Lecture 4 Flashcards
(27 cards)
what kind of secretion is exocytosis and what exactly does it secrete? what does exocytosis require?
bulk secretion, secretes hormones, neurotransmitters, proteins and enzymes
requires calcium and ATP
what type of vesicles are used in exocytosis and how do they exit the cell?
secretory vessicles formed by the Golgi
they exit by fusing with the plasma membran and are trafficked by COPs (coAT proteins)
what are the two pathways of exocytosis? Describe.
pathways: 1) constitutive- continuous exocytosis with no storing
2) regulated- store secretory vesicles in cytoplasm until they get a signal
porocytosis
quantal release of neurotransmitters
exosomes
example:
- are secreated by the cell into the extracellular space and carry with them unneeded membrane proteins
- some tumors release exosomes so they are used as a biomarker
ex: transferin protein brings iron into the precursur RBCs to make Hgb and once that is done, the cell needs to get rid of it and does so via exosomes
Proteins are made by:
ribosomes (no membrane) and rough endoplasmic reticulum
what’s the net charge of ribosomes? why? what is the dye used for ribosomes?
positive, so basophilic- due to phosphate groups on their surface, electron dense, likes hemotoxylin- dyes ribosomes blue
How many subunits do mitochondria have? what are they called?
2, 60S and 40S
s- sedimentation coefficient
how many types of rRNA exist? where are they synthesized
4, in the nucleoli
How are ribosomes synthesized?
subunits are synthesized and assembled in the nucleolus and then transferred out into the cytoplasm where they complex with rRNA and make up the ribosome- ONLY WHEN SYNTHESIZING PROTEINS
How does protein synthesis happen?
1) mRNA leaves the nucleus and goes into the cytoplasm
2) binds either:
A) Free polyribosomes to form proteins that are used IN the cell
or
B) bind rough endoplasmic reticulum with ribosomes on it and make proteins that are usually shipped outta the cell
are ribosomes found in mature erythrocytes?
NO
What are the proteins synthesized by FREE polyribosomes used for?
stuff inside the cell
- hgb in immature erythrocytes
- mitochondrial proteins
- proteins in peroxisomes
whats the difference between translocation and translation?
Translation is the making of the protein and translocation is the moving of that protein into different cellular structures
How does translation and translocation work with free polyribosomes?
Free polyribosomes get the mRNA and translate the protein free in the cytoplasm and translocate the protein into other organelles is need be via chaperone proteins and translocons (comprises the pore)
How does translation and translocation work in rER?
1) mRNA reach the ribosome and is translated with a signal recognition sequence
2) A signal recognition particle binds that sequence and causes the complex to transloacted over to the lumen of the rER
3) the signal particle bind the signal recognition receptor on the rER
4) both the particle and the receptor go away and the pore is with translocons, is opened
5) the new protein enters and loses the recognition sequence once has enough protein to be released into the rER
what are the proteins from the rER used for?
1) secretion
2) Membrane
3) lysosomes
4) synthesis of enzymes used in sER
5) modification of proteins- folding with carbs
what is done to change the protein post translation?
sugar carb moieties are added that help it to FOLD
-done in rER and moves on to Golgi
what happens when proteins can’t fold correctly?
-protein accumulates in ER =ER stress!
Can cause 1 of 4 things can happen:
1) increases synthesis of chaperone proteins to repair protein
2) you decrease translation of proteins
3) you can tx out of the ER into the cytoplasm and degrade via proteosome
4) worst case: apoptosis
what’s an example of a mutant protein that can’t fold correctly and aggregates in ER?
alpha antitrypsin deficiency
Targeting signals
sequences of a.a. that direct the protein to a specific organelle by binding to its receptor
Escort factors
the matchmakers! deliver target signals and their proteins to the specific organelle they belong with
what’s the soft ER used for?
1) glycogenolysis
2) steroid synthesis (testosterone/estrogen)
3) Cholesterol homeostasis
4) Phospholipid synthesis
5) detox of drugs/alcohol
6) storage, release and uptake of ca in striated muscle
von gierke disease
- defect in glucose-6-phosphatase that cleaves glycogen or glucose-6-phosphate transporter that gets glycogen into the sER
- results in glycogen accumulation in cytoplasm/nucleus
- liver enlargement, hypoglycemia, increased lactate
