Week 2 Review Flashcards
What function do cadherins serve? What about integrins? Selectins?
Cadherens are proteins involved in cell-cell junctions.
Integrins are involved in cell-matrix junctions.
Selectins are involved in temporary cell-cell junctions.
By what mechanism does pemphigus mess up the skin?
Antibodies destroy desmoglein (a cadherin - cell-cell adhesion molecule) that binds intermediate filaments in desmosomes and hemidesmosomes –> blistering.
Name and briefly describe the steps involved in specimen slide preparation.
- Accessioning (receiving, sorting, etc.)
- Fixation using formalin preserves the tissue
- Processing dehydrates the specimen; uses alcohol and subsequent removal of solvent
- Embedding with paraffin wax or epoxy resin
- Sectioning (cutting with a microtome)
- Staining
Is hematoxylin basic, or acidic? What charge does it carry? What does it bind to? What color is it? What about eosin?
Hematoxylin is a basic dye and has a (+) charge because it has picked up a proton. It stains negatively charged stuff like nucleic acids blue.
Eosin is an acidic dye and has a (-) charge because it has lost a proton. It stains positively charged stuff like cytoplasmic proteins pink/red.
How does trichrome stain connective tissue? Is that a distinguishing characteristic of the dye?
It stains connective tissue blue. Yeah its characteristic.
What is one class of molecules that are stained particularly well with PAS stain?
Carbohydrates/mucus
Do fluorescent stains use antibodies with dye attached as markers?
Yeah
Describe the differences of euchromatin, heterochromatin, and the nucleolus regarding histologic staining.
Euchromatin stains light
Heterochromatin is dark
Nucleolus is a dark round spot
Name two cellular organelles in which enzymes for protein glycosylation are found.
In the RER and the Golgi
Name five things that happen to a newly synthesized protein in the RER.
- Proteolysis of the signal peptide
- Protein folding
- Disulfide bonding
- Glycosylation
- Double-checking (quality control)
COPII secretory vesicles are used for transport from the _______ to the _______.
COP II: from RER to Golgi
Proinsulin is cleaved to insulin in the…?
secretory vesicle
What is the little thing called that recognizes N-terminal hydrophobic sequences on proteins undergoing translation and brings the ribosome/polysome over to the RER for docking? What is the thing that it all docks to?
The signal recognition particle (SRP) recognizes the N-terminal hydrophobic sequence.
It all docks on a translocon in the RER membrane.
What is a COPI vesicle?
A vesicle that is sent back from the Golgi to the RER that helps maintain the size of the Golgi.
Nascent ER membrane proteins are recognized by SRPs and docked to translocons on the RER in a similar manner to secreted proteins. What is the big difference with ER membrane proteins in the translation process?
As the nascent chain is fed through the translocon, a stop transfer sequence is encountered (a hydrophobic transmembrane sequence) and the translocon opens up to allow the protein to slide laterally into the membrane.
What happens when there is an accumulation of misfolded proteins in the ER?
The ER stress response happens:
- Increased chaperone synthesis and activity
- Reduction of protein translation
- Increased ub-proteasome activity
- Apoptosis if it gets bad
Outline the steps in carrier vesicle formation and fusion with the plasma membrane.
- Coat complexes help form vesicle
- Scissioning (budding)
- Rab proteins on vesicle bind to tethering factors on the inner PM to bring the vesicle close to the PM
- v-SNARE (on vesicle) and t-SNARE (on PM) bind to form a Trans-SNARE complex.
- Trans-SNARE complex zippers together to form a cis-SNARE complex
The terminal compartment of the endocytic system is the _______.
lysosome
Clathrin coated vesicles are used for _________ at the plasma membrane as well as for secretory vesicle formation at the _______ (sometimes). They use inner adapter proteins to grab hold of _______.
Clathrin coated vesicles are used for endocytosis
also used for some vesicle formation at the Golgi
inner adapter proteins grab hold of cargo
Explain the mechanism of action of tetanospasmin (tetanus neurotoxin).
Tetanospasmin causes spastic paralysis by cleaving t-SNAREs on inhibitory interneurons that regulate the activity of motor neurons. No regulation of motor neurons = uncontrolled release of Ach at the neuromuscular junction –> spastic paralysis.
Explain the mechanism of action of botulism toxin.
Botulism toxin cleaves t-SNAREs on the excitatory motor neuron that releases Ach. No Ach release = no muscle contraction (flaccid paralysis)
F-actin assembly is coupled to the hydrolysis of _____. F-actin’s monomers are globular proteins called _____ that assemble into spiraling rows. The “plus” end is the end that grows _______.
F-actin assembly is coupled to hydrolysis of ATP during assembly.
G-actin is the monomer
Plus end grows faster
Microtubule assembly is coupled to the hydrolysis of _____, which binds to ______. Microtubules are made from ______ and _______ _______ that assemble into tubes called ________. The “plus” end is the end that grows _______.
Microtubule assembly is coupled to GTP hydrolysis, which binds to B-tubulin.
Microtubules are made from a- and B-tubulin heterodimers that assemble into tubes called protofilaments
Plus end grows faster
What is one big consequence of not having polarity on intermediate filaments?
They can’t be used as tracks for molecular motors.
Keratin is an example of a(n)…?
Intermediate filament
What type of cytoskeletal protein is responsible for spindle formation during mitosis?
Microtubules
Adherens junctions can encircle the cell like a belt. They attach to ______ cytoskeletal proteins inside cells.
actin
Tight junctions stop ________ transport and attach to _______ cytoskeletal proteins inside cells.
Tight junctions stop paracellular transport (between cells) and attach to actin cytoskeletal proteins.
Desmosomes and hemidesmosomes attach to which class of cytoskeletal proteins inside cells?
intermediate filaments
What type of cytoskeletal proteins are involved in gap junctions?
Trick question! They don’t use cytoskeletal proteins. Connexins are the proteins used.
Pemphigus is an autoimmune disease that attacks desmoglein, a _________ protein involved in what type of cell-cell junction complex?
Desmoglein is a cadherin involved in desmosomes.
Kinesins move towards the ____ end of which which type of cytoskeletal protein? What is the fancy word for movement in the direction away from the microtubule organizing center?
Kinesin moves towards the (+) end of microtubules. Called anterograde movement.
Dyneins usually move towards the _____ end of which type of cytoskeletal protein? What is the fancy word for movement in the direction towards from the microtubule organizing center?
Dynein moves towards the (-) end of microtubules. Called retrograde movement.
The mechanical work of molecular motor proteins are usually coupled with…?
ATP hydrolysis
Define processivity in regards to molecular motors.
The motor’s ability to perform many chemo-mechanical cycles without disconnecting from the track.
A 25 year-old presents to your office for infertility. On physical exam you palpate his liver on his left side instead of his right. What is likely causing his infertility? How?
Primary ciliary dyskinesia/Kartagener’s - lack of dynein motors in cells so sperm cannot beat flagellum (a ciliary structure) for motility. Patients also have situs inversus.
During microtubule assembly, heterodimers bound to GTP form a _____ _____. When heterodimers within the growing microtubule hydrolyze GTP –> GDP, the microtubule becomes less _______. Catastrophe occurs when the ______ ______ is lost.
GTP-bound heterodimers on the growing end of the MT form a GTP cap.
GTP hydrolysis makes the MT less stable.
Catastrophe happens when the GTP cap is lost.