1.1: Microorganisms Flashcards
measurements/ timesing needed for cm to mm
x10
measurements/ timesing needed for mm to micrometers
x 1000
measurements/ timesing needed for micrometers to nm
x 1000
measurements/ timesing needed for nm to micrometers
divide by 1000
measurements/ timesing needed for micrometers to mm
divide by 1000
measurements/ timesing needed for mm to cm
divide by 10
magnification equation
actual size = image size/magnification
magnification calculation rule
Always measure the image in mm THEN multiply by 1000 to get image size in micrometers
Ribosomes function
Site of protein synthesis
Pili function
Attachment to cells and involved in sexual reproduction
Glycogen granules function
Store Carbohydrates for breakdown during respiration
Flagellum function
aids cell movement
photosynthetic lamellae function
contains chlorophyll. Site of photosynthesis
cell wall function
Made of peptidoglycan (murein). Physical barrier which prevents mechanical and osmotic damage to the cell
mesosome function
Helps form new cell walls & site of attachment of respiratory enzymes
cell surface membrane function
controls entry & exit of chemicals into/out of the cell
circular DNA function
contains genetic information of the cell
lipid droplet function
Lipid storage. May be converted to carbohydrate and used in respiration
Plasmid function
Small circle of DNA which contains genes which help bacteria survive adverse conditions
capsule function
Protection against desiccation and helps bacteria stick together
Label this Prokaryotic Cell
Look into your book for the answers
What structures are always present in prokaryotic cells
Ribosomes, Cell Wall, Plasma Membrane, Circular DNA
What is Gram’s stain used for?
Staining Bacteria as an aid to their identification for cell wall types
Who devised Gram staining?
Hans Christian Joachim Gram in 1884
What is Gram’s stain differentiating between in terms of two major cell wall types?
- bacteria species with a cell membrane surrounded by a thick cell wall (20-80nm thick) : Gram-positive
- bacteria species with a thin cell wall (2-3nm) : Gram-negative
What makes the bacteria gram-negative?
small quantities of peptidoglycan (muezzin) and an additional layer of lipopolysaccharide
What makes the bacteria gram-positive?
relatively large quantities of peptidoglycan (muezzin) and an no lipopolysaccharide
Method for carrying out a Gram Stain
- Heat fix a smear bacteria onto a clear microscope slide
- Flood with crystal violet
- Wash the smear with iodine to fix
- Decolourise with alcohol (ethanol)
- Counter stain with a red stain (e.g. safranin)
What happens to the gram-positive bacteria?
They retain the crystal violet/iodine complex and appear purple
What happens to the gram-negative bacteria?
Lose the crystal violet/iodine complex but take up the red stain
why is it that the gram-negative bacteria turns red?
Because the gram-negative cell well is thinner so it’s easily watched out with alcohol
typical gram-positive bacteria
- staphylococci (staphylococcus epidermis and staphylococcus aureus common causes of boil abscesses)
typical gram-negative bacteria
- whooping cough
- cholera
What does the lipopolysaccharide layer do?
forms an extra physical barrier which is more resistant to enzymes which normally destroy/inhibit bacteria. Therefore, infections due to gram-negative bacteria are harder to treat.
What shape is the cocci bacteria?
spherical
What is an example of the cocci shape bacteria and what disease can be caused by it?
Staphylococcus aureus
MRSA
What is an example of the bacilli shape bacteria and what disease can be caused by it?
Bacillus Anthracis
Anthrax
What is an example of the spirilla shaped bacteria and what disease can be caused by it?
Chlamydia trachomatis
Chlamydia
What is an example of the vibrio shaped bacteria and what disease can be caused by it?
Vibrio Cholerae
Cholera
What is the shape of the spirilla bacteria?
spiral shaped
What is the shape of the vibrio bacteria?
crescent moon shaped
What is the name for bacterial reproduction?
Binary Fission
What is the generation times for bacteria?
as little as 20 minutes but can be 15-20 hours
What is differs binary fission from mitosis?
- there are no spindle fibres
- chromatids are not pulled apart by the spindle
- cytokinesis does not occur
What are the 3 ways plasmids can be transferred to another bacterium?
conjugation, transformation, transduction
What are the characteristics of Plasmids?
- they are circles of DNA in their cytoplasm
- can replicate independently
- plasmids often carry genes which help baterium survive adversely
What are R-factors?
Causes resistance to antibiotics
Do plasmids contain R-factors?
Yes
What is transductions?
This occurs when new genes are inserted into the chromosome of a bacterium by a bacteriophage virus
What is a bacteriophage?
A virus that infects a bacteria cell
How do the two cells join in conjugation?
