UNIT 2- Cells, Cell replication and Immunity Flashcards
what does the nucleus do in a cell
contains genetic information needed for protein production and controls cell activities
what is chromatin made from and what does it form
a complex of DNA and histones that forms chromosomes
what does the nucleolus do
makes RNA which is made into ribosomes and moved out of the nucleus to the RER
what does the nuclear envelope do
double membrane which has nuclear pores to let relatively large molecules pass through
what is the structure and role of mitochondria
energy releasing cell
surrounded by a double membrane and the inner layers fold inwards to from cristae which projects into the matrix
the matrix contains enzymes needed for aerobic respiration.
there is also mitochondrial DNA and ribosomes in the matrix
what is the structure and role of the RER
consists of flattened membrane and they are studded with ribosomes.
it folds and processes proteins that have been made at the ribosomes
some of the proteins get secreted and some get put back onto the cell surface of the RER
what is the structure and role of the SER
consists of flattened membrane
synthesises and packages lipids
what is the structure an role of ribosomes
tiny organelles which can be found free in the cytoplasm or bound to the RER
consists of 2 subunits
is the site where proteins are made
what is the structure and role of the golgi apparatus
sack of fluid filled membrane bound flattened sacks
processes and packages new lipids and proteins also makes lysosomes
what is the role of Golgi vesicles
store lipids and proteins and transports them out of the cell`
what is the structure and role of lysosomes
spherical sacs surrounded by a single membrane
the Golgi vesicle contains digestive enzymes which digest cells and break down worn out cell components
what is the structure and role of centrioles
self-replicating organelles made up of microtubules and are only found in animal cells
they help organise cell division
what is the structure and role of microtubules
made of tubulin to help it provide structire to the cells cytoskeleton and also play a role in moving the daughter cells DNA into the daughter cell in mitosis
what are the structure and role of microvilli
cell membrane projections to increase the surface area for absorption
what is the structure and role of cilia
hair like projections made from microtubules to allow movement of substances over the cell surface
what is the structure and role of flagella
essential for the locomotion of individual organisms and are made of long microtubules
what is the structure and role of chloroplasts
small flattened scks surrounded by a double membrane
filled with liquid called stroma which contains sacks of thylakoid membranes containing chlorophyll called grana which are linked together by lamellae
photosynthesis happens in the grana and stroma
what is the structure and role of a vacuole
consist of a membrane called tonoplast filled with cell sap
maintains the pressure of the cell and keeps it rigid
what is the structure (in plants, fungi) and role of a cell wall how does it help with the transport of substances
in plants and algae - made of cellulose
in fungi it is made of chitin
provides structural support to help maintain the shape of the cell
there are pores within the cell wall called plasmodesmata which connects two cells together by their cytoplasm enabling the exchange and transport of substances
what is the role and structure of the plasma membrane
regulates movement of substances into and out of a cell
has receptor molecules allowing it to respond to chemical messengers and is made of a phospholipid bilayer
how is a red blood cell adapted for its function
they have a biconcave shape and do not contain a nucleus so there is as much space to transport oxygen as possible
how are neurons adapted for their function
have extensions called dendrites which allow communication with other neurons and a myelin sheath to insulate and speed up communication
how is a sperm cell adapted for its function
have the nucleus in the head containing half the normal number of chromosomes
has an enzyme called acrosome which is a digestive enzyme and helps break down the outer layer f the egg cell for fertilisation
has lots of mitochondria for movement
sometimes has a flagella to help with the locomotion of the cell
how are root hair cells adapted for their function
have thin walls so osmosis can happen quicker
mitochondria for active transport
a permanent vacuole to maintain the water potential of the cell
has a large surface area to increase absorption
how are xylem adapted for its function
have thickened outer walls strengthened with a substances called lignin
cells making up the xylem are virtually dead so water is allowed to flow freely
how are phloem adapted for their function
have very few subcellular structures allowing substances to flow easily
what is a tissue
a group of cells that work together to perform a particular function
what are the organelles a prokaryote has and what don’t they have
they have :
cytoplasm
ribosomes
cell wall
plasmids
capsules
flagellum
they dont have:
nucleus
membrane bound organelles
compare and contrast prokaryotic and eukaryotic cells
prokaryotic is smaller than eukaryotic
prokaryotic reproduces by binary fission and eukaryotic reproduces by mitosis or meiosis
DNA in prokaryotic is circular but in eukaryotic its linear
DNA in prokaryotic isn’t associated with histones but in eukaryotic it is
prokaryotic has no membrane bound organelles whereas eukaryotic has numerous types of membrane bound organelles
in prokaryotic the cell wall is made of murein in eukaryotic it is chitin or cellulose
what are the four structures of a virus
a nucleic acid core
a protein coat called a CAPSID
an envelope formed from the membrane of the host cell
attatchment proteins
what is magnification
how many times bigger the image is compared to the object
what is resolution
the ability to distinguish between 2 points
what conditions are needed for an electron microscope
vacuum
specimens are dead
what conditions are needed for a light microscope
no vacuum needed
specimens can be living or dead
compare and contrast electron and light microscopes
electron microscope
1. large and can b moved
2. vaccum needed
3. complicated sample prep
4. over 500,000 mag
5. 0.5 micrometers resolution
6. specimens are dead
7. uses electrons
light microscope
1. small and easy to move
2. no vacuum needed
3. easy sample prep
4. up to 2000 mag
5. 200 micrometers of resol.
