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)
What do multiple steps allow in transduction?
Allows the signal to be amplified and allows for more regulation
What does more regulation mean?
Multiple players in the pathway, the cell weighs them to get a response
Is a nuclear or cytoplasmic response quicker and why?
Cytoplasmic because you don’t have to wait for a protein to be synthesized
What is transduction?
The relay of signals from receptors to target molecules in the cell
What do second messengers do?
They play a role in passing along messages
What do GPCRs often activate?
The production of second messengers
What do RTKs activate?
Ras (G protein)
Are cells self contained?
No, they must interact with other cells and the environment
What is the middle lamella?
Part that holds two cell walls from two cells together
What do GPCRs contain and what does it do?
GTPase domain that shuts itself off
What do tight junctions restrict?
Passive movement.
Relationship of number of second messengers and pathways?
More than one second messenger in one pathway and one second messenger can be involved in multiple pathways
Properties of tight junctions
Can vary between tissues and they are dynamic (they can change. Loosen up in stomach after eating then tighten later)
Main components of cell walls?
Cellulose in plants and peptidoglycan in bacteria
What are the main components of the extracellular matrix?
Collagen and proteoglycans
What makes cAMP?
Adenylyl cyclase and ATP
What are the functions of cell walls?
Protection, maintain shape, prevent excess water uptake (can’t expand past a certain point)
Where are cell walls found?
Plants, bacteria, fungi, and some protists
What are the extracellular/intercellular levels of Ca+2 and how is it transported?
Ca+2 10,000 times higher outside the cell. It is actively transported out of the cell or into the smooth ER
What do RTKs do?
Attach phosphates to tyrosine residues
How does long distance signaling work?
Hormones travel through bloodstream to reach target cells
How do plasmodesmata form?
In plants, membrane lined channels through cell walls connect adjacent cells with tube/tunnel structures
What turns off cAMP (turns it back to AMP)
Phosphodiesterase
2 most common second messengers
Cyclic AMP (cAMP) and calcium ions (Ca+2)
What are the two changes in protein conformation in transduction that pass a message?
Phosphorylation and dephosphorylation
What are GPCRs?
G-protein coupled receptors that are plasma membrane receptors that are associated with G proteins
Overview of response in cell signaling
The cell responds in some way to the signal
What are abnormally activated RTKs associated with?
Many types of cancer
What are RTKs?
Receptor tyrosine kinases that are membrane receptors with enzymatic activity which attach phosphates to tyrosine residues
What do ion channel receptors do?
Binding of ligand causes conformational change that open a gate to allow specific ions to pass
What are second messengers?
Small, non-polar, water soluble molecules that can easily spread messages throughout the cell because they are water soluble
How do signaling molecules get to intracellular receptors? What types of molecules must they be?
They have to pass through the membrane. They include steroid hormones, thyroid hormones, nitric oxide, small, non-polar, and hydrophobic molecules
What must happen in order to respond to new signals?
Old signals must be shut off
What are the 3 stages of cell signaling?
Reception, transduction, and response
What are the three main types of membrane receptors?
G-protein coupled receptors, tyrosine kinase receptors, and ion channel receptors
What is cAMP?
Cyclic adenosine monophosphate. Its a second messenger
What does increasing Ca+2 concentrations cause?
Muscle contraction, secretion, cell division
How is it determined if a cell can respond to a certain signaling molecule?
If it has receptors that can bind the signaling molecule
How is a signal terminated? Examples?
The messengers return to their inactive forms
GTP hydrolyzes to GDP
cAMP is converted to AMP
Phosphatases remove phosphates to deactivate proteins
What does a cytoplasmic response do?
Activation of an already made protein
What is used in long distance cell signaling?
Hormones (endocrine signaling)
What is the extracellular matrix? Where is it found?
The stuff found outside of the cell in animal tissues
Why is a hear cell different from a liver cell in they share the same DNA?
Different genes are turned on in different cells and different cells therefore have different proteins
What are protein phosphatases?
In dephosphorylation. They are proteins that take off phosphate groups to turn off
Overview of reception in cell signaling
The signal is detected by the cell
What are kinases?
Enzymes that add phosphates
What is crosstalk?
Multiple pathways interact to modify a response. Pathways are complex and cross over and have multiple parts. The outcome of crosstalk is which path has the strongest signal
What do tight junctions do?
Form water tight seals between cells. No leaking or fluid movement
What are proteoglycans?
One of two main components of extracellular matrix made of protein and sugar
