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1. Microbiology > Structure and Function of Bacterial cells > Flashcards

Structure and Function of Bacterial cells Flashcards

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1
Q

What are the three regions of a bacteria?

A

Surface Appendages

Cell envelope

Cytoplasmic region

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2
Q

What makes up the surface appendage region of bacteria?

A

Either flagella and pili (fimbriae) are attached to cell surfaces

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3
Q

What does the cell envelope consist of?

A

Capsule (glycocalyx)

Outer membrane (only in gram negative cells)

Cell wall

Cytoplasmic membrane

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4
Q

What is the capsule also called?

A

Glycocalyx

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5
Q

What part of the cell envelope is only found in gram negative cells?

A

Outer membrane

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6
Q

What is found in the cytoplasmic region of a bacteria?

3

A

Chromosome (DNA)

Ribosomes

Inclusions

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7
Q

What are pili also called?

A

Fimbriae

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8
Q

What is the function of flagella?

A

Motility

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9
Q

What is the function of pili?

A

Adherence

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10
Q

What type of bacteria are flagella found on?

2

A

On both gram + and - bacteria

On many bacilli but not many cocci

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11
Q

What are the three parts of a flagellum?

A

Filament

Hook

Basal body

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12
Q

What is a filament?

A

A region of the bacterial flagella which is composed of flagellin (protein)

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13
Q

What protein is found in the filament of a flagellum?

A

Flagellin

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14
Q

What is the hook of a flagellum?

2

A

The wider region at the base of the filament

It connects the filament to the motor portion of the flagellum

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15
Q

What is the basal body of a flagellum?

3

A

The motor of a flagellum

It is anchored in cytoplasmic membrane and the cell wall

Consists of four ring shaped proteins stacked around a central rod

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16
Q

What is it called when a bacteria has a single flagellum?

A

Monotrichous

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17
Q

What is it called when a bacteria has flagella all over its surface?

A

Peritrichous

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18
Q

What is it called when a bacteria has a tuft of flagella at one end?

A

Lophotrichous

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19
Q

What is it called when a bacteria has a tuft of flagellum at either end?

A

Amphitrichous

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20
Q

How do flagella move?

4

A

By rotation like a propeller

This causes the bacteria to move in pulses along a line and tumble

A counterclockwise rotation leads to lines

A clockwise rotation leads to a tumbling motion

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21
Q

What are the benefits of being motile to a bacteria?

2

A

Motility serves to keep bacteria in an optimum environment via taxis

Motility assists in bacterial pathogenesis - move through mucous layer - attach to epithelial cells of the mucous membranes

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22
Q

What is taxis?

A

Motile response to an environmental stimulus

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23
Q

How does the flagella move when the bacteria is moving towards a gradient with favourable stimulus or away from an unfavourable one?
(2)

A

The frequency of tumbles is low

Trying to get to the favourable area quickly

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24
Q

How do the flagella move when the bacteria is moving towards an unfavourable stimulus or away from a favourable stimulus?
(2)

