Anatomy of the Bacterial Cell Flashcards Preview

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Flashcards in Anatomy of the Bacterial Cell Deck (189):
1

How would you describe a bacterial cell wall?

A complex, semi-rigid structure responsible for cell shape

2

The bacterial cell wall acts as an attachment point for the...

Flagella

3

The major component of bacterial cell walls is...

Peptidoglycan

4

How does the cell wall prevent the osmotic lysis of a bacterial cell?

The interior of the cell wall is at a higher pressure than it's surrounding environment, without the cell wall the bacteria would pop. In a hypotonic solution, water moves into the cell. If the cell wall is strong, it contains the swelling. If the cell wall is weak or damaged, the cell bursts, osmotic lysis.

5

What two sugars is peptidoglycan composed of?

N-acetylglucosamine and N-acetylmuramic acid

6

What is an isotonic solution?

A medium in which the overall concentration of solutes equals that found inside the cell

7

What is a hypotonic solution?

A hypotonic solution outside the cell is a medium whose concentration of solutes is lower than that inside the cell

8

What is a hypertonic solution?

A hypertonic solution is a medium having a higher concentration of solutes than inside the cell has

9

How do N-acetylglucosamine and N-acetylmuramic acid make the cell wall?

The pair form repeating disaccharides which create a polymer

10

Name two amino acids that form cross links between the disaccharide polymer chains.

Lysine and diaminopimelic acid (DAP)

11

What is special with the amino acids that make up the cell wall?

They are alternating between the L- and D- forms

12

Why are alternating L- and D- amino acid forms unique?

Usually only the L-form of amino acids are used in proteins in nature

13

How are N-acetylglucosamine and N-acetylmuramic acid linked to each other?

By a beta, 1-4 linkage glycosidic bond

14

How does the enzyme lysozyme damage cell walls?

By breaking the beta 1-4 linkage connecting the disaccharide

15

How are the sugar chains cross linked?

By amino acids connecting N-acetylmuramic acid

16

The more cross linking, the greater the...

Rigidity

17

What is DAP?

An amino acid found in the peptide linkages between NAM and NAG. Stands for diaminopimelic acid

18

How much of the cell wall does peptidoglycan make up in gram positive bacteria?

Up to 25nm

19

How much of the cell wall does peptidoglycan make up in gram negative bacteria?

2-5nm

20

In gram negative bacteria, the NAG-NAM chains are...

Directly linked

21

In gram positive bacteria, the NAG-NAM peptide chains are...

Linked by a pentapeptide bridge

22

B lactam antibiotics inhibit...

Transpeptidase enzymes which catalyses the formation of the final bond between two peptide chains

23

Give two examples of B lactam antibiotics

Penicillin and cephalosporins

24

Staphylococcus is

Gram positive

25

Bacillus is

Gram positive

26

Clostridium is

Gram positive

27

Listeria is

Gram positive

28

Corynebacterium is

Gram positive

29

90% of the cell wall is made up of peptidoglycan in a...

Gram positive bacterium

30

Teichoic acids are found in...

Gram positive bacteria

31

What are the teichoic acids that span the whole cell wall and link to the plasma membrane called

Lipoteichoic acid

32

What are the teichoic acids associated with the peptidoglycan called

Wall teichoic acid

33

Teichoic acids usually bind to

Sugars and D-alanine

34

Teichoic acids are polymers of

Glycerophosphate or ribitol phosphate

35

Roles of teichoic acids include

May bind and regulate the movement of cations due to -ve charge from phosphate groups. Structural stability. Provide antigenic specificity.

36

Five major parts of a gram positive bacterial cell wall:

Wall associated protein, wall teichoic acid, lipoteichoic acids, peptidoglycan and cytoplasmic membrane

37

What is the overall structure of a gram negative cell wall?

Outer membrane, periplasm and cytoplasmic membrane

38

Where is the peptidoglycan located in gram negative bacteria?

In the periplasmic space between the outer membrane and cytoplasmic membrane

39

Are there any teichoic acids in gram negative bacteria?

No homie!

40

How wide is the periplasm layer?

15nm

41

What does the periplasm contain?

Digestive enzymes and transporter proteins

42

The outer membrane is a...

