Topic 2.2 Prokaryotic Cells Flashcards
How else can you classify bacteria (not just by their cells walls)?
Shape e.g. cocci, bacilli, spirilla, vibrios
Respiratory requirements e.g. if they need oxygen or not, or if oxygen kills them(Obligate anaerobes)
What shape are cocci bacteria?
Spherical=cocci
What shape are bacilli bacteria?
Rod-shaped=bacillia
What shape are twisted bacteria?
Spirilla =twisted bacteria
Which bacteria are comma-shaped?
Vibrios=comma-shaped
Which bacteria need oxygen for respiration?
Obligate aerobes
Need oxygen for respiration
Which bacteria can use oxygen for respiration but can also manage without it?
Facultative anaerobes
use oxygen if available but can also manage without it
(Most human pathogens)
Which bacteria can only respire in the absence of oxygen?
Obligate anaerobes
Oxygen kills them
How are viruses classified?
Genome
Mode of replication
What are the different classifications of viruses?
DNA viruses
RNA viruses (positive and negative ssRNA)
RNA retroviruses
Classification of a DNA virus (what characteristics they have)
Genetic material = DNA
Viral DNA acts as a direct template (for both viral DNA replication and protein synthesis)
Examples of DNA viruses
Smallpox
Adenovirus (include colds and some bacteriophages)
Lambda phage
Classification of RNA viruses (characteristics they have)
Genetic material =RNA Do not produce DNA Mostly ssRNA (single stranded RNA)
What are the differences between positive and negative ssRNA viruses?
Positive ssRNA viruses can be directly translated at the ribosomes
Negative ssRNA viruses have to be transcribed before being translated
Examples of animal and plant diseases caused by positive ssRNA viruses
Tobacco mosaic virus
SARS
Polio
Hepatitis C
Classification of RNA retroviruses (characteristics they have)
Protein capsid
Lipid envelope
Single strand of viral RNA detects the synthesis of reverse transcriptase and is translated into viral DNA by reverse transcriptase
Viral DNA incorporated into host cell DNA and used as template for new viral proteins
Examples of RNA retroviruses
HIV(human immunodeficiency virus)
Some forms of leukaemia
Examples of diseases caused by negative ssRNA viruses
Measles
Influenza
Ebola
What’s a hypertonic solution?
a solution with a higher concentration of solutes and lower concentration of water/solvent than the surrounding solution
What’s peptidogylcan?
a large, net-like structure found in the walls of bacterial cells made up of many parallel polysaccharide chains with short peptide cross-linkages
Wat are pili?
thread like protein projections found on the surface of some bacteria
What are bacteriophages?
viruses that attack bacteria
What are flagella?
many-stranded helices of the protein flagellin found on some bacteria. they move the bacteria by rapid rotations
What are mesomes?
infoldings of the bacterial cell membrane
What is a nucleoid?
area of bacterium where single length, coiled DNA is found
What are plasmids?
small circular pieces of DNA that code for specific aspects of the bacterial phenotype
What is gram staining?
a staining technique used to distinguish different types of bacteria by their cells wall (positive or negative)
What are gram-positive bacteria?
bacteria that contain teichoic acid in their cell walls and stain purple/blue with gram staining
What are gram-negative bacteria?
bacteria that have no teichoic acid in their cell walls and stain red with gram staining
What is teichoic acid?
a chemical found in the walls of gram-positive bacteria
What is the purpose of a capsule?
protects the bacteria from phagocytosis from white blood cells and covers the cell markers on the cell membrane that identify the cell so it is undetectable by the immune system, made from starch, glycolipid, gelatin or protein
What is an envelope?
a coat around the outside of the virus derived from lipids in the host cell
What is the capsid?
the protein coat of a virus
What is the capsid made from?
simple repeating units called capsomeres, arranged in different ways to minimise the amount of genetic information needed to code for coat production and so that assembling the virus in the host cell is as simple as possible
State the advantage of an envelope
the virus can pass from cell to cell easier
State the disadvantage of an envelope
makes them vulnerable to substances that could dissolve the lipid membrane
What are capsomeres?
the repeating units which make up the capsule of a virus
What are virus attachment particles (VAPs)?
specific proteins/antigens that target proteins in the host cell surface membrane
What are DNA viruses?
