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MicroBiology > Cell Structure of prokaryotes in the domains Bacteria and Archaea, and Eukarya > Flashcards

Cell Structure of prokaryotes in the domains Bacteria and Archaea, and Eukarya Flashcards

1
Q

Prokaryotes differ from eukaryotes in ____ and _______

Elaborate

A

size and simplicity

  • most are smaller
  • most lack internal membrane systems
  • and no internal phospholipid bilayer membranes
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2
Q

prokaryotes are divided into 2 taxa, the domains are…

A

Bacteria and Archaea

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3
Q

pictures on slides 4-6

A

:)

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4
Q

Morphology is…

A

the cell shape

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5
Q

what are the 3 major cell morphologies?

A
  1. ) Coccus (pl. cocci): spherical or ovoid
  2. ) Bacillus (Rod; pl. Bacilli)): cylindrical shape
  3. )Spirillum: spiral shape
    * *Many variations on basic morphological types
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6
Q

diplococci (s., diplococcus) arrangement is….

A

pairs

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7
Q

streptococci arrangement is…

A

chains

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8
Q

staphylococci arrangement is…

A

grape like clusters

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9
Q

tetrads arrangement is…

A

4 cocci in a square

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10
Q

sarcinae arrangement is…

A

cubic configuration of 8 cocci all perpendicular to each other

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11
Q

the 5 Cocci are….

A 
diplococci
streptococci
staphylococci
tetrads
sarcinae
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12
Q

What are the 3 Bacilli? describe

A

Diplobacilli- 2 bacilli
Streptobacilli – chains of bacilli
Pallisade – several parallel cells along long axis

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13
Q

describe the shape and arrangement of Bacilli (s., bacillus)

A
  • rods

* coccobacilli – very short rods

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14
Q

describe the shape and arrangement of Vibrios

A

resemble rods, comma shaped

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15
Q

describe the shape and arrangement of Spirilla (s., spirillum)

A

rigid helices

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16
Q

describe the shape and arrangement of Spirochetes

A

flexible helices

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17
Q

describe shape and arrangement of Mycelium

A

network of long, multinucleate filamentous cells

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18
Q

describe shape and arrangement of Pleomorphic

A

organisms that are variable in shape

online definition: ability of some bacteria to alter their shape or size in response to environmental conditions

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19
Q

describe shape and arrangement of Archaea

A

pleomorphic, branched, flat, square, other unique shapes

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20
Q

What are the advantages of being a small cell?

A

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

  • This allows greater nutrient exchange per unit cell volume
  • Thus, small cells tend to grow faster than larger cells

*Slide 18 has a picture

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21
Q

Cellular organisms less than__ in diameter are unlikely

A

0.15 µm

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22
Q

_________tend to contain small cells (0.2–0.4 µm in diameter

A

Open oceans

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23
Q

starting from the outside going on, what are the 4 parts of the Prokaryotic Cell Structure?

A

1) Structures exterior to the cell wall
2) Cell Wall
3) Cell membranes
The three above together are also referred to as the cell envelope; there are differences in the cell envelope between Archaea and Bacteria
4) Structures within cell membrane

**Slides 21 and 22

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24
Q

describe prokaryote cell membranes (2)

A
  • Absolute requirement for all living organisms (all 3 domains)
  • Some prokaryotes (both domain Bacteria and Archaea) also have internal membrane systems (but these are different from the internal membrane systems in eukaryotes)
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25
Q

what are 5 functions of the cell membrane in all 3 domains? describe each function

A
  1. ) Maintains cell’s integrity - Vital barrier that separates cytoplasm from environment (if no cell membrane, no cell)
  2. ) Regulates transport - highly selective permeable barrier
  3. ) Energy metabolism in prokaryotes (not eukaryotes)
  4. ) Protein attachment
  5. ) Receptors for detection of and response to chemicals in surroundings
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26
Q

describe the Fluid Mosaic Model of Membrane Structure (all domains) (2)

A
  1. ) Membrane somewhat fluid, somewhat solid
  2. ) Lipid bilayers with floating proteins
    - amphipathic (having both hydrophilic and hydrophobic parts) lipids
    - polar ends (hydrophilic – interact with water)
    - non-polar tails (hydrophobic – insoluble in water)
    - membrane proteins
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27
Q

describe the Domain Bacteria Cell Membrane (2) and describe

A
  1. ) General structure:
    - phospholipid bilayer plus proteins (6–8 nm wide) ; no sterols, but +/- hopanoids or other molecules
    - Contain both hydrophobic and hydrophilic components
  2. ) Fatty acids point inward to form hydrophobic environment; hydrophilic portions remain exposed to external environment or the cytoplasm

**slides 28-31

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28
Q

what are 2 types of membrane proteins? describe them

this is not naming specific proteins

A

Peripheral
-loosely connected to membrane on cytoplasmic side
-easily removed
Integral
-amphipathic:embedded within membrane and project -outward or inward
-carry out important functions
-may exist as microdomains

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29
Q

proteins that completely cross the membrane from one side to the other are called what?

