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LCB > LCB1 > Flashcards

LCB1 Flashcards

1
Q

Why is microbiology important in veterinary medicine?

A
  • Understand disease.
  • Recognise emerging diseases
  • Improve the control of known infections to improve prevention and to reduce spread
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2
Q

What are the different groups of microorganisms in order of size (largest to smallest)?

A

Fungi (5micrometers), bacteria (1-5 micrometers), virus and prions (300 to 20 nanometers)

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3
Q

What are the basic structural properties of bacteria?

A

Cell membrane, capsule, cell wall, single haploid chromosome (circular), ribosomes and plasmid

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4
Q

Describe the bacterial genome

A

Consists of a haploid circular chromosome which contains essential and core genes (which define bacteria) and contains plasmid (small circular independent DNA)

  • plasmid not present in all bacteria
  • plasmid contains partitions genes involved in cell division
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5
Q

What is a nucleoid?

A

DNA in the chromosome organised into a protein complex

No nucleus - DNA packed closely by supercoiling using DNA gyrase

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6
Q

What are the function of histones?

A

Further pack the DNA into protein complexes

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7
Q

What type of ribosomes are present in eukaryotes?

A
  • Larger ribosomes
  • 80s
  • 40% rRNA 60% protein
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8
Q

What type of ribosomes are present in prokaryotes?

A
  • Smaller ribosomes
  • 70s
  • 60%rRNA 40%protein
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9
Q

What are the different groups of bacteria?

A

Gram negative, gram positive, acid fast and mycoplasmas

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10
Q

What are the structural features of gram negative bacteria?

A

Lipopolysacharides, double membrane, thinner capsule, lipoproteins, thinner peptidyglyocan layer

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11
Q

What are the structural features of gram positive bacteria?

A

Thicker capsule, thicker peptidyglyocan layer, single membrane

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12
Q

What are the structural features of acid fast bacteria?

A

Mycolic acids, D-galactose in cell wall, phylogenetically related to gram positive
Resist decolourization by acid-alcohol so remain and stained red the colour of the first stain in acid fast staining (carbol fuchsin).

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13
Q

Describe the gram stain

A

1) Crystal violet (dye-purple)
2) Iodine (mordant)
3) Alcohol (decolourisation)
4) Safranin (counterstain)

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14
Q

Describe the acid fast stain

A

1) Ziehl Neelsen carbofuchsin added to fusion slide and apply with heat
2) Acid alcohol added and washed with water
3) Counter stain added (methylene blue) and washed with water

Acid fast bacteria retain red colour, other blue

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15
Q

Describe some bacterial differences within different bacteria

A
  • LPS outer memrane of gram negative bacteria
  • capsules- protection against dessication, adherences and interefere with phagocytosis
  • flagella: used for motility
  • pili/fimbrae: adhesion function
  • endospores
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16
Q

What are the modes of motility in flagella

A

RUNS-straight lines

TWIDDLES- move on spot to rotate

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17
Q

What are endospores?

A

Highly resistant bodies produced by bacteria which survive adverse conditions

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18
Q

How are endospores developed?

A

1) Vegetative cell trigger to form spore in mother –> assymetric division and spore forms on one side
2) developing of spore coat –> synthesis of dipicolonic acid and accumulation of Ca2+
3) release of endospore due to cell lysis of mother
4) triggered to germinate by activation of heat, excretion of Ca2+

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19
Q

What are the 4 classes of lipids?

A

Fatty acids, triglycerides, phospo and sphingolipids, steroids

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20
Q

Which fatty acid has one or more carbon to carbon double bonds

A

Unsaturated fatty acids

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21
Q

Describe the structure of different fatty acids

A

Triaglycerol- glycerol and 3 fatty acids
Glycophospholipids- glycerol, 2 fatty acids, phosphate and polar head group
Sphingolipids- 2 sphingospine, fatty acid, phosphate, polar head group
Glycolipids- 2 sphingosine, fatty acid, monosaccharides

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22
Q

Give examples of hydrophilic and hydrophobic groups

A

Hydrophillic- phosphate, oxygen, carbon dioxide, nitrogen

hydrophobic tail- fatty acid tail

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23
Q

What are the functions of cell membranes

A

Protection, stability, adherence,

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24
Q

What is sphingomyelin lipidosis

A

Definciency of sphingomyelinase –> accumulation of sphingomyelin –> lysosmal catabolism

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25
Q

What is the role of cholesterol?

