GENERAL STRUCTURE OF A PROKARYOTE Flashcards
1
Q
GENERAL STRUCTURE OF A PROKARYOTE
A
Glycocalyx
Bacterial chromosome/ nucleiod
Pilus
Mesosome
Flagellum
Fimbriae
Inclusion/ granules
Cell wall
Cell membrane
Ribosomes
2
Q
STRUCTURES EXTERNAL TO THE CELL WALL
A
- Glycocalyx
- Flagella
- Axial Filaments
- Fibriae and Pili
- Cell Wall
3
Q
PROKARYOTIC CELLS are much more smaller than eukaryotic cells.
They have no____, they lack____
• They are encased by a____
• Many have a capsuled or a slime layer made of____
• Often have appendages or protrusions on their____
A
nucleus; organelles
cell wall
polysaccharide
surface
4
Q
Filamentous protein attached to the cell surfaces that provide swimming movement
A
Flagella
5
Q
- specialized appendage attached to the cell by a basal body that holds a long rotating filament.
The movement pushes the cell forward and provides motility
A
Flagellum
6
Q
Parts of flagella
A
filament
Hook
basal body
7
Q
Flagellum
• Primarily a motility organelle that enables movement and chemotaxis
• Bacteria can have one flagellum or several, and they can be
(1)_____ - one or several flagella at one spot
(2)_____ - several flagella all over the bacterium
A
polar
peritrichous
8
Q
1.______ - long, thin, helical structure composed of proteins
2._____ - curved sheath
3._____- stack of rings firmly anchored in cell wall
A
Filament
Hook
Basal body
9
Q
Flagellum
• Rotates_____
_____distributed over entire cell
A
360 degrees
1-2 or many
10
Q
Flagellar arrangements
A
(a) Monotrichous
(b) Amphitrichous
(c) Lophotrichous
(d) Peritrichous
11
Q
- no flagella
A
Atrichous
12
Q
• - flagella dispersed over surface of cell, slowest / flagella surrounding the bacterial cell
A
Peritrichous
13
Q
Family enterobacteriaceae if motile
A
• Salmonella typhi
• Escherichia coli
• Proteus spp. - highly motile organism
14
Q
- single flagellum at one end
A
Monotrichous
15
Q
- small bunches arising from one end of cell
Spirilla spp.
A
Lopotrichous
16
Q
- flagella at both ends of cell
Alcaligenes faecalis
A
Amphitrichous
17
Q
have flagella which project in all directions.
______rotation of flagellar motors results in random re-orientation for the bacterium, but ______rotation produces approximate straight-line motion.
A
E. coli
Clockwise (CV)
counter-clockwise (CC)
18
Q
is the directed motion of an organism toward environmental conditions it deems attractive and/or away from surroundings it finds repellent
A
Chemotaxis
19
Q
• Movement of flagellated bacteria such as Escherichia coli can be characterized as a sequence of…
A
smooth swimming runs punctuated by intermittent tumbles
20
Q
• last only a fraction of a second which is sufficient to effectivelv randomize the direction of the next run
A
Tumbles
21
Q
• tend to be variable in length, extending from a fraction of a second to several minutes
A
Runs
22
Q
The tendency to____ is enhanced when the bacterium perceives conditions to be worsening, or when an attractant concentrations decrease, or repellent concentrations increase.
