Chapter 4 - Cell Communication, Feedback Systems and Cell Cycle Control

Question 1

What is autocrine signaling? + one example

Answer 1

A cell releasing a ligand to signal and trigger a response in itself (such as mitosis)

Question 2

What is cell to cell signaling? Also talk about synaptic signaling which falls into this category

Answer 2

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===

Question 3

What is paracrine signaling? and give an example

Answer 3

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))

Question 4

What is endocrine signaling?

Answer 4

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)

Question 5

What is a ligand?

Answer 5

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)

Question 6

What are the three stages of cell signaling?

Answer 6

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

Question 7

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)

Answer 7

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

Question 8

What is a GPCR? How many kinds of these are there? How many responses can they trigger?

Answer 8

G protein linked receptor
thousands of different kinds
ONE response

Question 9

How do GPCRs get activated and transmit a signal?

Answer 9

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

Question 10

Are there GPCRs in plants?

Answer 10

No

Question 11

Give an example of a GPCR reaction

Answer 11

Smells, tastes, adrenaline

Question 12

What are some diseases caused by G-protein issues?

Answer 12

Cholera, pertussis, botulism, maybe a smattering of cancer if you don’t shut that spit down

Question 13

Are GPCR changes permanent?

Answer 13

No - temporary and reversible

Question 14

Where are GPCRs located?

Answer 14

Cell membrane

Question 15

What does ligand gated mean? (yet again i implore you to use your brain)

Answer 15

Ligand attaches, gate opens/closes, ligand detaches, gate reverts

Question 16

T or F: the nervous system uses ligand gated and voltage gated ion channels

Answer 16

true

Question 17

Describe what happens when testosterone enters the cell

Answer 17

1. Passes through membrane
2. Binds to receptor protein in cytoplasm and activates it
3. Hormone-receptor complex enters nucleus and binds to specific genes
4. Bound protein acts as a transcription factor (light switch for genes) and stimulates transcription of the gene into mRNA
5. the mRNA is translated into a specific shiny new protein that gets made

Question 18

What is transduction?

Answer 18

Transformations made to a ligand to convert it into a form that can be understood and trigger a response

Question 19

What do protein kinases do?

Answer 19

They yank phosphate groups off of ATP and transfer them to proteins - GO transduction

Question 20

What do protein phosphotases do?

Answer 20

They yank phosphate groups off of proteins and transfer them to ADP, forming ATP - STOP transduction

Question 21

Describe a phosphorylation cascade

Answer 21

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

Question 22

How does signal amplification happen?

Answer 22

each protein kinase in a phosphorylation cascade activates multiple kinases to increase number of messages and response

Question 23

What are some examples of second messengers?

Answer 23

cAMP and Calcium ions

Question 24

What is the difference between 1st and 2nd messengers?

Answer 24

1st - extracellular signaling molecule that binds to receptor (ligand)
2nd - Small, non protein, water soluble molecules or ions that spread through the cell

Question 25

What is the difference between second messenger molecules and phosphorylation cascade molecules?

Answer 25

not proteins, much stronger and more amplified reaction from the 2nd messenger (I THINK BUT AM NOT SURE)

Question 26

What is an example of a nuclear response?

Answer 26

Making a new protein with the freshly transcribed mRNA

Question 27

What is an example of a cytoplasmic response?

Answer 27

Enzyme-substrate complex (why did i write that on my big sheet???)/turning an enzyme on

Question 28

What could go wrong in a signaling pathway?

Answer 28

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.

Question 29

What are 2 types of signal transduction pathways?

Answer 29

Protein modification and phosphorylation

Question 30

Describe the liver G protein process (sorry Sarah)

Answer 30

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)

Question 31

What is the difference between a GPCR and a Tyrosine kinase receptor? What is the same?

Answer 31

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

Question 32

T or F: Ion channel receptors are only controlled by voltage (high concentration gradient = open, low gradient = close or vice versa)

Answer 32

False - some use ligands

Question 33

What are some common ions that activate ion channel receptors?

Answer 33

Ca2+, Na+, Cl-, K+
I can already tell AP chem is gonna be a joy

Question 34

T or F: Ion channel receptors are slow

Answer 34

F

Question 35

T or F: Ion channel receptors are specific.

Answer 35

T

Question 36

T or F: lipid signals are fast

Answer 36

F - think of puberty vs clenching your fist

Question 37

T or F: A lipid signal could trigger a phosphorylation cascade

Answer 37

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.

Question 38

T or F: phosphorylation cascade is response

Answer 38

F - transduction. Steps can be reception, transduction, response that triggers more transduction, response

Question 39

T or F: Reception ONLY happens with 1st messengers (NO 2ND MESSENGERS LIKE G PROTEINS AND STUFF)

Answer 39

True