Bilayer

43

What is the complement system?

The complement system consists of a number of small proteins found in the blood. The complement system is a part of the immune system that enhances (complements) the ability of antibodies and phagocytic cells to clear pathogens from an organism.

44

The outer membrane aids in evading...

Phagocytosis and complement

45

The outer membrane acts as a barrier to...

Certain antibiotics, penicillin, digestive enzymes

46

The outer membrane prevents molecules from the periplasm from being...

Lost

47

What are porins and where are they found?

Transporter proteins found in the outer membrane

48

What does LPS stand for?

Lipopolysaccharide

49

Where are lipopolysaccharides found?

In the outer membrane of a gram negative bacterium

50

What do lipopolysaccharides consist of?

Lipid A, the core polysaccharide and the O-polysaccharide

51

Three roles of the lipopolysaccharides present?

Stabilise the outer membrane
Increase the -ve charge
Protect from chemical attack

52

What is lipid A made of?

Phosphorylated glucosamine disaccharides decorated with multiple fatty acids

53

One of the main functions of LPS?

An endotoxin

54

An endotoxin is released when the bacteria dies and can cause symptoms to arise, such as..

Fever and vomitting

55

Does the gram negative bacteria have to be pathogenic to release endotoxins?

No

56

What is O-polysaccharide/O-antigen made of?

It's a sugar polymer

57

What is the long O-polysaccharide chains in some gram negative outer membrane of the cell wall called?

Smooth LPS

58

What is the short O-antigen chain called?

Rough LPS

59

Some bacteria with a rough LPS are ____ suseptible to hydrophobic drugs

more

60

The O-polysaccharide functions as an

Antigen

61

The O-polysaccharide is useful for distinguishing between

different bacterial species and strains

62

What does E.coli O157:H7 cause?

Enterohemorrphagic fever

63

List the main components of a gram negative cell wall?

Outer membrane including proteins, the lipopolysaccharide - O-antigen, core polysaccharide and Lipid A. The periplasm layer which has the peptidoglycan and then the cytoplasmic membrane

64

Escherichia is...

Gram negative

65

Salmonella is

Gram negative

66

Pseudomonas is

Gram negative

67

Legionella is

Gram negative

68

Wolbachia is

Gram negative

69

Serratia is

Gram negative

70

Helicobacter is

Gram negative

71

Neisseria is

Gram negative

72

Klebsiella is

Gram negative

73

Who came up with gram positive/gram negative staining method?

Christian Gram in 1884

74

What stain is used first to treat the heat fixed cells?

Crystal violet

75

The primary stain is washed off and smear treated with a mordant. The mordant stain used is

Iodine

76

After primary stain and the mordant stain is added, the cells are washed with a de-colourising agent. The de-colourising agent is

Alcohol

77

After the cells have been de-colourised. The smear is counterstained using

Safranin

78

Mycobacterium cell walls are different in what way?

They contain a thin layer of peptidoglycan with a layer of mycolic acid

79

What is a layer of mycolic acid?

Consists of a hydrophobic waxy lipid

80

Why does gram stain not work for mycobacterium?

The dyes can not get through the waxy myolic acid layer

81

What method is used to stain mycobacterium?

Acid-fast - carbonfuchsin binds to components in cystol
High affinity mycolic acids found in their cell membranes

82

What are wall-less bacteria called?

Mollicutes such as mycoplasma

83

What can mycoplasma cause?

Mycoplasma pneumonia

84

What do mollicutes have that is unique?

They contain sterols in their plasma membrane

85

What is the glycocalyx?

A viscous gelatinous polymer that surrounds the cell, secreted by most bacteria

86

What is the glycocalyx composed of?

Polysaccharides and/or protein

87

One type of glycocalyx is well organised and firmly attached to the cell. This is called

A capsule

88

One type of glycocalyx is unorganised and loosely attached to the cell wall. This is called

A slime layer

89

Capsules can be visualised. How?

By using negative staining

90

How can the glycocalyx assist in the formation of biofilms?

They assist with attachment

91

Steptococcus mutans can

adhere to teeth

92

Vibrio cholera can

adhere to the small intestine

93

Klebsiella can adhere/colonise

the respiratory tract

94

What does Bacillus anthracis cause?

