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Medicine Year 1 Semester 1 > Microbial Structure > Flashcards

Microbial Structure Flashcards

1
Q

Features of Eukaryotes (DNA)

A

Have a true nucleus (bound by a membrane)

Linear DNA

DNA organised into chromosomes; complexed with proteins

Large complex ribosomes with many types of rRNA & proteins

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2
Q

Features of Prokaryotes (DNA)

A

No nucleus; has a nucleoid; no physical boundary

Circular DNA (plasmids)

DNA nuceloid-associated proteins that help pack DNA into nucleotid, plasmids present

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3
Q

Features of Eukaryotes (membrane bound organelles)

A

Cytoplasm filled with large complex collection of organelles

Mitochondria with cristae are power plants of the cell.

Plants also have chloroplasts for photosynthesis.

Transcription and translation are physically separated.

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4
Q

Features of Prokaryotes (membrane bound organelles)

A

No membrane bound organelles independent of the plasma membrane.

Transcription and Translation occur simultaneously.

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5
Q

What type of cells are bacterial cells ?

A

Prokaryotic cells

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6
Q

What layers are bacterial cells surrounded by ?

A

Collectively called the cell envelope.

Consists of the capsule (glycocalyx, cell wall, plasma membrane)

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7
Q

Main components of bacterial cells

A

Glycocalyx
Cell Wall
Plasma Membrane
Nucleoid
Ribosome
Plamsid

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8
Q

Outer structure of bacterial cells

A

Pilus / Finbriae
Flagellum

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9
Q

Function of the glycocalyx capsule

A

Acts as a shield and protects the bacteria against phagocytosis and helps the bacteria to adhere to surfaces.

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10
Q

Structure of the glycocalyx capsule

A

Tightly organised polysaccharide layer that excludes small particles.

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11
Q

Structure of glycocalyx slime

A

More easily deformed polysaccharide layer, less tightly organised and doesn’t exclude small particles.

Loosely attached to cell surface and so can be easily lost

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12
Q

Function of glyocoalyx - slime

A

Protects cell from immune response
Can prevent access to antibodies

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13
Q

Function of Pili

A

Hair like structures that allows them to attach to other cells.

Forms a bridge to enable the transfer of plasmids between bacteria.

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14
Q

What are fimbriae ?

A

Shorter hair like structures on the external surface of bacterial cells.

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15
Q

Flagella

A

Long, whip-like protrusions that allow the bacteria to move.

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16
Q

What are flagella composed of ?

A

Flagellin protein

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17
Q

What are spores ?

A

Metabolically inert form of bacteria, triggered by adverse environmental conditions.

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18
Q

What is an advantage of spores ?

A

They are adapted for long-term survival, allowing regrowth under suitable conditions.

They have hard, multi-layered coats, making them difficult to kill.

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19
Q

What are round shaped bacteria called ?

A

Cocci

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20
Q

What are rod shaped bacteria called ?

A

Bacilli

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21
Q

What are spiral shaped bacteria called ?

A

Spirilla

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22
Q

What are oddly shaped bacteria called ?

A

Pleomorphic

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23
Q

What is the function of gram staining bacterial cells ?

A

Divides species into 2 groups, gram +/-
This is based on chemical and physical properties of the cell walls.

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24
Q

Cytoplasm

A

Gel-like substance, composed mainly of water that also contains cell components, enzymes and various organic molecules.

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25
Q

Plasma membrane function

A

Most important layer as it encloses the cytoplasm.

Also involved in respiration, photosynthesis and synthesis of lipids and cell wall components.

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26
Q

Ribosomes

A

Site of protein synthesis

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27
Q

Nucleoid

A

Contains the cell’s chromosomes

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28
Q

Chromosomes

A

Contain the genes needed to provide instructions for protein synthesis in the cell.

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29
Q

Plasmids

A

Contain extrachromosomal DNA
Plasmids often contain genes that confer a selective advantage to the bacterium such as resistance to antibiotics.

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30
Q

What are the main functions of the cell wall ?

A

Prevents the cell from rupturing.

Confers shape and rigidity to cels.

Helps differentiate whether bacteria are gram + or -

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31
Q

Gram + cell wall

A

Have a single THICK layer of peptidoglycan, above the plasma membrane.

