Chapter 4 - Cell Communication, Feedback Systems and Cell Cycle Control Flashcards
What is autocrine signaling? + one example
A cell releasing a ligand to signal and trigger a response in itself (such as mitosis)
What is cell to cell signaling? Also talk about synaptic signaling which falls into this category
A ligand from one cell’s membrane attaches to the receptor of another cell - it’s contact dependent.
A nerve cell releases neurotransmitter molecules into a synapse, stimulating the target cell (e.g. a muscle)
==3 . ‘ : . –> : . : ‘ E===
What is paracrine signaling? and give an example
One cell produces a ligand that is released and travels to another nearby (but not contact dependent) cell’s receptor (eg blood clotting and histamines (allergy chemicals))
What is endocrine signaling?
A ligand from one cell travels through the bloodstream (sometimes in a transport protein bc hydrophobic) to attach to the receptor on another cell in the body (ex. testosterone and estrogen and other hormones - think hair growth)
What is a ligand?
A ligand is a signaling molecule that is released from a cell and binds to a receptor protein to signal something (a response in a few steps)
What are the three stages of cell signaling?
Reception - ligand detected after binding to a receptor protein
Transduction - steps to convert the signal into a form that can give a response
Response - The response to the signal that is received - a lot of cell activity is activated this way
What kinds of messengers bind to the outside and what kinds bind to the inside of a cell membrane? (btw I mean receptors on the membrane not the membrane itself)
Large, water soluble messengers (like proteins) - bind outside (extracellular receptor) bc they don’t fit through the tails and they don’t mix with their hydrophobic-ness
Small, water insoluble messengers (like lipids) - bind inside (intracellular receptor) bc they shimmy on through and don’t get repelled
What is a GPCR? How many kinds of these are there? How many responses can they trigger?
G protein linked receptor
thousands of different kinds
ONE response
How do GPCRs get activated and transmit a signal?
1) a ligand binds to the GPCR, activating it
2) the GPCR changes shape and activates a g protein with GTP energy
3) the g protein diffuses along the membrane
4) it bonds with an enzyme, triggering a response
Step 1 is reception, steps 2 and 3 are transduction, step 4 is response
Are there GPCRs in plants?
No
Give an example of a GPCR reaction
Smells, tastes, adrenaline
What are some diseases caused by G-protein issues?
Cholera, pertussis, botulism, maybe a smattering of cancer if you don’t shut that spit down
Are GPCR changes permanent?
No - temporary and reversible
Where are GPCRs located?
Cell membrane
What does ligand gated mean? (yet again i implore you to use your brain)
Ligand attaches, gate opens/closes, ligand detaches, gate reverts
T or F: the nervous system uses ligand gated and voltage gated ion channels
true
Describe what happens when testosterone enters the cell
- Passes through membrane
- Binds to receptor protein in cytoplasm and activates it
- Hormone-receptor complex enters nucleus and binds to specific genes
- Bound protein acts as a transcription factor (light switch for genes) and stimulates transcription of the gene into mRNA
- the mRNA is translated into a specific shiny new protein that gets made
What is transduction?
Transformations made to a ligand to convert it into a form that can be understood and trigger a response
What do protein kinases do?
They yank phosphate groups off of ATP and transfer them to proteins - GO transduction
What do protein phosphotases do?
They yank phosphate groups off of proteins and transfer them to ADP, forming ATP - STOP transduction
Describe a phosphorylation cascade
1) relay molecule activated by receptor activates protein kinase 1
2) protein kinase 1 activates protein kinase 2
3) protein kinase 2 activates protein kinase 3
4) protein kinase 3 activates a cellular response to the signal
5) protein phosphatases remove the phosphate groups and make them inactive again
How does signal amplification happen?
each protein kinase in a phosphorylation cascade activates multiple kinases to increase number of messages and response
What are some examples of second messengers?
cAMP and Calcium ions
What is the difference between 1st and 2nd messengers?
1st - extracellular signaling molecule that binds to receptor (ligand)
2nd - Small, non protein, water soluble molecules or ions that spread through the cell
What is the difference between second messenger molecules and phosphorylation cascade molecules?
not proteins, much stronger and more amplified reaction from the 2nd messenger (I THINK BUT AM NOT SURE)
What is an example of a nuclear response?
Making a new protein with the freshly transcribed mRNA
What is an example of a cytoplasmic response?
Enzyme-substrate complex (why did i write that on my big sheet???)/turning an enzyme on
What could go wrong in a signaling pathway?
All of it with endless diseases to go with each mishap. For example, lets say you’re triggering cell division and it never turns off. Wham bam thank you banane you got cancer.
What are 2 types of signal transduction pathways?
Protein modification and phosphorylation
Describe the liver G protein process (sorry Sarah)
1) Epinephrine (ligand) binds to GPCR
2) G protein changes shape and releases an alpha subunit
3) Adenylyl cyclase in the cell membrane binds to the alpha subunit and converts ATP into cAMP (CYCLIC ADENOSINE MONOPHOSPHATE !!!)
4) cAMP, a second messenger, binds to the regulatory portions of a kinase and releases the catalytic portions
5) they get phosphorylated and act on enzymes throughout the cell
(again, sorry Sarah)
What is the difference between a GPCR and a Tyrosine kinase receptor? What is the same?
TK receptor
1) can activate multiple responses
2) doesn’t even need cAMP
3) releases phosphates
4) pairs up (do I have to know that? Who knows?¯_(ツ)_/¯ )
5) is associated with insulin and growth factors
They can BOTH activate phosphorylation cascades and BOTH use protein ligands
T or F: Ion channel receptors are only controlled by voltage (high concentration gradient = open, low gradient = close or vice versa)
False - some use ligands
What are some common ions that activate ion channel receptors?
Ca2+, Na+, Cl-, K+
I can already tell AP chem is gonna be a joy
T or F: Ion channel receptors are slow
F
T or F: Ion channel receptors are specific.
T
T or F: lipid signals are fast
F - think of puberty vs clenching your fist
T or F: A lipid signal could trigger a phosphorylation cascade
False - it just binds with the cytoplasmic receptor and diffuses along straight to the nucleus to (usually) act as a transcription factor for a protein.
T or F: phosphorylation cascade is response
F - transduction. Steps can be reception, transduction, response that triggers more transduction, response
T or F: Reception ONLY happens with 1st messengers (NO 2ND MESSENGERS LIKE G PROTEINS AND STUFF)
True
