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114 Cards in this Set

  • Front
  • Back
The three tenents of cell theory
i. The cell is the fundamental unit of structure and Function of all living structures
ii. All living organisms consist of one or more cells
iii. All cells arise from preexisting cells
Major discoveries of cell bio
i. 1665 Robert Hooke saw (dead) cork cells with a microscope.
ii. Later in the 1600’S A Leewenkoek viewed living cells from sperm and pond water
basic structure of cells
i. A cell membrane to separate the cell from the environment. It is usually semipermiable
ii. Genetic Material is always DNA (viruses don’t count b/c they are not LIVING!)
iii. A cytoplasm
iv. Ribosomes
units of measurement
i. m meter
ii. cm centimeter 10-2
iii. mm millimeter 10-3
iv. μm micrometer 10-6
v. nm nanometer 10-9
vi. Ǻ Angstrom 10-10
centimeter
10^-2
millimeter
10^-3
micron
10^-6
nanometer
10^-9
Angstrom
10^-10
i. Resolution
the minimum distance between two objects at which those two objects can appear distince
resolution on a light microscope
200-350 nm
resolution on an electron microscope
2-10nm
basic features of a light microscope
i. A light microscope uses light, can view dead and live cells, can view whole cells and large organelles such as (vacules, mitochondria, and the nucleus)
ii. Brightfield
1. basic light microscopy. It is inexpensive and simple to use. The only specimines that can be seen with brightfield microscopy are those with color or with light reflecting properties. Most specimens must be stained before being observed. Whole cells can be viewed or they can be sectioned. Cells in tissue have to be suspended and cut.
How do you prep for microscopy?
a. Fix specimine with an aldhyde
b. Dehydrate
c. embed sample in resin or wax
d. Cut with microtome (metal or glass for LM, diamond for EM)
iii. Phase-contrast
1. No stains
2. Living cells can be viewed
3. looks at differences in thickness and how much light is moved out of phase by different substances in the cell.
4. There is an extra phase ring on the microscope that makes this conversion
5. Image contrast is better than brightfield
iv. Differential interference contrast
1. similar to phase contrast but more sensitive because it uses a prism to split light in such a way that it can detect small changes in phase.
v. Fluorescence
1. Uses a flouraphore and light microscope
2. can be used with antibodies to detect a specific molecule or protein
3. GFP- Green Flourescent Protein from Jellyfish can track proteins over time by being attatched to a certain gene
4. Usually a UV light is used to excite the flouraphores, and the fluorescence is viewed as visible light
a. A barrier filter blocks UV light and lets through only flouraphor wave lengths.
3. GFP
Green Flourescent Protein from Jellyfish can track proteins over time by being attatched to a certain gene
a. A barrier filter
blocks UV light and lets through only flouraphor wave lengths.
5. The Two types of Immunoflourescence
a. Direct
i. Isolate protein
ii. Generate antibodies in another orgainsim
iii. Collect and label antibodies with flouraphores
iv. Antibodies bind to protein
v. A LOW signal is viewed because each antibody only has one flouraphor
b. Indirect
i. A primary antibody is generated and binds to protein
ii. A secondary antibody is flourescently labeled and is sensitive to the primary antibody
iii. Since more than one secondary antibody can bind to the primary antibody the fluorescence signal is larger.
iv. More than one secondary antibody with different colors can be used to view the location of two diff proteins and where they interact.
vi. Confocal microscopy
1. minimizes blurring by excluding out-of-focuslight from an image
2. a laser beam is used to produce an image on a single plane of the specimen at a time
vii. Prep Techniques for light microscopy
1. fixation- killing the cell while preserving the structural appearance. Usually acids and aldehydes are used
2. embed specimen in paraffin (must dehydrate specimen in alcohol first) or plastic or resin
3. slice into micrometer thin sections using a microtome
4. mount and stain sections
d. Electron Microscope basics
i. Uses electrons as the illumination source. Can see details of individual organelles and has a higher resolution. All cells are DEAD.
ii. Transmission Electron Microscope
1. Samples are stained with heavy metals. Dark regions of the electron micrograph are electron heavy
2. image is grainy, black and white
iii. Scanning electron microscope
1. looks at the electrons that bounce off of the surface of the sample instead of the ones that bounce through.
