BIOL 205 Chapter 16: Chapter 16 Book Notes Part Two

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20 Nov 2016

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Bio 205 wwu: vast majority of signal molecules are too large or hydrophilic to cross plasma membrane of target cell, instead they bind to cell surface receptor proteins that span the plasma membrane. In positive feedback, a component that lies downstream in the pathway acts on an earlier component in the same pathway to enhance the response to the initial signal. In negative feedback, a downstream component acts to inhibit and earlier component in the pathway to diminish the response of the initial signal. Feedback regulation can lead to complex responses. Once activated, these proteins can stimulate- or in other cases suppress- other proteins in the signaling pathway. They then persist in an active- or inactive- state until some process switches them on or off again: proteins that act as molecular switches fall mostly into one of two classes. The first and largest class consists of proteins that are activated or inactivated by phosphorylation (kinase and phosphatase. )

Related Questions

During neural development, outgrowing nerve cell axons must interact with their cellular environment in order to determine correct organization and connectivity. Cell adhesion molecules (CAMs) are prominent one pass transmembrane glycoproteins that mediate the signaling necessary to ensure correct targeting of these nerve axons.

a) How is a cell adhesion transmembrane protein sorted/translocated initially so that it will be inserted into the plasma membrane as a type I membrane protein? [Hint: Describe the specific steps that a type I transmembrane protein will go through in the RER for insertion into the membrane].

b) The binding of cell surface receptor to its ligand is the 1^st step in a signal transduction pathway which ultimately results in the activation of many cytoplasmic proteins in a step-wise fashion. Explain 2 reasons why this method of signaling is advantageous for a cell.

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

cerisehedgehog846

What is a caveolae?

A) âBubblesâ found on the surface of the plasma membrane
B) Small invaginations of the plasma membrane
C) Invaginations of the rough ER
D) Specialized vesicles

Using Figure 1, how many ways can estrogen signaling beinitiated in vascular endothelial cells (ECS)?

A) One
B) Four
C) Three
D) Two

What was one of the results scientists found after activation ofthe membrane-bound estrogen receptor?

A) Vascular protective effects
B) Accelerated cancerous growth in breast tissue
C) Stimulation of cell division in breast/uterine tissue
D) Accelerated cancerous growth in uterine tissue

Using the description of Fig. 1, how do ligand-activatedtranscription factors function?

A) They are membrane bound receptors that bind estrogen as aligand.
B) They are imported into the nucleus as dimers afterligand-binding and then help initiation transcription.
C) None of these are correct.
D) They are always bound to the DNA, but require ligand binding tofunction.

What is one result of estrogen binding a membrane-bound estrogenreceptor in vascular tissue, thereby activating the rapid,non-nuclear signaling pathway?

A) Decreased cell growth
B) Decreased cell migration
C) Production of nitric oxide

The membrane-bound estrogen receptor is located________________.

A) somewhere in the membrane (i.e., researchers do not know theanswer)
B) as a transmembrane protein
C) on the intracellular leaflet of the membrane
D) on the extracellular leaflet of the membrane

The timing of estrogen therapy during menopause in women mayaffect the role estrogen plays in the cardiovascular system.

A) True
B) False

What ligand is used in this study to activate the membrane-boundestrogen receptor?

A) A G-protein
B) Estrogen dendimer conjugate (EDC)
C) Nitric oxide
D) 17b-Estrogen

Does estrogen dendimer conjugate (EDC) activate estrogenreceptors that are non-membrane bound (i.e., cytoplasmic ornuclear)?

A) No
B) Yes

10.

The ligand EDC causes cell migration and proliferation in whichof the following tissues? (Check all that apply)

A) Vascular (i.e., vessel) tissue
B) Ovarian tissue
C) Breast tissue
D) Uterine tissue

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BIOL 205 Chapter 16: Chapter 16 Book Notes Part Two

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