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Microbiology > Prokaryote Structure > Flashcards

Prokaryote Structure Flashcards

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Biology 101 flashcards
1
Q

All cells have the following in common:

A

Cytoplasmic membrane
Cytoplasm
Ribosomes
DNA chromosome

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2
Q

Viruses are…

A

Not considered cells• Composed, as a minimum, of protein coat and nucleic acid genome• No metabolic abilities of their own, some carry enzymes• Rely completely on biosynthetic machinery of infected cell• Infect nearly all types of cells• Smallest virus is 10 nm in diameter

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3
Q

Prokaryotic cells generally have a what kind of chromosome?

A

Single, circular DNA molecule: chromosome

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4
Q

DNA aggregates to form the

A

nucleoid region (not confined by membrane)

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5
Q

Prokaryotes also may have small amounts of extra-chromosomal DNA called

A

Plasmids

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6
Q

Coccus (pl. cocci):

A

spherical or ovoid

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7
Q

Rod:

A

cylindrical shape, aka bacillus (pl. bacilli)

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8
Q

Spirilla:

A

spiral shape

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9
Q

Size range for prokaryotes:

A

0.2 μm to > 700 μm in diameter

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10
Q

Size range for eukaryotic cells

A

10 to > 200 μm in diameter

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11
Q

Examples of large prokaryotes

A

sturgeon gut inhabitant

sulfur oxidizing chemolithotroph

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12
Q

There are advantages to being small:

A

Small cells contain more surface area relative to cell volume than large cells (i.e., higher S/V)

  • support greater nutrient exchange per unit cell volume
  • tend to grow faster than larger cells
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13
Q

Lower Limits of Cell Size

A

Cellular organisms < 0.15 μm in diameter are unlikely
Open oceans tend to contain small cells 0.2–0.4 μm dia. (maximize nutrient exchange
Many of these small cells also have small genomes (under 500,000 bp)
minimal existence
Intracellular pathogens also small with minimal genomes
ex:Prochlorococcus marinus

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14
Q

Cytoplasmic membrane: thin structure that surrounds the cell

A

6–8 nm thick
Vital barrier that separates cytoplasm from environment
Highly selective permeable barrier; enables concentration of specific metabolites and excretion of waste products

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15
Q

The Cytoplasmic Membrane in Bacteria

A

General structure is phospholipid bilayer
Contain both hydrophobic and hydrophilic components
Fatty acids point inward to form hydrophobic environment; hydrophilic portions remain exposed to external environment or the cytoplasm

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16
Q

What are key building blocks of membrane phospholipids in Bacteria and Archaea

A

Fatty acids(Bacteria and eukaryotes) and isoprene(Archaea)

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17
Q

? help stabilize membrane by forming ionic bonds with negative charges on the phospholipids

A

Mg and Ca

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18
Q

Phospholipids are amphipathic

The head region ? The tail region is ?

A

Head: contains highly polar covalent bonds
•Consists of glycerol, a phosphate, and a charged group(varies)
hydrophillic

Tail: hydrophobic: contains highly polar covalent bonds •Consists of a glycerol, a phosphate, and a charged group(varies)

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19
Q

Membrane-Strengthening Agents are

A

Sterols and Hopanoids

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20
Q

Sterols

A

Rigid, planar lipids found in eukaryotic membranes• Strengthen and stabilize membranes
Cholesterol

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21
Q

Hopanoids

A

Structurally similar to sterols• Present in membranes of many Bacteria

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22
Q

Archaeal Membranes have ? linkages

A

Ether

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23
Q

Bacteria and Eukarya that have ? linkages in phospholipids

A

Ester

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24
Q

Archaeal lipids lack ? , have isoprenes instead

A

fatty acids

25
Q

diglycerol tetraethers is a

A

lipid monolayer and does not separate easily due to heat easily

26
Q

Three major classes of transport systems in prokaryotes

A

Simple transport
Group translocation
ABC system

27
Q

Simple transport uses

A

PMF

28
Q

Group translocation uses

A

chemical modification driven by phosphoenolpyruvate

29
Q

ABC system uses

A

ATP

30
Q

The Phosphotransferase System in E. coli

A

AKA how E.coli eats sugar
Type of group translocation: substance transported is chemically modified during transport across the membrane
•Moves glucose, fructose, and mannose
•Five proteins required
•Energy derived from phosphoenolpyruvate (PEP!
)•The phosphoryl group on PEP is eventually transferred to the sugar after it passes through 4 proteins
•The resulting compound is larger and won’t easily move back across the membrane leading to a concentration gradient of sugar

