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Microbiology > Prokaryotes > Flashcards

Prokaryotes Flashcards

1
Q

Prokaryotes versus Eukaryotes

A

Prokaryotes: -smaller

  • lack internal membrane system around organelles -cell size is 0.5-4.0 um wide
  • spherical prokaryotes (coccus) are very small

Eukaryotes: -have inner membranes around organelles -cell size 10-20 um wide

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2
Q

Coccus

A

spherical or oval shaped (little spheres)

diplococcus- 2 cocci linked together

streptococcus- chains of cocci linked together tetrad- 4 cocci group together

sarcinae- 8 cocci linked together

staphylococcus- many cocci bunched together in a bundle

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3
Q

Bacillus

A

cylindrical rod shaped

diplobacilli- 2 bacilli

streptobacilli- chain of bacilli

palisade- several parallel cells lined up next to eachother

vibrios- comma shaped rods

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4
Q

Spirillum

A

spiral shaped

spirilla- rigid helix

spirochetes- flexible helices

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5
Q

Mycelium

A

network of long, multinucleate filaments

prefix: (-myces)

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6
Q

Pleomorphic

A

organisms that are variable in shape

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7
Q

Surface area to volume ratio and Growth Rates

A

small cells have more surface area relative to their volume than larger cells (larger S/V ratio) which means there is greater nutrient exchange per unit cell volume

-more area for exchange relative to volume allows small prokaryotes to grow and replicate faster than larger cells

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8
Q

Functions of cell membrane (all domains)

A
  • maintain cell’s integrity (separates cytoplasm from environment)
  • regulates transport by being a highly selective permeable barrier
  • energy metabolism in prokaryotes (not eukaryotes)
  • proteins attachment (receptors/channels)
  • receptors for detection and response to chemicals outside of cell
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9
Q

General Structure of Domain Bacteria membrane

A

phospholipid bilayer plus proteins

-no sterols but contain hopanoids

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10
Q

Membrane proteins (list)

A

Peripheral, Integral, Transmembrane

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11
Q

Peripheral proteins (fluid mosaic membrane)

A

loosely connected to membrane on cytoplasmic side -easily moved

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12
Q

Integral proteins (fluid mosaic membrane)

A

amphipathic (polar and nonpolar regions) -embedded within membrane and project outward or inward -carry out important functions

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13
Q

Transmembrane proteins (fluid mosaic membrane)

A

completely crosses membrane from one side to the other

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14
Q

Membrane strengthening lipids

A

sterols and hopanoids

-saturation levels of membrane lipids reflect environmental conditions such as temperature

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15
Q

Sterols

A
  • rigid, planar lipids found in eukaryotic membranes
  • strengthen and stabilize membranes
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16
Q

Hopanoids

A
  • structurally similar to sterols
  • present in membranes of many Bacteria
17
Q

Membrane fluidity

A

cell membrane has properties of both liquid and solid

-membrane needs to be at right fluidity which is temperature dependent

too cold= solidification (gelling)

too hot= thermal lysis (cell death)

18
Q

Adjusting to maintain correct membrane fluidity

A
  • adjust fatty acid composition of phospholipids
    1. cold- more unsaturated fatty acids (minimize van der waals forces)
    2. hot- more saturated fatty acids (maximize van der waals forces *van der waals forces strength determines if fatty acid tails attract and stick to eachother or not
  • adjust ratio of sterols, hopanoids, or other lipids in the membrane to maximize or minimize van der waals forces
19
Q

Transport in prokaryotes

A

active transport is always facilitated in prokaryotes

-no endocytosis/exocytosis in prokaryotes

20
Q

Group translocation

A

simultaneous transport and chemical modification of transported substance

-energy (ATP) dependent transport that chemically modifies molecule as it is brought into the cell

21
Q

Domain Bacteria Cell Walls

A

mostly structural polysaccharides and peptides/proteins -prevents osmotic lysis

-gram (+) and gram (-) cells

peptidoglycan- structural polysaccharide in cell walls of domain Bacteria

22
Q

Osmotic lysis

A

pressure from water entering cell causing a rupture of the cell membrane and death of the cell

