Dr Nanetti’s Lectures Flashcards
What are the main parts of a prokaryote?
Cell wall
Plasma membrane
Capsule
Cell wall
Circular DNA
Flagellum
Cytoplasm
Plasmids
Ribosomes (70s)
What are the main parts of a eukaryote?
Cytoplasm
Cell membrane
Golgi body
Rough endoplasmic reticulum
Smooth ER
Mitochondria
Ribosomes (80s)
Nucleus
What are the differences between eukaryotes and prokaryotes?
Prokaryotes have circular DNA/Nucleoids whilst eukaryotes have a nucleus
Prokaryotes have a cell wall and capsule whilst eukaryotes only have a cell wall
There are organelles in eukaryotes as well as compartmentalisation in eukaryotes
What makes up the cytoskeleton?
Microfilaments - which support cell shape
Intermediate filaments - which provide strength
Microtubules - which provide force and movement
Name the parts which make up the nucleus
Nuclear envelope - provides an inner and outer section to the nucleus
Nuclear pores - regulate movement of molecules
Nucleus lamina - provide support and regulates DNA replication
Nucleolus - Synthesises ribosomal RNA and where subunits assemble
Chromatin
What is the endomembrane system?
It is a system which connects the nucleus, endoplasmic reticulum, Golgi body, vesicles and lysosomes by continuous membranes which acts as a secretory pathway of proteins
Rough endoplasmic reticulum
Large subunits sit on their membranes. It’s involved in synthesis, sorting and packaging of proteins
Smooth endoplasmic reticulum
Part of the production of lipids and the detoxification of drugs
What is the function of the Golgi body
They modify proteins and lipids and play a part in sorting and exporting proteins
They are made up of setbacks of cisternae
What is the function of a lysosome?
Intracellulair waste bin. Digests worn out organelles, cytoplasm and microorganisms after phagocytosis. They contain enzymes for digestion such as protease or nuclease
What is the function of a vesicle?
It is part of the cell transport mechanism, it is basically just a mini bilipid ball which hold anything being transported in it
What is the function of a peroxisome?
It is the degradation of fatty acids and amino acids by oxidation. It also decomposes H2O2 using catalase wand turns it into water and O2
What is the function of a mitochondria?
They make ATP using the electron transfer chain, it is the site of metabolic reaction and regulates apoptosis (cell suicide - happens in the intermembranal space)
What is DNA made up of?
A deoxyribose (2’ Carbon) molecule which is attached to a phosphate group (on the 5’) and a nitrogenous base (on the 1’ C)
What are the complimentary base pairs
DNA: A to T and G to C
RNA: A to U and G to C
Purines always go to pyrimidines. A and G are purines, as they have a double ring
How many H bonds are in the A to T/U base pairs?
2 H bonds
How many H bonds attach C to G base pairs
3 H bonds
How are antiparallel sequences written
5’-ATC GAT TGA-3’
3’-TAG CTA ACT-5’
A group of 3 is a codon
What packs DNA molecules into chromatin?
Hi stones
Describe the first step of DNA replication (Fork formation)
Helicase begins the process by splitting the DNA into the fork formation at the origin sequence. Primase makes a small piece of RNA called a primer which acts as a starting point for the creation of the new sequence
Describe the second step of DNA replication (initiation)
What are microorganisms?
Organism too small to be seen by the eye
What are the major groups of microbes
Bacteria
Fungi
Parasites
Micro algae
Viruses
What are the two types of cellular microorganisms?
Eukaryotic and prokaryotic
What are the microorganisms without a cellular structure
Acellular
Less than 1% of microbes cause diseases (pathogens)
What are the types of shapes bacteria come in?
Coccus - Ball
Bacillus - Rod
Vibrio - curved
Coccobacillus - oval
Spirillum - rigid spiral
Spirochete- flexible
What is peptidoglycan
It’s a rigid multilayer network made of linear chains of disaccharide units (NAG + NAM) it’s an alternating copolymer. Attached to NAM is a tetrapeptide chain which is involved in cross bridges.
Chains are linked by peptide cross bridges
What are the two sections of fungi?
Yeasts and moulds (pluricellular)
What are the two types of eukaryotes?
Protozoa and helminths (pluricellular)
Viruses replicate by taking over cells to create new particles
What are prions?
Simpler infectious particles made up of only proteins
What does the plasma membrane of a bacteria have differently ?
No cholesterol, instead contains hapanoids (similar to cholesterol)
Can have mesosomes which are infoldings of the membrane
What are the two classifications of cell wall
GRAM+ and GRAM-
What does penicillin target in a bacteria
The cross bridges of tetrapeptides
What is the defining factor of Gram+
Is a thick structure of peptidoglycan, separated by periplasmic space which contains enzymes which break down molecules too big to pass
Contains techoic acids which are made up of an alcohol and phosphate group. They regulate the movement of cations.
What is in a Gram- structure
Has a thinner peptidoglycan layer, more complex and susceptible to mechanical breaking.
Has an additional layer of lipopolysaccharide which is it’s phosphobilayer. Along with the bilayer are purines which are pores that allow the passage of molecules
What is the staining technique for gram staining?
Add crystal violet, then iodine, then ethyl alcohol then safranin.