2. The sample is coated with gold
3. image looks 3D and very detailed
III. Scientific Method
a. Make initial observations
b. Form a hypothesis (or many hypotheses)
i. A hypothesis is a tenable explanation of observations/ experimental results
ii. Must be testable
c. Design an experiment
i. You need controls
1. positive control makes sure whatever you are testing works
2. negative control makes sure whatever you are testing is doing the work not some other reason
d. collect Data
e. interpret results
i. need to take statistics
ii. think of ways to present your data
iii. how your data is presented can affect future experiments
f. draw conclusions
hypothesis
is a tenable explanation of observations/ experimental results
ii. Must be testable
1. positive control
makes sure whatever you are testing works
2. negative control
makes sure whatever you are testing is doing the work not some other reason
a. Differences between Prokaryotes and Eukaryotes
PROPERTY PROKARYOTIC CELLS EUKARYOTIC CELLS
Size Small; gen. a few micrometers in length or diameter Large; 10-50 times the length or diameter of prokaryotic cells
Membrane bound nucleus No Yes
Organelles No Yes
Microtubules No Yes
Microfilaments No Yes
Intermediate filament No Yes
Exocytosis and endocytosis No Yes
Mode of cell division Cell fission Mitosis and meiosis
Genetic information DNA molecule complexed with relatively few proteind DNA complexed with proteins (histones) to form chromosomes
Processing RNA Litlle Much
Ribosomes Small large
V. Subcellular Fractionation
a. Basic steps and theory
i. Break a percentage of cells into fraction
ii. Separate by organelle size shape and density
iii. Analyze fraction by microscopy, biochemically, or through proteomice
iv. Assign function to organelles
b. Ways to Break open cells
i. FIRST: mix cells with homogenizing medium to disrupt cells. Mix with cold isotomic solution of 0.3 Molar sucrose. The medium is cold so that you keep protein function
ii. Mortar and Pestle
1. used for plant material to break open the cell wall
iii. Sonication
iv. Detergent solubilization
1. make sure to ude the right detergent at the right concentration so that cell organells are not sheered
v. French Press
1. for algae, press liquid a cells through small opening
vi. Ground Glass homogenization
1. rough ground glass surrounds the outside of the psdtle and bottom of the tube. Cells will be sheered at the bottom of the tube.
vii. Mechanical Lysis
1. if you start with whole organs
2. acts like a grinder
what to do before you try to break open cells
mix cells with homogenizing medium to disrupt cells. Mix with cold isotomic solution of 0.3 Molar sucrose. The medium is cold so that you keep protein function
ii. Mortar and Pestle
1. used for plant material to break open the cell wall
iv. Detergent solubilization
1. make sure to ude the right detergent at the right concentration so that cell organells are not sheered
v. French Press
1. for algae, press liquid a cells through small opening
vi. Ground Glass homogenization
1. rough ground glass surrounds the outside of the psdtle and bottom of the tube. Cells will be sheered at the bottom of the tube.
vii. Mechanical Lysis
1. if you start with whole organs
2. acts like a grinder
viii. Homogenate
- a suspension of organelles, small cellular components, and molecules
VI. Centrifugation
a. Types of motors
i. Fixed angle- less subject to mechanical failure, faster
ii. Swinging- cleaner separation but takes longer and can break if unbalenced
b. Differential centrifugation
used for enrichment not purification/fixed angle motor/ separation by size and density/ Big particles separate faster.
i. Size plays a big role
ii. Based on sedimentation speed
procedure fro differential centrifugation
1. First spin at low force of gravity for a short time (1000G’for 10 min)
2. At end of first spin, bottom has a solid pellet with large organelles and solid unbroken cells and any polymerized cytoskeleton
3. The liquid (supernatant) has everything else
4. Put nuclear pellet on ice for later use.
5. Repeat spin, increasing G’s and time at each step
6. SECOND PELLET: mitochondria, Lysosomes, large organelles
7. THIRD PELLET: (Microsomal pellet) Fragmented Golgi, smooth Er, rough ER, plasma membrane.
a. The supernatant is called the postmicrosomal supernatant
8. FOURTH PELLET: free ribosomes, large macromolecules, viruses
a. Supernatant is cytosol
first pellet of differential centrifugation has
nucleus
second pellet of differential centrifugation has
mitochondria, Lysosomes, large organelles
third pellet of differential centrifugation has
Microsomal pellet) Fragmented Golgi, smooth Er, rough ER, plasma membrane.
