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Microbial Structure
Fichas del conjunto (31)
- 1What are the differences in genetic material between eukaryotes & prokaryotes?• E - has a true nucleus, bound by a double membrane; P - no nucleus, has a nucleoid w/ no physical boundary
• E - linar DNA, organised into chromosomes w/ associated proteins; P - 'naked' circular DNA w/ plasmids present
• E - 80s ribosomes; P - 70s ribosomes - 2What are the differences in structure between eukaryotes & prokaryotes?• E - cytoplasm filled with complex collection of organelles; P - no membrane bound organelles
• E - mitochondria w/ cisternae = energy centres; P - mesosomes are used for aerobic respiration
• E - transcription requires mRNA formation & movement from nucleus to cytoplasm for translation; P - transcription & translation occur simultaneously - 3Name 5 structural components of bacterial cells• Capsule
• Pili
• Flagellae
• Spores
• Slime - 4Describe the capsuleLoose polysaccharide structure which protects cells from phagocytosis (by preventing recognition) & desiccation (outside the body)
- 5Describe piliPilus = hair
• composed of oligomeric pilin proteins
• appendages used for bacterial conjunction, forming a tube or bridge to enable transfer of plasmids between bacteria
• highly antigenic
• may contian lectins which regocinse oligosaccharide units on host cells
• facilitate bacterial attachement to host cells - 6Describe flagellaeOrgans of locamotion
• composed of flagellin proteins
• driven by rotatory engine at anchor point on inner cell membrane - 7Describe sporesMetabolically inert form of bacteria which are triggered by adverse environmental conditions
• adapt for long term survival allowing regrowth under suitable conditions
• hard multi-layered coats make them hard to kill - 8Give 3 examples of sporesBotulism - Clostridium Botulinum
Tentanus - Clostridium Tetani
Anthrax - Bacillus Antracis - 9Describe slimePolysaccharide material secreted by some bacteria growing in biofilms
• protect against immune attack & against eradication by antibiotics - 10Why do gram positive & gram negative bacteria stain differently?Gram positive bacteria stain purple due to their thick peptidoglycan cell wall
Gram negative bacteria stain pink/reddish due to their thin peptidoglycan layer which is surrounded by plasma membrane - 11Describe the 4 stages of gram staining1. Primary stain - Crystal violet dye
• stains all bacterial cells purple
2. Trapping agent - Gram's iodine
• forms a CVI complex in the cell wall - larger than CV so not as easily washed out of the PGN layer
3. Decolorisation - Alcohol / Acetone
• interacts w/ lipids in the cell wall
• Gram -ve loses out layer of lipoproteins; exposes inner PGN layer; coloured complexes mainly washed away --> decolourised
• Gram +ve comes dehydrated & traps the complexes in thicker PGN layer --> colour remains
4. Counterstain - Safranin
• Gram -ve = pink/reddish
• Gram +ve = purple - 12Describe the cell wall of Gram +ve bacteria2 layers:
• thick peptidoglycan layer
• cytoplasmic membrane
Lipoteichoic acid (LTA) - 13Describe the cell wall of Gram -ve bacteria3 layers:
• outer membrane
• thin peptidoglycan layer
• cytoplasmic membrane
Lipopolysaccharide - 14What is PGN?Peptidoglycan
• polymer of sugars & amino acids which forms a mesh-like layer outside the plasma membrane
• sugar component = alternating residues of N-acetylglucosamine & N-acetylmuramic acid - 15What is LTA?Lipoteichoic Acid
• a complex of teichoic acid & lipids which provide cell rigidity & recognition by host cells - 16What is LPS?Lipopolysaccharides
• essential for the functioning of the outer membrane
• elicit potent immune & inflammatory response in host cells
• produce endotoxins - 17What are OMPs?Outer Membrane Proteins
• lipoproteins & porins
• contribute to virulence - 18Describe bacterial replication in the genomeAsexual or Binary fission
• Circular DNA replication starts at 'origin' & replicates in 2 directions (bi-directional replication), 2 replication forks split off from the origin & meet at the bottom - 19Describe the 4 phases of Bacterial growth1. Lag phase - period of active growth, bacteria prepare for reproduction (synthesising DNA & enzymes for division)
2. Log / Exponential phase - uniform replication & max. rate of division
3. Stationary phase - cessation of growth due to exhaustion of nutrients, accumulation of inhibitory end products of metabolism or oxygen availability
• no. of cells dying = no. of cells produced
4. Death phase - no. of cells dying > no. of new cells & hence no. of viable cells declines - 20Describe the 3 types of bacterial recombinationConjunction:
• 1 bacteria connects to another through pilus & genes are transferred (leads to antibiotic resistance)
Transformation:
• some bacteria are capable of taking in DNA from their environment
Transduction:
• involves the exchange of bacterial DNA through bacteriophages - 21Name 5 characteristics of bacteria used for classification• gram staining
• cell shape - cocci, bacilli or helical/spiral
• atmospheric preference - aerobic, anaerobic or micro-aerobic
• key enzymes
• fastidiousness - complexity of nutritional requirements - 22What are 4 structural components of viruses?Nucleic acid -
• dsDNA, dsRNA, ssDNA or ssRNA
Capsid -
• protein coat composed of protein subunits (capsomeres) which consist of aggregated protomeres
• various shapes - rod-like, poly-helical or complex
Envelope -
• atmospheric structure composed of lipid, protein & carbohydrate
Spikes -
• glycoprotein projections arising from the envelope which may have enzymatic, adsorptive or haemogglutin activity - 23What are the 6 steps of viral replication?1. Adsorption - virus binds to host cells
2. Penetration - injects its genome into the host cell via fusion, binding or ingestion
3. Replication - capsid digestion & viral genome replication
4. Assembly - viral components & enzymes produces + start to assemble
5. Maturation - virus fully develops
6. Release - of naked or enveloped viruses - 24Describe the process of release of naked virusesOccurs at the site of nucleic acid replication
• viral enzymes break down hosts cell wall, RNA viruses releases as they are produced & DNA viruses are expelled as cells autolyse in inclusion bodies - 25Describe the process of release of enveloped virusesViruses migrate to the plasma or nuclear membrane --> enveloped form around the nucleocapsids by 'budding' --> slow continuous release of mature viral particles w/ no inclusion bodies
- 26What are Protazoa?Single celled eukaryotes, Classified as
• Sporazoa - intracellular parasites
• Flagellates - flagella for locamotion
• Amoeba - uses temporary cell-body projections (psuedo-pods)
• Ciliates - move by beating cilia - 27What are fungi?Multi-nucleated or Multi-cellular eukaryotes
• that have a thick carbohydrate wall containing chitin & glucans
• usually grow as hyphae - thread-like filaments
• that reproduce asexually - 28Mycoses =a fungal infection
- 29Name 4 common fungal infections• Candidiasis - candida albicans (yeast)
• Cryptococcosis - cryptococcis neoformans
--> affects lungs & meninges
• Aspergillosis - aspergillus flavus
--> immune response, hypersensitivity & pneumonitis results
• Ringworm - tine corporis
--> affects scalp, skin, nails & feet - 30What is Helminths & what are the 3 main types?A term used for all parasitic worms
• Cestoda - tape worms
• Trematoda - flukes
• Nematoda - round worms - 31What are the 4 routes of helminths transmission?• intermediate host
• fecal-oral route
•active skin penetration
• injection by blood-sucking insect
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- MD2001 Fichas sobre Microbial Structure, creado por Lareyna Mcmenemy el 04/08/2018.
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- Lareyna Mcmenemy
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