Positive will be purple as the thick peptidoglycan layer is dehydrated by the alcohol which forms crystals so the dye stays
The negative will go pink to the counter stain as the alcohol dissolves the outer membrane which leaves holes
What is glycocalix
It is the capsule or slime layer. The final outer layer.
Flagellum are appendages which propel the bacteria using ATP.
What does fimbriae do?
Hairlike appendages which allow for attachments
Bacterial cell cycle
- Cell elongates which enlarges its volume and DNA is replicates
- Cell wall and plasma membrane begin to constrict
- Cross-wall forms completely, separating the two DNA copies
- Cells separate into two complete bacteria
LAG, LOG, STATIONARY, DEATH GRAPH
Lag - adapting and metabolising getting ready to divide
Log - Cell have an exponential increase
Stationary - Deaths=Replication
Death phase - Death over replication
N0 x 2^number of generations
What are biofilms?
Slimes or hydrogels that adhere to surfaces. Big colony that share nutrients and shelter bacteria from environment
What are the general requirements for bacteria growth
Physical - pH, temperature, osmotic pressure
Chemical - O2, N2, S, P, C, Ions and organic growth factors
What is culture medium?
Nutrients prepared for microbial growth
Selective media is…
Using set environment to suppress unwanted microbes and encourage desired ones
Enriched culture is…
Encourages the growth of a desired microbe by increasing small numbers to detectable ones
What is a pure culture?
A culture grown from one cell.
How do you obtain a pure culture
Sterilise looped rod on a Bunsen burner then inoculate loop. Apply one streak to the agar plate. Re-sterilise loop and make a second streak vertically compared to the last one. Repeat one more time and swab the other side of the agar. Incubate and observe
What are the two technique types to count microbial cells?
Direct - plate count (dilution plating), filtration, direct microscopic count
Indirect - Turbidity, metabolic activity, dry weight
What is membrane filtration?
Solution gets passed through a cellulose filter (o.45micrometres) that collects and retains bacteria. Filter is added to Petri dish and bacteria is allowed to grow and colonies to be counted
Microscopic count is…
Counting bacteria with a special grid and slide. Bacteria are stained to be visualised.
NO. Of cells counted/volume of area counted
What is an indirect method of counting bacteria?
Turbidity/cell mass - measurement of cloudiness and optical density of liquid using a spectrophotometer
Metabolic activity - amount of metabolic product is proportional to population size
Dry mass
What are endoscopes?
Resting/dormant form of bacterial cells. They are produced by 2 Gram+ genera - Bacillus and clostridium.
Sporulation and Germination are…
Endospore formation and the returning of the spore to a vegetative state.
§porulation is a process of differentiation, started when growth ceases due to lack of nutrients or environmental stress
Endospore resistance includes
Heat, chemicals and radiation. Much more resistant than the vegetative bacteria
What are the terms used for antimicrobial control measures
Sterilisation - all destroyed even Endospore
Disinfection - reduces the number of pathogenic microorganisms (not Endospore) until they no longer cause diseases
Sanitisation - reduces microbes to a safe, public level standard
Antimicrobial chemotherapy - drug treatment for specific infection to SELECTIVELY kill or inhibit growth of microbes within a host.
Which type of heat is more effective at killing bacteria?
Moist heat (autoclave)
What is Mutualism
Both species benefit from each other
What is Commensalism
One species benefits, the other has neither benefit or loss
What is Parasitism
One species benefits whilst the other is harmed
What is the difference between yeasts and moulds?
Yeasts are mono cellular whilst moulds are pluricellular
Yeasts are on Asexual whilst spores can be asexual or sexual reproduction
Viruses are Acellular, they are not cells
What are viruses called due to them being unable to divide on their own?
Obligate intracellular parasites
What is a mature virus called
Virion - nucleic acid (DNA OR RNA)
- Capsid
- Envelope (sometimes)
- Matrix proteins/enzymes
Envelope glycoproteins protrude outside the virus. How are they synthesised and what is their function?
Synthesised by the ribosomes of the host
Their function is to bind onto the surface of the host’s cell
What are capsids made out of?
Capsomers - helical/polyhedral/complex
What is viral tropism?
The specificity of what cell a virus can infect
What are bacteriophages
Viruses which only infect bacteria
What are the steps of virus replication
1.
Must collide with target cell
Attachment must be specific to receptors on cell surface using protruding proteins
2.
Penetration of membrane by endocytosis
3.
Virion uncoating - disassembly of the caspid which releases the genetic material of the nucleus to the cell
4.
Viruses hijacks the cells replication machinery and begins to replicate their genome
5.
New genome and capsids are formed
6.
New Virion are released after the complete synthesis
What must happen for a virus to cause disease?
Enough virus enters host
Virus can access cells and start replicating
Local antiviral system is overcome or absent
Describe the acute viral infection
Short incubation periods
rapid oneset of disease
brief period of symptoms
Quick resolution
Latent infection
No symptoms
Viruses not detectable by body
May reactivate due to change in immunity
What is a persistent viral infection
It occurs gradually over time
Herpesvirus reactivation can be due to
Sunlight, psychology stress, fever, menstruation, surgical resection
How do viruses cause cancer?
Encode proteins to act as oncogenes themselves
Activate cellular proto-oncogenes to oncogenes
This inactivate tumou suppressor genes
Cell cycle is not stopped and checked at previous check points
Cell cycle is always on
