Cell Physiology L4/5: Vesticular Transport Flashcards
What are the 2 functions of vesticular transport?
- Transport unusual or large substances through the membrane for which there isn’t a specific carrier protein
- Store a substance prior to release to the ECF
Materials are transferred between ____ and_____ or between structures within cell in ______, small membranous sacs that form at or fuse with the cell membrane. It also requires energy from _____.
ECF; ICF; vesicles; ATP
What is endocytosis?
Vesticular transport into the cell
What is exocytosis?
Vesticular transport out of the cell
What are the 5 steps of endocytosis?
- Trigger (ligand, presence of object)
- Indentation of the membrane (becomes larger)
- Pouch formed on membrane
- Neck of pouch sealed off
- Vesicle detached from membrane
What are the 2 types of vesticular transport?
- Endocytosis
- Exocytosis
What is receptor-mediated endocytosis?
Uptake of specific substances bound to membrane surface receptors
What is pinocytosis in endocytosis?
“cell drinking”
- Uptake of extracellular fluid
What is phagocytosis in endocytosis?
“cell eating”
- Uptake of solid objects such as bacteria, cell debris, etc.
What are the 3 types of endocytosis?
- Receptor-mediated endocytosis
- Pinocytosis - “cell drinking”
- Phagocytosis - “cell eating”
How does transport via vesicles occur in receptor-mediated endocytosis?
Collection of specific molecules
How does transport via vesicles occur in pinocytosis?
- Cell drinking”- vesicle forms filled with ECF
- Similar process to receptor-mediated
- endocytosis but not as selective
- not initiated by ligand binding
- Target seems to be general ECF contents
- Performed by most cells
How does transport via vesicles occur in phagocytosis?
- Engulfs solid objects - may be as large as the cell itself
- Performed by specialised cells eg. macrophages (WBC)
- Vesicle (called phagosome)
- Fuses with lysosome
- Lysosomal enzymes digest contents
- Remains may be exocytosed
Transport via vesicles in pinocytosis has a similar process to ________.
Receptor-mediated
Transport via vesicles in pinocytosis is endocytosis but ___(more/less) selective and not initiated by ______ binding.
less; ligand
Transport via vesicles in pinocytosis is performed by ____ cells.
Most
Transport via vesicles in phagocytosis engulfs ______ objects. _____ (may/may not) be as large as the cell itself.
May
Transport via vesicles in phagocytosis has a vesicle called ______.
phagosome
Transport via vesicles in phagocytosis are performed by ________ cells. Give an example.
specialised; macrophages (WBC)
Transport via vesicles in phagocytosis are fused with _____.
Lysosome
Transport via vesicles in phagocytosis have ______ enzymes which digest content.
Lysosomal
Transport via vesicles in phagocytosis remain to be ______.
Exocytosed
Exocytosis is the functional reverse of ______.
Endocytosis
In exocytosis, vesicles are created in ___________ or ______ within cell cytoplasm
Endoplasmic Reticulum (ER); Golgi apparatus
What are the 4 forms of vesicles (which some are related to exocytosis)?
- Transfer vesicles
- transfer enzymes between ER and Golgi apparatus and between saccules of Golgi apparatus
- Lysosomes
- contain intracellular enzymes
- Secretory vesicles
- allows cell to secrete products such as hormones
- Membrane renewal vesicles
- contain new/recycled membrane components
- e.g. phospholipids, carrier proteins, receptors
Transfer vesicles, lysosomes, membrane renewal vesicles and secretory vesicles
What 2 structures produce transfer vesicles?
- Endoplasmic reticulum
- Golgi apparatus
What is the main function of the endoplasmic reticulum (ER)? What are 3 other functions?
Produces transfer vesicles
- Synthesises and stores proteins, carbohydrates and lipids
- Detoxifies drugs or toxins
- Transfers products to the golgi bodies (via transfer vesicles) for further processing
What is the endoplasmic reticulum (ER)?
Network of intracellular fluid-filled tubules and flattened sacs
What is the main function of the golgi apparatus? What are 4 other functions?
Produces lysosomes, membrane renewal vesicles, secretory vesicles and transfer vesicles = all forms of vesicles
- Processes material from ER into final form
- Synthesises & packages enzymes for use within the cell
- Synthesises & packages secretions, such as hormones etc, for release through exocytosis
- Produces new membrane and membrane structures
What is the golgi apparatus?
Sets of stacked, flattened membraneous discs called “saccules”
What is the lysosome?
Produced by the Golgi apparatus, contain digestive enzymes.
- Eg. phagocytosis
What are the 2 functions of lysosome?
- Bind to vesicles to form secondary lysosomes.
- Digest or modify the contents of other vesicles, which may be released into to cytosol or be exocytosed
What are the 2 functions of membrane renewal vesicle?
- Add new lipids and proteins to cell membrane
- Allows cell to change number and types of carrier proteins or receptors in cell membrane thus changing sensitivity of cell
What are the 3 functions of the secretory vesicles?
- Produced by Golgi apparatus of cells specialised for secretion of hormones or enzymes
- Vesicles bud off from the Golgi apparatus and then fuse with cell surface membrane to release products to ECF
- Secretory vesicles may release products constitutively (unregulated) or may remain in the cell until release is triggered (regulated) o Storage- until needed (needs trigger)
Secretory vesicles can either be ______ or _______.
Constitutive; regulated
What is a constitutive secretory vesicle?
continuous, unregulated output of material
What is a regulated secretory vesicle?
- e.g. neurons, exocytosis regulated at a synapse:
- Action potential opens voltage-gated Ca++ channels, Ca++ triggers the exocytosis of neurotransmitter
What is the function of endocytosis and exocytosis?
maintain its size and membrane surface area –> balance between the intake of cell membrane during endocytosis and the incorporation of membrane during exocytosis
What are the 3 mechanisms of transport across membranes?
- Diffusion (including osmosis)
- Carrier-mediated transport
- Vesicular transport
What is the B-cell of the pancreas?