6. specimens can be living or dead
7. uses light waves with long wavelength
what is an artifact
appear on the micrograph but aren’t part of the actual specimen normally are bubbles or dust.
compare and contrast TEM and SEM
TEM:
1. uses an electron gun to produce a beam that is focused onto the sample by an electromagnet
2. specimen needs to be as thin as possible so beam can pass through
3. gives resolution of up to 0.1 nanometers
SEM:
1. scans a beam of electrons across the surface of the spec. and electrons are scattered and gathered at the cathode ray tube
2. doesn’t need to be a thin sample as electrons are scattered by the specimen
3.can build up a 3D image by a computer
4. has a resolving power of around 20 nanometres
what is the equation for magnification
magnification= image size / actual size
what are the 3 steps in cell fractionation
- homogenisation
- filtration
- ultracentrifugation
describe homogenisation in cell fractionation
grinding the cells in a blender to break up the plasma membrane in a homogeniser and release organelles
the solution must be:
1. isotonic to prevent osmosis bursting cells
2. ice cold to reduce activity of enzymes that break down organelles
3. buffered to maintain pH o stop the denaturing of enzymes and proteins
describe filtration in cell fractionation
homogenised cell solution is filtered through a gauze to separate any large cell debris
describe ultracentrifugation in cell fractionation
cell fragments are poured into a tube and it is spun at a low speed and the heaviest organelles collect as a sediment and the supernatant is drained off and poured into another tube and spun at a higher speed and repeat
what is the usual order in cell fractionation or organelles
- nuclei
- chloroplasts
3.mitochondria - lysosomes
- RER and SER
- ribosomes
what is the order of stages in mitosis
- interphase
- prophase
3.metaphas
4.anaphase - telophase
- cytokinesis
what happens in interphase
G1 phase cells makes RNA and enzymes and other proteins ad receives signal to divide
S phase when the DNA replicates
G2 phase is when the cell continues to grow and the new DNA that has been synthesised is checked and errors are usually repaired
what happens in prophase
- chromosomes condense and become visible
- sister chromatids are joined together at the centromere
- the two centrosomes move towards opposite poles
- spindle fibers begin to emerge from the centrosomes
- nuclear envelope breaks down
what happens in metaphase
- centrosome reach opposite poles
- spindle fibres continue to extend from centrosome
- chromosomes are lined up at the equator of the spindle s they are equidistant to the two centrosomes pole
- spindle fibre reach the chromosomes are attach to the centromeres
what happens in anaphase
- sister chromatids separate at the centromere
- spindle fibres begin to shorten
- the seperated sister chromatides are pulled to opposite poles by the spindle fibres
what happens in telophase
- chromosomes arrive at opposite poles and begin to decondense
- nuclear envelopes begin reform around each set of chromosomes the spindle fibres break down
what happens in cytokenesis
- cytoplasm divides forming two genetically identical cells
- in animals cleavage forms and separated the daughter cells in plants the cell plate forms at the site of the metaphase plate and the new daughters cells are separated
what causes cancer
cancer arises due to uncontrolled mitosis and cancerous cells dividing repeatedly and uncontrollably when a change in the genes occurs to from an oncogene
what are carcinogens
environmental agents that increase the chance of cancer
what are treatments of cancer
anything that slows the rate of mitosis in cancerous cells down like chemotherapy
what happens in binary fission and what is the final result
- single circular DNA undergoes DNA replication
- any plasmids present undergo DNA replication
- the parent cell divides into two cells with the cytoplasm roughly halved between the two
- the two daughter cells contains one copy of the circular DNA molecule and a variable number of plasmids
what happens in viral replication
- virus attachment proteins bind to complementary receptor proteins on host cell surface membrane
- the virus injects its DNA or RNA into the host cell