A

Transmembrane proteins

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30
Q

describe the outer surface of cytoplasmic membrane

A

can interact with a variety of proteins that bind substrates or process large molecules for transport

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31
Q

describe the inner surface of cytoplasmic membrane

A

interacts with proteins involved in energy-yielding reactions and other important cellular functions

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32
Q

what are 2 membrane strengthening agents? describe them

A
  1. ) Sterols
    - Rigid, planar lipids found in eukaryotic membranes -Strengthen and stabilize membranes
    - Only found in a very few prokaryotes (typically wall-less prokaryotes (ie, Mycoplasma))
  2. ) Hopanoids
    - Structurally similar to sterols
    - Present in membranes of many Bacteria
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33
Q

Saturation levels of membrane ______ reflect __________ such as _________

A

lipids; environmental conditions; temperature

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34
Q

True or False: Bacterial membranes lack sterols but do contain sterol-like molecules.
Explain Answer

A

True.
hopanoids stabilize the membrane
(found in petroleum)

35
Q

describe the cell membrane fluidity that applies to nearly all domains

A

liquid crystal; some properties like liquid, some like solid; needs to be at right fluidity which is temperature dependent

36
Q

if the cell membrane is too hot it results in…

A

thermal lysis (cell death)

37
Q

if the cell membrane is too cold it results in…

A

solidification (gelling)

38
Q

to maintain the correct fluidity in the cell membrane…

A

Adjust fatty acid composition of phospholipids

39
Q

to correct the fluidity in the cell membrane if it’s too cold….

A

more unsaturated fatty acids – minimize van der Waals forces

40
Q

to correct the fluidity in the cell membrane if it’s too hot….

A

more saturated fatty acids – maximize van der Waals forces

41
Q

to maximize or minimize van der waals forces ……

A

Adjust ratio of sterols, hopanoids or other lipids to phospholipids

42
Q

what is passive transport?

A

transport which does not require ATP or other cellular energy to be used by the cell (but energy of molecules are involved)

43
Q

what is active transport?

A

transport which requires the cell to expend its own energy in the form of ATP (or other cellular energy)

44
Q

what is simple transport?

A

transport which does not require a transport protein

45
Q

what is facilitated transport?

A

transport which requires a transport protein

46
Q

what is Diffusion?

A

the movement of a molecule due to its inherent kinetic energy from a region where it is in higher concentration to a region(s) where it is in lower concentration
(it is passive transport)

47
Q

what is Osmosis?

A

the diffusion of water across a membrane

passive transport

48
Q

How a molecule gets across a phospholipid bilayer/protein membrane depends on 3 factors:

A

1) The charge on the molecule – ionic, polar, non polar
2) The size of the molecule
3) The shape of the molecule

49
Q

To pass across a phospholipid bilayer/protein membrane a molecule can go either: (2)
*also state the type of transport for both methods

A

1) Between the phospholipids (simple transport) – must be non polar or a very small polar molecule (water)
2) Through a transport protein (facilitated transport) – all ions and nearly all polar molecules

50
Q

what is simple diffusion?

A

diffusion between the phospholipids (passive and no transport proteins) – non polar molecules; water

51
Q

what is facilitated diffusion? describe

A

diffusion through a transport protein (passive)

  • common in eukaryotes; less common prokaryotes; In direction of concentration gradient (High to low)
  • for ions and polar molecules
52
Q

what is active transport?

A

any transport which requires the cell to expend its own energy (usually ATP); in prokaryotes, active transport is always facilitated (proteins required) and is in the direction against the concentration gradient (low to high)

53
Q

active transport can be…..

active transport cannot be….

A

Can:ions, polar molecules and sometimes bigger non polar molecules
Cannot: No endocytosis/exocytosis in prokaryotes***

54
Q

What are the three transport events possible?

A

uniport, symport, and antiport

55
Q

what is uniport transport?

A

transport in one direction across the membrane

56
Q

what is symport transport?

A

function as co-transporters

57
Q

describe antiport transport?

A

a molecule across the membrane while simultaneously transporting another molecule in the opposite direction

58
Q

describe Receptor-Mediated Transport Systems

A
  • ligand binds specific protein receptors on cell surface
  • Show saturation effect
  • Highly specific
59
Q

what is group translocation?

