Cells Flashcards
What are antigens
Proteins on the surface of cells that cause an immune response
Allows immune systems to recognise : pathogens , cells from organisms of the same species, abnormal body cells, toxins
Self antigens
On our own cells
Non- self
Foreign
What is a pathogen?
Organisms that cause disease, destroy host cells.
Cellular immune response
Phagocytosis and t-cells
Humoral response
B-cells and plasma cells
What is bacteria
Living cells that can multiply rapidly, attack tissues in host and release toxins
What are viruses
Burst out of host cell into bloodstream, difficult to treat without affecting the host
Phagocytosis:
First line of defence
Identifies the foreign antigen and engulfs it into the phagocytic vacuole.
Lysosomes fuse with the phagocytic vacuole which break the bacteria down.
Components of cell: red blood cell
Contains haemoglobin which carries oxygen around the body
Plasma
Contains salts, sugars and proteins. Distributes materials and hormones throughout the body. Also carries waste products
Platelets
Bits of dead cell to help clot the blood
White blood cell
Destroy invading microbes
Active immunity
When you make your own antibodies
Natural - produce antibodies + memory B cells
Artificial - vaccination
Slow, long term , make memory cells, exposed to antigen
Passive immunity
When you are given antibodies by another organism
Natural - mother to child
Artificial - given someone else’s antibodies (blood transfusion )
Fast, short term, dont make memory cells, no exposure to antigen
T-cells
Made in the bone marrow Mature in the thymus Carry out cell mediated response Recognise and destroy abnormal cells Produce a protein that makes holes in the cells surface membrane TH cells active B cells TC kill pathogens
B-cells
Made in and mature in the bone marrow
Responsible for antibody production
B cell with the complimentary antibody forms antigen-antibody complex
Selected b cels divides and clones itself
Plasma cells
Clones of the selected B cell
Make monoclonal antibodies
Stick pathogens together = agglutination
When infections is over , plasma cells are saved as memory b cells
Lymphocytes
Have an englarged nucleus because they are producing lots of ribosomes|+mRNA. Produced in the bone marrow
Antibody
A molecule made by b lymphocytes in response to stimulation by the appropriate antigen
Also known as immunoglobins
Specific to a particular antigen
Usually a protein or glycoprotein
Structure of an antibody :
4 polypeptide chains held together by disulfide brides
A genetic constant region allowing antibodies to attach to phagocytic cells
Variable regions which is specific to a particular antigen this depends on amino acid sequence
Hinge region which allows the antigen to flex in order to bind to more than one antigen
Primary immune response
Slow- phagocytosis
Pathogen multiplies - feel symptoms
After the infection you save memory cells
Secondary immune response
Same pathogen infects you
Faster+stronger
No symptoms
What is the Elisa test
Test to see if patients have a specific antibody or antigen
Direct elisa test
Only one antibody used test for antigens
1) immobilised antipodes attached to a wall
2) sample added (e.g blood plasma )
3) if blood plasma companies antigen an antigen- antibody complex formed
4) rise to remove unbound antigens
5) antibody+ enzyme added
6) rinse
7) add substrate = if there’s a colour change it is a positive test
Indirect Elisa test
Uses two antibodies( a primary antibody and a secondary enzyme )
1) antigen is fixed to the well
2) sample is added - if complimentary an antigen-antibody complex formed
3) rinsed to remove unbound antibodies
4) different antibody added + enzyme
5) will only bind if 1st antibody is present
6) rinses to remove antibodies are unbound
7) substrate added = colour change
Vaccine
Contains antigens from a dead/weakened pathogen
Stimulates immune system to produce antibodies/plasma cells/ memory cells without causing illness
If infected post vaccine you undergo secondary response
Why don’t you feel ill from a vaccine
Because they contain an unactivated form of the pathogen killed by heat treatment
Herd immunity
The higher % that are vaccinated, the fewer people there are to pass on the disease
Antigenic variability
Antigens on the surface of pathogens change due to mutation
Antigen is no longer complimentary to the antibody
Infected again - primary response
Some pathogens may have strains - vaccines only work on some strains
The MMR controversy
1998- scientific paper speculated that the MMR vaccine causes autism
The vaccine could damage the bowel allowing the toxins cause autism in the brain
The authors did not prove that this was the case but still recommended that doctores stopped administering the MMR vaccine until more research was done
Virus reproduction
1) virus attachment proteins binds to receptor of the host (th cells)
2) reverse transcriptase makes double stranded DNA from RNA
3) DNA enters nucleus via nuclear pore
4) TH cells makes copies of virus, genetic material and protein
5) reforms capsid
6) leaves host cell taking on envelope from hosts membrane
What are monoclonal antibodies
Identical antibodies made from same B cell/ plasma cell
Uses : targeting medication
Used to deliver drugs
Bind to only target cell
Attach drugs to antibodies
Uses : medical diagnosis
1) monoclonal antibodies added to a plate
2) sample added - if antigen present it forms an antigen-antibody complex
3) rinsed to remove unbound antigens
4) same monoclonal antibody is added with an enzyme/ colour attached
5) rinsed again
6) observe for a marker - colour change
Formation of monoclonal antibodies
1) antigen is injected into a mouse
2) the mouse naturally produces lymphocytes
3) spleen cell produce lymphocytes are removed
4) spleen cells are fused with cancerous white blood cell to form hybridoma cell
5) the hybridoma cells divide and produce millions of monoclonal antibodies specific to the original antigen.
