BIOL2000 Lecture Notes - Lecture 10: Platelet-Derived Growth Factor, Intermediate Filament, Cell Junction

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5 May 2020

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Three types of cell-surface receptors (based on the way they are activated) G protein-coupled receptors associate with g proteins bound to gtp and gdp. When a g protein is bound to gtp, it is active; when it is bound to gdp, it is inactive. When a ligand binds to a g protein-coupled receptor, the receptor binds to and activates the g protein by replacing gdp with gtp. When ligand binds the ligand binding site, receptor kinases become active, phosphorylating other proteins and transmitting the signal from outside the cell to inside the cell. The phosphate groups provide binding sites for intracellular signaling proteins. When we get a cut, platelets in the blood release proteins, including pdgf (platelet derived growth factor). Pdgf binds to pdgf receptor kinases on the surface of the cell. In the map kinase pathway, the cytoplasmic signaling protein ras is activated.

Related Questions

When would you need one form of cell signaling versus another? What're the costs/benefits?

(Thinkning about: Direct, Autocrine, Paracrine, and Endocrine Signaling; as well as Signal transduction pathways like Ligand-gated ion channels, Receptor enzymes, G-protein coupled receptors, and Intracellular receptors)

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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Cell biology Questions

1. Where is the sugar-phosphate backbone located in a DNA strand within the DNA double helix?

a) Alternates between outside and inside

b)Inside

c)Outside

d)Varies between purines and pyrimidines

e)Depends on the species

2) Which of these statements defines paracrine cell signaling?

A messenger molecule released into the blood stream to bind to a receptor on a cell far away from the release site.

A messenger molecule released by a cell into the extracellular space that binds to receptors on the surface of the same cell.

A messenger molecules released by a cell into the extracellular space that travels short distances to bind to a receptor in a nearby cell.

A messenger molecule release by a tissue into the lumen of an organ that diffuse to bind to receptors far away from the release site.

e)All of the above.

3. Which effect has the binding of the ligand to a G-protein coupled receptor on intracellular G-protein?

a)		ATP is hydrolyzed, activating phosphorylation
b)		GTP is exchanged for GDP on the G protein, inactivating the G protein
c)		GDP is exchanged for GTP on the G protein, activating the G protein
d)		GMP is released from the G-protein, inactivating the receptor
e)		None of the above

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BIOL2000 Lecture Notes - Lecture 10: Platelet-Derived Growth Factor, Intermediate Filament, Cell Junction

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