A

Moderator of membrane fluidity.
Makes structure more rigid.
Interacts and immobilises ends of phospholipid hydrocarbon chains.
Prevents crystillisation (phospholipids coming together)

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26
Q

What is the function of an ABC transporter?

A

Defense mechanism against harmful substances.
ATP binding casssette via active transport.
Composed of P-glycoprotein.

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27
Q

Why do you need to be careful when administrating antibiotics to border collies?

A

Border collies have a deletion mutation with MDR1 gene (frame shift mutation) resulting in a premature stop codon in MDR1 which results in a non functional P-glycoprotein.

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28
Q

What are lipid rafts and what are their functions?

A

Formed by interaction of lipids
Control membrane composition
External side= receptors Cytoslic side= intracellular signalling

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29
Q

Explain the Fluid Mosaic model

A

The fluid part represents the fluidity of the phospholipid bilayer composed of the hydrophobic tail.
The mosaic part represents the patchwork of proteins in the phospholipid bilayer.
The phospholipids move about more rapidly than larger proteins

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30
Q

What is the function of the fluid mosaic model?

A

It is a barrier.

Allows flexible change in shape/membrane composition

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31
Q

Explain the steps in bleaching

A

1) Membrane protein of interest is flourescently labelled
2) Laser beam bleaches specific area
3) Flourescent intensity develops as bleached molecules move away

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32
Q

What is Chromatin?

A

Linear DNA and proteins (histones) arranged in the chromosome

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33
Q

What are nucleosomes?

A

Building blocks of chromatin.
Composed of 8 histone proteins.
Nucleosomes separated from each one by linker DNA

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34
Q

Describe the organisation of DNA

A

DNA is organised into chromosomes. Within a chromosome you have chromatin which is made up of nucleosomes and histone proteins.

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35
Q

Describe differences between prokaryotic DNA and eukaryotic DNA

A

Prokaryotic DNA is organised into a haploid chromosome, and can sometimes be organised into a plasmid.
Eukaryotic DNA is organised into a diploid/homologous chromosomes.

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36
Q

Describe DNA replication in prokaryotes

A

1) Double stranded DNA separated into parental (template) strand and daughter (new) strand
2) Replication occurs at replication fork
3) 2 daughter cell /DNA molecules form

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37
Q

Describe DNA replication in eukaryotes

A

1) Double stranded DNA separated into parental and daughter strand
2) replication occurs in opposite direction between 2 new strands at replication fork
3) 2 daughter DNA strands formed

38
Q

What is the function of DNA topoisomerase?

A

Unwinds double helix by cutting and resealing tangled DNA

39
Q

What are telomeres?

A
  • GGGTTA repeats
  • forms longer DNA- repeats on 5’
  • 3’ FILLED by DNA synthesis
40
Q

What are the different types of damage DNA can undergo?

A 
Spontaneous damage:
-glycosidic link binding purines to sugars is unsrtable and bases break off --> C + A deaminate to U + hypoxanthine
Chemical damage:
-o2 free radicals 
-UV light and carcinogens
41
Q

How does DNA repair itself?

A

Via DNA repair nucleases: recogniion and removal of area then via DNA polymerase on opposite strand and DNA ligase

42
Q

What is the genome composed of?

A

Exons- coding
Introns- non coding
Open reading frame ORF- determine translation
5’ contains promoter- where transcription proceeds
Repeated sequences- transposons, macrosatelites, microsatelites

43
Q

What are transposons?

A

Lines- long interspersed repeated sequences
Sines- short (aluin in humans)
Function unknown

44
Q

Name the different single repetitive DNA sequences

A

Macrosatellites- composed of 5-500 bases and repeated MILLIONS of times
-located in chromatin
Microsatellites- cmposed of 2-6 base pairs and repeated 12-40 times
-used as genetic markers to identify unique traits

45
Q

Describe the process of transcription

A

1) DNA helicase breaks H-bonds between bases exposing the template strand
2) RNA polymerase joins free complementary nucleotides
3) transcription occurs from 5’ to 3’
4) RNA polymerase reaches a stop codon and forms pre-mRNA
5) pre mRNA spliced to remove introns

46
Q

What are s-values

A

Rate of sedimentation in ultracentrifuge. The greater the S valie the larger the rRNA

47
Q

What occurs during mRNA processing?

