/ml

Answer 117

membrane filtration concentrates microbes by filtration filter is incubated on appropriate agar medium measuring biomass turbidity is proportional to concentration of cells measured with spectrophotometer measuring biomass total weight can be measured typically only used for filamentous organisms that do not readily separate into individual cells for valid plate counts cells in liquid culture centrifuged; pellet is weighed dry weight can be determined by heating pellet in oven detecting cell products pH indicators Durham tubes (inverted tubes) to trap gas CO2 production ATP production using enzyme luciferase to produce light

Answer 118

required elements major elements make up cell components carbon source distinguishes different groups heterotrophs use organic molecules as carbon source autotrophs use inorganic carbon as CO2 (carbon fixation) nitrogen required for amino acids, nucleic acids many use ammonia (some convert nitrate to ammonia) nitrogen fixation important iron, phosphorus often limiting trace elements usually available (cobalt, zinc, copper molybdenum, manganese)

Answer 119

Organic molecules are the molecules of life and are built around chains of carbon atoms that are often quite long. There are four main groups of organic molecules that combine to build cells and their parts: carbohydrates, proteins, lipids, and nucleic acids. Inorganic molecules: molecules other than organic molecules - generally simple and not normally found in living things. Although all organic substances contain carbon, some substances containing carbon, (ex: diamonds) are considered inorganic. CO2 – as source of available carbon in the carbon cycle, atmospheric carbon dioxide is the primary carbon source for life on Earth

Answer 120

energy sources: sunlight, chemical compounds phototrophs obtain energy from sunlight plants, algae, photosynthetic bacteria chemotrophs extract energy from chemical compounds mammalian cells, fungi, many types of prokaryotes sugars, amino acids, fatty acids common sources CHEMOSYNTHESIS->some prokaryotes use inorganic chemicals such as hydrogen sulfide, hydrogen gas

Answer 121

Until late 19th century, patients undergoing even minor surgeries were at great risk of developing fatal infections physicians didn’t know their hands could pass diseases from one patient to the next did not understand airborne microbes could infect open wounds During the 1800s, puerperal fever was widespread in Europe and a common cause of maternal death.

Answer 122

In 1842 Oliver Wendel Holmes, Boston physician, spent a year researching puerperal fever by going through case reports and other medical literature in Boston. 1843 - published "The Contagiousness of Puerperal Fever," in The New England Quarterly Journal of Medicine and Surgery Puerperal fever is spread through physicians and midwives who make contact with the disease and carry it from patient to patient. Physicians who plan on attending to pregnant women should not take part in autopsies on patients who died of puerperal fever. If they do attend an autopsy, they should properly clean themselves and wait a full day before attending to pregnant patients. If a physician has three closely connected puerperal fever cases, then that physician should be regarded as the reason for the spread of the disease. Widespread cases of puerperal fever under any physician should not be seen as a misfortune but as crime.

Answer 123

Ignaz Semmelweis July 1818 – 13 August 1865 Hungarian physician/scientist Hospital at University of Vienna 1847 - noticed women giving birth with midwives had much lower incidence of childbed fever than those giving birth in doctor's maternity ward…

Answer 124

1861 Louis Pasteur published germ theory of disease: some diseases are caused by microorganisms

Answer 125

Joseph Lister (1827-1912) British surgeon - introduced methods to prevent infection of wounds Impressed with Pasteur’s work, he wondered if ‘minute organisms’ might be responsible for infections -applied carbolic acid (phenol) directly onto damaged tissues, where it prevented infections -improved methods further by sterilizing instruments and maintaining clean operating environment

Answer 126

aseptic technique: procedures that minimize the chance of unwanted microbes being accidentally introduced sterilization: removal of all microorganisms sterile item is free of microbes including endospores and viruses (but does not consider prions) disinfection: elimination of most or all pathogens some viable microbes may remain disinfectants used on inanimate objects: biocides, germicides, bactericides antiseptics used on living tissues pasteurization: brief heating to reduce number of spoilage organisms, destroy pathogens foods, inanimate objects decontamination: reduce pathogens to levels considered safe to handle sanitized: substantially reduced microbial population that meets accepted health standards-not a specific level of control preservation: process of delaying spoilage of foods and perishable products -adjust conditions -add bacteriostatic (growth-inhibiting) preservatives