By pili
How does conjugation work?
- the donor bacteria passes a plasmid called the F-factor (fertility factor) to the recipient
- This provides the recipient bacterium with everything needed to be a donor including the capacity to synthesise the sex pilus
How may the Fertility factor (F - factor) exist?
As a free element in the cytoplasm or incorporated into the bacterial chromosome (so it will be replicated)
What is the transformation (bacteria reproduction)?
This occurs when one bacterium releases DNA which is absorbed by a second bacterium.
The second cell therefore acquires new characteristics - allows them to survive in unfavourable conditions
What are protoctista?
Eukaryotes which include: protozoa, nucleated algae and the slime moulds
Just not animals, plants or fungi.
What are the key features of Protoctista?
- Eukaryotes, single cells
- found where moisture is present
- move using cilia, flagella or pseudopodia (false foot)
- have contractile vacuole to remove excess water
- gas exchange by diffusion
What nutrition does protoctista use?
Autotrophs, heterotrophs, saprotrophs
What are autotrophs?
make own food E.g. plants
What are Heterotrophs?
Eat other organisms
What are saphrotrophs?
Eat dead things
What is the importance of plasmodium vivax?
causes malaria using female Anopheles mosquitoes as a transmission vector
What organism causes malaria?
plasmodium vivax
What nutrition does plasmodium vivax use?
phagocytosis
What is phagocytosis?
process by which certain living cells called phagocytes ingest or engulf other cells or particles
What is the importance of paramecium caudatum?
recycling organic waste - sewage treatment
What nutrition does paramecium caudatum use?
cilia beat and sweep food towards oral groove where it engulfs dead/decaying matter
What is the importance of trypanosome gambiense?
causes sleeping sickness
What nutrition does trypanosome gambiense use?
Human parasite, lives in blood plasma and soluble nutrients diffuse into the cell
What is the importance of phytopthora infestans?
causes potato blight, caused the Irish potato famine 1845-1852
What is the nutrition that trypanosome gambiense uses?
Secretes enzymes to digest food then absorbs soluble nutrients
What are examples of fungi?
yeast, candida (thrush), penicillium
What are some important features found in fungi?
- found everywhere
- eukaryotic with a chitin cell wall
- single cell (yeast) or multicellular (mushrooms)
- heterotrophic
- both obligate aerobes and facultative anaerobes
What does obligate aerobes mean?
won’t survive without oxygen
What does facultative anaerobes mean?
Grows best when oxygen is available but can survive in anaerobic conditions
What is fungi threads called?
hyphae
What does hyphae branches form?
where does hyphae grow?
-mycelium
-only grow at their tips
What is the cellular structure for viruses?
There is none, it’s acellular
What are viruses, in terms of reproduction?
they are obligate parasites, that can only reproduce when inside other cells.
What is the size of viruses compared to bacteria?
50 times smaller than bacteria (20nm to 300nm)
What microscopes can be used to see viruses?
Electron microscopes
How do viruses function?
- chemical machinery
- enzymes
- They don’t contain the chemical machinery to carry out chemical reactions for life
- viruses carry only one or two enzymes that control gene expression and replication.
- Viruses must have a host cell, viruses can’t function outside of a host cell.
Where is DNA contained in a virus?
In a core, they are either double or single stranded DNA or RNA.
What is a capsid?
A protective coat made up of capsomeres (made of protein)
Where is the lipoprotein envelope?
They are around the capsule
What is a DNA virus?
Has DNA as a genetic material and replicates using a DNA dependent polymerase (produces polymers of DNA)
What is a RNA virus?
A virus that has RNA as its genetic material. The nucleic acid is usually single-stranded, but may be double -stranded RNA
What does every enzyme end in?
- ase
What are the 3 types of virus shapes?
Helical, polyhedral, complex
What is the method of endocytosis? (how viruses enter host cells)
- Non-enveloped virus encounters the host cell
- endocytosis takes place
- the whole virus is engulfed into a vacuole
- vacuole fuses with the endoplasmic reticulum of the host cell
- virus enters endoplasmic reticulum.
What is the lysosome method? (how viruses enter host cells)
- Viral envelope sticks to cell membrane, endocytosis takes place and virus engulfed into a vacuole
- The vacuole containing the virus fuses with a lysosome
- enzymes released into the vacuole causes the viral envelope to fuse with the vacuole membrane
4+5: The nucleocapsid is released into the cytoplasm.
What is the final method for how viruses enter host cells?
- enveloped virus
- viral envelope fuses with host membrane
- viral envelope forms part of host cell membrane
- nucleocapsid is released directly into the cytoplasm
What is the purpose of the viral envelope forming part of the host cell membrane?
