exam 3 Flashcards
What does endocytosis take up?
- Macromolecules
- Particulate substances
- In some cases other cells
What does phagocytosis mean, and what does it use?
- cell eating
- use phagosomes > 250nm diameter
What does pinocytosis mean and what does it take up?
- cell drinking
- fluid and solutes with pinocytic vesicles about 100nm diameter
What are two types of endocytosis?
- phagocytosis
* pinocytosis
What do phagosomes ingest?
*larger particles (microbes, dead cells)
What do phagosomes fuse with?
*lysosomes and they are digested
Where are digested products released into?
*cytosol to be used for growth
Where is indigestible material released?
*expelled via exocytosis
What are two professional phagocytes?
*macrophages and neutrophils
Where do MO and neutrophils develop from?
*hemopoetic stem cell
What do MO and neutrophils ingest?
*foreign invaders
What does MO also scavenge for?
*old/dead cells and degrades them
What does phagocytosis require?
*that a particle must bind to the surface of the phagocyte
What process is a triggered process?
*phagocytosis
What process requires the activation of receptors that transmit signals to the cell interior?
*phagocytosis
What process is a constitutive process (happens automatically)?
*pinocytosis
What is always happening regardless of the needs of the cell?
*pinocytosis
What triggers phagocytosis?
- binding of an antibody to an antigen
- Recognition of compliment components
- Recognition of oligosaccharides
- Recognition of apoptosis
What will not phagocytize?
*living animal cells (contain do not eat me signal)
What are living animal cells made of?
*cell surface proteins
What do living animal cells bind to?
- inhibitor receptors on MO and prevents phagocytosis
What do pinocytic vesicles form from?
*coated pits in the plasma membrane
What do all eukaryotic cells continually ingest?
*bits of their plasma membrane in the form of small pinocytic vesicles
What percent of their plasma membrane do MO and fibroblast ingest?
- MO: 25% each hour
* F: 1% per minute
How does cell surface to volume remain unchanged?
*endocytosis and exocytosis are balanced
What is the endocytic- exocytic cycle?
- Same amount of membrane being removed by endocytosis is being added to the cell surface by the converse process of exocytosis
Where is the endocytic-exocytic cycle particularly strict?
*specialized structures characterized by high membrane turnover, such as the neuronal synapse
How does the endocytic part of the cycle begin?
*with clathrin-coated pits
What is the lifetime of clathrin coated pits?
*about 1 minute after formation
What forms after the clathrin coated pit lifetime is over?
*clathrin coated vesicle
What is shed within seconds of being formed, then what does it fuse with?
*their coat, then fuse with early endosomes
What cleaves the clathrin from the plasma membrane?
*dynamin
What do some pinocytic vesicles have if they are not clathrin coated?
*caveolae “little cavities”
What were caveolae originally recognized for?
*Originally recognized for ability to transport molecules across endothelial cells
What are caveolae thought to form from?
*lipid rafts
What is a major structural protein that does not extend across the membrane?
*caveolins
What does caveolins mediate?
*pinocytosis
What is a Family of unusual integral membrane proteins
that Inserts a hydrophobic loop in the membrane from the cytosolic side?
*caveolins