31
Q

ABC (ATP-Binding Cassette) Systems

A

200 different systems identified in prokaryotes
• Often involved in uptake of organic compounds (e.g., sugars, amino acids), inorganic nutrients (e.g., sulfate, phosphate), and trace metals
•Typically display high substrate specificity andaffinity
•Contain periplasmic binding proteins

32
Q

Gram Negative Cell wall

A

at least 2 layers of cell wall

33
Q

Gram + cell wall

A

thicker but only a single molecule type

34
Q

Rigid layer that provides strength to cell wall in Bacteria

A

Peptidogylcan

35
Q

Gram-Positive Cell Walls

A

Can contain up to 90% peptidoglycan

Common to have teichoic acidsembedded in their cell wall
•Teichoic acids impart negative charge to wall, help attract cations
•Lipoteichoicacids: teichoic acids covalently bound to membrane lipids

See diagram

36
Q

Name Prokaryotes that Lack Cell Walls

A

Mycoplasmas
•Group of pathogenic bacteria
•Have cholesterol in membrane like Eukaryotes

37
Q

The Outer Membrane of Gram-Negative Bacteria has what?

A

Total cell wall contains ~10% peptidoglycan
•Most of cell wall composed of outer membrane(aka Lipopolysaccharide[LPS] layer)

LPS consists of core polysaccharide and O-polysaccharide

LPS replaces most of the phospholipids in outer half of outer membrane
Endotoxin: the toxic component of LPS, attributed to lipid A

38
Q

Porins:

A

channels for movement of hydrophilic low molecular-weight substances

39
Q

Periplasm:

A

space located between cytoplasmic and outer membranes
• ~15 nm wide
• Contents have gel-like consistency
• Houses many proteins (hydrolytic, binding, chemoreceptors)

40
Q

What are bacteria are responsible for differences in the Gram stain reaction?

A

Structural differences between cell walls of gram-positive and gram-negative

41
Q

? dehydrates the peptidoglycan

A

Alcohol

42
Q

Become impermeable to the crystal violet

A

gram +

43
Q

cells are washed free of crystal violet

A

gram -

44
Q

Cell Walls of Archaea

A

No peptidoglycan
•Typically no outer membrane
•Somehave Pseudomurein:
•Found in cell walls of certain methanogenic Archaea
•Polysaccharide similar to peptidoglycan
•Composed of N-acetylglucosamine and N-acetylalosaminuronic acid

45
Q

S-Layers:

A

found in other Archaea
• “Paracrystalline surface layer”
• Most common cell wall type among Archaea
• Consist of protein or glycoprotein

46
Q

Cell Surface Layers: Capsules and Slime Layers

A

Polysaccharide layers
•Assist in attachment to surfaces
•Aid in evasion of immune system
•Resist dessication
•Capsule tighter matrix, often bonded to cell wall
•Slime layer loose, less connected to cell

47
Q

Pili

A

Filamentous protein structures
• Typically longer than fimbriae
• Assist in surface attachment
•Facilitate genetic exchange between cells (conjugation)
• Pili involved in twitching motility and colonization in Vibrio cholerae

48
Q

Fimbriae

A

Filamentous protein structures

• Enable organisms to stick to surfaces or form pellicles

49
Q

Endospores

A

Highly differentiated cells resistant to heat, harsh chemicals, and radiation
• “Dormant” stage of bacterial life cycle
• Ideal for dispersal via wind, water, or animal gut
• Only present in some gram-positivebacteria
• Most studied in Clostridium and Bacillusspecies

50
Q

Endospore Structure

A

•Resistant to dyes
•Special stains like malachite green
•Characteristic component is dipicolinic acid •
Also enriched in Ca2+
•Dehydrated core, gives high heat tolerance
•Small acid soluble proteins complex with DNA; stabilize, condense and protect

51
Q

Flagella:

A 
structure that assists in swimming
•   Different arrangements: peritrichous, polar, lophotrichous
•   Helical in shape
•   Filament composed of flagellin
•   Move by rotation
52
Q

flagellated cells move more rapidly and typically spin around

A

polarly

53
Q

What type of flagellated cells move slowly in a straight line

A

Peritrichously

54
Q

Taxis

A

directed movement in response to chemical or physical gradients

55
Q

Nutrients

A

Supply of monomers (or precursors of) required by cells for growth

56
Q

Macronutrients

A

Nutrients required in large amounts

57
Q

Essential elements

A

CHNOPS Se

58
Q

Autotrophs

Heterotrophs

A

inorganic

organic

Microbiology (12 decks)

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