____ is suppressed and cells keep running when they detect that conditions are improving.
A
tumble
23
Q
enclosed between cell wall & cell membrane of spirochetes
Motility (corkscrew fashion )
A
Internal Flagella
24
Q
Internal flagella
A
Axial Filaments
Periplasmic filaments
25
Appendages for Attachment
Fimbriae
Pili
26
fine hairlike bristles (oligomeric protein pilin) from the cell surface; “common pili or attachment pili”; 100-600 filaments per cell
For adhesion to other cells and surfaces
FIMBRIAE
27
Pilus/pili (special types)
Appendages for____ (sex pili, conjugative pili, F pilus) rigid tubular structure pilin (VirB2);
elongate and retract commonly seen in all_____
Function:_____
Mating
Gram negative bacteria
joins bacterial cells for DNA transfer (conjugation)
28
adhesion/adherence to cell surfaces, aggregation of microorganisms (biofilm formation), twitching motility
Type IV Pili
29
- Fine, hairlike bristles from the cell surface that help in adhesion to other cells and surfaces
Fimbriae
30
- an elongate, hollow appendage used in transfers of DNA to other cells and in cell adhesion
Pilus
31
Bacterial Surface Coating – Cell envelope
Glycocalyx
Cell wall
32
external to the cell wall
polysaccharides (sugars/carbohydrates) and/or proteins
Glycocalyx
33
FUNCTIONS
▪ Attachment; receptors
▪ inhibits killing or phagocytosis by white blood cells or predatory protozoa
Glycocalyx
34
Glycocalyx
2 TYPES:
Capsule
Slime layer/ biofilm
35
Glycocalyx
highly organized
tightly attached
capsule
36
Glycocalyx
loosely organized and attached
slime layer / biofilm
37
is a complex, multilayered structure that serves to protect these organisms from their unpredictable and often hostile environment
bacterial cell envelope
38
• N-acetylglucosamine (NAG)
• N-acetylmuramic acid (NAM)
• Linked by polypeptides
provides strong, flexible support to the bacterial cell
Maintains cell integrity
PEPTIDOGLYCAN
39
– Peptidoglycan
Murein
40
Gram-positive Cell Wall -color
•thickness– several layers of peptidoglycan
purple
15-80 nm thick
41
• endotoxin
• may serve as receptor & block immune response
• With Braun lipoproteins & porins
(Omp C, Omp F, Omp A)
Lipopolysaccharides or LPS
42
Atypical Cell Walls
Mycobacterium, Nocardia
Mycoplasma
43
Gram-positive cell wall with mycolic acid
basis for acid-fast stain
Mycobacterium, Nocardia
44
no cell wall
pleomorphic
Membrane is stabilized by sterol-like molecules
Mycoplasma
45
Cell wall-less forms
spheroplasts, or protoplasts
46
> surrounded by a thin, peptidoglycan cell wall which itself is surrounded by an outer membrane containing lipopolysaccharide
Gram-Negative Bacteria
47
-> lack an outer membrane but are surrounded by layers of peptidoglycan many times thicker than in gram negatives.
Threading through the layers of peptidoglycan are the long anionic polymers called_____
Gram-Positive Bacteria
TEICHOIC ACIDS
48
• External covering outside the cytoplasm Composed of two basic layers:
(1) cell wall and
(2) cell membrane
49
A vast polymer consisting of interlocking chains of identical peptidoglycan monomers
Peptidoglycan
50
consists of two joint amino sugars and acetyl glucosamine or (NAG) and N-acetylmuramic acid or (NAM) with a pentapeptide coming off of the NAM.
peptidoglycan monomer
51
Peptidoglycan is a rigid wall that gives the cell its structure and protects the plasma membrane, and it also prevents…
osmotic lysis
52
macromolecule composed of a repeating framework of long glycan chains cross-linked by short peptide fragments
provides strong, flexible support to keep bacteria from burstingor collapsing because of changes in osmotic pressure
Peptidoglycan
53
The two major functions of the cell wall are:
1. maintaining shape
2. withstanding turgor pressure
54
It is important to note that not all bacteria have a cell wall.
Most bacteria (about 90%) have a cell wall and have one of two types:
1. Gram-positive cell wall
2. Gram-negative cell wall
55
The two different cell wall types can be identified in the laboratory by____
Developed in 1884, used ever since
differential stain, known as the Gram stain
56
Consists of a homogenous sheath of peptidoglycan 20-80nm thick
Gram positive cell wall
57
tightly bound acidic polysaccharides including, teichoic acid and lipoteichoic
acid cell membrane
Retain crystal violet and stain blue or purple.
Gram positive cell wall
58
In a gram positive cell wall, it is:
Surrounds the cytoplasmic membrane
Decorated with teichoic acids, polysaccharides and proteins
Plays a major role in bacterial physiology since it maintains cell shape and integrity during growth and division
Acts as the interface between the bacterium and its environment
Peptidoglycan
59
Which is more complex? Gram positive or negative cell wall?