A
  • capping on 5’ –> by addition of 7-methylguanosine
  • polyadenylation at 3’ –> poly(adenosine) tail to make mRNA in nucleus occur
  • introns removed –> splicing occurs in spliceosomes
48
Q

What happens within the promoter region?

A
  • On the end of DNA. Includes a TATA box
  • Upstream of transcription start site
  • Controls CAAT + GG boxes
  • Acts a as mediator: binds RNA polymerase
49
Q

What happens within the enhancer region?

A
  • Generally upstream

- increases amount of transcribed RNA

50
Q

What are the structural modifications of chromatin needed to activate the promoter region?

A
  • Chromatin remodelled via nucleosome
  • histone modifications
  • modification of DNA via methylation of C –> CG nucleotide at promoter –> represses gene expression
51
Q

Explain process of gene expression: activation of transcription

A

1) nucleosomes are removed, revealing the promoter
2) transcription factors bind to promoter DNA (+enhancer if required)
3) Mediator proteins complete initation event
4) initiation complex recruits RNA polymerase
5) many points where control over rate of initation of mRNA transcript is possible

52
Q

Explain process of gene expression- down regulation

A

1) Termination singal in gene-termination + releases transcripts
2) transcription factors inactivated
3) dephosphorlyation
4) transcription terminates

53
Q

What are the different types of mutations?

A

Mis-sense mutation- insertion of incorrect amino acid
Frame-shift mutation- assembly abnormal sequence of amino acids: STREPTOMYCIN + RETROVIRUS
Pre-mature termination - non sense mutation- single base change could code for stop codon

54
Q

What is the structure of a tRNA molecule?

A 
Clover leaf structure
80 nucleotide in length
At 3' amino acid receptor 
D loop, t loop
Anti-codon (GAA) opposite amino acid receptor
55
Q

What is Wobble hypothesis?

A

First 2 bases confer most of specificity

56
Q

Explain how tRNA-amino acid complex formed?

A

1) Adenylation of amino acid - addition of AMP

2) Transfer of amino acid to tRNA

57
Q

What is the mechanism for protein synthesis?

A

1) INITIATION
ribosome composed of large and small subunits
mRNA scanned by small subunit and bound by initiator tRNA
Recruitment of initiation factors
tRNA binds to AUG on mRNA –> GTP binding/hydrolysis
2) ELONGATION CYCLE
Positioning of aminoacyl on tRNA in A site (ribosome)
Peptide bond formation
Translocation
3) TERMINATION - UAA, UAG, UAC
GTP hydrolysis alters ribosome function and ribosome dissociates

58
Q

What antibiotics target small sub units?

A

Tetracycline, streptomycin, hydromycin B

59
Q

What antibiotics target large sub units?

A

Chlorampheniol, erthrymycin, streptogramin B

60
Q

What are the post-translational modifications?

A
  • Proteolytic cleavage
  • disculfide bond formation
  • glycosylation/hydroxylation/phosphorylation
  • lipophillic modification- add a lipid
61
Q

Name the bonds that stabilize proteins

A

Covalent, non covalent (ionic, hydrogen and van der waals)

62
Q

What is the structure of an amino acid?

A
  • R side chain (variable)
  • Carboxyl group
  • Amino acid group
63
Q

What enables folding of a protein?

A
  • Covalent bonds allow free rotation = flexible (rotation about C-C + C-N
  • Non covalent bonds in side chain do not allow roation
  • polar molecules form bonds with +’ve dipole H+ in H2O forming a non-covalent hydrogen bond
64
Q

What is the primary structure of a protein?

A
  • Linear chain of amino acids
  • C backbone- non polar
  • 6 classes of R side chains
  • peptide bonds forming polypeptide
65
Q

What is the secondary structure of a protein?

A
  • coiling/pleating of polypeptide chain
  • alpha helix- side chains extending outwards
  • beta pleated sheets- side chains point in opposite directions
  • connected by beta turns or omega loops
66
Q

What is the tertiary structure of a protein?

A
  • secondary structure folded into a 3D shape
  • hydrophobic interactions on inside (tail)
  • hydrophillic head on outside
  • globular- spherical, soluble i.e Hb
  • fibrous- long filamentous, insoluble i.e. collagen
67
Q

What is the quaternary structure of a protein?

