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What does it do?
What makes its endocytosis different from the other two?
What makes its endocytosis similar?
- stimulates cell division (especially epidermal)
- receptors aren't recycled
- same pit forms
In EGF, explain the receptors?
only aggregate in clathrin pits after they bind, whereas transferrin can aggregate before H binds iron
There are two fates for receptors in EGF.
- recycled back (which is rare)
- broken down= reduce the number of receptors on the surface
- response to EGF (receptor decreases regulation)
Why is degradation of the receptors in EGF good?
How does the ligand terminate the signal?
- energy efficient
- stops uncontrolled growth
- by being taken in by the cell
Speaking in terms of the clathrin coat formation, what other proteins are involved with dynamin?
synaptogenin which dephosphorylates PIP2 (which facilitates binding of assembly proteins)
What gets rid of the clathrin coat?
probably recepto rproteins in membrane of vesicle that react with receptor proteins in the membrane of the endosome
Cell-cell adhesion and recognition
-depends on the __
- explain what it can be?
- in what type of organisms is adhesion in?
- how many?
- depends on the molecule
- cell to cell or cell to matrix
- -animal membranes (adhesion)
- several different types depending on the kind or type of molecule
Two basic ways of adhesion
junctions (tight, gap, etc.) and desmosomes
What do adhesion and recognition allow?
- allows cells to recognize each other
- holds cell together to give chance to form intercellular junctions (interaction)
Explain recognition in embryo
when isolated retina and liver cells were mixed together, they regrouped into their liver group and retina group
How do cell-cell adhesion molecules (CAMs) interact?
- homophilic: alike
- heterophilic: different from each other
- linker molecule (located in the cytoplasm)= rare
Cell-cell adhesion molecules are divided into two groups. What are they?
calcium dependent and calcium independent
Why would CAMs need calcium?
- respiration for tissues
- specific cell-cell binding
- creating cell-cell junctions
- how many?
- allows what?
- how many in membrane?
- prominent in __
- more than one type (over 30 that we know of; separate gene for each)
- allows similar cells to recognize each other
- virtually all membranes have more than one type
- main adhering molecule in embryo and adult tissues
- if mutation: deformation or embryo can fall apart
How many cadherins can you have?
Another fx of cadherins?
- more than one type but that can change as the embryo develops
- can send signals from ECM to cell cytoplasm (influence)= 2 types
Basic structure of cadherins
- -all glycoproteins
- - 700-750 amino acids (not large)
- - most of protein outside of cell; small cytoplasmic part
- - large part folded into domains (usually five)
- ----> three of these domains bind Ca2+, whcih will form bridges
Cadherins can be available in __ and __.
Has a very __.
- it is almost like a zipper, the way they overlap. The more overlap, what?
- what kind of binding?
- pairs and overlap
- small cytoplasmic portion
- stronger the adhesion
What is the main recognition molecule?
What is the deal with the term CAM
it is a general name for cell-cell adhesion molecules, but it also relates to a specific group
The CAMs (specific group) are __.
They belong to a family of proteins called __.
- calcium independent
- immunoglobulin superfamily
How are Ig superfamily of CAMs named?
- similarly to others
- n-CAMs: nervous system
- V-CAMs: vascular
__ have been studied the best.
- how many?
- from how many genes?
- at least several different types
- all from one gene by recombination and splicing
What kind of binding do Igs do?
- if interacting with another CAM, it tends to be homophilic
- if another molecule= heterophilic
Summary: What are Igs?
superfamily of CAMs
When using the term CAM in a broader sense, what are they?
- Ig-superfamily of CAMs
Cells bind to the __.
Some cells are really close, while others are far apart and have __.
Where is the material from?
- tight junctions (most membranes fuse together)
- extensive ECMs
- from the cells themselves
Main fx of integrins?
- connect animal cells to the ECM
- - a bit in C-C adhesion
How many types? FOund where? Bind to what?
What's so good about low affinity?
- more than one
- in virtually all animal cells
- proteins with relatively low affinity depending on prtotein
- present in high concentrations
- allows cell mobility
- tend to what?
- how many types?
- interactive where?
- calcium dependent or independent?
- form more transient cell-cell adhesion (not permanent at all)
- - E-selectins: endothelium
- - P-selectins: platelets
- - L-selectins: leukocytes
- in bloodstream
Example of selectin activity.
- in response to inflammation, some WBC leave BS and BV and go to lymph nodes or site of inflammation
- Function of selectins is to slow down WBC so they can leave a BV
What does selectin cause?
only causes slowing down
How is selectin stored in cells?
Explain its response to some inflammatory signal?
- in vesicles
- through exocytosis, it will secrete whatever is in it, which will bring selectin onto the surface
For any leukocyte and selectin bonding, what will selectin do?
it will slow it down
Selectiiin gets __ from one to another>As leukocytes slows down and binds to selectin, it will bind to __, which will activate __.
- platelet-activating factor (PAF) receptor
In response to some inflammatory response, this vesicle will fuse with the p. membrane, bringing __ into the membrane at the same time that __ gets __.
__ and __ are added to teh membrane at the same time.
Once on the surface of the membrane of the endothelial cells, what can happen?
the selectin can bind the leukocytes
Selectins are __.