2.2 prokaryotic cells Flashcards
describe the structure and function of a bacterial cell wall
consists of a layer of peptidoglycan
water tends to move into bacterial cells by osmosis and the cell wall prevents them from swelling and bursting
it also helps them to maintain their shape and give support and protection to the contents of the cell
what’s the function of the slime capsule
protects bacterium from phagocytosis, covers the cell markers on the membrane that help identify the cell
name the dna tangle found in bacterial cells
nucleoid
what are the type and functions of ribosomes in bacterial cells
70S ribosomes that carry out protein synthesis
describe the process of gram staining bacteria
bacteria are often colourless and a crystal violet/ iodine complex is added to the bacteria
what would the different results be in gram positive bacteria and gram negative bacteria
the gram positive bacteria have a thick peptidoglycan walls and would be purple/blue after
gram negative have thin peptidoglycan walls and the cells would appear red
what are antibiotics
drugs that are used against bacterial pathogens
how do antibiotics work ?
different antibiotics affect different types of bacteria (gram positive/negative)
some inhibit the formation of the peptidoglycan layer of the cell wall (gram positive) which is vital to their wall structure
what are the alternative ways of classifying bacteria
can be identified by their shape
-spherical, comma shaped, rod shapes, twisted ect.
can be identified by their respiratory requirements
what is a virus
obligate intracellular parasites, that only exist and reproduce in the cells of other living organisms
usually cause damage or disease
describe the structure of a virus
usually made of geometric shapes and of similar structures but VARY in genetic material
centre is double or single stranded DNA or RNA, surrounded by a capsid, made of capsomeres, sometimes have an envelope (derived from host cell) then receptors on the outside
what is a virus’ protein coat made up of
it is a capsid made up of capsomeres
how are viruses classified, and describe the different forms
-classified by their genome and mode of replication
-DNA viruses, genetic material is DNA, used as a template for new DNA and RNA
-RNA viruses 70%, more likely to mutate
-RNA retroviruses, special type of RNA virus that have a capsid and lipid envelope
what is a bacteriophage
a virus that attacks bacteria
describe how viruses get into the cell
taken into the body by endocytosis, host cell digests the capsid and releases the genetic material , viral envelope fuses with cell surface, releasing the rest of the virus into the membrane
describe the process of infection (latency) the lysogenic pathway
viruses are non virulent through the lysogenic pathway
insert their dna into the host dna (provirus), so its replicated when the cell divides
virus doesn’t affect the host cell, virus is said to be latent
describe the process of infection; the lytic pathway
genetic material is replicated independently of the host dna
host cell bursts, releasing large numbers of new virus particles that invade other cells
what is a positive ssRNA virus
viruses that contain a single strand of RNA, that is a sense strand, used directly as mRNA for translations into proteins
what is a negative ssRNA virus
contain a single strand of RNA that is an antisense strand, and before it can be used it must be transcribed into a sense strand
what is an RNA retrovirus
they have viral RNA as their genetic material and is translated into DNA by the enzyme reverse transcriptase
how do viruses cause the symptoms of disease
they cause symptoms by the lysis of the host cells, causing them to release their own lysosomes, or by the production of toxins that inhibit cell metabolism
why are viruses often specific to particular tissues
due to the presence or absence of cell markers on the surface of the host cell
each cell has specific markers and each virus only binds to a certain marker
describe foot and mouth disease and how it’s spread
weakens and kills a high percentage of young animals and spread through body secretions and transmitted in breath and faeces
describe ebola and how it’s spread
severe illness caused by ebola virus and spreads to humans through faeces, blood and meat of infected animals
spreads from human to human through contact of skin
why are viruses hard to kill
live inside cells and are not living cells that can be killed
describe ways in which antiviral treatments can work
-they target virus replication
-target receptors that help viruses recognise host cells
-target enzymes that help translate or replicate DNA or RNA
-inhibit enzymes that allow the virus to bud from host membranes
what is an epidemic
when the levels of people with a disease are much higher than expected
name 6 ways that people can control the spread of disease
-rapid identification of disease
-nursing in isolation
-preventing transmission from one individual to another by handwashing, disposal of bodily fluids ect.
-sterilising or disposing of equipment after use
-wearing of protective clothing
-identifying those who have come in contact with the disease
describe the process of the development of a new medicine
-chemicals go through research and testing on animal tissue and cultures
-animal testing
-three phases of human testing
name the factors that are taken into account if a drug were to be fast tracked
-severity of the disease
-availability of other treatments
-community consent
name reasons against fast tracking untested drugs
-not ethical
-could produce unexpected side effects
-hard decision on who gets the drug
why do gram positive bacteria appear their colour when they’re stained
they have a thick layer of peptidoglycan which contains chemicals like teichoic acid. the crystal violet/ iodine complex gets trapped by these chemicals so it resists decolouring when it is dehydrated using alcohol
why do gram negative appear their colour when they’re stained
-they have a thin layer of peptidoglycan
no teichoic acid, the outer membrane made up of lipopolysaccharides. after the crystal violet/ iodine complex is applied, it’s dehydrated in ethanol, complex is washed out
peptidoglycan takes up the red counterstain
what are the different types of bacteria according to their respiratory requirements
-obligate aerobes need oxygen to respire
-facultative anaerobes use oxygen if it’s available, but can manage without it
-obligate anaerobes can only respire in the absence of oxygen- oxygen will kill them