Anthrax

95

What does Streptococcus pneumoniae cause?

Pneumonia

96

How can capsules aid in the evasion of the immune system?

Capsule prevents phagocytosis

97

What are fimbriae?

Short, hair like, proteinaceous appendage

98

What protein makes fimbriae?

Curlin protein

99

What type of bacteria have fimbriae?

Mostly gram negative, very few gram positive bacteria have fimbriae

100

Where are fimbriae found?

At poles or along the entire length

101

Fimbriae have a tendency to stick to...

each other as well as to surfaces

102

How are fimbriae involved in biofilm formation?

Help bacteria adhere to epithelial surfaces of the body.

103

E.coli when fimbriated adhere to the lining of the small intestine. What happens when fimbriae are absent?

Colonisation does not occur

104

What are pili?

Hair like, proteinaceous appendages

105

How do they differ from fimbriae?

Typically longer and only one/two found per cell

106

What do sex pili do?

Facilitate genetic exchange between cells - conjugation

107

What are the pili that are associated with motility called?

Type IV pili

108

How do motility pili work?

Involves synthesis of pili until it reaches a surface then retraction of pili as it is dismantled

109

There are two types of motility by the type iv pili, what are these called?

Twitching motility and gliding motility

110

Describe twitching motion.

Short, jerky, intermittent motion

111

Describe gliding motion

Smooth, continuous motion

112

Give an example of a bacteria that uses gliding motion from its pilus.

Myxococcus

113

What is the flagella?

A tail-like appendage

114

Where is the flagella found? Gram pos or gram negative

It is found in both

115

What is the main function of the flagella?

Locomotion - they are said to be motile and swim

116

What is the shape of the flagella?

Helical

117

What is the difference between flagella and fimbria/pilli?

The flagella is longer and thicker

118

What are bacteria without a flagella called?

Atrichous

119

Bacteria with flagella all over the surface are called?

Peritrichous

120

If the flagella has only one flagella at one pole of the bacterium, it is said to be...

Monotrichous

121

If there are multiple flagella at a pole it is said to be...

Lophotrichous

122

If a bacteria is polar and has flagella at both ends it is known to be

Amphitrichous

123

The flagella consists of which three parts?

The filament, the hook and the basal body

124

The filament of a flagellum is composed of...

Flagellin (globular protein)

125

The flagellin is unique to the bacteria, how is this an advantage?

Useful in identifying the bacteria

126

The flagellin is arranged as...

Chains, they interwine to form a hollow tube

127

The filament of a flagellum is not generally covered with a membrane, why is this key?

Because eukaryotic flagella are covered with a membrane

128

What is the hook in a flagella?

The hook is the connecting region between the filament and the basal body

129

The hook acts as an...

Universal joint

130

The basal body of the flagella serves what purpose?

Anchors the flagella to the cell wall and plasma membrane

131

How does the basal body allow the flagella to move?

It serves as the motor allowing the flagella to move

132

Describe the structure of the basal body of a flagella in a gram negative bacterium.

Gram negative bacteria have two pairs of rings. The outer pair is anchored to the cell wall. The inner pair anchored to the plasma membrane.

133

Describe the structure of the basal body of a flagella in a gram positive bacteria.

Gram positive bacteria only have the inner pair of rings anchored to the plasma membrane

134

The flagella can rotate clockwise and anticlockwise. True or false?

True

135

The speed of flagella rotation can be altered between?

200-17,000 rpm

136

Runs by flagella are interrupted by changes in directions called...

Tumbles

137

Flagella with a polar arrangement can have two types of flagella, one being reversible flagella, the other being...

Unidirectional flagella where they move rapidly and typically spin around

138

Cells can move toward a favourable or away from an adverse environment by their flagella, what is this called?

Taxis

139

What are two types of stimuli and what would the movement be?

Chemical and light. Chemotaxis and phototaxis

140

Describe the motion of a bacterium when near a positive stimulus

Many runs and few tumbles

141

Describe the motion of a bacterium when near a negative stimulus

Frequency of tumbles increase

142

What is the axial filament?