a. The supernatant is called the postmicrosomal supernatant
fourth pellet of differential centrifugation has
: free ribosomes, large macromolecules, viruses
c. density gradient (Velocity) centrifugation
Separation is better than differential/ separate by size and density
i. separation bsed on size and density
ii. better separation of organelles closer in size
procedure for desity gradient centrifugation
1. Fill test tube with sucrose at a gradfient so that the bottom is 20% sucrose and the top is 5% sucrose.
2. Load homogenate or supernatant on the top
3. Small, medium and large particles migrate to the bottom at different speeds. (big is fast)
4. Collect the different molecules by piercing the bottom of the tube and collecting the liquid into tubes.
a. Some mixing can occur as the liquid drips out
5. assay for particular organelle
d. Equilibrium density sentrifugation
separation by density
procedure for equilibrium desity centrifugation
i. Start with homogenate or supernatant
ii. Use a VERY high sucrose gradient 20% to 70%
iii. Load and spin
iv. Molecules go to where they are boyant and can’t go any further
1. perox 1.25g/cm3
2. mito 1.19g/cm3
3. Lysosomes 1.12g/cm3
e. Marker enzymes
a test that is used to ID what organelle is in what fraction
i. Nuclei- fuelgen stain turns nucleus pink
ii. Mitochondria- cytochrome oxydase
iii. Peroxisomes- catalase
iv. Lysosomes – hydrolases (ie a protease, lipase, glycosylase)
v. Golgi- alpha-mannosidase (cleaves manose in Golgi)
vi. Plasma membrane – adenylate cyclase turns AMP to cAMP
vii. Cytosol- lactate dehydrogenase
viii. Smooth ER- glucose-6-phosphatase
ix. When testing it is smart to test for “nearby” organelles
Marker enzymes for nuclei
fuelgen stain turns nucleus pink
Marker enzymes for mitochondria
cytochrome oxydase
Marker enzymes for peroxisomes
catalase
Marker enzymes for lysosomes
hydrolases (ie a protease, lipase, glycosylase)
Marker enzymes fro Golgi
alpha-mannosidase (cleaves manose in Golgi)
Marker enzymes for plasma membranes
adenylate cyclase turns AMP to cAMP
Marker enzymes for cystol
lactate dehydrogenase
Marker enzymes smooth ER
glucose-6-phosphatase
How were lysosomes discovered
i. Lysosomes were accidentally found by Dvve . He was looking for the location of Glucose-6-phosphatase which turns glucose-6-phosphate into glucose and inorganic phosphate
ii. To find the location of the phosphatase he wanted to fractionate liver cells. He used acid phosphatase as a control enzyme for the experiment.
iii. Results: Found glucose-6-phosphatase activity in the microsomal pellet. If he added acid phosphatase to the fresh pellet there was low enzymatic activity. Over time though, acid phosphatase activity in the microsomal pellet was high
iv. When the Mitochindrial fraction was resuspended and recentrifuged the pellet showed acid phosphatase activity????
a. Structural characteristics of membranes
i. Membranes are sheetlike, about 2 molecules wide and 6-12 nm thick
ii. Membranes consist of lipids, proteins, and some carbs.
iii. Membrane lipids are antipathic
iv. The function of membrane proteins
1. usually transport
v. Membranes are an assembly of noncovalently linked molecules and are therefore fluid
vi. Membranes are asymmetric
vii. Membranes are fluid
what is the ratio of lipid to protein in a plasma membrane?
1. The ratio of proteins to lipids depends on cell type
a. Bacteria have a lot of membrane proteins because all of the life processes take place on one membrane
what is antipathic?
1. They have polar head groups and nonpolar hydrocarbon tails
a. Ions can pass through membranes
b. The membrane is selectively permeable
c. Transport is regulated by proteins
how are proteins linked to the PM
v. Membranes are an assembly of noncovalently linked molecules and are therefore fluid
1. that is also why a detergent like SDS can break apart a membrane. It can get inbetween the non covalent linkages.
2. Some membrane proteins (anchored proteins) are covalently linked to the membrane and need to be pretreated with a lipase to break those bonds
What is freez fracture and what does it do?
a. FREEZE FRACTURE- a way to prepare cells for TEM to see leaflette structure to say something about the distribution of proteins within the membrane.
i. Freeze cells in liquid nitrogen
ii. Place cells in a vacuum
iii. Fracture cells with a diamond knife at a low temp. The fractures will take place at the weak point in the membrane (in between leaflette)
iv. Proteins will go with either one leaflette or anotherand will appear as a bump or a crator on the TEM
what does it mean to be a fluid Mem?