- the host cell uses the nucleic acid and ribosomes from the virus to produce new viral proteins
- host cell bursts open and releases the new viral proteins and takes a section of the membrane with it to create an envelope
why is the phospholipid bilayers described as fluid mosaic
fluid- proteins can move around and phospholipids mainly move sideways within their own layers
mosaic- the scattered pattern produced by proteins within the phospholipid bilayer
what happens if you mix phospholipids with water
they from spheres with the hydrophobic tails pointing inwards and the hydrophilic heads facing out called a micelle
describe the structure of a phospholipid membrane
hydrophobic tails point inwards
hydrophilic heads point inwards
individual phospholipids move by diffusion
what is the role of the phospholipid bilayer
act as a barrier to water soluble substances and ensure that they cant leak out of the cell as well
what is the role of cholesterol in the membrane
regulate the fluidity of the membrane and contribute to the impermeability of the membrane and increase its strength and stability
they also prevent the membrane from fractioning in low temperatures and bid with the phospholipids in high temperatures to stabilise the cell membrane and stopping it becoming too fluid
where are cholesterol found in a cell and what type of cell
in between phospholipids and only in eukaryotes
what do glycolipids and glycoproteins do in the cell membrane
act as receptor sites allowing them to bind to certain substances
they also help with adhesion and stabilization and and act as signaling receptors for hormones and neurotransmitters
some act as cell markers or antigens from cell to cell recognition
what do transport proteins do in the cell surface membrane and why is it important
they allow substances like ions and polar molecules to travel through the membrane as they cant get through the phospholipid bilayer
what is diffusion
diffusion is the net movement of a substance from a region of its higher concentration to a region of lower concentration
what four factors effect the rate of diffusion
concentration gradient
temperature
surface area
properties of molecules or ions
what is facilitated diffusion for
it allows substances hat cant diffuse through the phospholipid bilayer of cell membranes cross
what is the structure of a channel protein and what does this allow to happen
has hydrophillic and hydrophobic amino acids that fold over to form a channel that is water filled allowing charged substances through by facilitated diffusion
what is the structure of a carrier protein and what does it do in order to perform its function
they switch shapes to let substances pass as the binding site to be open on one side of the protein at a time
it opens to let the substance through one end and then shuts that end and opens the other end to let it through again
what is the definition of osmosis
the diffusion of water particles from a dilute solution to a more concentrated solution across a semi permeable membrane
what happens if a plant is put in a pure or dilute solution of water
- water will enter the plant cell through its partially permeable membrane by osmosis
what happens if a plant is placed in a solution with lower water potential then the plant cell water
1.the plant cell water will leave the plant cell through its partially permeable membrane by osmosis
2.As water leaves the vacuole of the plant cell the volume of the plant cell decreases
3.The protoplast gradually shrinks and no longer exerts pressure on the cell wall and as it continues to shrink it begins to pull away from the cell wall and this is known as plasmolysis.
what happens if an animal cell is placed in a solution with lower water potential than the cell
cell water will leave the cell through its partially permeable membrane by osmosis and the cell will shrink and shrivel up this occurs in a hypertonic environment
what happens if an animal cell is placed in pure water or a dilute solution
water will enter the cell through its partially permeable membrane by osmosis as the pure water has a higher water potential. The cell will continue to gain water by osmosis until the cell membrane is stretched too far and the cell burst as it has no cell wall the withstand the pressure- cytolysis. This occurs in a hypotonic environment.
