Lecture 11 Flashcards
what do lysosomal enzymes utilize to be sorted and transported at the Trans Golgi Network (TGN) ?
Clathrin-coated vesicles
Where and what are lysosomal proteins tagged with? What occurs when tagged?
Tagged in the Cis-Golgi with phosphorylated mannose
once tagged, they’re recognized / captured by mannose 6-phosphate receptors
what initiate membrane curvature and recruits adaptors?
G-Protein attached to the clathrin coated vesicles
from where do packed secretory granules arise from? When are they released?
When secreted proteins released by regulated secretion form selective aggregates which become secretory granules
They’re released after stimulation by a hormone or nerve impulse
What are the steps that occur between vesicle budding and vesicle fusion?
- movement of vesicle towards target compartment (by microtubules & motor proteins)
- Tethering of vesicles to target compartment (by tethering proteins)
- docking vesicles to target compartment (by interaction of integral proteins)
- Fusion of vesicle and target membrane
What are Rabs and how do they cycle?
Family of small G proteins
cycle between active GTP and inactive GDP states
True of False?
Rabs are associated with one type of membrane compartment.
False, they are associated with many different membrane compartments
What are SNAREs and their function? what are the 2 types and where are they located?
Family of proteins localized to specific compartments
They bring vesicles and target compartments within close contact
v-Snare is found in transport vesicles
t-Snares are found in target compartments
How many T and V snares are located in nerve cells and where can they be found?
How do they interact with each other?
2 t-snares on the plasma membrane
1 v-snare on the synaptic vesicle
Interact to form 4 strand bundles which pulls the lipid bilayers very close together
What is exocytosis and what triggers it?
Discharge of secretory vesicle / granule
triggered by Ca2+ increases
how do fusion pores form?
when vesicle and plasma membranes form together
True or false?
Extracellular vesicles can move through the body unnoticed by the immune system?
True. They can!
True or False?
The hydrolytic enzymes in lysosomes can hydrolyze nearly every macromolecule in the body?
True
Where do Lysosomal enzymes have optimal activity for acid hydrolases?
In the Acidic Lumen
Single-cell organisms and phagocytic White Blood Cells can digest materials by fusing what together?
by fusing phagosomes and lysosomes
What is involved in the process of autophagy?
When lysosomes regulate organelle turnover
How are autolysosomes formed to degrade organelles?
a phagophore envelops an organelle.
This double membraned vesicle created is called an autophagosome
The autophagosome fuses with a lysosome which creates an autolysosome which can now degrade the enclosed materials
What is the benefit to Autophagy?
intracellular protection (abnormal proteins / bacteria)
Cancer prevention
What are the 2 mechanisms to move materials into cells? what is the difference?
Endocytosis - cell - surface receptors and bound extracellular ligands
Phagocytosis - uptake particulate matter
What are the 2 categories of Endocytosis and what do they uptake?
Bulk phases endocytosis: non-specific uptake of ECF
Receptor mediated endocytosis: uptake of specific macromolecules that bind to receptors on membrane
What mediates Receptor mediated endocytosis? What does it result in?
Clathrin. results in coated pits that can pinch off the membrane into the cytoplasm
What does each Clathrin molecule contain? What assembly does it form?
3 heavy chains and 3 light chains. forms a triskelion
what do coated vesicles contain two dozen of and what does it form? what are some of the roles?
2 dozen proteins that form a dynamic network of interacting molecules
Have roles in cargo recruitment, coat assembly and membrane bending
What is Dynamin and what is it required for?
G protein required for fission of the vesicle from the membrane
what are endosomes?
Vesicle bound materials transported in vesicles and tubules
Where are early endosomes located?
Near the edge of the cell membrane
What are low-density lipoproteins made of? what are they for
Complex of cholesterol and proteins
taken up by receptor mediated endocytosis at the membrane for use by the cell
What is the purpose of phagocytosis?
uptake of relatively large particles
What is a phagosome and phagolysosome?
- the vacuole pinched off the membrane
- the product of the phagosome (vacuole) and lysosome fusing together
What are Peroxisomes, what do they contain and involved in?
small membrane enclosed organelles
contain enzymes
involved in metabolic reactions for metabolism
What are the 2 sub compartments of peroxisomes where an imported protein can be placed?
the boundary membrane and internal matrix
What 2 complexes do mitochondria use for importing proteins?
the TOM complex for outer membrane
the TIM complex for inner membrane
▪ Distinguish the functions of the different types of vesicle transport.
▪ Explain the functions of lysosomes.
▪ Explain the processes involved in the bulk transport of materials
into the cell.
▪ Describe how proteins are taken up by mitochondria, chloroplasts,
and peroxisomes.