This allows them to retain the staining dye.

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32
Q

Gram - cell wall

A

Have a thinner layer of peptidoglycan sandwiched between the surface membrane and the plasma membrane.

These cannot retain the dye.

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33
Q

Peptidoglycan function

A

PGN - forms a mesh like layer outside the plasma membrane

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34
Q

Peptidoglycan Composition

A

Polymer of sugars and amino acids

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35
Q

Lipoteichoic Acid type of gram cell wall

A

Gram + bacteria

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36
Q

Function of Lipoteichoic Acid

A

Provides cell rigidity

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37
Q

Composition of Lipoteichoic Acid

A

Complex of teichoic acids + lipids

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38
Q

Lipopolysaccharide type of gram cell wall

A

Gram - bacteria

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39
Q

Function of Lipopolysaccharide

A

Elicits potent immune and inflammatory host responses
Produces endotoxins

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40
Q

Steps in gram staining

A

Primary Stain
Trapping Agent
Decolourisation
Counter stain

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41
Q

Primary Stain function

A

Stains all the bacterial cells PURPLE
(crystal violet dye)

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42
Q

Trapping Agent function

A

Forms crystal violet iodine (CVI) complexes in the cell wall (larger than CV so not to be easily washed out of the peptidoglycan (PGN) layer)

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43
Q

Decolorisation (with alcohol) function

A

Interacts with lipids in the cell wall

Gram negative: loses outer LPS layer; exposes thin inner PGN layer; coloured complexes mainly wash away

Gram positive: becomes dehydrated and traps the complexes in thicker PGN layer of cell wall

44
Q

Counterstain results

A

Gram -ve : Pink/Reddish

Gram +ve : Purple

45
Q

Why do Gram + cells stain Purple ?

A

Gram positive: becomes dehydrated and traps the complexes in thicker PGN layer of cell wall

46
Q

Why do Gram - cells stain red ?

A

Gram negative: loses outer LPS layer; exposes thin inner PGN layer; coloured complexes mainly wash away

47
Q

How do bacterial cells replicate ?

A

By Binary fission.
1 cell reproduces to give 2 daughter cells

48
Q

Steps in Bacterial Replication

A

Prokaryotic parent cell initiates replication

A copy of the cell’s DNA is created

Cell elongates and cross wall forms

Cross wall forms completely and daughter cells separate.

49
Q

Where is the genetic information found in bacterial cells ?

A

Circular DNA
- distributed equally between daughter cells

50
Q

Bacterial Replication of GENOME stages

A

Circular DNA replication starts at the Origin.
The replisome binds and initiates synthesis.

Bi-directional replication (opposite directions)

Replication ends at the terminus of replication, releasing 2 chromosome copies.

51
Q

What are the phases in bacterial GROWTH ?

A

Lag phase
Log phase
Stationary phase
Death phase

52
Q

What happens in the lag phase of bacterial growth ?

A

Period of active growth
Bacteria prepare for replication

53
Q

What happens in the log phase of bacterial growth?

A

Cells divide at maximum rate
Uniform replication
Graph line is almost straight

54
Q

What happens in the stationary phase of bacterial growth?

A

Exhaustion of nutrients
Cessation of growth
Number of cells dying balances the number of new cells.

55
Q

What happens in the death phase of bacterial growth ?

A

Number of cells dying exceeds the number of newly born cells.

56
Q

How are genes transferred ?

A

Horizontal Gene Transfer

57
Q

Stages in Horizontal gene transfer

A

Transformation
Transduction
Conjugation
Outer membrane synthesis

58
Q

What is transformation in horizontal gene transfer ?

A

Bacteria take up DNA from their environment.

59
Q

What is transduction in horizontal gene transfer ?

A

Bacteriophages (bacterial viruses) move genes from one cell to another

60
Q

What is conjugation in horizontal gene transfer ?

A

One bacterium connects itself to another through the pilus.

Bacteria directly transfer genes to another.

61
Q

What are some ways to identify bacteria ?

