BIOL 150 Lecture Notes - Lecture 20: Adenylyl Cyclase, Autocrine Signalling, Paracrine Signalling

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15 Mar 2018

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Biol 150 principles of molecular & cellular biology. We briefly reviewed the mechanism of secretion, in order to begin discussing how cells communicate with each other. Cells generally communicate via chemical signals, either proteins secreted through the er, golgi, and vesicles, or small secreted molecules such as steroid hormones. How cells respond to those signals depends on the type of receptors that those cells have. Receptors must be located in the plasma membrane in order to respond to proteins (which can"t cross the membrane). Receptors to steroid hormones (which can cross membranes) are usually located in the cytoplasm. In paracrine signaling, cells signal to other nearby cells (e. g. neurons signaling to muscles to tell them to contract). Endocrine signaling, in which the signal molecule is carried throughout the body by the vasculature, signals to the entire body (e. g. adrenaline, estrogen, testosterone, or ecdysone in insects).

Related Questions

1/What is the fate of a protein with no N-terminus Signal Sequence?

(a)Transport through the constitutive secretory pathway

(b)Dispersal throughout the cytoplasm

(c)Transport into the nucleus

(d)Transport to the rough endoplasmic reticulum (RER)

2/ In nerve cells, Botulinum toxin-A degrades a subunit of a T-snare localized on the plasma membrane, how would this affect vesicular trafficking?

(a) It blocks the co-translational import of neurotransmitter proteins into the Endoplasmic reticulum via the translocon.

(b) It prevents the addition of carbohydrates to translated proteins

(c)It blocks the fusion of neurotransmitter-containing vesicles with the plasma membrane because theT-snare would not be able tophysically interact with the V-snare.

(d) None of the above

What is the correct order of events of Clathrin-mediated endocytosis?

1. Uncoating of Clathrin- coated vesicle

2. Recruitment of Clathrin and selection of cargo

3. Fusion of vesicle with early endosome

(a) 1, 2, 3

(b) 2, 1, 3

(d) 3, 1, 2

4/ Vesicles traveling anterogradely will eventually fuse with the cell membrane.

Which of the following elements does NOT participate in the fusion event?

(a) v-snare

(b) t-snare

(d) clathrin coat protein

When a cell releases a hormone into the bloodstream and a number of cells in a

distal location respond, this type of signaling is...

(a) Autocrine signaling

(b) Endocrine signaling

(d) Juxtacrine signaling

taupereindeer397

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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1.A researcher alters the DNA-binding domain of a glucocorticoid receptor to that of an estrogen receptor. How would the cells respond to exposure to glucocorticoids?

a. They would bind estrogen, and initiate estrogen-dependent synthesis

b. They would bind glucocorticoids, and initiate testosterone-dependent synthesis

c. They would bind estrogen, and initiate testosterone-dependent synthesis

d. They would bind glucocorticoids, and initiate estrogen-dependent synthesis

e. They would bind neither hormone

2. All of the following statements about mitochondria are valid except:

a. The outer membrane of the mitochondrion is more like a eukaryotic cell plasma membrane.

b. The outer membrane of the mitochondrion is more like a prokaryotic outer membrane.

c. Mitochondria have ribosomes that are a different size from those in the rest of the cell.

d. Mitochondria have their own DNA that encodes very few proteins.

e. Mitochondria store Calcium ions

3.The unique length-tension relationship of muscle is due to:

a. the limit on the amount of ATP the muscle can produce.

b. the fact that tension is proportional to the amount of overlap between actin fibers and myosin heads

. c. the ability of kinesin to move along filaments.

d. the limit imposed on cross-sectional area of muscle in organisms.

e. the shortening of actin filaments.

4.The enzyme âFlippaseâ causes the flip-flop of dolichol phosphate from one side of a membrane to the other as part of the process leading to:

a. binding of a receptor by a ligand

b. glycosylation of newly synthesized proteins

c. transfer of proteins to the golgi apparatus.

d. membrane fusion during secretion

e. formation of coated vesicles

5. What do the photosystems of a chloroplast capture from the splitting of water during the light reactions?

a. ATP

b. Protons

c. electrons

d. neutrons

e. oxygen

BIOL 150 Lecture Notes - Lecture 20: Adenylyl Cyclase, Autocrine Signalling, Paracrine Signalling

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