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Prokaryote Structure 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
diglycerol tetraethers is a
lipid monolayer and does not separate easily due to heat easily
26
Three major classes of transport systems in prokaryotes
Simple transport Group translocation ABC system
27
Simple transport uses
PMF
28
Group translocation uses
chemical modification driven by phosphoenolpyruvate
29
ABC system uses
ATP
30
The Phosphotransferase System in E. coli
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
ABC (ATP-Binding Cassette) Systems
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
Gram Negative Cell wall
at least 2 layers of cell wall
33
Gram + cell wall
thicker but only a single molecule type
34
Rigid layer that provides strength to cell wall in Bacteria
Peptidogylcan
35
Gram-Positive Cell Walls
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
Name Prokaryotes that Lack Cell Walls
Mycoplasmas •Group of pathogenic bacteria •Have cholesterol in membrane like Eukaryotes
37
The Outer Membrane of Gram-Negative Bacteria has what?
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
Porins:
channels for movement of hydrophilic low molecular-weight substances
39
Periplasm:
space located between cytoplasmic and outer membranes • ~15 nm wide • Contents have gel-like consistency • Houses many proteins (hydrolytic, binding, chemoreceptors)
40
What are bacteria are responsible for differences in the Gram stain reaction?
Structural differences between cell walls of gram-positive and gram-negative
41
? dehydrates the peptidoglycan
Alcohol
42
Become impermeable to the crystal violet
gram +
43
cells are washed free of crystal violet
gram -
44
Cell Walls of Archaea
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
S-Layers:
found in other Archaea • “Paracrystalline surface layer” • Most common cell wall type among Archaea • Consist of protein or glycoprotein
46
Cell Surface Layers: Capsules and Slime Layers
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
Pili
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
Fimbriae
Filamentous protein structures | • Enable organisms to stick to surfaces or form pellicles
49
Endospores
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
Endospore Structure
•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
Flagella:
``` structure that assists in swimming • Different arrangements: peritrichous, polar, lophotrichous • Helical in shape • Filament composed of flagellin • Move by rotation ```
52
flagellated cells move more rapidly and typically spin around
polarly
53
What type of flagellated cells move slowly in a straight line
Peritrichously
54
Taxis
directed movement in response to chemical or physical gradients
55
Nutrients
Supply of monomers (or precursors of) required by cells for growth
56
Macronutrients
Nutrients required in large amounts
57
Essential elements
CHNOPS Se
58
Autotrophs | Heterotrophs
inorganic | organic

Microbiology (12 decks)

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