Cell III Flashcards
What are the five distinct pathways for endocytosis?
- Macropinocytosis
- Clathrin-mediated endocytosis
- non-coated mediated endocytosis
- Caveolae-mediate endocytosis
- Phagocystosis
Where does macropinocytosis occur?
in thyroid cells as they take up thyroglobulin
dendritic cells of the immune system
What is the molecular structure necessary for macropinocytosis?
Actin
How specific is macropinocytosis?
Not very
Where does clathrin-mediated endocytosis occur?
At clathrin coated pits
What is the enzyme that is involved in clathrin-mediated endocytosis?
Dynamin (a GTPase) required to pinch off vesicle
What are the two specific molecules that used the clatharin-mediated endocytosis?
cholesterol of the LDL
Protein hormones
Cargo receptors are used in clatharin mediated endocytosis. What is the protein that is necessary for this to happen?
Adaptin (on the intracellular side)
What happens to the clathrin coated pits once they are taken up by the cell?
become uncoated
Recycling of synaptic vesicles is mediated through what process?
Clathrin coated pits
How does salmonelle gain entry into cells?
Through macropinocytosis
How do cholera and shiga toxins gain entry into the cell?
through non-coated vesicles
How does the simian virus 40 gain entry into the cell?
Caveolae mediated endocytosis
True or false: you need to have receptors in clatharin mediated endocytosis?
False- can have them, but not needed
What is neovascular development?
Development of new blood vessels-takes place in atherosclerosis
True or false: caveolin-mediated transport is bidirectional?
True
What is phagocytosis?
Cell eating–ingestion of large particles
What is the molecular structure that phagocytosis is dependent on?
Actin
What are phagosomes?
The foreign material surrounded by a membrane in a cell after being phagocytized
What happens to the phagosome?
Attached to a lysosome for degradation
True or false: phagocytosis is usually mediated by receptors
True
True or false: phagocytosis can only be utilized for biological material
False
What is exocytosis?
bulk secretion
What are the three types of cellular excretion?
Exocytosis
Porocytosis
Exosomes
What is secreted through exocytosis (3)?
- Proteins and enzymes
- Hormones
- neurotransmitters
What are the two pathways of exocytosis?
Constitutive
Regulated
What is the constitutive pathway of exocytosis?
a continuous excretory process that is not stored in granules
What is the regulated pathway of exocytosis?
Where secretory products are stored in secretory vesicles until a signal is received
What does exocytosis require to be function?
Ca and ATP
What is porocytosis?
Quantal secretion of substances (like neurotransmitters)
Through what pathway are antibodies secreted from B-cells?
Constitutive exocytosis
What are exosomes?
Secretory products released into the ECM WITH a membrane
What are the functions of exosomes?
To discard unneeded membrane proteins
CA may release exosomes and be a marker
What are reticulocytes? How do they release their tranferrin receptor into the blood?
Immature RBCs.
Released via exosomes.
What is transferrin used for?
transfer of heme groups to immature RBCs
What are ribosomes basophilic?
Negative PO3 groups
what is the size of ribosomes?
20x30 nm
Where is rRNA synthesized?
Nuceloi
What are the two subunits for nuclear ribosomes?
40s and 60s form the 80s
Where does protein synthesis take place?
cytoplasm
How do ribosomes get rRNA?
Transported into, then out of nucleus
Ribosomes appears as what two types?
Individual granulse (subunits)
Polyribosome (mRNA +ribosome)
True or false: mature RBCs have ribosomes
false
Polyribosomes are found where?
Free in cytosol or bound to rER
What types of protein are synthesized in the cytsol
ones used for use inside the cell:
- Hb in RBC formation
- Mt proteins
- proteins in peroxisome
What is the destiny of proteins synthezied at the rER?
Secreted
Is rER acidophilic or basophiliic?
Basophilic (has ribosomes)
What are is the intercellular network found within the ER called?
Cisternae
The ER is continuous with what other organelle?
The nucleus
what protein is needed to bring ribosomes to the translocon of the rER, in order for the protein to be secreted into the rER?
SRP
what do SRPs bind to?
signals on the newly synthesized protein
What is needed for the translocon to become usable?
un-corking
What removes the signal part of the newly synthesized protein once in the rER?
Signal peptidase
Post-translational translocation of proteins involve what?
chaperones
What is the function of translocating protein synthesis to the rER?
synthesis of:
- proteins for secretion
- enzymes in the rER
- modification of proteins
What does every cell that is heavily involved in protein synthesis have?
