Forensic biology - Prokaryotic cells I – structure and metabolism

  • Created by: aarafa11
  • Created on: 01-06-20 19:39
What are the 5 kingdoms
monera; protista; fungi; plantae; animalia
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What does the kingdom monera contain
bacteria and archaea (prokaryotic cells)
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The size of archaea
similar to bacteria
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what is thearchaea's cell wall made of
but not always present and when present, made of Pseudopeptidoglycan
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where can you find archaea
soil, the ocean and human gastrointestinal tract
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How do archaea get food
Autotrophs, i.e. photosynthetic – Cyanobacteria (blue green algae); Others are Chemoautotrophs –chemosynthetic; But most are chemoheterotrophs
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how does archaea respire
aerobically: Glycolysis – Cytoplasm, TCA cycle – Cytoplasm, Electron transport chain; Anaerobically - fermentation
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What colour dye does Gram positive bacteria retain
violet dye
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what colour dye does Gram negative bacteria retain
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What is the similarities between Gram positive and negative bacteria
cell wall made from peptidoglycan- a polymer of alternating N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG); Polymer chains are linked together by peptide bridges between NAM molecules
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What does positive gram bacteria have
Cell wall a thick layer of peptidoglygan; Peptidoglycan polymers extensively bridged; A ploysccharide, Lipoteichotic acid (LTA), attached to cell membrane extend through cell wall; LTA recognised by immune system as foreign (i.e. is an antigen)
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What does negative gram bacteria have
Cell wall a thin layer of peptidoglygan; Peptidoglycan polymers less extensively bridged than gram +ve; Outer membrane on outside of peptidoglygan is covered in lipopolysacchrides (LPS)
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What is lipopolysacchrides (LPS) made of
Lipid A of LPS is an endotoxin; Polysaccharide of LPS is an antigen
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Why is the Gram stain important
very important in identifying bacteria; Different classes of antibiotics can be used against gram +ve and –ve bacteria; Lysozyme is effective against +ve, but not –ve
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WHat does lysozome do to gram strain bacteria
hydrolyses the bonds between NAG and NAM in peptidoglycan
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WhAt is The bacterial genome
Single double strand of DNA in circle; No nucleus, just a dense region of DNA, the Nucleoid; Less genes than a eukaryotic genome -1,000 X less DNA; plasmid contain 24 genes
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DNA replication of bacteria
unzip DNA double strand so both strands can be replicated; DNA polymerase synthesises the second DNA strand from the template provided by each of the original two stands of DNA; Replication occurs in both directions around the DNA circle
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what is the name of bacteria reproduction
binary fission - asexual
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how does binary fission work
DNA replicates into two and the cell splits forming two identical daughter cells
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how is binary fission not the same as mitosis
no spindle apparatus are involved
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what are bacteria resistant to
Survive drought; Temperature (over 100 oC); Time (50-300 years)
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how is sporalation replicated
One copy will form the endospore and it directs spore formation
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how is Endospore septum formed
from cell membrane; Ends in double layer of membrane surrounding proto-spore; Both layers of membrane synthesise peptidoglycan into the intra membrane space – forming the cortex
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what does the cortex for sporulation
protects spore against osmotic pressure
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what is spore coat made from and its purpose
Spore coat, formed by mother cell, coats the outside of the membrane; Coat formed from keratin–like protein; Coat forms a barrier impervious to most chemicals
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ways in which genetic material can pass from one bacterium to another
Transformation; Transduction; Conjugation
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What is necassary for transformation to work
Only DNA similar to that of the bacterium is transported as foreign alleles can replace native alleles in this way
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how does transformation work
Fragment of DNA Transported into cell by carrier protein; DNA fragment recombines with native DNA - replacing native DNA sequence
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how does crossing over work in transformation
gene transfer produce slightly diploid cell containing fragments of dona cells chromosome; 2 crossover insert segments of donor chromo into intac; fragment degraded
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when does bacterial tranduction occur
during viral replication
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what are the ways that bacterial tranduction occur
a piece of host DNA becomes attached to the viral genome; Or the viral genome is replaced by a fragment of host DNA
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what does the completed virus particle contain after bacterial transduction
carries the host DNA to next cell it ‘infects’
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how does bacterial transduction work
Viral DNA included in bacteria chromosome; DNA is fragmented & packaged into viral coats; Lysis, but some viruses contain bacterial DNA
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What does the donor cell contain for bacterial conjugation
contains the F plasmid (genes for conjugation) to construct conjugation pilus.
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What does conjugation pilus do
contact F- cell - forms a conjugation bridge
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what happens to the plasmid in conjugation
Double stranded plasmid DNA separates; One strand is transferred into the F- cell
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how to form High Frequency of recombination (Hfr)
conjugatio interupted; F+ plasmid becomes reversibly incorporated into the genomic DNA; leads to the transfer of genomic DNA/ leads to the whole chromosome being transferred
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what does happen in High Frequency of recombination (Hfr)
does lead to much higher recombination
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what is required for conjugation to work
F factor DNA - found in the F factor plasmid in F+ cells or incorporated into the genomic DNA of the High Frequency of recombination (Hfr) strains
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how to identify bacteria and fungi
by isolating and culturing organism
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what are the physical condition to culture successful
temperature, pH, humidity, oxygen level, nutrients
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what does the very complex growth media contains
Carbohydrates; amino acids; vitamins; DNA (purine & pyrimidine) bases; more complex molecules such as peptides, nucleotides and coenzymes; peptones; extracts; natural enricchment; organic compound; minerals
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Peptones - media components
crude peptides prepared from proteins treated with proteolytic enzymes
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extracts - media components
lean meat treated with hot water, contains B vitamins, amino acids, minerals
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natural enrichemnt - media components
Animal blood, serum, milk
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organic compounds - media components
sugars, coenzymes, purine & pyrimidine bases, fatty acids
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minerals - media components
P, Mg, Mn, Fe, Co, Na, Ca, Zn, Cu
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buffers - media components
keep pH in range 6.8 – 7.2
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broth - media components
water based, media components added
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agar- media components
sulphated polysaccharide derived from seaweed; Forms a gel with water when heated to above 100oC & then cooled to below 42oC; Microorganisms cannot digest agar; Forms ideal, moist surface for microbial growth – gel 98.5% - 94% H2O
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natural broth
commonly used to grow bacterium, including human pathogens; contains 0.3% beef extract, 0.5 % peptone
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natural agar
Nutrient broth, but with 1.5% agar added to form a solid gel when cooled
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type sof media
selective; differential; enriched
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What does the kingdom monera contain


bacteria and archaea (prokaryotic cells)

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The size of archaea


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Card 4


what is thearchaea's cell wall made of


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Card 5


where can you find archaea


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