Negative cell wall
60
• Consists of an outer membrane containing proteins, phospholipids and lipopolysaccharide (LPS)
• thin shell of peptidoglycan
• periplasmic space
• inner membrane
Gram negative cell wall
61
• Lose crystal violet and stain red or pink from safranin counterstain
• Protective structure while providing some flexibility and sensitivity to lysis
Gram negative cell wall
62
T or F
Gram negative cell wall also contains Peptidoglycan
True
Although only a couple of layers representing 5-10% of the total cell walls
63
GRAM-NEGATIVE CELL WALL
• Most notable is the presence of a plasma membrane located outside of the peptidoglycan layers known as the________
outer membrane
64
In gram negative cell wall
Makes up the bulk of the Gram-negative cell wall
Composed of a lipid bilayer, very similar in composition to eh cell membrane with polar heads, fatty acid tails and integral proteins.
Outer membrane
65
Gram negative cell wall
It differs from the cell membrane by the presence of large molecules known as the ________ which are anchored into the outer membrane and project from the cell into the environment.
lipopolysaccharide (LPS)
66
COMPONENTS OF THE LIPOPOLYSACCHARIDE
Three different components
1. O-Antigen / O-Polysaccharide -
2. Core polysaccharide
3. Lipi A
67
Lypopolysaccharides
1. - outermost part of the structure
2.
3. - anchors the LPS into the outer membrane
O-Antigen / O-Polysaccharide
Core polysaccharide
Lipi A
68
Chemical composition: Positive vs Negative
P:
Peptidoglycan
Teichoic acid
Lipoteichoic acid
N:
Lipopolysaccharide
Lipoprotein
Peptidoglycan
69
Thickness: Positive vs Negative
P: Thicker (20-80 nm)
N: Thinner (8-11 nm)
70
Outer membrane: Positive vs Negative
P: none
N: yes
71
Positive vs Negative
Periplasmic space
Porin proteins
Permeability
P:
Narrow
No
More penetrable
N:
Extensive
Yes
Less penetrable
72
Bacteria of the genus_______ which causes tuberculosis, and Hansen's disease (leprosy)
- These do not stain easily with the gram stain because these organisms are stained with______, hence the name Acid fast organisms
• They contain waxy lipids in their cell walls/ so called _____
Mycobacteria
Acid-fast stain
MYCOLIC ACID
73
The genus_____ is also acid fast
Nocardia
74
This stain is used to identify certain parasites like Cryptosporidium
Acid fast
75
PLASMA (CYTOPLASMIC MEMBRANE)
• Also called as the
INNER MEMBRANE
76
• Thin structure lying inside the cell wall and enclosing the cytoplasm of the cell
Provides protection for a cell
• Provides a fixed environment inside the cell
PLASMA (CYTOPLASMIC MEMBRANE)
• Also called as the INNER MEMBRANE
77
• Composition of inner membrane
phospholipids and proteins
78
Cytoplasmic membrane/ Inner membrane
FUNCTIONS
1. Transport nutrients into the cell
2. Transport toxic substances out of the cell
3. Plasma membrane will have proteins on it which interacts with other cells
79
Dense, gelatinous solution of sugars and amino acids and salt
Mostly of the composition of this is 70-80% of water
Serves as a solvent of materials used in all cell function
Inner membrane
Cytoplasmic membrane
80
single, circular, double-stranded DNA molecule
NUCLEOID: CHROMOSOME
81
contains all the genetic information required by a cell
A mass of genetic material/ DNA
the regulatory center
NUCLEOID: CHROMOSOME
82
• The region regulates growth reproduction, and function of the prokaryotic cell.
• The previously mentioned proteins and enzymes are essential in these processes.