A well developed rER
What are the functions of the rER?
synthesis of proteins for secretion/insertion into membranes or for lysosomal proteins
Synthesize sER enzymes
Protein modification
What are the four options for cells in the unfolded response?
- increase chaperones
- Decreased protein synthesis
- export misfolded proteins to cytosol for degradation (ubiquitination/proteosomes)
- activate apoptosis
What happens to the rER in alpha-1-antitrypsin deficiency?
mutant proteins aggregate in the rER
What are the “targeting signals” of proteins?
AA sequence that targets the protein for translocation to a particular organelle
How do targeting signals of proteins work?
direct proteins to their target compartments by binding to receptors that are specific for the organelles. Escort factors may deliver the protein to the target organelle.
What does glycosylation do for the cell (2)?
Adds signal sequence
Helps in folding
What are the functions of the sER? (6)
- steroid syn
- cholesterol homeostasis
- syn phospholipids
- glycogen metabolism
- detox drugs
- storage, release, and uptake of Ca
How do the cisternae appear in the sER?
tubular
What is von-gierke disease?
defect in glucose-6-phosphatase causing accumulation of glycogen
What happens to the sER in EtOH tolerance?
increases to increase the p450 enzymes
the sER is used in phospholipid synthesis, but it is only on the outside of the membrane. what is needed to get it on the inside?
flipases
true or false: phospholipids synthesize in the sER go to other organelles by simple excretion
False– there is an exchange mechanism for this
What is malignant hyperthermia?
Affected individuals possess mutant ryanodine-1 receptors that allow excessive movement of Ca2+ from the SR into the cytoplasm in response to the anesthetic agent (e.g., halothane, succinylcholine). Heat is generated, causing hyperthermia, when the SR-Ca2+ pump consumes large quantities of ATP as a means to ramp up its reuptake of Ca2+.
Is macropinocytosis energy dependent? What molecules are needed to produce the movement?
Yes, need actin to move the membrane
How does the organism Salmonella typimurium gain entry into the cell?
Through macropinocytosis
What are the two toxins discussed that can enter the cell through nonclatharin/noncaveolar transport?
Cholera and Shiga toxins
What are the steps for clathrin endocytosis?
- External signals/proteins bind to a receptor on the plasma membrane,
- Clathrin binds on the cytosolic surface of the newly formed pit, until new vesicle is formed.
- Clatharin uncoats the vesicle and is recycled, while the vesicle goes on to fuse.
Is clatharin endocytosis energy dependent? What molecules are needed (2)?
yes, GTP is used, as well as a dynamin protein to pinch off vesicle
What are the proteins that pinches off the newly formed vesicles n the clatharin dependent transport?
Dynamin -GTPase
adaptin
LDL endocytosis is mediated through which endocytotic pathway?
clatharin
Famililal hypercholestremia is the result of what?
Change in the LDL receptor on the clatharin side
What is neovasculaziation? When does it occur?
Formation of new blood vessels–occurs in artherosclerosis
How does clatharin mediated endocytosis work in neurotransmitter reuptake?
takes a part of the plasma membrane with pumps in it, and forms an empty vesicle. The pumps will take in Ca.
How does Caveolin-mediated endocytosis appear on EM?
Many small vesicles take in outside substance
How does asbestos appear when it is phagocytozed by macro-phages?
Sperm
Where does the synthesis of sER enzymes take place?
rER
Where does protein modification take place (besides the Golgi)?
rER
Where does the synthesis of proteins that are destined for secretion take place?
rER
What amino acid is used to serve as an attachment point on proteins for N-linked carbs?
Asparagine (N)
What is the protein that signals degradation of a protein through the proteosome pathway?
Ubiquitin
Where does steroid synthesis take place?
sER
Where does cholesterol homestasis take place in the cell?
sER
Where does the synthesis of phospholipids take place in the cell?
sER
Where does glycogen metabolism take place in the cell?
sER
Where does the detoxification of drugs take place in the cell?
sER
Where is Ca stored in the cell?
sER
What is von Gierke’s disease?
An accumulation of glycogen in cells d/t an issue with either:
- G6P transporter into the sER
- glucose-6-phosphatase
What is the cause of malignant hyperthermia?
A defective ryanodine Ca transporter that is sensitive to succinyl choline and halothane