1. lipids are free to diffuse within the plane of the membrane
2. flip-flop is uncommon
a. only occurs by help of enzymes called FLIPases especially during membrane synthesis
How does lipid composition effect fluidity?
i. sauturation: no double bonds in hydrocarbon tail
1. tail are straight and more tightly bonded
2. the membrane is less fluid
ii. unsaturated: one or more double bonds in the tail
1. kinks are formed by double bonds
2. membrane is more fluid
a. to prevent freezing, plants try to become more fluid by increasing the number of unsaturated tails
iii. cholesterol
1. up to 50% of the membrane can be cholesterol
2. At a HIGH temp cholesterol makes
3. At Low temp cholesterol makes membrane more fluid
how does saturation of lipid tails effect fluidity and why?
no double bonds in hydrocarbon tail
1. tail are straight and more tightly bonded
2. the membrane is less fluid
How does unsaturation of lipid tails effect fluidity and why?
one or more double bonds in the tail
1. kinks are formed by double bonds
2. membrane is more fluid
a. to prevent freezing, plants try to become more fluid by increasing the number of unsaturated tails
How does cholesterol effect mem fluidity?
1. up to 50% of the membrane can be cholesterol
2. At a HIGH temp cholesterol makes
3. At Low temp cholesterol makes membrane more fluid
c. Functions of membranes
i. Membranes act as selectably permeable membranes
ii. Compartmentalization allows for more efficient reactions/function
iii. Posses transport proteins that facilitate the transport and regulate the movemement of solutes and other molecules
iv. Detect and transmit signals chemically or electrically
v. Allow for intracellular communication (between cells)
vi. Act as a physical scaffolding for biochemical activities
vii. Energy transduction
1. membrane bound ATPases
isolation techniques for membrane proteins
i. Start with prokaryotic plasma membrane that has been isolated
1. get rid of cell wall (enzymatically)
2. Get rid of the iside of the cell
a. Freeze then thaw cells
3. pellet membranes
ii. Solubilize the membranes, especially the proteins
1. use a detergent such as SDS (sodium dodecylsullffate)
a. SDS looks like a phospholipid
b. It sneaks in between membrane and disrupts noncovalent links and unfolds proteins (SDS coated proteins)
iii. separate different proteins based on SIZE not charge
1. SDS is negative so coating all of the proteins with a negative charge allows separation by size only
2. Use SDS-Page (polyacrylamide gel electrophoresis)
How does SDS break apart the mem?
a. SDS looks like a phospholipid
b. It sneaks in between membrane and disrupts noncovalent links and unfolds proteins (SDS coated proteins)
How soes SDS page separate proteins?
iii. separate different proteins based on SIZE not charge
1. SDS is negative so coating all of the proteins with a negative charge allows separation by size only
2. Use SDS-Page (polyacrylamide gel electrophoresis)
a. Lipids are so small that when run on the gel they move out of the gel
b. The Page needs:
i. Poly acrylamide
ii. A crosslinker
1. (bis-acrylamide)
iii. a catalyst
1. (ammonium persulfate)
iv. an accelerant
c. An average of one SDS molecule binds to two amino acids in the protein
d. All proteins are negatively charged and migrate to the positive charge.
what do you need for PAGE of SDS page?
i. Poly acrylamide
ii. A crosslinker
1. (bis-acrylamide)
iii. a catalyst
1. (ammonium persulfate)
iv. an accelerant
How can membrane proteins can be divided before running the gel
by sequential extraction
a. Treat membrane with salt and high pH (alkaline) to extract PERIPHERAL membrane proteins from transmembrane proteins
b. Treat with SDS to extract transmembrane proteins (integral membrane proteins)
c. You can run these two types of proteins in separate wells to get the number and size of peripheral membrane proteins versus number and size of integral membrane proteins.
d. Cut out band, get rid of SDS, sequence protein, predict NT sequence and look in the database for gene that codes for that protein
possible treatments for SDS-Page:
a. For membrane proteins, treat the proteins with glycosidases to cleave off carbs because the sugar resuiduce can effect mobility
b. Treat with lipases to get rid of links to lipids in lipid anchored proteins
c. Cleave disulfide bonds with DTT
iv. Hypotonic shock
1. To break open an erythrocyte (red blood cell) put it in a solution with less solutes outside so that water rushes in and the cell bursts.
b. Classes of Membrane Proteins
i. Integral membrane proteins
ii. peripheral membrane protein
iii. Lipid anchored membrane proteins
i. Integral membrane proteins
1. The hydrophobic region of the protein is embedded within the membrane interior, and cannot be easily removed from the membrane.