23
Q

Breaking Bacterial cell walls

A
  1. Lysozyme- breaks the bond between N-acetyl glucosamine and N-acetylmuramic acid in cell wall
  2. Penicillin- inhibits peptidoglycan synthesis of cell wall

*breakdown of cell wall causes influx of water to rush into the cell from the hypotonic environment outside the cell, causing the cell to burst through lysis

24
Q

Bacteria without cell wall

A

Mycoplasma: -does not produce a cell wall -plasma membrane stronger (has sterols) more resistant to osmotic pressure -hyper regulates internal solute concentration to stay slightly hypertonic (so cell doesn’t become dehydrated)

25
Q

Gram positive and Gram negative bacteria (quick facts and staining)

A

gram (+): stain purple, thick layer of peptidoglycan

order- membrane, thick cell wall on outside

gram (-): stain pink, thin peptidoglycan wall

order- thin cell wall in between two membranes

26
Q

Peptidoglycan Cell Wall Structure

A

mesh-like polymer wall of identical subunits forming long strands (structural polysaccharide with amino acids surrounding cell)

basic subunit- disaccharide of two alternating modified sugars (N-acetylglucosamine *NAG and N-aceylmuramic acid *NAM) joined by Beta glycosidic bonds

27
Q

Peptidoglycan Cross-linked strands

A
  • strands have a helical shape
  • cross linked by covalent bonds between the tetrapeptides (4 amino acids) for strength
  • In gram (-) bacteria crosslinks are directly between amino acids in the tetrapeptide
  • In gram (+) bacteria, there are often interbridges of additional amino acids betwee the tetrapeptides
28
Q

Gram Positive Cell Walls

A

composed primarily (90%) of peptodoglycan

-also contains large amounts of teichoic acids (negatively charged)

Teichoic acids function to: help maintain cell envelope, may bind to host cells, and may store phosphate (PO4) *may attract cations

  • some gram (+) bacteria have layer of proteins on surface of peptidoglycan
  • also have lipoteichoic acid which attaches to cell membrane

Picture: teichoic acid circled

29
Q

Periplasmic Space

A

lies between plasma membrane and cell wall and is smaller than that of gram (-) bacteria

  • has relatively few proteins
  • enzymes secreted by gram (+) bacteria called exoenzymes (aid in degradation of large nutrients)
30
Q

Gram Negative Cell Walls

A

consist of a thin layer of peptidoglycan surrounded by an outer and inner plasma membrane

-outer membrane composed of phospholipids, lipoproteins, and lipopolysaccharides

*Lipopolysaccharides- make up the outer part of outer membrane (no phospholipid heads)

*NO TEICHOIC ACIDS

-peptidoglycan is 5-10% of cell wall

Periplasmic space:

many enzymes present in periplasmic space (transport proteins)

-Braun’s lipoproteins connect outer membrane to peptidoglycan wall

31
Q

Lipopolyssaccharides (LPS)

A
  • contributes to negative charge on outer cell membrane surface
  • helps stabilize outer membrane structure
  • may contribute to attachment to surfaces and biofilm formation
  • creates a permeability barrier
32
Q

Gram-Negative Outer Membrane Permeability

A

-more permeable than plasma membrane due to presence of porin proteins and transporter proteins

*porin proteins form channels to let small molecules pass

33
Q

Mechanism of Gram Stain Reaction

A

gram stain reaction due to nature of cell wall

  • shrinkage of the pores of peptidoglycan layer of gram-positive cells (constriction prevents loss of crystal violet during decolorization step)
  • thinner peptodoglycan layer and larger pores of gram (-) bacteria does not prevent loss of crystal violet
34
Q

Structures Exterior to Cell Wall

A

glycocalyx, capsule, slime layer

35
Q

Glycocalyx

A

polysaccharide rich (glucose or modified gluose subunits) material exterior to cell wall

*sometimes has protein component (2 types-capsule or slime layer)

36
Q

Capsule

A

dense, tightly attached, regular arrangement of polysaccharides

*visible to light microscope

37
Q

Slime layer

A

diffuse, loosely attached, irregular arrangement of polysaccharides

functions: attachement to solid surfaces, reserve source of energy, anti-phagocytic for some pathogens, prevents virus attachement *may aid in motility

Microbiology (6 decks)

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