HIV
Human immunodeficiency virus
Infects t-helper cells so the immune system becomes weak and develops AIDS
Doesn’t kill you directly
AIDS
Acquired immune deficiency syndrome
Eukaryotic cell organelles :nucleus
Nucleus= where chromosomes are found, controls activities s
Eukaryotic- RER
RER= usually attached to nucleus, covered in ribosomes, modifies and folds proteins
Eukaryotic - SER
SER= not attached to the nucleus, modifies and folds proteins
Eukaryotic - golgi apparutus
Golgi apparatus = modify and package proteins and lipids and put them in vesicles for transport. Make lysosomes
Eukaryotic=lysosomes
Lysosomes = contain digestive enzymes, used to hydrolyse pathogens
Eukaryotic - mitochondria
Mitochondria = make ATP, site of aerobic respiration.
Eukaryotic - chloroplast
Grana is a stack of thykaloid, double membrane
Site of photosynthesis
Eukaryotic - cell wall
Strong that protects the cell from changing shape
Eukaryotic - vacuole
Contains sugar and salt ( cellulose ), keeps cell fugid
Eukaryotic - ribosomes
Makes proteins, attached to RER, made of proteins and RNA
Prokaryotic - plasmid
Small loop of dna
Can be passed between bacteria
Carry useful genes
Prokaryotes - cell wall
Made of a glycoproteins
Strength = shape
Prokaryotes - flagella
Rotates to move the cell
Prokaryotes - small ribosomes
Makes proteins
Prokaryotes- loop of dna
No nucleus , dna is free in the cytoplasm
Prokaryotes- capsule
Slime layer, adds protection
Prokaryotes - cell membrane
Controls what goes in and out
Cell fractionation
1) break cells open -
Keep ice cold to prevent enzyme activity
Keep isotonic to prevent osmosis
Use buffer to keep pH same
2) filter solution - removes cell debris and whole cells
3) ultra centrifugatiom-
Spin the test tube , heaviest organelles compressed into a pellet at the bottom
Remaining liquid is poured off
Spin again
Repeat …
Order of organelles in cell fractionation
Ribosomes at the top
Nuclei at the bottom then chloroplast then mitochondria
Light microscope
Easy to use Cheap Colour image Much lower magnigfication Can’t see small organelles - ribosomes
Scanning electron microscope
Much better magnification + resolution than light
3D image
Don’t need a thin section
Can’t see internal structures s
Transmission electron microscope
Best magnification + resolution -shorter wavelength of light Internal structure Can’t see living cells Specimen needs to be in a vacuum Use thin slice No colour
Why do specimens have kept in a vacuum for an electron microscope
Electrons are absorbed by molecules in air , this would prevent the electrons reaching the specimen §
Microscope calculation
Imagine size= actual x magnification
What happens in Interphase
DNA replicates
Chromosomes are loosely coiled = chromatin
What happens in prophase
Chromosomes condense
Nuclear membrane centrioles move to the poles
Two chromatids joined at the centrometre
What happens in metaphase
Double chromosome line up at the equator , spindle fibres forms
Translocation of chromosomes
What happens in anaphase
Centrometres spit
Chromatids are pulled to opposite poles
What happens in telophase
Nuclear membrane reforms
Cytokinesis - cytoplasm divides
Mitosis and cancer
= uncontrolled cell division
Mutation in the oncogene and proncogene that switch on and off the proces
Malignant, cancerous tumors may spread from their origin . They develop their own blood supply which can transport malignant cells to other sites in the body
Structure of the cell surface membrane
=phospholipid belayer
Hydrophilic heads face outward
Hydrophobic tails face inwards
Phospholipids can slide over each other = fluid mosaic model
Diffusing through the cell membrane
Small non polar molecules diffuse through
Large polar molecules cant diffuse through easily
Cholesterol and the cell surface membrane
Cholesterol binds to hydrophobic tails, makes the membrane more rigid , for strength and support
What is diffusion
Net movement of molecules from high to low concentration and is passive
Carries on till equilibrium is reached
How does concentration gradient affect rate of diffusion
The steeper the concentration gradient the faster the rate of diffusion
How does surface area affect rate of diffusion
Bigger surface area, faster rate of diffusion
Ficks law
Rate of diffusion = surface area x concentration gradient / thickness of membrane
What is facilitated diffusion
The passive movement of molecules across the cell membrane via a specific transmembrane protein
Has a slower rate
Carrier proteins = intrinsic globular proteins
Carrier proteins are specific for the molecules they transfer
Active transport
Against the concentration gradient
Uses energy from atp
Via a carrier protein
Affected by temperature, enzyme availability and cellular glucose concentration
Co transport
Via carrier protein
Moves 2 molecules at one
One goes down its concentration gradient and one going against
Absorption of glucose
1) sodium ions are transported out of epithelial cells by a sodium-potassium pump into the blood. - this maintains a much higher concentration of sodium ions in the lumen of the intestine than inside the epithelial cells
2) sodium ions diffused into the epithelial cells down the concentration gradient through a co-transport protein. As they diffuse they carry either amino acid molecules or glucose molecules with them
3) the glucose/amino acid pass into the blood plasma by facilitated diffusion using another type of carrier.
What is osmosis
The passage of water from a region of higher water potential to a region of lower water potential through a selectively permeable membrane.
What is a solute
Any substance that is dissolved in a solvent
Water potential
High water potential - high % of water molecules, low % of solute , hypotonic. Pure water has a high water potential when its next to a solute
Low water potential ‘ lower % of water molecules, high % solute , hypertonic
The more solute that is added, the lower its water potential
