6A Flashcards
All bacteria have :
- Cell wall
- Cell surface membrane
- Nucleotide
- 70S ribosome
Cell wall (contain peptidoglycan)
Cell surface membrane
Nucleotide (single, circular strand of DNA)
70S ribosome (protein synthesis)
Some bacteria have :
= Pili
= Flagella
= Capsule / slime layer
= Mesosome
= Plasmid
= Infolding of cell surface membrane
Pili = enable bacteria to attach to other cells or surfaces (involve in gene transfer during sexual reproduction)
Flagella = movement
Capsule / slime layer = protect from drying out
Mesosome = site of cellular respiration
Plasmid = additional DNA
Infolding of cell surface membrane = allow photosynthesis / carry out nitrogen fixation
All virus have :
= Capsid
= Nuclei acids
= VAP
Capsid = protein coat made up of capsomeres
Nuclei acids = act as genetic material
VAP = specific protein (antigen) that target protein in host cell surface membrane
Some virus have :
Lipid envelope
Lipid envelope
- cover genetic material and protein coat
- produced from host cell membrane
- easier for virus to pass from cell to cell
DNA virus
Viral DNA act as template for new viral DNA / mRNA needed to induce synthesis of viral protein
Eg) smallpox virus, bacteriophages
RNA virus
- Have RNA as genetic material
- Mutation more likely to occur in RNA virus than DNA virus
- Contain single strand of RNA
Eg) influenza, Ebola virus
Retrovirus
- Have protein capsid / lipid envelop
- Single strand of viral RNA control synthesis of special enzyme : reverse transcriptase
- This enzyme catalyst production of viral DNA from single strand of RNA
- New viral DNA incorporated into host DNA where it acts as template to produce viral protein and RNA
Eg) HIV
Lysogenic pathway
- Viral DNA (provirus) inserted into host DNA
- mRNA is not produced because viral gene coding for depressor protein prevents viral DNA from being transcribed / translated
- Every time hot DNA copies itself, viral DNA also copied
- Virus is latent during this pint
- Virus become activated and enter lyric pathway
Activation occur as a result of :
- host cell damage
- low nutrient levels inside a cell
Lytic pathway
- Viral genetic material is transcribed, producing new viral components
- Viral components are then assembled to form mature virus which will accumulate inside host cells
- Host cells burst, releasing all virus which can be used to infect other cells
- Result in disease
Ebola virus
- contain envelope
- RNA (single-stranded)
- helical capsid
Tobacco mosaic virus
- contain envelope
- RNA (single-stranded)
- helical capsid
HIV
- contain envelope
- RNA (single-stranded)
- cone-shaped capsid
Lambda phage
- non-enveloped
- DNA (double-stranded)
- complex capsid
Binary fission (bacterium divide in two)
- Enzymes break open circular piece of DNA (allow strand of DNA to unwind / replicated)
- Plasmid undergo DNA replication
- Parent cell divides into two cells with cytoplasm halved between two daughter cells
- Two daughter cells each contain single copy of circular DNA molecule / plasmids
Lag phase
Population size increase as microorganism population adjust to its new environment / gradually start to reproduce
Exponential phase
With high availability of nutrients / plenty of space, population move into exponential growth (population double with each division)
Stationary phase
- Population reach its max as it’s limited by its environment
- Growing curve level off
- Microorganisms dying = number being produced by binary fission
Eg) lack of resources - As numbers multiply exponentially, decrease level of nutrients available
- Insufficient to support further growth / reproduction
- Limit growth of population of bacteria in culture
Eg) toxic waste product - As cell numbers rise, toxic material accumulates
- Become sufficient to inhibit further growth / to poison / kill culture
Death phase
- Due to lack of nutrients / build up of toxic waste build up, death rate exceeds rate of reproduction
- Population start to decline
Requirements to grow microorganisms
- Nutrients
- Oxygen
- Optimum pH
- Favorable temperature
Aseptic technique
Method used to prevent contamination with other microorganisms
Eg) carry out work beside Bunsen burner
Eg) use sterilized equipment
Eg) wearing gloves, washing hands
Eg) minimize time that culture exposed to air
Aseptic culture techniques
- Obtain the culture
- Provide with correct type of nutrients to facilitate growth
- Nutrient medium kept under sterile condition
- Provide selective medium
- Inoculation
- Avoid contaminations (Petri dish covered with lid / flasks sealed with sterile cotton wool stopper)
- Label medium
- Inculcate a around 20 degrees (temperature needed for enzyme to function)
Cell counts
- Use haemocytometer
1. Make slide of cells from blood
2. Use stain ; acetic or Erin
3. Heating stain / using acid
4. Look for mitosis features