A

The frequency of tumbles increases

Allows the cell to reorient itself and move towards a more suitable environment

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25
What are pili? | 3
Thin filamentous protein structures They extend from the surface of the bacterial cell They have a shaft composed of pilin (protein)
26
On what type of bacteria are pili found?
Found on nearly all gram-negative bacteria but not many gram positive bacteria
27
What protein is found in the shaft of pili?
Pilin
28
What are the two main types of pili?
Short attachment pili Long conjugation pili
29
What are short attachment pili also called?
Fimbriae
30
Write a note on fimbriae. | 4
These are organelles of adhesion They allow bacteria to colonize environmental surfaces or cells and resist flushing There is an adhesive tip structure at the end of the shaft These tips have a shape corresponding to specific glycolipid or glycoprotein receptors on a host cell
31
What is the function of fimbriae? | 2
They allow bacteria to colonize environmental surfaces or cells They allow bacteria to resist flushing
32
What is found at the end of the shaft on fimbriae ?
An adhesive tip
33
What is the role of the adhesive tips on fimbriae?
Their shape corresponds to specific glycolipid or glycoprotein receptors on a host cell
34
Why are fimbriae needed?
Since both the bacteria cell and the host cell have negative charges
35
How do fimbriae work?
They enable bacteria to bind to host cells without getting very close (avoid electrostatic repulsion)
36
What are long conjugation pili also called? | 2
F pili sex pili
37
What is the function of long conjugation pili?
They are important in conjugation
38
What is conjungation?
The transfer of genetic material between bacteria through direct cell-to cell contact
39
What is spread through conjugation?
This genetic transfer facilitates the spread of virulence and antimicrobial resistance genes to other bacterial cells
40
What is the overall role of the glycocalyx?
Protection and adherence
41
What is the overall role of the outer membrane in gram negative bacteria?
Structure and permeability
42
What is the overall role of the cell wall?
Shape and protection
43
What is the overall role of the cytoplasmic membrane?
Transport
44
What is the glycocalyx?
A viscous covering of fibres outside of the cell wall
45
When is the glycocalyx called a capsule?
If it appears as an extensive tightly bound accumulation of gelatinous material adhering to the cell wall
46
When is the glycocalyx called a slime layer?
If it appears unorganized and more loosely attached
47
What are the three functions of the glycocalyx?
Protection Immune evasion Formation of a biofilm
48
Explain the protection function of the glycocalyx.
Shields bacteria from drying out, chemicals and environmental stresses
49
Explain the immune evasion function of the glycocalyx.
Capsulated bacteria are difficult to detect by phagocytic cells e.g. meningitis
50
What is biofilm?
A common secreted adhesive matrix
51
What is special about the bacteria in a biofilm?
Biofilm allows bacteria to communicate with one another through quorum sensing The bacteria live a community
52
What are the advantages of biofilm? | 4
Bacteria are better able to adhere and resist flushing Bacteria are better able to resist phagocytosis Bacteria better at trapping nutrients Bacteria better able to resist antibiotic attacks
53
Give four examples of places where biofilm can form.
Catheters/IVs - indwelling lines Medical implants Medical devices - endoscope channels Water supply systems
54
Give three examples of bacteria that form biofilm.
Pseudomonas Enterobacterales Staphylococcus
55
What are the two main functions of the cell wall?
Allow the cell to withstand internal pressure - prevent lysis Give shape and rigidity to the cell
56
What does the cell wall contain?
``` A tough mesh of polysaccharide and peptidoglycan (tight-knit complex) ```
57
What is peptidoglycan also called?
Murein
58
What does peptidoglycan do?
Gives strength and rigidity to the cell
59
Describe the structure of peptidoglycan. | 3
A polymer consisting of interlocking chains of identical monomers Each monomer consists of two joined amino sugars (G and M) with a pentapeptide coming off M Long sugar chains are joined together by cross links between the peptides off each M
60
Why is peptidoglycan a vulnerability for bacteria?
Peptidoglycan is unique to bacteria Cell wall antibiotics (penicillin) prevent bacteria from forming peptidoglycan
61
How do gram negative cells make up for their lower amounts of peptidoglycan?
They have an outer membrane outside the cell wall
62
Where is the layer of peptidoglycan located in the gram negative bacteria?
Located in the periplasm which is surrounded by the outer membrane
63
What is the periplasmic space? | 2
The space either side of the peptidoglycan layer It is between the cell membrane and the outer membrane
64
What does the outer membrane consist of? | 2
Consists of a lipid bilayer Additional polysaccharide
65
What forms the lipopolysaccharide layer (LPS) in gram negative bacteria?
Lipid A from the outer membrane and a polysaccharide
66
What are the three main functions of the outer membrane?
Structure Permeability - it is semi-permeable Pathogenicity
67
How does the outer membrane add to pathogenicity? | 2
The toxicity of the lipopolysaccharide layer This LPS acts as an endotoxin and is released when the bacteria lyse
68
What is the cytoplasmic membrane also known as? | 2
The cell membrane The plasma membrane
69
What is the cytoplasmic membrane?
A thin inner layer that surrounds the bacterial cell constituents
70
What is the main function of the cell membrane?
It is the barrier separating the cytoplasm from the environment
71
What happens if the cell membrane is broken? | 2
The integrity of the cell is destroyed The cytoplasm will leak out and the cell will die
72
Explain the permeability function of the cell membrane. | 4
The cytoplasmic membrane is a highly selective permeability barrier This allows the cell to take in specific metabolites and excrete waste material It is a phospholipid bilayer (40%) with proteins (60%) suspended at the surface and spanning layers Materials move across by passive diffusion or active transport using carrier proteins
73
Explain the structure of a phospholipid bilayer. | 2
The fatty acids point inward to form a hydrophobic environment The hydrophilic components remain exposed to the aqueous environment
74
Explain the role of the proteins that make up part of the cytoplasmic membrane.
Some of these function as selective transport proteins across the membrane Others function as enzymes during chemical reactions
75
What is the cytoplasmic membrane referred to as due to its ever changing nature?
A fluid mosaic
76
What is the cytoplasm in terms of bacteria?
Everything enclosed by the cytoplasmic membrane
77
What is the cytoplasm composed of?
80% water
78
What is the cytosol?
The liquid component of the cytoplasm
79
What is the liquid component of the cytoplasm?
The cytosol
80
What does the cytoplasm contain? | 6
Nucleic acids (DNA and RNA) Enzymes Amino acids Carbohydrates Lipids Inorganic ions
81
What two types of metabolic reactions take place in the cytoplasm?
Catabolic reactions Anabolic reactions
82
What do catabolic reactions do in bacterial cells?
They break down molecules in order to obtain building block molecules for more complex cellular molecules
83
What do anabolic reactions do in bacterial cells?
They synthesize cellular molecules
84
What governs all living process of all cells?
Genes
85
What is a gene?
A segment of DNA that encodes a protein
86
In what form is the genome present in bacteria?
The genome is encoded on one long single double-stranded molecule called a chromosome
87
What is a chromosome also known as?
A bacterial nucleoid
88
What does the bacterial chromosome do?
Its the genetic control centre of the cell which determines all the properties and functions of the bacterium
89
Why are most prokaryotes haploid?
As they usually only have one single chromosome
90
What are plasmids?
They are tiny loops of DNA suspended in the cytoplasm
91
What are ribosomes? | 2
Small dense structures that assemble proteins They act by translating genetic information into proteins
92
What are inclusions also called?
Granules
93
What type of bacteria produce endospores?
Gram positive bacteria
94
What is an endospore?
A resistant, dormant survival form of the organism
95
List the four main parts of an endospore.
Exosporium Spore coat Cortex Core
96
What is the exosporium?
The outermost layer of an endospore
97
Where is the spore coat found?
Between the exosporium and the cortex
98
Where is the cortex found?
Between the spore coat and the core
99
What does the core of an endospore contain? | 3
A chromosome Ribosomes Cellular essentials
100
What are endospores resistant to?
High temperatures Most disinfectant Antibiotics Physical agents e.g. radiation, boiling and drying

1. Microbiology (12 decks)

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