Answer 127

the destruction or removal of all microbes through physical or chemical means filtration heat irradiation certain chemicals – a sterilant is a chemical that destroys all microbes

Answer 128

disinfectant – a chemical that destroys many microbes. Disinfectants are substances that are applied to non-living objects to destroy microorganisms living on the objects. antiseptics used on living tissues An antiseptic is a disinfectant non-toxic enough to be used on skin

Answer 129

brief heating to reduce number of spoilage organisms, destroy pathogens foods, inanimate objects Wine has been briefly heated in China since the 1100’s. Pasteurization slows microbial growth. 1864 Louis Pasteur originally used heating to prevent spoilage of wine and beer. Later, used for milk. Flash pasteurization: 71ºC for 15 seconds

Answer 130

reduce pathogens to levels considered safe to handle

Answer 131

substantially reduced microbial population that meets accepted health standards -not a specific level of control make clean and hygienic "new chemicals for sanitizing a pool"

Answer 132

BACTERIOSTATIC – prevents the growth of, but does not kill, bacteria BACTERICIDAL – kills bacteria

Answer 133

situational considerations: microbial control methods depend upon situation and level of control required daily life washing and scrubbing with soaps and detergents achieves routine control soap aids in mechanical removal of organisms beneficial skin microbiota reside deeper on underlying layers of skin, hair follicles -not adversely affected by regular use Hand washing with soap and water most important step in stopping spread of many infectious diseases! Mask wearing during COVID 19 pandemic

Answer 134

minimizing microbial population very important danger of healthcare-associated infections (HAIs) patients more susceptible to infection may undergo invasive procedures (surgery) pathogens more likely found in hospital setting feces, urine, respiratory droplets, bodily secretions instruments must be sterilized to avoid introducing infection to deep tissues prions relatively new concern; difficult to destroy

Answer 135

1. other patients 2. healthcare environment (Pseudomonas aeruginosa) 3. healthcare workers (Clostridium difficile, Staphylococcus aureus) 4. patient’s own microbiota

Answer 136

routinely work with microbial cultures use rigorous methods of control must eliminate microbial contamination to both experimental samples and environment careful treatment both before (sterile media) and after (sterilize cultures, waste) aseptic techniques used to prevent contamination of samples, self, laboratory CDC guidelines for labs working with microbes Biosafety levels range from BSL-1 (microbes not known to cause disease) to BSL-4 (lethal pathogens for which no vaccine or treatment exists) primary risks that determine levels of containment: infectivity, severity of disease, transmissibility, and the nature of the work conducted. Origin of the microbe, or agent in question, and route of exposure also important.

Answer 137

the application of safety precautions that reduce a lab worker’s risk of exposure to a potentially infectious microbe and limit contamination of the work environment and, ultimately, the community. Biosafety Level 4 Organisms viruses known to cause viral hemorrhagic fever such as Marburg virus, Ebola virus, Lassa virus, Crimean-Congo hemorrhagic fever.

Answer 138

perishables retain quality longer when contaminating microbes destroyed, removed, inhibited heat treatment most common and reliable mechanism can alter flavor, appearance of products irradiation approved to treat certain foods chemical additives can prevent spoilage FDA regulates because of risk of toxicity facilities must keep surfaces clean and relatively free of microbes pharmaceuticals, cosmetics, deodorants must not carry microbial contamination

Answer 139

ensure drinking water free of pathogens chlorine traditionally used to disinfect water can react with naturally occurring chemicals form disinfection by-products (DBPs) some DBPs linked to long-term health risks some organisms resistant to chemical disinfectants Cryptosporidium parvum (causes diarrhea)

Answer 140

Selection of effective procedure complicated ideal method does not exist each has drawbacks and procedural parameters Choice depends on numerous factors: 1. type of organisms 2. number of organisms 3. environmental conditions 4. risk of infection 5. composition of infected item

Answer 141

multiple highly resistant microbes bacterial endospores: most resistant, only extreme heat or chemical treatment destroys them protozoan cysts and oocysts: resistant to disinfectants; excreted in feces; causes diarrheal disease if ingested Mycobacterium species: waxy cell walls makes resistant to many chemical treatments Pseudomonas species: resistant to and can actually grow in some disinfectants non-enveloped viruses: lack lipid envelope; more resistant to disinfectants

