BIOL 1107 Lecture Notes - Lecture 12: Signal Transduction, Intracellular Receptor, Cell Membrane

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8 Nov 2016

School

Northeastern University

Department

Biology

Course

BIOL 1107

Professor

Melissa Mc Elligott

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Document Summary

Unicellular organisms: bacteria can communicate with each other and the environment acquire resistance to antibiotics, resistant layer. Cost to the organism: energy, has to check in with other cells, uses macromolecules (proteins are always the answer), all the proteins must be encoded for in the genome = added genes. Essential elements for communication: signaling cell: releases ligand, signaling molecules: ligand, binds to receptor, may be able to get through plasma membrane (other intracellular receptors, receptor molecule: receptor on surface of cell, receptor cell: Stage 2: signal transduction, transmitted to the interior of the cell buy a signal transduction pathway. Stage 3: response, the cell responds by activating an enzyme or turning on transcription of a gene. How are the signals being transduced: proteins called kinases (enzyme) phosphorylates other molecules = adds a phosphate group to a molecule = makes it unstable/ changes the shape.

Related Questions

1. What types of biological macromolecules are most cell walls and extracellular matrices composed of? (Choose ALL correct answers)

[]

proteins

[]	nucleic acids

[]

lipids

[]	carbohydrates

2. What is a "second messenger"?

a.	a protein that phosphorylates another substrate

b.	a molecule that is produced or released intracellularly as a result of receptor activation

c.	a signaling molecule that is released extracellularly

GTP

3. How can the activation of a protein kinase be important in signal transduction?

a.	kinases bind to receptors to prevent the signal from binding the receptor

b.	kinases prevent signal amplification by ensuring other proteins are not active

c.	kinases can activate or deactivate existing proteins by phosphorylation

d.	kinases are secreted by the cell as a signaling molecule

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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 1107 Lecture Notes - Lecture 12: Signal Transduction, Intracellular Receptor, Cell Membrane

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