2. They have hydrophilic regions that extend outward from the membrane into both the E (extracellular) and P (plasma (in cell)) sides
3. integral monotopic proteins
a. are embedden in and protrude from only one side of the membrane
4. transmembrane proteins
a. most integral proteins that span the whole membrane
3. integral monotopic proteins
a. are embedden in and protrude from only one side of the membrane
4. transmembrane proteins
a. most integral proteins that span the whole membrane
5. transmembrane segment
a. a segment that crosses the lipid bilayer. There can be many transmembrane segments
b. usually an alpha helix
c. 20-30 amino acids long
d. almost all hydrophobic R groups
e. sometimes Beta Barrel (esp porins)
i. porins are mainly found in bacterial membranes, chloroplasts and mitochondria
6. Transmembrane domain
a. A functional region of the protein
ii. peripheral membrane protein
1. proteins lacking discreet hydrophobic regions that are not integrated into the lipid bilayer
2. They are bound to the surface of the bilayer with noncovelent interactions
3. They can be removed from the bilayer with high pH
iii. Lipid anchored membrane proteins
1. Bound by covelent linkages to one of the surfaces of the membrane to the lipid molecules
2. can be on either side
c. Predicting structure of protein
i. A hydropathy plot identifies cluster of hydrophobic and hydrophilic regions of a protein based on the amino acid sequence. From this plot regions that cross the membrane can be identified
1. The protein must be isolated and purified.
2. The amino acid sequence must be found
a. Glycophorin
i. Function unknown
ii. Abundant in red blood cells
iii. Highly glycosilated
c. Types of transport
simple
ii. Facilitated (DOWN a concentration gradient)
iii. active transport (AGAINST concentration gradient)
simple transport
1. Water, Co2, and O2 can diffuse in and out of the cell based on concentration gradient
ii. Facilitated (DOWN a concentration gradient)transport
1. requires a protein carrier if the molecule is large or charged
2. proteins can be channels or carriers
a. channels are hydrophilic channels that span the membrane
b. porins
c. ion channels
i. highly specific
ii. Na+ , Cl- , K+ , CA++
b. porins
i. cannels in bacteria, chloroplasts and mitochondria
ii. they are large and non specific pores
iii. Aquaporins
1. water channels needed by some cells that need large amounts of water in a short time where simple diffusion is just not enough
2. they are highly specific
3. Integral membrane proteins with six helical transmembrane segments.
4. The functional unit is a tetramer of four identical monomers that appear side by side
5. Nephrogenic diabetes is a lack of AQP 2 which caused dehydration and dilute urine
6. AQP2 increase in pregnant women causes too much water retension and can lead to congenital heart failure
5. Nephrogenic diabetes
a lack of AQP 2 which caused dehydration and dilute urine
6. AQP2 increase in pregnant women
causes too much water retension and can lead to congenital heart failure
c. ion channels
i. highly specific
ii. Na+ , Cl- , K+ , CA++
3. protein carriers
a. An example of a protein carrier is GLUT for Glucose transport into the cell
i. Integral membrane protein
ii. 12 transmembrane domains
1. glucose binds to the binding site of GLUT open to the outside of the cell
2. binding causes a conformational change in GLUT
3. GLUT opens to the inside of the cell and glucose is released
4. GLUT returns to its original conformation
5. Glucose inside the cell is transformed by hexokinase into Glucose 6 phosphate so it cannot easily leave the cell
GLUT
i. Integral membrane protein
ii. 12 transmembrane domains
1. glucose binds to the binding site of GLUT open to the outside of the cell
2. binding causes a conformational change in GLUT
3. GLUT opens to the inside of the cell and glucose is released
4. GLUT returns to its original conformation
5. Glucose inside the cell is transformed by hexokinase into Glucose 6 phosphate so it cannot easily leave the cell
iii. active transport (AGAINST concentration gradient)
1. Requires proteins
2. direct active transport
a. the accumulation of solute molecules or ions on one side of the membrane is coupled directly to an exergonic chemical reaction (usually ATP hydrolysis)
b. incudes transport ATPases or ATPase pumps
c. Na+/K+ pump- Three Sodium ions go down their concentration gradient and two potassium ions against their gradient into the cell
3. secondary active transport
a. depends on the simultaneous transport of two solutes with the movement of one solute DOWN its gradient driving the movement of another molecule UP its gradient.