Answer 142

opportunistic pathogen; major cause of healthcare-associated infection, important in lung infections and wound infections, especially thermal burns Forms biofilms signs and symptoms: chills, fever, skin lesions, shock pigments (fluorescent yellow pyoverdin and blue pyocyanin) yield characteristic green color Gram-negative rod with polar flagellum found in soils, water aerobic; respires anaerobically in absence of O2 if nitrate is present

Answer 143

lack lipid envelope; more resistant to disinfectants Adenoviruses Papovaviruses Parvoviruses Rotaviruses Rhinoviruses Polioviruses Noroviruses Astroviruses

Answer 144

time for heat, chemicals to kill affected by population size fraction of population dies during given time interval large population = more time decimal reduction time gauges commercial effectiveness D value: time required to kill 90% of population under specific conditions

Answer 145

dirt, grease, body fluids can interfere with heat penetration, action of chemicals important to thoroughly clean microorganisms in biofilm are more resistant pH, temperature can influence effectiveness sodium hypochlorite (household bleach) solution can kill suspension of M. tuberculosis at 55°C in half the time as at 50°C even more effective at low pH

Answer 146

medical instruments categorized according to risk for transmitting infectious agents critical items come in contact with body tissues must be sterile include needles and scalpels semicritical instruments contact mucous membranes but do not penetrate body tissues must be free of viruses and vegetative bacteria few endospores blocked by mucous membranes includes endoscopes and endotracheal tubes non-critical instruments contact unbroken skin only low risk of transmission countertops, stethoscopes, blood pressure cuffs

Answer 147

some sterilization and disinfection methods inappropriate for certain items heat inappropriate for plastics and other sensitive items irradiation provides alternative, but damages some types of plastic moist heat, liquid chemical disinfectants cannot be used to treat moisture-sensitive material

Answer 148

heat treatment useful for microbial control reliable, safe, relatively fast, inexpensive, non-toxic can be used to sterilize or disinfect sterilization using pressurized steam autoclave used to sterilize using pressurized steam increased pressure raises temperature; kills endospores sterilization longer for larger volumes flash sterilization at higher temperature can be used

Answer 149

irreversibly denatures proteins boiling destroys most microorganisms and viruses does not sterilize: endospores can survive pasteurization destroys heat-sensitive pathogens, spoilage organisms high-temperature–short-time (HTST): most products milk: 72°C for 15 s; ice cream: 82°C for 20 s ultra-high-temperature (UHT): shelf-stable boxed juice and milk; known as “ultra-pasteurization” milk: 140°C for a few seconds, then rapidly cooled

Answer 150

uses industrial-sized autoclave called retort designed to destroy Clostridium botulinum endospores -virtually impossible to have so many endospores critical because otherwise endospores can germinate in canned foods cells grow in low-acid anaerobic conditions and produce botulinum toxin canned food commercially sterile

Answer 151

less effective than moist heat; longer times, higher temperatures necessary 200°C for 90 minutes vs. 121°C for 15 minutes hot air ovens oxidize cell components, denature proteins used for glass, powders, oils, dry materials incineration a method of dry heat sterilization oxidizes cell to ashes used to destroy medical waste and animal carcasses laboratory inoculation loop sterilized by flaming

Answer 152

some materials can’t withstand heat treatment filtration retains bacteria filtration of fluids used extensively membrane filters small pore size (0.2 µm) to remove bacteria thin depth filters thick porous filtration material (cellulose) larger pores electrical charges trap cells filtration of air high-efficiency particulate air (HEPA) filters remove nearly all microbes

Answer 153

Irradiation can induce genetic damage and chemical changes in key biological macromolecules electromagnetic radiation: radio waves, microwaves, visible and ultraviolet light, X rays, and gamma rays energy travels in waves; no mass ionizing radiation can remove electrons from atoms gamma rays and X rays important forms destroys DNA damages cytoplasmic membranes reacts with O2 to produce reactive oxygen species high energy gamma-rays used to sterilize heat-sensitive materials generally used after packing approved for use on foods, although consumer resistance has limited use ultraviolet radiation destroys microbes directly damages DNA used to destroy microbes in air, water, and on surfaces poor penetrating power thin films or coverings can limit effect cannot kill microbes in solids or turbid liquids most glass and plastic block must be carefully used since damaging to skin, eyes microwaves kill by generated heat, not directly microwave ovens heat food unevenly, so cells can survive