Wraps around the cells of spirochete bacteria

143

Two examples of spirochete bacteria

Treponema pallidum that causes syphilis and Borrelia burgdoferi that causes Lyme disease

144

How is Lyme disease transmitted?

Through the bites of infected ticks

145

How is Syphilis transmitted?

Sexually transmitted

146

Where is the axial filament?

Enclosed in the space between the outersheath and the cell wall

147

The rotation of the axial filament causes what type of movement for spirochete bacteria?

Corkscrew-type movement

148

What advantage do spirochete bacteria have?

Most live in bodily fluids, The axial filament can allow them to swim through mucus - propel through

149

Size of plasma membrane?

7nm

150

Function of the plasma membrane

Separate cytoplasm from the env, selective permeability enables movement

151

The phospholipid bilayer contains hydrophobic and hydrophilic components, what makes the hydrophobic environment?

The fatty acids - they point inwards

152

The glycerophosphate heads exposed to the external environment or the cytoplasm are

Hydrophilic

153

Proteins found on the surface of the bilayer of the plasma membrane are called

Peripheral proteins

154

Proteins found in the bilayer of the plasma membrane are called

Integral proteins

155

Proteins that go through the bilayer of the plasma membrane are called

Transmembrane proteins

156

The plasma membrane is described to be _________ permeable

Selectively

157

Is simple diffusion across a plasma membrane a passive or an active process?

Passive

158

Facilitated diffusion involves

Transmembrane proteins

159

Active transport involves movement

against a concentration gradient

160

Does the bacterial cytoplasm contain a cytoskeleton?

No babes

161

What is the nucleoid in a bacterial cell?

The region containing the bacterial chromosome

162

The site of protein synthesis and there are 10,000+ of these per cell...

Ribosomes

163

In a bacterial cell, the ribosomes are composed of two subunits, what are these

A small subunit of 30S and a large subunit of 50S to make a 70S ribosome

164

The function of inclusion bodies is

To act as energy reserves or reservoirs of structural building blocks

165

Can inclusion bodies be observed?

Yes by light microscopy after staining

166

What are metachromatic granules?

They contain inorganic phosphate and a reserve of high energy phosphate

167

Polysaccharide granules (starch/glycogen) contain

a reserve carbon and energy source

168

Lipid inclusions...

reserve carbon and energy source

169

Sulphur granules as a

energy reserve

170

Gas vacuoles

for buoyancy

171

Carboysome inclusion bodies

for co2 fixation

172

Magnetosomes iron oxide inclusion bodies for

orienting and migrating along geo-magnetic field lines

173

Endospores are

An endospore is a dormant, tough, and non-reproductive structure produced by certain bacteria

174

Endospores work because they are

resistant to heat, harsh chemicals and radiation

175

Endospores are produced in the ______ stage of a bacterial life cycle

Dormant

176

They are usually produced by gram negative or gram positive bacteria?

Gram positive such as bacillus and clostridium

177

Define sporulation

Endospore formation

178

Define germination

Returning to vegetative state

179

When does sporulation begin and how long does it take?

When a key nutrient becomes scarce, it takes several hours long

180

What happens in the first stage of endospore sporulation?

The newly replicated bacterial chromosome and a small portion of the cytoplasm become isolated by the ingrowth of the plasma membrane (spore septum)

181

What happens in the second stage of endospore sporulation?

The mother cell engulfs the spore leading to a double layered membrane that surrounds the chromosome and cytoplasm -> forespore

182

What happens in the third stage of endospore sporulation?

A thick layer of peptidoglycan is laid down between the two membanes

183

What happens in the fourth stage of endospore sporulation?

The spore coat is laid down around the outer membrane - endospore

184

What happens in the fifth and final stage of sporulation?

The original cell ruptures releasing the spore

185

There are different types of spores, what are the three?

Terminal, subterminal and central spores

186

What are the three distinct phases of endospore germination?

Activation, germination and outgrowth

187

What causes the activation of the germination stage?

Heating, for example the cytoplasm may activate at 100 degrees

188

What happens in the germination stage of endospore germination?

In the presence of nutrients and amino acids, the spore becomes metabolically active

189

What happens in the outgrowth stage of endospore germination?

Uptake of water. RNA, DNA protein synthesis begins and the vegetative cell emerges