Nucleoid: chromosome
83
small circular, DOUBLE-STRANDED DNA.
different than chromosomal DNA
• all genetic material found in an organism's chromosomes
PLASMIDS
84
free or integrated into the chromosome
duplicated and passed onto offspring
not essential to bacterial growth & metabolism
PLASMIDS
85
may encode antibiotic resistance, tolerance to toxic metals, enzymes & toxins
used in genetic engineering-readily manipulated & transferred from cell to cell
PLASMIDS
86
replicates independently of chromosomal DNA
PLASMIDS
87
FUNCTIONS
may contain genes that enhance the survival of an organism either by killing other organisms or by defending the host cell by producing toxins
some plasmids facilitate the process of replication in bacteria
since plasmids are so small, they usually only contain a few genes with a specific function as opposed to a large amount of non-coding DNA
Plasmid
88
Functions of plasmid
may contain genes that enhance the survival of an organism either by killing other organisms or by defending the host cell by producing toxins
some facilitate the process of replication in bacteria
since they are so small, they usually only contain a few genes with a specific function as opposed to a large amount of non-coding DNA
89
• Site of protein synthesis
RIBOSOMES
90
• microscopic factories found in all cells including bacteria
• they translate the genetic code from the molecular language of nucleic acid to that of amino acids in which amino acids are the building blocks of proteins
Ribosomes
91
• are the molecules that perform all the functions of cells and living organisms
Proteins
92
•intracellular storage bodies/reserve deposits
Inclusions and granules
93
• important component of metabolism in many organisms spanning the bacterial eukaryotes and archaeal domains
• the parts of the cell that store the cell's energy reserves as well as other important metabolites
Inclusions and granules
94
• resting, dormant cells
produced by some Gram (+) genera -Clostridium, Bacillus & Sporosarcina
ENDOSPORES
95
ENDOSPORE
• have a 2-phase life cycle
vegetative cell
endospore
96
Endospore
TWO PROCESSES
- formation of endospores
- return to vegetative growth
Sporulation
Germination
97
• withstand extremes in heat, drying, freezing radiation & chemicals
Ensure the survival of bacteria in adverse environmental conditions such as: Nutrient deficiency; carbon deficiency; overpopulation
Endospore
98
Endospore
Spores that form within the cells mainly in bacteria
formed within bacterial vegetative cells or mother cells known as______
SPORANGIA
99
Basis for acid- fast stain
Mycolic acid
100
Gram positive cell wall with mycolic acid
Mycobacterium, Norcardia
101
• Serves as the site for electron transport processes & systems (ETS), enzyme ATP synthetase
Cytoplasmic Membrane or Plasma Membrane
102
• Highly sensitive to changes in the environment (permeability barrier)
Cytoplasmic Membrane or Plasma Membrane
103
• Composed of 40% phospholipid, 60% protein; arranged in fluid mosaic model
Cytoplasmic Membrane or Plasma Membrane
104
An aqueous, dense gelatinous solution of:
Macromolecules: proteins (enzymes), mRNA, tRNA
Small molecules of energy sources, precursors of macromolecules, metabolites or vitamins
Various inorganic ions and cofactors
Cytoplasm
105
Cytoplasm is ______% water; solvent for materials used in cell functions
70-80%
106
Primary components of cytoplasm
nucleoid, ribosomes, inclusions
107
single, circular DNA molecule, free in the cytoplasm, coiled/supercoiled & anchored by proteins
Bacterial Chromosome (Nucleoid)
108
= the total DNA content (contains all the genetic information)
Cell genome
109
Self-replicating, small circles of extrachromosomal DNA
duplicated & passed on to offspring
Plasmids
110
Encodes for antibiotic resistance, toxic metal tolerance, enzymes & toxins
readily manipulated & transferred (genetic engineering )
Plasmids
111
Distinct granular appearance in the cytoplasm
Composed of proteins and RNA; site of protein synthesis
Ribosomes
112
Are distinct granules; intracellular storage bodies
Inclusions
113
Dormant, resting cells (cryptobiotic)
Intracellular but to be released as free endospores
Endospores
114
Highly resistant to environmental stresses: high temperature, irradiation strong acids, disinfectants, etc.
Bacillus, Clostridium species
Endospore
115
Endospores
resistance linked to high levels of
calcium & some acids (Calcium dipicolinic acid)
116
Endospore
Longevity:
Control: pressurized steam at ____for 20-30 minutes
25 - 250 million years
120 C
117
Gram-positive or Gram-negative
Acid fast or non-acid fast
Cocci, bacilli, spiral or spirochete
In singles, pairs, clusters, chains, palisades
Cell wall
118
Encapsulated or non-encapsulated
Smooth, mucoid or rough colonies
Capsule
119
Endospore-forming or non-sporulating
Centrally, terminally, subterminally located
Endospores