A

Morphology - coccus, bacillus, spiral…
Arrangement - single, chain, clusters…
Gram Stain
Atmospheric preference
Key enzymes
Fastidiousness

62
Q

Gram + coccus arrangement

A

Cluster, grape like

Staphylococcus Aureus

63
Q

Gram - coccus arrangement

A

2 attached bugs

Neisseria Meningitidis

64
Q

Gram + bacillus arrangement

A

Single rods

Listeria Monocytogenes

65
Q

Gram - bacillus arrangement

A

Single rods

Esterichia Coli

66
Q

Structural components of viral cells

A

Nucleic acid
Capsid
Envelope
Spikes (antigens)

67
Q

What does it mean that viruses are intracellular obligate parasites ?

A

Only contains the parts needed to enter and control a host cell.

68
Q

How is genetic material stored in viruses ?

A

DNA or RNA

69
Q

Capsid

A

Protective protein coat

70
Q

Shapes of capsids

A

Icosahedral
Helical
Complex

71
Q

Spikes

A

Highly antigenic

72
Q

Viral Life Cycle

A

Viral antigens attach to host cell

Viral DNA is inserted into the host cell

Viral DNA is replicated by host cell enzymes

New viral particles are assembled and packaged into new virions

They are released from the cell

73
Q

What type of cells are fungi ?

A

Eukaryotic cells - multicellular

74
Q

Structure of Fungi

A

Same structure as eukaryotic cells
Contains a bud with a vesicle, ribosomes and septum

75
Q

What is the body of a fungus called ?

A

Thallus

76
Q

What is hyphae ?

A

Long branched filaments in mould

77
Q

What is the cell wall made of in fungi ?

A

Thick carbohydrate wall containing CHITIN and glucans.

78
Q

How do fungi replicate ?

A

Asexually by BUDDING, and occasionally by binary fission.

79
Q

Conidia

A

Ending in the name of fungal types

80
Q

Mycoses

A

Fungal Infection

81
Q

What type of cells are protozoa ?

A

Single celled eukaryotes

82
Q

How are protozoa classified ?

A

Based on motility

83
Q

Sporozoa

A

Non-motile, INTRAcellular parasites

84
Q

Flagellates

A

Possess tail-like structures for motility

85
Q

Ameoba

A

Use temporary cell-body projections

86
Q

Ciliates

A

Move by beating cilia

87
Q

What are protozoa and helminths ?

A

Parasites

88
Q

PARASITES

Diplomonads and parabasalids location

A

Live in the intestinal tract (ANOXIA)

89
Q

Features of diplomonads

A

Diplomonads are defined by the presence of a nonfunctional, mitochrondrial-remnant organelle called a mitosome.

90
Q

Features of parabasalids

A

Parabasalids are characterized by a semi-functional mitochondria referred to as a hydrogenosome

91
Q

Protozoa disease example

A

Malaria

92
Q

Kinetoplastid

A

Kinetoplastids are a group of flagellated protozoans that are distinguished by the presence of a DNA-containing region, known as a “kinetoplast,” in their single large mitochondrion.

93
Q

How to characterise alveolata ?

A

BY the presence of alveoli

94
Q

What are the 2 kinds of nuclei that ciliates possess ?

A

Macronucleus
Micronucleus

95
Q

Function of macronucleus (parasites)

A

Regulates basic cellular function

96
Q

Function of micronucleus

A

Controls sexual reproduction

97
Q

Helminths

A

Term used for all parasitic worms

98
Q

Cestoda

A

Tapeworms

99
Q

Trematoda

A

Flukes

100
Q

Nematoda

A

Roundworms

101
Q

Schistosomiasis

A

Urinary and Intestinal infections
FLATWORM

102
Q

Trichiuriasis

A

Intestinal infections
ROUNDWORM (Human whipworm)

103
Q

Tapeworm

A

Acquired from ingesting worms or eggs in undercooked pork
Reside in large intestine

104
Q

What is a scolex ?

A

The anterior end of a tapeworm, bearing suckers and hooks for attachment.

105
Q

Name the types of gram + bacteria

A

Bacillus
Clostridium
Staph
Strep

106
Q

Name the types of gram - bacteria

A

Coli
Pylori
Neisseria

Medicine Year 1 Semester 1 (37 decks)

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