BIOL 2021 Lecture Notes - Lecture 11: Cell Membrane, Autocrine Signalling, Paracrine Signalling

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turquoisehamster570

13 May 2018

School

York University

Department

Biology

Course

BIOL 2021

Professor

Patricia Lakin- Thomas

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• Question: human communication

o Which of the following forms of human communication are analogous to

which forms of cell signaling?

o A. a text message to one friend→ synaptic signaling

o B. talking to several friends at a party → paracrine

o C. a radio broadcast → endocrine

o D. talking to yourself → autocrine

• Types of receptors

• Fig 15-3a cell-surface receptors

o Hydrophilic signal molecule → cell-surface receptor protein.

• Fig 15-3b intracellular receptors

o Hydrophobic signal molecule → intracellular receptor protein.

o In most cases, receptors are transmembrane proteins on the target-cell

surface. When these proteins bind an extracellular signal molecule (a

ligand), they become activated and generate various intracellular signals

that alter the behavior of the cell. In other cases, the receptor proteins are

inside the target cell, and the signal molecule has to enter the cell to bind

to them: this requires that the signal molecule be sufficiently small and

hydrophobic to diffuse across the target cell’s plasma membrane.

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Related Questions

1. Specific extracellular signal molecules require a cell surface receptor. What about the chemistry of these signals prevents them from diffusing across the cell membrane?

2. What is the difference between endocrine signaling, paracrine signaling and autocrine signaling?

3. Why do cellular signal molecules bing to a receptor using noncovalent forces rather than a covalent bond?

4. What is the different between kinases and phosphates? How do they impact activity of the target protein. Please give an example that involves kinases and phosphates.

5. How do kinases recognize their substrates and the proteins they act on?

6. What is the difference between the active form and inactive form of GTPase superfamily of proteins?

7. How are second messengers different from first messengers?

brownmoose258

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 2021 Lecture Notes - Lecture 11: Cell Membrane, Autocrine Signalling, Paracrine Signalling

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