7 - Cell Cell Interactions Flashcards
chapter 8
What does ECM stand for?
extracellular matrix found in animals
What are integral proteins?
transmembrane proteins intracellular connection with actin - in they cytoskeleton binds with fironectins
Where would the ECM components be synthesized?
Rough ER
_______ bind with actin intracellurally and __________ fibers extracellularly
Integrins Fibronectin
ECM varies in the amount present based on what?
ECM varies upon which tissues - highly found in areas requiring structural support - skin & bones
Cartilage secretes what?
collagen
What is a tight junction?
The proteins that stitch cells together, like quilting
Which ECM does leaky gut syndrome affect?
it breaks tight junctions
What is the adhesion protein that rivets the cells together called?
desmosomes
What are the three characteristics of a desmosome?
- contains cadherin proteins - trans membrane protein that binds it
- only binds to the same kind of cadherin
- intracellularly binds to intermediate filaments
___________ channels are between animals cells and allow for communication and exchange of ions
Gap Junctions
What are the gaps between plant cells that allow for passage of ions and small molecules
plamodesmata
Where in the body do you find a prevalence of gap junctions?
in the heart tissue
Define gap junctions
they are the connection between adjacent calls specialized as protein channels, allow H20, a-a sugar and nucleotides to move
list the three main forms of communication between cells
1 - paracrine - localized chemical signals 2 - nerves - neurotransmitters 3- hormones & growth factors
Why do only some cells react to cellular communication?
signal receptors are specific and determine the response
briefly describe how lipid soluble signal transduction works this may be incorrect - standby
hormonal -> lipid soluble interacts directly inter-cellularly through direct signaling processing
The bacteria vibrio cholera permanently turns on a G protein resulting in the activation a pumps that secrete Na +, Cl-, K+ and other ions. What are the implications of this?
the cell is loosing hydrophilic ions which would draw out H20 from the body and encourage elimination
briefly describe how lipid insoluble signal processing works
- cannot x mb Reception
-
Reception:
- binds @ mb surface
- changes shape reception site
-
Processing:
- signal transduced from one form to another, eg G protein linked
- Amplifies = 2nd messanger turns on pumps, genes
What is signal amplification?
name the major types
how a small message can turn on a huge response
intracellularly
2 types: enzyme linked & G Proteins
name the two general actions of signal transduction
- reception
- processing
Great question for the final: describe the process of either G protein related cell to cell interaction, or communication via enzyme linked receptors
know how to do this
Why would a G Protein be non-responsive?
hhmmmm - I can’t remember the answer to this, but I was sure that it would be a test Q possibly from cross talk
What is cross talk?
the interaction of simultaneous communication between cells that can be excitatory, inhibitory or hold a response
How are G Proteins and Enzyme linked receptors similar?
The both can cause both or either Phosphoralization cascades or 2nd messangers
How is an enzyme linked receptor different than a G protein receptor?
the receptor acts as an enzyme (changes shape) & has a higher capacity to activate more transduction pathways
How is the signal transduction phosphorylation cascade turned off?
- ligand moves away from the receptor
- enzymes deactivate in the cells eg in the G protein GTP -> GDP
- PHOSPHATASES protein - removes Pi from enzyme or dephosphoralates
- to stay operational - extracellular signal ahs to contine or it`s shut down
Name the three 2nd messengers reviewed in class
Ca+ cyclic GMP cyclic AMP
What do 2nd messangers do?
- turned on by an activated enzyme
- Change which genes are being expressed in a target cell
- Activate/deactivate target protein that already exists in a cell eg mb channel, activating gene
What is protein kinase?
an enzyme that phosphorylates - that crops Pi’s off
Signal transduction has 2 responses, what are they?
- converts extracellular messages to intracellular messages
- in many cases it causes the message to amplify
T/F Are send messengers proteins?
no they are enzymes
When a ligand binds to an enzyme linked receptor on two inactive monomer, what is formed?
a dimer
What must be completed before a dimer can become an enzyme?
needs to be Phosphorylated
list the sequence of events in the signal transduction pathway
- signal is received
- signal is transduced
- signal is amplified
- cellular response
What is cross talk?
- diverse signals can increase
- decrease signal response
Where can ECM be found in plants
they can`t, ECM is a fibre composite of protein found in animals
In the animal world how are cells connected
desmosomes gap junctions tight junctions
How are plant cells held together
tight junctions plasmodesmata held together by gelatenous proteins & sugars hydrophiliic keeps lamina wet
List the steps of how a G Protein triggers the production of a 2nd messanger
- ligand binds to mb R = binding of inactive G protein (+GDP) - R
- GTP displaced GTP = activation station for the G protein
- Activates G Protein to bind to Enzyme => change of shape E
- Activated E => response -> amplification
- Ligand leaves -> G protein hydrolyses GTP ->GDP = inactive
list the steps in signal transduction via enzyme-linked receptors
- 2 Ligands bind to 2 inactive monomers => dimer
- Dimerized + Pi = phosphorlated => enzyme
- inactive protein => activation cellular responce => phosphorylation cascade
some phosphorylation cascades cause what
production of 2nd messangers
how does signal transduction help the system
- increases the response time
- can be shut down quickly
- highly sensitive to small changes in hormones or signals
What is the correct order for the following events in the interaction of a cell with a signal?
- Alteration of cell function
- signal binds to receptor
- signal released from source
- signal transduction
Select one:
A. 1234
B. 2314
C. 3214
D. 3241
E. 3421
which one is it
D
Why do some signals (first messengers) trigger second messengers to activate target cells?
Select one:
- The first messenger requires activation by ATP
- The first messenger is not water soluble
- The first messenger binds to many types of cells
- The first messenger cannot cross the plasma membrane
- There are no receptors for the first messenger.
The function of the extracellular matrix (ECM) in most multicellular organisms is
Select one:
1. To provide structural support
2. To provide strength
3. To organize cells
4. Cell signalling
5. All answers apply
The activation of receptor tyrosine kinases is characterized by
Select one:
- Dimerization and phosphorylation
- Dimerization and calcium release
- A phosphorylation cascade
- GTP hydrolysis
- Channel protein shape change
1
Plasmodesmata and gap junctions
Select one:
- Allow small molecules and ions to pass rapidly between cells
- Are both membrane-lined channels
- Are present only on either side of a cell
- Are involved in cell recognition
1
Clostridium perfringens is a bacterium wich secretes several toxins, one which causes the break down of collagen and another which causes the breakdown of cell adhesion molecules. Explain the impact these toxins would have on cells
- the matrix would start to disintigrate
- the binding between gap junctions and desmosomes would break. terrible outcomes of bleeding, keeping things out that are supposed to stay out
- intracellular communication difficult
A cell receives a signal to manufacture integrins. Where in the cell would these proteins be produced
indomembrane system
Compare and contrast gap junctions and plasmodesmata
They both are pores between cells for the passage of small molecules and ions
gap junctions = animal cells
plasmodesmata = plant cells
Where would you expect to find te receptor for the teroid hormone aldosterone - inside the cell or in the mb. Why
intracellularly
lipid soluble = passes through mb and directly to receptors
What is protein kinase, and what is its role in a signal transduction pathway
an enzyme that phosphorylates from ATM to another protein usually protein kinase = turns on the phosphorylated protein = series = cellular response therefore carrying the signal from outside the cell to the protein that brings about the cellular response
Excessive levels of an enzyme-linked receptor called HER2 has been found in some breast cancers. When activated, this receptor stimulates cell proliferation. How could you develop a drug to thwart cancer cell growth in HER2 positive cancers
bind down the receptor sites where HER2 binds