Answer 154

used in pasteurization of commercial foods -guacamole- avoids problems with high temperature pasteurization employs high pressure up to 130,000 psi (pound force/sq. inch) destroys microbes by denaturing proteins, altering cell permeability products maintain color, flavor associated with fresh food

Answer 155

potency of germicidal chemical formulations sterilants destroy all microorganisms - also called sporocides heat-sensitive critical instruments high-level disinfectants destroy viruses, vegetative cells do not reliably kill endospores semi-critical instruments intermediate-level disinfectants destroy vegetative bacteria, mycobacteria, fungi, and most viruses disinfect non-critical instruments low-level disinfectants destroy fungi, vegetative bacteria except mycobacteria, and enveloped viruses do not kill endospores, non-enveloped viruses disinfect furniture, floors, walls

Answer 156

toxicity: benefits must be weighed against risk of use activity in presence of organic material many germicides inactivated compatibility with material being treated liquids cannot be used on electrical equipment residues: can be toxic or corrosive cost and availability storage and stability concentrated stock decreases storage space environmental risk agent may need to be neutralized before disposal

Answer 157

alcohols aldehydes biguanides: extensive use as antiseptics ethylene oxide: gaseous sterilant halogens: oxidize proteins, cellular components metal compounds ozone (O3) peroxygens phenolic compounds (phenolics) quaternary ammonium compounds (quats)

Answer 158

chemical preservatives food preservatives must be non-toxic for safe ingestion weak organic acids (benzoic, sorbic, propionic) ltaer cell membrane function control molds and bacteria in foods reducing available water accomplished by salting, adding sugar, or drying food addition of salt, sugar increases environmental solutes causes cellular plasmolysis (water exits bacterial cells) some bacteria grow in high salt environments Staphylococcus aureus drying often supplemented by salting lyophilization (freeze drying) foods coffee, milk, meats, fruits, vegetables drying stops microbial growth but does not reliably kill Many cases of salmonellosis from dried eggs nitrate and nitrite used in processed meats inhibit endospore germination and vegetative cell growth stops growth of Clostridium botulinum higher concentrations give meats pink color shown to be carcinogenic—form nitrosamines low-temperature storage refrigeration inhibits growth of pathogens and spoilage organisms by slowing or stopping enzyme reactions psychrotrophs, psychrophilic organisms can still grow freezing preserves by stopping all microbial growth Some microbial cells killed by ice crystal formation, but many survive and can grow once thawed

Answer 159

Metabolism is the sum total of chemical reactions for energy generation and biosynthetic processes within a cell. During metabolism, cells take energy stored in nutrients such as glucose and redistribute that energy to other molecules, building more complex cellular structures. A set of ordered reactions is required to extract and redistribute the energy stored in a molecule of glucose.

Answer 160

FERMENTATION LEADING TO EXCRETION OF LACTATE FERMENTATION LEADING TO EXCRETION OF ALCOHOL AND CO2

Answer 161

All cells need to accomplish two fundamental tasks harvest energy to power reactions synthesize new parts cell walls, membranes, ribosomes, nucleic acids sum total of chemical reactions in cell called metabolism

Answer 162

catabolism processes that degrade compounds to release energy cells capture to make ATP anabolism biosynthetic processes assemble subunits of macromolecules use ATP to drive reactions processes intimately linked

Answer 163

energy is the capacity to do work two types of energy potential: stored energy (chemical bonds, rock on hill) kinetic: energy of movement Cells convert potential energy, usually in the form of C-C covalent bonds or ATP molecules, into kinetic energy to accomplish cell division, growth, biosynthesis, and active transport

Answer 164

photosynthetic organisms harvest energy of sunlight convert kinetic energy of photons to potential energy of chemical bonds powers synthesis of organic compounds from CO2 CO2 + H2O => C6 H12O6 + O2 chemoorganotrophs obtain energy from chemical bonds in organic compounds C6 H12O6 + O2 => CO2 + H2O - they depend on activities of photosynthetic organisms …or in certain environments like thermal vents they depend on organic compounds produced by chemolithoautotrophs that obtain energy by oxidizing inorganic compounds.

