Chapter 11: Cell-Cell Interactions Flashcards
What can quorum sensing lead to?
Large populations of unicellular organisms working together to form one thing like a multicellular organism. Like biofilms and slime molds
How does signaling occur in unicellular organisms?
The process of reception and signal transduction very similar between unicellular and multicellular organisms. The unicellular organisms sort of act as one multicellular organism
Adrenaline (epinephrine) signaling molecule example
Binds to cells with receptors for it. Cells respond differently depending on what proteins are present. Inhibit digestion, excite heart rate, etc.
What is quorum sensing?
Unicellular organisms way of giving cells an idea of what’s around them. Their response to population density
What does a nuclear response do?
Protein synthesis
Overview of transaction in cell signaling
The signal is converted into a form that can cause some type of cellular response (relay it inside)
What are protein kinases? What do they do?
In phosphorylation. They are critical proteins that add phosphate groups to turn on
What do plasmodesmata do?
In plants, tube/tunnel that connects two cytoplasms to allow passage of ions and small molecules between neighboring cells
What is a phosphorylation cascade and how does it work?
One kinase phosphorylates the next, which does the next, etc. This makes it a cascade. It could activate multiple kinases and not just one to amplify the signal
What do gap junctions do?
In animals, allow passage of ions and small molecules between neighboring cells
What does Ca+2 do?
It is used as a second messenger in both G proton and tyrosine kinase receptor pathways
What are the two ways messages are passed in transduction?
Activates enzyme to produce second messengers or activates phosphorylation cascade
When are G proteins on?
When GTP is bound
What do G proteins act as?
An on/off switch
What is response in cell-signaling?
The whole point of the signal is to tell the cell to do something. This is the cell doing something
What do desmosomes do?
Bind the cytoskeletons of adjacent cells together with deep connections. Like bolts that work with the cytoskeletons. Cell-cell adhesions are selective
Two types of cell-cell attachments
Tight junctions and desmosomes
What happens in reception of cell signaling?
A receptor protein on the surface of the cell (or inside the cell) binds the signaling molecule (ligand) and transmits the signal
Where does Ca+2 flow in and out of?
Out of the cell, into smooth ER, into mitochondria
Whats outside of a cell?
The extracellular matrix in humans and other animals and cell walls in plants
How do gap junctions form?
In animals, membrane proteins line up to form channels between cells
What are the functions of the extracellular matrix?
Support, segregate tissues (different extracellular matrix in different tissues and blood, bone, and other connective tissues), and regulation of intercellular communication
How specific is binding and what does binding cause?
Very specific and causes the receptor to change shape
Is the binding of signaling molecules to receptors reversible?
Yes
What are cadherins?
Proteins in desmosomes that link cells (adhesion molecules). They are calcium dependent and vary between tissues.
How do intracellular receptors work?
The signaling molecules binds to the receptor in the cytoplasm, the receptor is transported to the nucleus, and it triggers a change in gene expression (on or off)
Two types of cell-cell gaps
Gap junctions in animals and plasmodesmata in plants
How is the message often passed in transduction?
A change in protein conformation
What does vibrio cholerae do?
Produces a toxin that causes a G protein to be unable to hydrolyze GTP to GDP so it remains stuck in on position, continually activating cAMP. Levels of cAMP causes salt to be excreted into the intestines and water follows = diarrhea
When are G proteins off?
When GDP is bound
What does being amplified mean?
Small signal can get a big response
Two ways cells respond to signals
Change in gene expression (protein synthesis) and regulate the activity of a protein (turn on already made protein)