Informs other viruses/immune system which cells have been invaded
What is the lytic cycle?
viruses infect and destroy host bacteria
The infection brings sudden death and lysis of the host cell
What are examples of cells that go through the lytic cycle?
bacteriophage
common cold
influenza
rabies
What is the lysogenic cycle?
When viruses that do not replicate once inside the host cell. Instead the nucleic acid becomes incorporated into the DNA of the host cell.
The virus is then known as a provirus and is inactive
What makes the lysogenic cycle start to enter the lytic cycle?
When a stressful condition occurs and the prophage DNA is excised from the main bacterial DNA which causes it to enter the lytic cycle
What are the 5 stages of the lytic cycle?
- Attachment - the phage attaches to the surface of the host
- penetration - the viral DNA enters the host cell
- biosynthesis - phage DNA replicates and phage proteins are made
- Maturation - new phage particles are assembled
- Lysis - the cell lyses, releasing the newly made phages
What are the stages of the lysogenic cycle?
- the phage infects a cell
- the Phage DNA becomes incorporated into the host genome
- the cell divides, and prophage is passed onto daughter cells
What stressful situations cause the lytic cycle from the lysogenic cycle?
- lack of food sources
- competition with other bacteria
- lack of resources
How do viruses leave host cells?
- bursting their host cells
- budding : taking an envelope of host membrane as they leave
What genetic material is found in HIV?
Single stranded RNA
What is HIV?
A retrovirus
What enzyme do HIV carry to infect cells?
reverse transcriptase
What does the reverse transcriptase do?
converts viral RNA to DNA
What is a provirus?
When the DNA copy of the viral genes is inserted into the host cell chromosomes
What does the viral infection do before the provirus is expressed to make new virus particles?
stay latent (dormant)
What happens when the host cell divides?
The provirus is replicated so the number of infected cells increase
What does the HIV infect?
A white blood cell called a T helper lymphocyte.
How long can the HIV lay inactive?
10 years
What are the methods of transmission for HIV?
- exchange of bodily fluids (blood)
- unprotected sex
- unscreened blood transfusions
- un-sterile surgical equipment
- hypodermic needles shared
- across placenta/child birth
What is the HIV life cycle?
- infection
- reverse transcription
- integration
- transcription
- budding
HIV life cycle - infection
virus infects RNA into host cells
HIV life cycle - reverse transcription
reverse transcriptase uses RNA template to make HIV DNA
HIV life cycle - integration
HIV DNA inserts itself into host DNA
HIV life cycle - transcription
the viral DNA codes for viral RNA and proteins
HIV life cycle- budding
new virus particles assemble and split off from host cell
How do you develop AIDs?
when the level of T cells drop below critical level due to cell lysis
What is the receptor on the target cell of HIV
CD4 chemokine receptor
what happens after the viral and host cell membranes fuse in HIV?
HIV RNA and proteins enter the cell
where does the viral DNA in HIV migrate to?
Host nucleus and is integrated into the genome
What is it called when the viral DNA is integrated into the host chromosomes/genome?
provirus
What does cell activation result in HIV?
Transcription and translation of viral genes (produce viral proteins to produce new viral particles)
What do the viral proteins and RNA genome migrate to in HIV?
cell surface membrane on host cells
How is a mature infectious virus produced?
HIV buds from the cell (and is surrounded by host cell membrane)
HIV treatments - PEP
Post exposure prophylaxis
- given to a person within 72 hours of exposure.
- Can be used before sex (unprotected)
- people who have had unsafe sex, been raped or sexually assaulted must get PEP
HIV treatments - vaccines (preventative)
designed to protect HIV - negative people from becoming infected
HIV treatments - vaccines (therapeutic)
aimed at boosting the immune system in those already infected
Problems with the HIV vaccine
- constantly changing virus with many subtypes
- hard to develop a single vaccine which works on all strains
Other preventative HIV treatments
Not sharing hypodermic needles
HIV treatments - Antiviral drugs (under development)
- fusion of entry inhibition (stop virus from gaining entry to the cell)
- inhibitors of reverse transcriptase
- integrase inhibition (block the action of HIV enzyme)
HIV treatments - Antiviral drugs (in trials)
TNX-355 (blocks HIV from binding to a protein on the cell surface)
PRO 140 (contains genetically engineered to fight infections)
KP - 1461 (unique approach to fighting HIV, called viral decay acceleration - increase HIV immunisation rate)
what is the process of binary fission?
- DNA replication
- cell growth
- DNA segregation
- cell splitting
label the bacteriophage, what does it include?
head, collar, sheath, tail, baseplate, tail fibre