Answer 165

phototrophs get energy from light autotrophs use CO2 as a carbon source heterotrophs use an organic nutrient to make organic compounds

Answer 166

free energy is energy available to do work energy released when chemical bond is broken compare free energy of reactants, products: exergonic reactions: reactants have more free energy energy is released in reaction energy released from exergonic reactions powers endergonic reactions free energy is energy available to do work endergonic reactions: products have more free energy reaction requires input of energy change in free energy is same regardless of number of steps involved (converting glucose to CO2 + H2O) cells use multiple steps when degrading compounds

Answer 167

biological catalysts: speed up conversion of substrate into product by lowering activation energy

Answer 168

series of chemical reactions that convert starting compound to end product may be linear, branched, cyclical

Answer 169

adenosine triphospate (ATP) is energy currency of the cell adenosine diphospate (ADP) acceptor of free energy cells produce ATP by adding Pi to ADP using energy release energy from ATP to yield ADP and Pi adenosine triphosphate composed of ribose, adenine, three phosphate groups three negatively charged phosphate groups repel bonds inherently unstable, easily broken releases energy to drive cellular processes high energy phosphate bonds denoted by ~ ATP 🡪 ADP + Pi

Answer 170

substrate-level phosphorylation exergonic reaction oxidative phosphorylation proton motive force photophosphorylation sunlight used to create proton motive force

Answer 171

When electrons move from a molecule that has a relatively low electron affinity (tends to give up electrons) to one that has a higher electron affinity (tends to accept electrons), ENERGY IS RELEASED. (glucose to O2) Energy transfer increases energy content of one system while decreasing energy content of other system by same amount. Transfer characterized by quantity of energy transferred: an atom with higher electronegativity is better able to attract electrons. Transfer occurs in a process that changes state of each system. WHEN ELECTRONS MOVE FROM A MOLECULE THAT HAS A LOW ELECTRON AFFINITY TO ONE THAT HAS A HIGHER ELECTRON AFFINITY, ENERGY IS RELEASED. More energy is released when the difference in electronegativity is greater Electron donor: energy source Acceptor: terminal electron acceptor

Answer 172

The molecule that looses one or more electrons is OXIDIZED by the reaction; the one that gains those electrons is REDUCED. substance loses electrons - oxidized substance gains electrons - reduced electron-proton pair or hydrogen actually moves dehydrogenation = oxidation hydrogenation = reduction prokaryotes remarkably diverse in using energy sources and terminal electron acceptors organic, inorganic compounds used as energy source O2 or other molecules used as terminal electron acceptor electrons removed through series of oxidation-reduction reactions (redox reactions)

Answer 173

CELLS INITIALLY TRANSFER THE ELCTRONS TO ELECTRON CARRIERS NAD+/NADH, FAD/FADH2 and NADP+/NADPH Reduced electron carriers represent reducing power because they can transfer their electrons to another chemical that has a higher affinity for electrons. NADH and FADH2 transfer their electrons to the electron transport chain, which uses the energy to drive a proton motive force

Answer 174

role of electron carriers energy harvested in stepwise process electrons transferred to electron carriers, which represent reducing power (easily transfer electrons to chemicals with higher affinity for electrons) raise energy level of recipient molecule NAD+/NADH, NADP+/NADPH, and FAD/FADH2 NAD+/NADH oxidized and reduced forms of nicotinamide adenine dinucleotide FAD/FADH2 Oxidized and reduced forms of flavin adenine dinucleotide NADP+/NADPH Oxidized and reduced forms of nicotinamide adenine dinucleotide phosphate

Answer 175

Electrons carried by NADPH are used in biosynthesis whereas those carried by NADH are passed to the electron transport chain.

