BIOL 1000 Lecture Notes - Lecture 34: Cyclic Adenosine Monophosphate, Protein Kinase, Conformational Change

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4 Jun 2019

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Lots of signalling molecules are located on the surface of the cell. How does the cell get the information from the outside (its receptors), to the inside where it can produce a response. Signal transduction: a signal receptor molecule binds to the receptor on the outside of the cell, and this triggers a cascade on the in the inside of the cell. 1st reason is because it is a way of allowing the cell to amplify the signal, instead of having it be a 1:1 ratio where 1 receptor triggers 1 response. The 2nd reason is so that the pathway can be regulated by other pathways. If one pathway is triggered, then another pathway is trigged, the second pathway can actually go and inhibit the rst pathway. This is important for things like mitosis, where the cell wants to divide then other pathways in the cell tell it not to divide.

Related Questions

Cell signaling is a complex process that involves a signal binding to a signal receptor, a signal transduction pathway, and ultimately, a change in the cell (cellular response).

a) When acetylcholine binds to a signal receptor in a muscle cell, the receptor undergoes a conformational change, allowing Na+ to diffuse into the cell, causing the muscle to contract. Based on what you know about cell signaling, do you predict this response will be fast or slow? Why?

b) Our sense of smell relies on a G protein-linked receptor, a G protein, adenylyl cyclase, and cyclic AMP to open an ion channel that allows Na+ to enter the cell. Based on what you know about cell signaling, do you predict this pathway will lead to signal amplification? Why?

Signal transduction ispart of a cell's response to an external signal. Althoughsignaltransduction pathways can differ in their details, there aresome common elements. Determine which of the statements belowaccurately describe signal transduction pathways. Select the sixcorrect statements.

1. A receptor changes conformation uponbinding, transmitting a signal acrossthe cellmembrane.

2. Signal transductioncascades, often involvingprotein kinases, amplify a signal intracellularly.

3. Signal transductioncascades directly transmit asingle stimulus to a single target.

4. A second messengermay carry a signal from thecell membrane to an organelle.

5. A ligand, such as a hormone, binds to a specific cell surfacereceptor on a target cell.

6. A ligand phosphorylates protein residues, ending the signalingcascade inside thecell.

7. A receptor may pass on a signal by interacting withanother protein or by acting as an enzyme.

8. Phosphatases remove phosphoryl groupsfrom polypeptides, regulating a cell's response.

9. A second messengercarries a signal from atissue or organ to a target cell.

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QUESTION 1

Which of the following is an example of an extracellular signal molecule?

	a.	IP₃
	b.	cAMP
	c.	Insulin
	d.	Diacylglycerol

2 points

QUESTION 2

Nuclear hormone receptors _____

	a.	Bind to water soluble ligands
	b.	Activate second messengers
	c.	Regulate transcription in response to ligand binding
	d.	Are normally located on the plasma membrane

2 points

QUESTION 3

Which of the following does not occur when a receptor tyrosine kinase is bound by ligand?

	a.	Phosphorylation of the RTK
	b.	Cytoplasmic proteins bind the phosphorylated RTK
	c.	Dimerization of the RTK
	d.	The RTK binds to DNA to regulate transcription

2 points

QUESTION 4

Which of these is a logical signal-transduction pathway?

	a.	An intracellular receptor activates phospholipase C, which cleaves a membrane protein to form IP₃, which then activates the opening of an ER channel protein, which releases cyclic AMP into the cytoplasm, where it binds to an intracellular enzyme that carries out a response.
	b.	A G-protein-linked receptor activates G protein, which activates phospholipase C, which cleaves a membrane lipid to form IP₃, which binds to a calcium channel on the ER, which opens to release calcium ions into the cytoplasm, which bind to an intracellular enzyme that carries out a response.
	c.	An ion-channel receptor opens, allowing a steroid hormone to enter the cell; the steroid hormone then activates protein kinases that convert GTP to GDP, which binds to an intracellular enzyme that carries out a response.
	d.	A tyrosine-kinase receptor activates adenylyl cyclase, which activates phospholipase C, which converts ATP into cyclic AMP, which binds to an intracellular enzyme that carries out a response.

2 points

QUESTION 5

Which of the following is an example of signal amplification?

	a.	activation of an enzyme molecule
	b.	activation of a specific gene by a growth factor
	c.	Breakdown of many cAMP molecules
	d.	activation of 100 molecules by a single signal binding event

2 points

QUESTION 6

Consider a signal transduction pathway that utilizes cAMP as a second messenger to activate PKA (Protein Kinase A). Which of the following situations will result in the cellular response?

		The G protein releases GDP and binds to GTP
		The target protein (adenylyl cyclase) is inactive
		The regulatory subunits of PKA (Protein Kinase A) are bound to the catalytic subunits
		The appropriate G protein is bound to GDP

2 points

QUESTION 7

Which of the following is found in only some signal transduction pathways? [In other words, which is not found in all signal transduction pathways?]

		Receptor protein
		Extracellular signal molecule
		Intracellular signaling molecule
		Cellular response
		Effector protein

2 points

QUESTION 8

The enzyme that specifically catalyzes the conversion of ATP to cAMP is:

		Adenylyl phosphatase
		Adenylyl kinase
		Adenylyl dehydrogenase
		Adenylyl cyclase

2 points

QUESTION 9

If an animal cell suddenly lost the ability to produce GTP, what might happen to its signaling system?

		It would use ATP instead of GTP to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.
		It would not be able to activate and inactivate the G protein on the cytoplasmic side of the plasma membrane.
		It would employ a transduction pathway directly from an external messenger.
		It would be able to carry out reception and transduction but would not be able to respond to a signal.

2 points

QUESTION 10

A hormone signal is sent from the brain to other parts of the body via the bloodstream. Why do only certain cells respond to this signal?

		Hormones do not last long enough in the bloodstream to stimulate a cellular response
		Only cells that have a specific transcription factor gene will be able to respond to the signal
		Only cells in the immediate vicinity of the cell sending the signal will respond
		Only cells that have a receptor for the specific signal will be able to respond to it

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BIOL 1000 Lecture Notes - Lecture 34: Cyclic Adenosine Monophosphate, Protein Kinase, Conformational Change

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