Optical methods (turbidity)
- Measure concentration of substance by measuring amount of light pass through it
- Use spectrophotometer
- As no.bacterial cells in culture increase, turbidity increase
Dilution plating
- Determine total viable cell count (measure no.cells that are alive in specific volume of culture)
- Nutrient broth transfer to agar ; bacteria use nutrients in agar gel to reproduce
- Produce mass of identical cells ; colony
- Diluting original cultures before transferring sample to agar
- Reduce no.cells in original sample ; individual colonies visible on agar plate
Area and mass of fungi
Measure diameter of individual area of fungal mycelium (fungi form mass of elongated cells)
Measure dry mass of fungi (filtering or centrifugation)
Vector
Living organism that transmit infection from one host to another
Inhalation
- Cough, sneeze, talk cause droplets from respiratory tract will suspend in air
- Droplets contain pathogens inhaled by healthy people
- Airway provide entry point into respiratory system of host / other infection occurs
ingestion
Indigest contaminated food cause pathogens to enter digestive system
Formites
- Indirect contacts
- infected individual touch / cough on objects; touched by healthy people
Direct contact
- Require host (skin, body fluid) to make direct contact with healthy individuals
- Pathogen pass through mucous membrane / enter bloodstream
Inoculation
Pathogens inoculate into body directly through break in skin
Method of spread
Vector
Inhalation
Ingestion
Formites
Direct contact
Inoculation
Barriers to entry
Skin
Skin flora
Gut
Stomach acid
Mucus
Skin
= Impenetrable layer strengthen by keratin
- Physical barrier
- Sebum produced (contain chemicals that inhibit growth of microorganisms)
Skin flora
= Produce substance that inhibit growth of microorganisms
- Washing hands too often : reduce resistance to disease
- Destroy natural pH balance, natural skin flora
Gut
= Saliva ahas bactericidal property
- Polypeptide produced in salivary gland destroy bacteria / slow down bacterial growth
- Gut flora produce anti-microbial compounds
Stomach acid
= produce hydrochloride acid with 2pH
- Destroy microorganisms
Mucus
= produced in respiratory system ; constantly move towards outside body
= on lining of urinary system constantly wash with urine
= Lila move mucus in reproductive tracts
Symptoms of Tuberculosis
- Fever, loss of weight
- Cough ; infection in lungs and produce liquid from their lungs (sputum)
- Damaged lung tissue / blood coughed up in sputum
- Alveoli break down to produce large, inefficient air space
- Affect gas exchange (insufficient oxygen to meet demand of patient)
TB cause death
- X obtain enough oxygen from air through damaged lungs
- Organs fail through lack of nutrition
- TB affect immune system ; vulnerable to infection
HIV infection steps
- HIV surface protein binds to CD4 cell receptors on host cell membrane and enter helper T cells
- Virus envelope fuses with cell surface membrane
- Virus reverse transcriptase copies viral RNA into viral DNA
- Integrate incorporate DNA copy into host cell genome
- It sues host cell’s enzyme to produce more viral components which are assembled to for m new viruses
- These bud from host cell / enter blood where they can infect other helper T cells
How HIV is transmitted
- Direct exchange of bodily fluid
- Inoculation through infected blood
- Mother to her fetus in early stage of pregnancy
From someone with HIV positive /active AIDS
HIV positive
Someone who has antibodies to HIV in their blood, indicating that they been infected with virus and at risk of passing it on to other people
- Show no symptoms
Factors that affect speed of diseases progress from HIV to AIDS
- Fit, well-nourished, healthy person
- Better genetic resistance to infection ( Immune system respond more effectively to HIV )
- Rapid medical treatment
Stage 1 : acute HIV syndrome
- Fever, headache, tiredness, swollen glands
- Some no symptoms
- HIV antibodies appear in the blood
Stage 2 : asymptomatic or chronic stage
- Once infection established, all symptoms disappear
- Virus replicate, infecting T helper cells
- Kept under control by T killer cells
- Secondary infections develop
Stage 3 : symptomatic disease
- Immune system starts to fail
- Weight loss, fatigue, diarrhea, night sweats
Stage 4 : advanced AIDS
- T helper cell numbers fall
- Major weight loss, dementia as brain cells become infected, cancer
- Death
Prevention of HIV
- Celibacy
- Only have one sexual partner
- Use condoms to prevent spread of virus
- Use clean needles
Reasons for X effective vaccination
- Virus mutate rapidly; antigen on viral coat keep changing after infection
- Harder for immune system to recognize virus / destroy it
- Rate of change only slow down as T cell count starts to fall to very low level (selection pressure on virus reduced)