Answer 176

precursor metabolites are intermediates of catabolism that can be used in anabolism serve as carbon skeletons for building macromolecules pyruvate can be converted into amino acids: alanine, leucine, or valine E. coli can grow in glucose-salts medium contains just glucose, inorganic salts glucose is energy source glucose is starting point for all cellular components including proteins, lipids, carbohydrates, nucleic acids some glucose molecules completely oxidized for energy; others used in biosynthesis

Answer 177

three central metabolic pathways oxidize glucose to CO2 catabolic and precursor metabolites as well as reducing power can be diverted for use in biosynthesis amphibolic - dual role glycolysis splits glucose (6C) to two pyruvates (3C) generates modest ATP, reducing power, precursors pentose phosphate pathway primary role is production precursor metabolites, NADPH tricarboxylic acid cycle oxidizes pyruvates from glycolysis generates reducing power, precursor metabolites, ATP

Answer 178

directly phosphorylating ADP with a phosphate and energy provided from a coupled reaction.

Answer 179

when ATP is generated from the oxidation of NADH and FADH2 and the subsequent transfer of electrons and pumping of protons. That process generates an electrochemical gradient, which is required to power ATP synthase.

Answer 180

respiration transfers electrons from glucose to electron transport chain electron transport chain generates proton motive force harvested to make ATP via oxidative phosphorylation *aerobic respiration O2 is terminal electron acceptor *anaerobic respiration molecule other than O2 as terminal electron acceptor also use modified version of TCA cycle fermentation if cells can’t respire, run out of carriers available to accept electrons glycolysis will stop fermentation uses pyruvate or derivative as terminal electron acceptor to regenerate NAD+ so glycolysis can continue

Answer 181

enzymes are biological catalysts name reflects function; ends in –ase has active site to which substrate(s) bind(s) weakly causes enzyme shape to change slightly, induced fit existing substrate bonds destabilized, new ones form enzymes are highly specific for substrate(s) cofactors assist some enzymes cofactors can assist different enzymes; include magnesium, zinc, copper, other trace elements

Answer 182

coenzymes are organic cofactors include electron carriers FAD, NAD+, NADP+, fewer types needed derived from vitamins (B vitamins) Coenzymes are organic molecules that transfer atoms from one molecule to another, may bind to a number of different enzymes, and are synthesized from vitamins.

Answer 183

enzymes have narrow range of optimal conditions temperature, pH, salt concentration 10°C increase doubles speed of enzymatic reaction up until maximum proteins denature at higher temperatures low salt, neutral pH usually optimal

Answer 184

enzyme activity controlled by binding to allosteric site distorts enzyme shape, prevents or enhances binding regulatory molecule is usually end product allows feedback inhibition

Answer 185

The activity of the first enzyme of the pathway is inhibited by the end product, thus controlling production of end product.

Answer 186

site to which inhibitor binds determines type competitive inhibitor binds to active site of enzyme chemical structure usually similar to substrate concentration dependent; blocks substrate example is sulfa drugs blocking folic acid synthesis non-competitive inhibitor binds to a different site than active site allosteric inhibitors are one example; action is reversible some non-competitive inhibitors are not reversible mercury oxidizes the S—H groups of amino acid cysteine, converts to cystine cystine cannot form important disulfide bond (S—S) enzyme changes shape, becomes nonfunctional

Answer 187

converts: 1 glucose to 2 pyruvates yields: net 2 ATP (2 in 4 out) reducing power: 2 NADH + 2H+ precursor metabolites: end product, pyruvate investment phase: 2 phosphate groups added glucose split to two 3-carbon molecules Intermediates: glucose-6-phosphate fructose6-phosphate dihydroxyacetone phosphate pay-off phase: 2 3-carbon molecules converted to 2 pyruvates Intermediates: 3-phosphoglycerate phosphoenolpyruvate generates 4 ATP, 2NADH total converts 1 glucose to 2 pyruvates; yields net 2 ATP (substrate level phosphorylation) 2 NADH

Answer 188

A carboxyl group is removed from pyruvate, releasing carbon dioxide. NAD+ is reduced to NADH. An acetyl group is transferred to coenzyme A, resulting in acetyl COA.

Answer 189

brings carbon atoms from glycolysis (pyruvate) to the citric acid cycle to be oxidized for energy production All genomes sequenced to date encode enzymes that use CoA as a substrate.