A

Several polypeptide chains

68
Q

What is a structural domain?

A

An element of overall structure within a protein which forms a discrete, self contained section of polypeptide e.g. calcium binding domain

69
Q

What is a protein motif?

A

Sequence of a small number of amino acids unrelated to structure
Can make up a domain

70
Q

What is the generation time?

A

The length of time required for one complete cycle of cell division - for a bacterial cell to divide into 2 daughter bacterial cells

71
Q

How can you measure the growth of bacteria?

A
  • Optical density (absorbance)
  • Microscopically: direct counting
  • Colony counting: serial dilutions, spread plate, pour plate, mile-micra, membrane filtration
72
Q

What is a psychrophile?

A

Grow in temperature below 25 degrees Celsius

73
Q

What is a thermophile?

A

Bacteria that grow in temperatures above 40

74
Q

Where does a chemoheteroptroph get its energy and carbon from?

A

Energy- oxidase chemical compounds

Carbon- organic compounds

75
Q

Where does a chemoautotroph get its energy and carbon form?

A

Energy- oxidase in organic chemical compounds

Carbon- CO2

76
Q

What is the difference between fastidious and non fastidious bacteria?

A

Fastidious bacteria require specific supplements to grow

77
Q

What are examples of nutrition for bacteria and where do they get it from?

A

Carbon- glucose
N2- peptides and amino acids
Phosphates- nucleic acids and compounds with energy rich bonds
Sulphates- form sulfur containing amino acids
Mg, K, Ca, Fe- co-factors in enzymes and processes

78
Q

How can you preserve an organism?

A
  • Sub culturing- labour intensive
  • Freeze drying- lyophilisation
  • Freeze with cryoprotection (DM or glycerol)
79
Q

What is the structure of the cytoskeleton?

A

Microfilaments- actin
Intermediate filaments-keratin family
Microtubules - alpha and beta tubulin

80
Q

What is the role of the cytoskeleton?

A
  • Maintenance of cell shape- mechanical support
  • Movement
  • Contraction
  • Internal organisation i.e. in chromosomes
81
Q

Describe the self assembly of microtubules

A

B tubulin + alpha tubulin –> protofilament –> microtubule

82
Q

What are the 2 molecular motor proteins that travel along MT?

A

Kinesin (- to +)

Dynein (+to -): cytoplasmic dynein and axonal, beating of cilia and flagella, fastest

83
Q

What are the types of axonal transport?

A

Anterograde by Kinesin - provides synapse region with proteins
Retrograde by dynein- recovers material for lysosomal degradation

84
Q

What is the structure of actin?

A
  • Helical polymers
  • polarised
  • used in muscle contaction
  • actin monomer exists as G-ACTIN
  • filamentous polymer exists as F-ACTIN
85
Q

What are the functions of actin filaments (microfilaments)

A
  • surface crawling
  • produce stable projections e.g. microvilli
  • form contractile bundles
86
Q

How does actin and tubulin produce polar filaments?

A

Actin binds to ATP and Tubulin binds GTP

  • if ATP/GTP on end = addition of subunit
  • if ADP/GTP on end= loss of subunits by dynamic instability and treadmilling
87
Q

Explain the process of dynamic instability

A

It is the process of microtubulels depolymerising very quickly composing of GDP

  • GTP = ‘CAP’ dimer on (+)
  • microtubule depolymerises and polymerises on (+) end
  • can occur in microfilaments with actin
88
Q

Explain the process of treadmilling

A

[G-actin] > Cc of barbed (+) end +

89
Q

What is the self assembly of intermediate filaments

A

Monomer –> coiled coiled dimer –> staggered tetramere of 2 coiled coiled dimers antiparallel –> 2 etrameres packed together –> many tetrameres packed together in a helical array (16 dimers)

90
Q

What is the structure of cilia and flagella?

A

Axoneme ( 9 outer doublet microtubules surrounding pair of central microtubules)

  • CLILA: bending of axoneme causes movement of cilia
  • dynein
91
Q

Explain 3 step process of surface crawling

A

1) PROTRUSION- actin rich structures pushed to the front of cell
2) ATTACHMENT- adhesion to substratum via focal contact–> slows movement –> actin polymerisaation at (+) and protrudes lamellipodium
3) TRACTION- contraction generated by myosin motor proteins at rear and propels body cell forward

LCB (3 decks)

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