composed of DNA as their genetic materia
What are RNA viruses?
composed of RNA as their genetic material
What are retroviruses?
a special type of RNA virus that control DNA production corresponding to the viral RNA and insert it to the host cell DNA
What is reverse transcriptase?
an enzyme synthesised in the lifecycle of a retrovirus that makes DNA molecules corresponding to the viral RNA genome
Define non-virulent
a microorganism that is not disease-causing
Define virulent
a microorganism that is disease causing
What is a provirus?
the DNA that is inserted into the host cell in the lysogenic pathway of reproduction of viruses
What is lysogeny?
the period when a virus is part of the reproducing host cell but does not affect it adversely
Define latency
the state of a non-virulent virus within the host cell
What is ebola?
a highly infectious viral disease that causes fever and internal bleeding and death in around 50% of cases
Define mortality rate
a measurement of the number of deaths in a given population or due to a specific cause
Define a pandemic
an epidemic that takes place in several countries at once
What is the process for the development medicines?
- takes up to 10 years
- early phase research (4-6 years)
- pre-clinical testing (1 year)
- 3 phase clinical trials (6-7 years)
- regulatory review
- scale up to manufacturing (0.5-2 years
- post market surveillance is continuous
What are the ethical factors that need to be considered before fast-tracking a drug in an epidemic?
- severity of the disease
- availability of other treatments
- effectiveness of standard disease control measures in halting the spread of disease
- transparency about the process and informed consent of those given the treatment
- freedom of choice over participation
- involvement of the affected community- community consent more valuable than individual consent
- collection of clear medical data
State the reasons against using untested drugs
- people feel it is unethical
- unexpected side effects could worsen the situation
- difficulty deciding who gets the treatment
- informed consent depends on level of education
- issues of trust between individuals and healthcare workers, especially when supplies are limited
State the characteristics of viruses
- obligate intracellular parasites=can only exist + reproduce as parasites in the cells of other living organisms
- not cells
- invade and take over other cells which causes damage and disease
- can withstand drying + long periods of storage, still maintaining the ability to infect cells
- very few drugs effect viruses
State the structure of viruses
- geometric shapes and similar basic structures
- variation of genetic material, structure of protein coat and envelope or not
- protein coat/capsid made up of simple repeating proteins (capsomeres) arranged in different ways
- repeating units minimise the amount of genetic material needed for coat production + ensures assembling the coat is simple
- lipid envelope males it easier to pass from cell to cell but makes it more vulnerable to substances that can dissolve the lipid membrane
What are the ways of classifying viruses?
- VAPs (virus attachment particles) target the proteins in the host cell membrane
- viruses are specific in the tissue they attack
- classified by genomes and mode of replication
- genetic material: DNA or RNA nucleic acid: single or double stranded
Define DNA viruses
viral DNA acts directly as a template for new viral DNA and mRNA needed for synthesis of viral proteins
Give examples of DNA viruses
smallpox, adenoviruses and lambda phage
Define RNA viruses
70% of viruses have RNA as their genetic material and are more likely to mutate than DNA viruses. they don’t produce DNA as part of their lifecycle. positive ssRNA viruses have RNA that can be directly translated at the ribosomes. negative ssRNA viruses cannot be directly translated
Examples of positive ssRNA viruses
tobacco mosaic virus, SARS, polio, hepatitis C
Examples of negative ssRNA viruses
measles, influenza, Ebola
Define RNA retroviruses
have a protein capsid and lipid envelope, single strand of RNA directs synthesis of enzyme reverse transcriptase- goes on to make DNA molecules corresponding to the viral genome. the DNA is then incorporated into the host cell DNA and used as a template for new viral proteins
Examples of RNA retroviruses
HIV and some forms of leukaemia
How do RNA retroviruses reproduce/ what is their life cycle?
- the retro virus attacks an animal cell
- viral RNA enters the host cell. this RNA cannot be used a mRNA
- viral RNA is translated into viral DNA by reverse transcriptase in the cytoplasm
- viral DNA is incorporated into the host DNA, it directs the production of new viral genome RNA, mRNA and coat proteins
- new viral particles are assembled and leave the host cell by exocytosis. viral DNA remains in the nucleus so the process is repeated