b. Uses the fact that because the sodium potassium pump there is a low concentration of sodium inside, letting sodium into the cell releases energy that lets things in (ie glucose)
c. Na+/K+ pump
Three Sodium ions go down their concentration gradient and two potassium ions against their gradient into the cell
i. The pump takes up three Na+ from the inside of the cell
ii. ATP phosphorylates the alpha subunit of the protein
iii. A conformational change occurs in which the 3 Na+ are released outside of the cell
iv. The pump is open to the outside and accepts two K+ ions
v. The potassium triggers a dephosphorylation of the protein that triggers a conformational change
vi. 2 K+ are expelled inside the cell
d. inhibitors used to study Na+K+ ATPase
i. oliabain binds and inhibits the pump
ii. this can determine if a certain function is driven by the membrane potential that is set up by the pump
and example of secondary active transport is the NA+glucose symporter
b. Uses the fact that because the sodium potassium pump there is a low concentration of sodium inside, letting sodium into the cell releases energy that lets things in (ie glucose)
i. In the intestines, the epithelial cells that line the intestinal wall have a high concentration of glucose inside relative to the leumen.
ii. They need to get glucose in from leumen into the blood.
iii. The sodium potassium pump has pumped out sodium so it want to get back in
iv. The Na+/glucose symporter protein is open to the outside of the cell and lets two sodium ions bind
v. Binding of sodium ions allows glucose binding and a conformational change
vi. The protein opens to the inside of the cell’
vii. Sodium is let into the cell but is quickly pumped back out by the sodium potassium pump
viii. Glucose enters the cell
ix. Release of glucose causes a conformational change that makes the protein open towards the outside of the cell again
symptons of Cystic fibrosis
coughing, weezing shortness of breath, lung mucous is sticky and unhydrated. Lots of bacterial infections. Salty sweat. Pancreatic enzymes are not transported to the intestine
ii. Genetic defect in CF
1. lack of Cl- transport out of the cell causes a lack of sodium and water transport out of the cell
2. due to ineffective or nonexistent protein called Cystic Fibrosis transmembrane conductance regulator (CFTR)
CFTR
a. CFTR is in the plasma membrane
b. Has 2 transmembrane domains with 6 segments each
c. There are 2 nucleotide binding domains on the cell side for ATP binding
d. There is a regulatory domain on the cell side that regulates the channel opening and can be reversibly phosphorylated
mutants of CFTR
1. most CF patients have a mutation in one of the ATP binding domains
2. others have mutations in the transmembrane domains
3. few in the regulatory domain
4. some do not have a copy of the protein in the plasma membrane at all
a. in the ER the mutant is recognized as misfolded and is degraded by the ER
iv. CFTR function
1. cell receives an extracellular signal
2. a second messenger (cAMP) activates protein kinase A (PKA)
3. PKA adds a Phosphate to the CFTR serine residue in the regulatory domain
4. The regulatory domain undergoes a change that allows ATP to bind to the Nucleotide domain
5. ATP drives Cl- transport
6. Cl- leaving the cell causes salt and water to leave the cell
7. water hydrates mucous etc…
v. Treatments for CF
1. Pulmozyne helps to break down mucous
2. hypertonic saline draws water out of cells and into lungs
3. Antiinfectives are used against pseudomonas
4. enzyme replacement for pancreas
5. Gene therapy in aerosol for lungs
6. antiinflammatories
i. Influenza facts
1. Three types (A,B,C) with type A being the most problematic to people
2. Three known A subtypes: H1N1, H1N2, H3N2
3. virus has a lipid bilayer
4. ss RNA genome template
5. genome is in 8 separate segments
6. three different proteins embedded in the bilayer
a. Hemaglutinin (HA)
b. Neuraminidase (N)
c. Matrix proteins
a. Hemaglutinin (HA)
i. A transmembrane glycoprotein (looks like spikes on an electron micrograph)
ii. Binds to sialic adic residues on host cell surface, allowing the virus to enter cells by receptor-mediated endocytosis
iii. Once in the cell HA mediates fusion between viral lipid bilayer and the host cell membrane
iv. Genome is released, replicated, etc… and the virus is assembled
b. Neuraminidase (N)
i. Catylizes the cleavage of terminal sialic acid residues of glycoproteins on the cell surface so that the virus can exit the cell
ii. Flu Variation
1. antigenic variations in HA and NA occur every year so that immunity lasts for only a year
prevention of flu
1. yearly vaccine
2. Tamiflue
a. Inhibits Neuraminidase
b. Virus can infect and reproduce but cannot leave the host cell
c. Only effective if taken within a day of symptom appearance.