what is active transport
movement of molecules and ions through a cell membrane from a region of lower concentration to a region of higher concentration using energy from respiration
why is ATP needed in active transport
ATP is needed to make the carrier proteins change shape to allow the transfer of molecules or ions
where is active transport crucial in humand and plants
reabsorption of molecules into the blood after filtration in the kidneys
absorption of some products of digestion
loading inorganic ions from the soil into root hair cells
what is co transport
the coupled movement of substances across a cell membrane via a carrier protein involving a combination of facilitated diffusion and active transport
how does co transport happen in the epithelial cells lining the ileum
- the active transport of sodium ions from the epithelial cells into the blood lowers the concentration of sodium ion in the cell of the epithelial cells and generates a concentration gradient of sodium ions
- sodium ions then diffuse into the cells from the ileum by facilitated diffusion through a co transporter protein while carrying a glucose molecule along with them
- then the glucose can diffuse into the blood via facilitated diffusion
what factors effect simple diffusion
surface area
diffusion pathway
concentration gradient
temperature`
what factors effect the rate of facilitated diffusion
concentration gradient
number of channel or carrier proteins
how are root hair cells adapted for diffusion
they have thin walls for a short pathway
a permanent vacuole to maintains high water potential
a specialised shape to increase SA
how are epithelial cells of the small intestine adapted for diffusion
have microvilli to increase Sa
villi have constant blood supply to maintain high concentration gradient
how are kidney cells adapted for faciliated diffusion
have high amount of channel proteins in the cell membrane
how are neurones and muscle cells adapted for facilitated diffusion
have cell membranes containing lots of channel proteins
name the 4 antigen presenting cells
pathogens
abnormal body cellls
cells from other individuals of the same species
cells that have been invaded by a virus
what is an antigen
molecule that can stimulate an immune response by the body
what are the two types of antigens and explain the difference
self-antigens are produced by the organisms body and dont stimulate an immune response
non self antigens are not produced by the organisms own body cells and stimulate an immune response
what is antigen variability
antigens present on the surface change due to genetic mutations
why is antigen variability a problem
poses a problem for the immune system as lymphocytes and memery cells that are specific to the shape of an anitgen will no longer be able to bind to them and therefore host gets infected again with the same disease
what happens in phagocytosis
phagocyte recognises the foreign antigens on a pathogen
cytoplasm of the phagocyte moves arounf the pathogen engulfing it
pathogen is now contained in a phagocytotic vacuole
lysosomes fuse with the phagocytotic vacuole and the lysozymes hydrolyse and digest the pathogen
the phagocyte then presents the pathogens anitgens on its cell surface to activate other immune system cells and acts as an anitgen presenting cell
where are t cells produced and mature
in the bone marrow before birth and mature in the thalamus
what happens when a t cell is activated
t-lymphocytes are activated when they encounter their specific antigen that is being presented by one of the hosts cells
These activated lymphocytes divide by mitosis to increase in number and differentiate into two types of T cell:
1.Helper Tcells
2.Cytotoxic Tcells
what is the role of a anitgen presenting cell
help recruit other immune cells to produce a specific response
what do helper t cells do
assist other WBC in the immune system
release cytokines which stimulate:
1. the production of b memroy cells
2. activation of cytotoxic t cells
what do cytotoxic t cells do
attatch to the foreign antigens and secrete perforins and granzymes to kill the cell
where are b cells stored/made
in bone marrow and then spread out to spleen and lymph nodes
what do b cells differenciate into
memory b cells- remain circulating in the blood for a long time and help spped up the secondary immune response
plasma cells- secrete lots of anitbodies into the blood but are short lived themselves
what is the structure of an antibody
globular protein that have a quaternary structure with 2 light and 2 heavy polypeptide chains
what is aggulintation
an antibody has two binding sites so it can bind to two pathogens at one time which means pathogens can be clumped together
what does the binding of antibodies to antigens do
either neurtralises the pathogen or acts like a marker for phagocytes
what is the celluar response
T cells and other immune cells they react with like phagocytes
what is the humoral response
b-cells, clonal selection and the production of monoclonal antibodies
what is involved in the primary immune response
when an antigen enters the body for the first time it causes an immune response which is slow as there arent any b-cells with the complementary antibodies for the pathogens antigen
eventually the body mounts a response big enough to kill the disease while the pateint is showing symptoms
the the t cells and b cells produce memory cells whcih remain in the body and will recognise the anitgen if infected with it again
what is involved in the secondary response
the pathogen enters the body for a second time and the immune response starts again but is much quicker and stronger due to the memory cells circulting the blood and there should be no symptoms
b-cells circulating the blood
produce plasma cells very quickly so the needed antibodies are made quicker
memory t cells divide into the right type of t cell and to kill the pathogen
what is a vaccine
a suspension of antigens put into the body artificially to produce an imune response
what are the advantages and disadvanted to vaccines
advantages:
1. lifetime of protection
2. generally harmless and dont cause disease
3. help herd immunity and protect the vunerable
disadvantages:
1. people can have poor responses to them
2. they are often tested on animals