A
  • simultaneous transport and chemical modification of transported substance
  • Energy dependent transport that chemically modifies molecule as it is brought into cell
60
Q

Best known translocation system is…

A

phosphoenolpyruvate: sugar phosphotransferase system (PTS)

61
Q

True or False: Most prokaryotes (Bacteria and Archaea) have a cell wall; only a very few exceptions

A

true

62
Q

Cell walls are _______ to cell membrane, rigid and mostly __________________ and _______ or ________

A

exterior; structural polysaccharides and peptides or protein

63
Q

For _________ and ______________, the primary function of the cell wall is to prevent _________

A

unicellular; colonial prokaryotes;osmotic lysis

64
Q

what is osmotic lysis?

A

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

65
Q

describe Hypotonic environments (3)

A
  • solute concentration outside the cell is less than inside the cell, and water concentration is higher
  • water moves into cell and cell swells
  • cell wall protects from lysis
66
Q

describe Hypertonic environments (3)

A
  • solute concentration outside the cell is greater than inside, water concentration lower
  • water leaves the cell
  • plasmolysis occurs
67
Q

slide 48-49

A

:)

68
Q

what is a cell that does not have a cell wall? describe it (prokaryote)

A

Mycoplasma

  • does not produce a cell wall
  • plasma membrane stronger ( has sterols (rare in prokaryotes) more resistant to osmotic pressure
  • Hyper regulates internal solute conc. to stay just slightly hypertonic
69
Q

slide 51-52

A

KNOW THIS WELL

70
Q

describe Peptidoglycan Structure

A

Mesh-like polymer of identical subunits forming long strands; a structural polysaccharide with amino acids that surrounds the cell

71
Q

describe the basic sub-unit of peptidoglycan structure

A

-disaccharide of two alternating modified sugars joined by Beta glycosidic bonds
N-acetylglucosamine (NAG)
N- acetylmuramic acid (NAM
-And alternating D- and L- amino acids in a tetrapeptide (4 amino acids) attached to muramic acid that forms cross links with other tetrapeptides

*slides 53-55

72
Q

Peptidoglycan strands have a ______ shape

A

helical shape

73
Q

peptidoglycan strands in gram negative vs gram positive

1 for each

A
  1. ) negative: crosslinks are directly between amino acids in the tetrapeptide
  2. ) positive: there is often an interbridge of additional amino acids between the tetrapeptides
74
Q

Peptidoglycan chains are crosslinked by _________ between the _______ for strength

A

covalet bonds; tetrapeptides

75
Q

describe Gram-Positive Cell Walls

A

Composed primarily (~90 %) of peptidoglycan
Also contains large amounts of teichoic acids (negatively charged) embeded in wall
-help maintain cell envelop
-may bind to host cells
-may store PO4; may attract cations
Some gram-positive bacteria have layer of proteins on surface of peptidoglycan
Also have lipoteichoic acid which attaches wall to cell membrane
SLIDES 59-63

76
Q

describe the Periplasmic Space of Gram + Bacteria

A

-Lies between plasma membrane and cell wall and is smaller than that of gram-negative bacteria
-Periplasm has relatively few proteins
-Enzymes secreted by gram-positive bacteria are called exoenzymes
(aid in degradation of large nutrients)

77
Q

describe Gram-Negative Cell Walls

A
  • More complex than Gram- positive
  • Consist of a thin layer of peptidoglycan surrounded by an outer membrane
  • Outer membrane composed of phospholipids, lipoproteins, and lipopolysaccharide (LPS)
  • No teichoic acids
78
Q

for Gram-Negative Cell Walls, Peptidoglycan is _____ of cell wall weight and in periplasmic space

A

~5-10%

79
Q

for Gram-Negative Cell Walls, does Periplasmic space differ from that in gram-positive cells?
Explain

A

yes!
-may constitute 20–40% of cell volume
-many enzymes present in periplasm
(hydrolytic enzymes, transport proteins and other proteins)

80
Q

slides 67-68

A

:)

*Make sure to look at!

81
Q

what does LPS stand for?

A

Lipopolysaccharide

82
Q

LPS consists of 3 parts. describe them

A
  1. ) lipid A (endotoxin)
  2. ) core polysaccharide
  3. ) O side chain (O antigen)
    * Lipid A embedded in outer membrane
    * Core polysaccharide, O side chain extend out from the cell
    * *slide 70
83
Q

what are the 6 Importances of LPS?

A
  1. ) Contributes to negative charge on cell surface
  2. ) Helps stabilize outer membrane structure
  3. ) May contribute to attachment to surfaces and biofilm formation
  4. ) Creates a permeability barrier
  5. ) Protection from host defenses (O antigen)
  6. ) Can act as an endotoxin (lipid A)

MicroBiology (17 decks)

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