CB 3 Flashcards
Endocytosis
5 pathways
- macropinocytosis
- clathrin mediated endocytosis
- non coated mediated endocytosis
- caveolae mediated endocytosis
- phagocytosis
macropinocytosis
occurs in thyroid cells as they take up thyroglobulin and dendritic cells
- actin based process
- nonspecific ingestion of fluids and solutes
- triggered by bacteria
clathrin mediated endocytosis
occurs at clathrin coated pits, dynamin is required to pinch of the vesicle, can be mediated by receptors or not
cholesterol
taken up by clathrin mediated endocytosis in the form of LDL
coated pits
clathrin mediated endocytosis
- cargo receptors located here
- adaptin associates
- coated vesicles form and become quickly uncoated after formation
atherosclerosis
occurs when there is a decrease or defect in the LDL receptor
(clathrin mediated endocytosis)
non coated mediated exocytosis
Shiga and Cholera toxins
phagocytosis
- cell eating, ingestion of large particles via receptors
- dependent on actin
- doesn’t need clathrin
- phagosomes
- fuse with lysosomes
Secretion
- exocytosis
- porocytosis
- exosomes
- exsosome like vesicles
exocytosis
bulk secretion
sectretion of cellular synthetic products like proteins, enzymes, hormones, and neurotransmitters
secretory vesicles
perform in exocytosis
formed by the golgi, fuse with plasma membrane
in charge of intracellular trafficking
2 pathways of exocytosis
constitutive
regulated
constitutive exocytosis
continous secretory processes, secretory product is not stored in secretory granules
regulative exocytosis
secretory product is stored in secretory vesicles until a signal causes the product to be secreted
porocytosis
involved with secretion
release of neurotransmitters
exosomes & vesicles
- secretory products are released into the extracellular environment
- discard unneeded membrane proteins
- some tumors release exosomes and may represent a biomarker
ribosomes
basophillic
involved in protein synthesis
occur as: indv granules, polyribosomes that can be free or attached
NOT found in mature erythrocytes
free polyribosomes
polysomes
mRNA + ribosomes
protein synthesis for use in the cell
hemoglobin, mitochondrial proteins, peroxisomal proteins
rough ER
membranous, basophillic
intracellular network of cisternae
continuous with outer membrane of nuclear envelope that is studded with ribosomes
polyribosomes involved with Co translational translocation
attached to rER, translocation of growing polypeptide chains
- signal recognition polypeptide
- signal recognition particle and SRP receptor
- protein translocator
- *post translational translocation requires chaperone proteins
Post Translational Functions
- synthesis of proteins for secretion, membrane proteins, and lysosomal proteins
- synthesis of enzymes assosciated with sER
- modification of proteins like adding carbs to make glycoproteins
ER stress
accumulation of unfolded misfolded proteins in the ER cisterna
Unfolded protein response
1- chaperone protein synthesis increases
2-decreased synthesis of proteins
3- misfolded proteins are exported from ER to cytosol and then get degraded by proteasomes
4- caspases are activated which leads to apoptosis
alpha antitrypsin deficiency
AAT- mutant protein aggregates in ER
Targeting signals
- sequences of amino acids in the protein
- direct proteins to their target compartments by binding to receptors that are specific to organelles
smooth ER
lacks polyribosomes, acidophillic, continuous with rER, cisternae are more tubular
functions of smooth ER
- cholesterol homeostasis via HMG coa reductase
- steroid synthesis
- phospholipid synthesis
- glycogenolysis
von gierke disease
defect of glucose 6 phosphatase or glucose 6 transporter
symptoms: liver enlargement, hypoglycemia, increased lactate
ethanol ingestion
increases the sER volume and cytochrome p450 enzymes which leads to a greater rate of its detoxification
syntheis of phospholipids
occurs on cytosolic lipid monolayer
phospholipid translocators catalyze the flip flop of phospholipids from one monolayer to the other
malignant hyperthermia
causes a rapid rise in body temp and muscle rigidity, mutant ryanodine 1 receptor, excessive movement of Ca from SR into the cytoplasm, SR-Ca pump
***FUNCTIONS OF RER
- synthesis of proteins for secretion, insertion into membranes, and lysosomal proteins
- synthesis of sER enzymes
- protein modification
- cells actively involved with protein synthesized are well endowed with rER
*****SMOOTH ER functions
- steroid synthesis
- cholesterol homeostasis
- synthesis of phospholipids
- detox of drugs
- storage, release, uptake calcium ions in striated muscle