Answer 190

For I molecule of glucose TCA cycle produces: 4 ATP 6 NADH 2 FADH2 precursor metabolites The release of carbon dioxide is coupled with the reduction of NAD+ to NADH

Answer 191

Uses reducing power (NADH, FADH2) generated by glycolysis, transition step, and TCA cycle to synthesize ATP electron transport chain generates proton motive force drives synthesis of ATP by ATP synthase now called chemiosmotic theory electron transport chain: membrane-embedded electron carriers pass electrons sequentially, eject protons in process prokaryotes: in cytoplasmic membrane eukaryotes: in inner mitochondrial membrane

Answer 192

ATP synthase—harvesting the proton motive force to synthesize ATP energy required to establish gradient released when gradient is eased ATP synthase allows protons to flow down gradient in controlled manner uses energy to add phosphate group to ADP 1 ATP formed from entry of ~3 protons

Answer 193

oxidase test chromogenic reducing agent changes color when oxidized. If the test organism produces cytochrome c oxidase, the oxidase reagent will turn blue or purple within 15 seconds. OX+ bacterium contains cytochrome c oxidase and can therefore use oxygen for energy production with an electron transport chain Neisseria, Pseudomonas, Campylobacter, Helicobacer pylori Legionella pneumophila OX- bacterium does not contain cytochrome c oxidase and, therefore, either cannot use oxygen for energy production with an electron transport chain, or employs a different enzyme for transferring electrons to oxygen. Enerobactericeae (family includes many genera among which is E. coli)

Answer 194

some carriers accept only hydrogen atoms (proton-electron pairs), others only electrons spatial arrangement in membrane shuttles protons to outside of membrane when hydrogen carrier accepts electron from electron carrier, it picks up proton from inside cell or mitochondrial matrix when hydrogen carrier passes electrons to electron carrier, protons released to outside of cell or intermembrane space of mitochondria net effect is movement of protons across membrane establishes concentration gradient driven by energy released during electron transfer

Answer 195

Complex I (NADH dehydrogenase complex) accepts electrons from NADH, transfers to ubiquinone pumps 4 protons Complex II (succinate dehydrogenase complex) accepts electrons from TCA cycle via FADH2, “downstream” of those carried by NADH transfers electrons to ubiquinone Complex III (cytochrome bc1 complex) accepts electrons from ubiquinone from Complex I or II 4 protons pumped; electrons transferred to cytochrome c Complex IV (cytochrome c oxidase complex) accepts electrons from cytochrome c, pumps 2 protons terminal oxidoreductase, meaning transfers electrons to terminal electron acceptor (O2)

Answer 196

in prokaryotes: glycolysis: 2 NADH🡪 6 ATP transition step: 2 NADH 🡪 6 ATP TCA cycle: 6 NADH 🡪 18 ATP; 2 FADH2 🡪 4 ATP total maximum oxidative phosphorylation yield = 34 ATP slightly less in eukaryotic cells NADH from glycolysis in cytoplasm transported across mitochondrial membrane to enter electron transport chain requires ~1 ATP per NADH generated

Answer 197

Different prokaryotes have different components in their electron transport chain, and proton motive force can be used for purposes other than ATP generation.

Answer 198

The TCA cycle: glycolysis: 2 NADH🡪 6 ATP TCA cycle: 6 NADH 🡪 18 ATP 2 FADH2 🡪 4 ATP

Answer 199

Cells ferment if a suitable terminal electron acceptor is not available, or if they lack an electron transport chain.

Answer 200

In order to be able to re-enter glycolysis with NAD+. …the cells must oxidize NADH, otherwise they would run out of NAD+ and glycolysis would come to a halt.

Answer 201

Lactic acid bacteria create ATP without oxygen. …to produce NAD+ which can re-enter glycolysis. example: Streptococcus sp.

