Cell biology III Flashcards
What are the three secretory pathways?
1) Exocytosis (bulk secretion)2) Porocytosis (quantal secretion)3) Exosomes and exosome-like vesicles
Exocytosis secretes what types of products?
1) Proteins and enzymes2) Hormones3) Neurotransmitters
In exocytosis, where are the secretory vesicles formed?
Golgi complex
In exocytosis, what do the secretory vesicles fuse with?
Plasma membrane
In exocytosis, what molecules are responsible for the intracellular trafficking of vesicles?
COPs (COat Proteins)
What are the two pathways specific to exocytosis?
1) Constitutive - continuous secretory process - no storage involved2) Regulated - secretory product is stored in secretory vesicles until a signal causes secretion
What is the definition of constitutive exocytosis?
Continuous secretion - no storage involved
What is the definition of regulated exocytosis?
Secretory product is stored in secretory vesicles until a signal causes secretion
What molecules are required for exocytosis?
Calcium and ATP
Calcium and ATP are required for what secretory pathway?
Exocytosis
What is porocytosis?
Quantal release of neurotransmitters
Quantal release of neurotransmitters is characteristic of what secretory pathway?
Porocytosis
What three characteristics define exosomes and exosome-like vesicles?
1) Secretory products are membrane-bound when released into the ECM 2) Discard of unneeded membrane proteins (e.g. TfR)3) May represent biomarker (e.g. for tumor cells)
Where are ribosomes synthesized?
Nucleolus
Where are the proteins in ribosomes synthesized?
Cytoplasm
What are two ways ribosomes are present in the cytoplasm?
1) Individual granules (subunits)2) Polyribosomes (mRNA + ribosomes)
What are two characteristics of polyribosomes?
1) Free in the cytoplasm2) Bound to the ER to form rER
Are ribosomes found in mature erythrocytes?
No
Are polyribosomes found in immature erythrocytes?
Yes
What role do polyribosomes have in immature erythrocytes?
Hemoglobin synthesis