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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
Plasma membrane function
Most important layer as it encloses the cytoplasm. Also involved in respiration, photosynthesis and synthesis of lipids and cell wall components.
26
Ribosomes
Site of protein synthesis
27
Nucleoid
Contains the cell's chromosomes
28
Chromosomes
Contain the genes needed to provide instructions for protein synthesis in the cell.
29
Plasmids
Contain extrachromosomal DNA Plasmids often contain genes that confer a selective advantage to the bacterium such as resistance to antibiotics.
30
What are the main functions of the cell wall ?
Prevents the cell from rupturing. Confers shape and rigidity to cels. Helps differentiate whether bacteria are gram + or -
31
Gram + cell wall
Have a single THICK layer of peptidoglycan, above the plasma membrane. This allows them to retain the staining dye.
32
Gram - cell wall
Have a thinner layer of peptidoglycan sandwiched between the surface membrane and the plasma membrane. These cannot retain the dye.
33
Peptidoglycan function
PGN - forms a mesh like layer outside the plasma membrane
34
Peptidoglycan Composition
Polymer of sugars and amino acids
35
Lipoteichoic Acid type of gram cell wall
Gram + bacteria
36
Function of Lipoteichoic Acid
Provides cell rigidity
37
Composition of Lipoteichoic Acid
Complex of teichoic acids + lipids
38
Lipopolysaccharide type of gram cell wall
Gram - bacteria
39
Function of Lipopolysaccharide
Elicits potent immune and inflammatory host responses Produces endotoxins
40
Steps in gram staining
Primary Stain Trapping Agent Decolourisation Counter stain
41
Primary Stain function
Stains all the bacterial cells PURPLE (crystal violet dye)
42
Trapping Agent function
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)
43
Decolorisation (with alcohol) function
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
Counterstain results
Gram -ve : Pink/Reddish Gram +ve : Purple
45
Why do Gram + cells stain Purple ?
Gram positive: becomes dehydrated and traps the complexes in thicker PGN layer of cell wall
46
Why do Gram - cells stain red ?
Gram negative: loses outer LPS layer; exposes thin inner PGN layer; coloured complexes mainly wash away
47
How do bacterial cells replicate ?
By Binary fission. 1 cell reproduces to give 2 daughter cells
48
Steps in Bacterial Replication
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
Where is the genetic information found in bacterial cells ?
Circular DNA - distributed equally between daughter cells
50
Bacterial Replication of GENOME stages
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
What are the phases in bacterial GROWTH ?
Lag phase Log phase Stationary phase Death phase
52
What happens in the lag phase of bacterial growth ?
Period of active growth Bacteria prepare for replication
53
What happens in the log phase of bacterial growth?
Cells divide at maximum rate Uniform replication Graph line is almost straight
54
What happens in the stationary phase of bacterial growth?
Exhaustion of nutrients Cessation of growth Number of cells dying balances the number of new cells.
55
What happens in the death phase of bacterial growth ?
Number of cells dying exceeds the number of newly born cells.
56
How are genes transferred ?
Horizontal Gene Transfer
57
Stages in Horizontal gene transfer
Transformation Transduction Conjugation Outer membrane synthesis
58
What is transformation in horizontal gene transfer ?
Bacteria take up DNA from their environment.
59
What is transduction in horizontal gene transfer ?
Bacteriophages (bacterial viruses) move genes from one cell to another
60
What is conjugation in horizontal gene transfer ?
One bacterium connects itself to another through the pilus. Bacteria directly transfer genes to another.
61
What are some ways to identify bacteria ?
Morphology - coccus, bacillus, spiral... Arrangement - single, chain, clusters... Gram Stain Atmospheric preference Key enzymes Fastidiousness
62
Gram + coccus arrangement
Cluster, grape like Staphylococcus Aureus
63
Gram - coccus arrangement
2 attached bugs Neisseria Meningitidis
64
Gram + bacillus arrangement
Single rods Listeria Monocytogenes
65
Gram - bacillus arrangement
Single rods Esterichia Coli
66
Structural components of viral cells
Nucleic acid Capsid Envelope Spikes (antigens)
67
What does it mean that viruses are intracellular obligate parasites ?
Only contains the parts needed to enter and control a host cell.
68
How is genetic material stored in viruses ?
DNA or RNA
69
Capsid
Protective protein coat
70
Shapes of capsids
Icosahedral Helical Complex
71
Spikes
Highly antigenic
72
Viral Life Cycle
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
What type of cells are fungi ?
Eukaryotic cells - multicellular
74
Structure of Fungi
Same structure as eukaryotic cells Contains a bud with a vesicle, ribosomes and septum
75
What is the body of a fungus called ?
Thallus
76
What is hyphae ?
Long branched filaments in mould
77
What is the cell wall made of in fungi ?
Thick carbohydrate wall containing CHITIN and glucans.
78
How do fungi replicate ?
Asexually by BUDDING, and occasionally by binary fission.
79
Conidia
Ending in the name of fungal types
80
Mycoses
Fungal Infection
81
What type of cells are protozoa ?
Single celled eukaryotes
82
How are protozoa classified ?
Based on motility
83
Sporozoa
Non-motile, INTRAcellular parasites
84
Flagellates
Possess tail-like structures for motility
85
Ameoba
Use temporary cell-body projections
86
Ciliates
Move by beating cilia
87
What are protozoa and helminths ?
Parasites
88
# PARASITES Diplomonads and parabasalids location
Live in the intestinal tract (ANOXIA)
89
Features of diplomonads
Diplomonads are defined by the presence of a nonfunctional, mitochrondrial-remnant organelle called a mitosome.
90
Features of parabasalids
Parabasalids are characterized by a semi-functional mitochondria referred to as a hydrogenosome
91
Protozoa disease example
Malaria
92
Kinetoplastid
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
How to characterise alveolata ?
BY the presence of alveoli
94
What are the 2 kinds of nuclei that ciliates possess ?
Macronucleus Micronucleus
95
Function of macronucleus (parasites)
Regulates basic cellular function
96
Function of micronucleus
Controls sexual reproduction
97
Helminths
Term used for all parasitic worms
98
Cestoda
Tapeworms
99
Trematoda
Flukes
100
Nematoda
Roundworms
101
Schistosomiasis
Urinary and Intestinal infections FLATWORM
102
Trichiuriasis
Intestinal infections ROUNDWORM (Human whipworm)
103
Tapeworm
Acquired from ingesting worms or eggs in undercooked pork Reside in large intestine
104
What is a scolex ?
The anterior end of a tapeworm, bearing suckers and hooks for attachment.
105
Name the types of gram + bacteria
Bacillus Clostridium Staph Strep
106
Name the types of gram - bacteria
Coli Pylori Neisseria

Medicine Year 1 Semester 1 (37 decks)

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