Answer 202

microbes can use variety of compounds excrete hydrolytic enzymes; transport subunits into cell degrade further to appropriate precursor metabolites polysaccharides and disaccharides amylases digest starch; cellulases digest cellulose disaccharides hydrolyzed by specific disaccharidases lipids fats hydrolyzed by lipases; glycerol converted to dihydroxyacetone phosphate, enters glycolysis fatty acids degraded by β-oxidation to enter TCA cycle proteins hydrolyzed by proteases; amino group deaminated carbon skeletons converted into precursor molecules

Answer 203

chemolithotrophs can directly provide electrons to the electron transport chain, while chemoorganotrophs must generate their own cellular reducing power by oxidizing reduced organic compounds (such as glucose) Chemolithotrophs bypass this by obtaining their reducing power directly from the inorganic substrate or by the reverse electron transport reaction.

Answer 204

prokaryotes unique in ability to use reduced inorganic compounds as energy sources inorganic molecules (sulfate, nitrate) serving as terminal electron acceptors to produce hydrogen sulfide (H2S), ammonia (NH3) by anaerobic respiration important example of nutrient cycling four general groups 1. hydrogen bacteria oxidize hydrogen gas (H2) - use hydrogen as an electron donor), - has high redox potential and can couple with oxygen or carbon dioxide or sulfate. Facultative autotrophs; include both aerobes and anaerobes mixotrophic – some aerobes also can have heterotrophic growth and use organic compounds for energy 2. sulfur bacteria oxidize hydrogen sulfide (H2S) Sulfur (non-photosynthetic) bacteria - some live at low pH (sulfuric acid – reduced product) 3. iron bacteria oxidize reduced forms of iron (Fe2+) 4. nitrifying bacteria: 2 groups - one oxidizes ammonia (NH3), forming nitrite the other oxidizes nitrite (NO2), forming nitrate.

Answer 205

plants, algae, several groups of bacteria can be considered in two distinct stages 1. light reactions (light-dependent reactions) capture energy and convert it to ATP 2. light-independent reactions (dark reactions) use ATP to synthesize organic compounds involves carbon fixation reaction-center pigments donate excited electrons to electron transport chain *chlorophyll a (plants, algae, cyanobacteria) *bacteriochlorophylls (anoxygenic bacteria) cyanobacteria: photosystems in membranes of stacked structures inside cell - termed thylakoids plants, algae: thylakoids in stroma of chloroplast-endosymbiotic theory explains purple bacteria (anoxygenic): in cytoplasmic membrane, extensive infoldings green bacteria (anoxygenic): specialized chlorosomes attached to cytoplasmic membrane

Answer 206

two distinct photosystems (I and II) cyclic photophosphorylation photosystem I alone produces ATP reaction-center chlorophyll is terminal electron acceptor non-cyclic photophosphorylation used when cells need both ATP and reducing power electrons from photosystem II drive photophosphorylation are then donated to photosystem I photosystem II replenishes electrons by splitting water generates oxygen (process is oxygenic) electrons from photosystem I reduce NADP+ to NADPH electrons from photosystem II drive photophosphorylation, water used as an electron donor, oxygen produced electrons from photosystem I reduce NADP+ to NADPH

Answer 207

Chemolithoautotrophs and photoautotrophs use CO2 to synthesize organic compounds: carbon fixation in photosynthetic organisms: light-independent reactions consumes lots of ATP, reducing power Calvin cycle most commonly used three essential stages -incorporation of CO2 into organic compounds -reduction of resulting molecule -regeneration of starting compound six “turns” of cycle: net gain of one fructose-6-phosphate consumes 18 ATP, 12 NADPH per fructose molecule

Answer 208

synthesize subunits using central metabolic pathways if enzymes lacking, end product must be supplied fastidious bacteria require growth factors lipid synthesis requires fatty acids and glycerol fatty acids: 2-carbon units added to acetyl group from acetyl-CoA glycerol: dihydroxyacetone phosphate from glycolysis nucleotide synthesis DNA, RNA initially synthesized as ribonucleotides purines: atoms added to ribose 5-phosphate to form ring pyrimidines: ring made, then attached to ribose 5-phosphate can be converted to other nucleobases of same type

Answer 209

each has single photosystem cannot use water as electron donor, so anoxygenic use electron donors such as hydrogen gas (H2), hydrogen sulfide (H2S), organic compounds purple bacteria: photosystem similar to photosystem II energy of electrons insufficient to reduce NAD+ instead expend ATP to use reversed electron transport green bacteria: photosystem similar to photosystem I electrons can generate proton motive force or reduce NAD+

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