3. antigenetic variation can make them ineffective
describe a live vaccine
containes a weakened athogen that multiplies slowly allowing the body to recognise it and prpoduce an immune response
evaluate a live vaccine
+ tend to produce stronger and longer lasting responses
-They can be very unsuitable for people with weakened immune systems
describe a inactivated vaccine
Contains whole pathogens that have been killed and they cannot cause disease
evaluate inactivated vaccines
+ safer for people with weakened immune systems
- dont trigger a long lasting immune repsonse and therefore boosters are often required
what is herd immunity and why is it important
When a sufficiently large proportion of the population has been vaccinated which makes it difficult for a pathogen to spread within that population
+ Those who aren’t immunised are protected and unlikely to contract the disease as the levels are so low which allows individuals who cant get vaccines be protected
what is active immunity
Acquired when an antigen enters through the body triggering a specific immune response
Naturally acquired through exposure to microbes or artificially acquired through vaccinations
The body produces memory cells alone with plasma cells giving the person long term immunity
The secondary response has a very high antibody concentration and takes a much shorter period
what is passive immunity and why isnt it as good as active immunity
give an example of artificial and natural passive immunity
Acquired without an immune response and are not produced by the infected person
As the persons immune system has not been activated then there are no memory cells that can produce antibodies in a secondary response
Artificial passive immunity occurs when a person us given an injection or transfusion of antibodies
Natural passive immunity occurs when a foetus receives antibodies across the placenta or when a baby receives the first breast milk with antibodies
how is HIV spread
though bodily fluids
e.g sex, needles and a mother to her foetus through milk or the umbilical chord
what is HIV made up of
two RNA strand, proteins, a viral envelope and attachtment proteins
what are the steps to HIV replication
- viral RNA is injected into the cell when HIV attacthment proteins binds to human cell receptor site
- viral reverse trancriptase ezymes produce a DNA copy of the RNA
- the DNA copy is inserted into the chromomosomes of the cell
- cell divides and copies viral DNA
what happens when the viral DNA in host cells becomes active in HIV
it takes control of the helper t cells and more HIV particles are produces which causes helper t cells to die and as b cells are no longer activated no antibodies are produces and this eventually leads to AIDS
describe the stages of infection with AIDS symtom wise
inital infection is cold/flu like symptoms
dormancy- virus recplicating no symptoms but more sucepitable to infections
immunocomprimised- suffer from minor diseases
how do antibiotics work
antibiotics interfere with the metabolism of bacterial cells while others prevent proteins synthesis
what are monoclonal antibodies
Monoclonal antibodies are antibodies produced from a single group of genetically identical B-cells
how can we use monoclonal antibodies to detect tumours
- Inject mice with human tumour cells
- Activates plasma cells to produce antibodies against human tumour cells
- Collected from the mouse spleen
- Plasma cells are fused with tumour cells to form a hybridoma
- Radioactive chemical is attached to antibody making them radioactively labelled
- A gamma ray camera is used to detect where the radioactively labelled antibodies have attached to a protein in human indicating where blood clots or tumours are.
You can also use this to treat them ny adding a drug to the antibodies and they will accumulate on the tumour markers
how are monoclonal antibodies used in pregnancy tests
- Application area contains antibodies that are complimentary to the hCG protein bound to a blue coloured beam
- when urine is applied any hCG will bind to the antibody on the beads forming an antigen-antibody complex
- The urine moves up the stick to the test strip carrying any beads with it
- The test strip contains antibodies to hCG stuck in place (immobilised)
- If there is hCG preset the test strip turns blue because the immobilised antibodies bind to the hCG
what are the ethical issues of vaccines
All vaccines are tested on animals before they can move onto human trials
Animal based substances are sometimes used in the production of vaccines, but some people disagree with this
Even at the human trial stage there is a risk the person gets disease or unpredicted side effects
When new epidemics happen, we struggle to decide who should be vaccinated first
what are the ethical issues with monoclonal antibodies
Often tested on animals
Use animals to produce the cells for monoclonal antibodies
describe the direct elisa tests
1.Antigens from patients’ blood are bound to the inside of a well
- A detection antibody with an enzyme attached that is complimentary to the antigen of interest is added
- Well is then washed out to remove any unbound antibodies
- Substrate solution is added, and a colour change will happen
explain the indirect ELISA test to test for antibodies in HIV
- HIV antigens are bound to the bottom of the reaction vessel
- A blood plasms sample is taken from the patients and added to the reaction vessel
- Any HIV specific antibodies that are present in the blood will bind to the HIV antigens. These antibodies are known as the primary antibodies
- Any other antibody is unbound and washed out
- A second antibody with an enzyme attached is added to the reaction vessel and these are known as secondary antibodies and these bind to the primary antibody
- The reaction vessel is washed out again to remove any unbound secondary antibodies
- Add solution of substrate that reacts with enzyme to from a coloured product indicating hte patient has HIV as they have the antibodies in their blood for it.
describe the indirect ELISA test for testing for antigens
- Antibodies are bound to the bottom of the reaction vessel
- Blood plasma sample is added
- Secondary antibody added
- Substrate added forming a coloured product
