BISC401 Lecture Notes - Lecture 5: Heme, Cell Membrane, Guanosine Triphosphate

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greenhippopotamus619

27 Sep 2016

School

University of Delaware

Department

Biological Sciences

Course

BISC401

Professor

Dr.Salil Lachke

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Document Summary

Proteins function depends on specific interactions with other molecules. Two proteins bind through interactions between their complementary surfaces. Causes a change in the shape of a protein. The most common quantitative measure of affinity: the stronger the interaction between a protein and a ligand, the lower the valve of kd. The ligands of enzyme are called substrates. Some are secreted and function at the extracellular sites such as blood. Like all catalysts, enzymes increase the rate of a reaction, but they do not affect the extent of a reaction. A(cid:374) e(cid:374)zy(cid:373)e"s a(cid:272)tive site bi(cid:374)ds su(cid:271)strates a(cid:374)d carries out catalysis. Active site: makes up only a small part of the total protein, consists of the functionally important regions, 1. Responsible for the remarkable specificity of enzymes. Alteration of the stru(cid:272)ture of a(cid:374) e(cid:374)zy(cid:373)e"s su(cid:271)strate (cid:272)a(cid:374) result i(cid:374) a variant molecule that is no longer a substrate of the enzyme.

Related Questions

16.Globular proteins fold up into compact, spherical structures that have uneven surfaces. They tend to form

multisubunit complexes, which also have a rounded shape. Fibrous proteins, in contrast, span relatively large

distances within the cell and in the extracellular space. Which protein is not classified as a fibrous protein?

(a)elastase (b)collagen (c)keratin (d)elastin

17.You have two purified samples of protein Y: the wild-type (nonmutated) protein and a mutant version with a

single amino acid substitution. When washed through the same gel-filtration column, mutant protein Y runs through

the column more slowly than the normal protein. Which of the following changes in the mutant protein is most likely

to explain this result?

(a)the loss of a binding site on the mutant protein surface through which protein Y normally forms dimers

(b)a change that results in the mutant proteinâs acquiring an overall positive instead of a negative charge

(c)a change that results in the mutant proteinâs being larger than the wild-type protein

(d)a change that results in the mutant proteinâs having a slightly different shape from the wild-type protein

18.Which of the following statements is true?

(a)Disulfide bonds are formed by the cross-linking of methionine residues.

(b)Disulfide bonds are formed mainly in proteins that are retained within the cytosol.

(c)Disulfide bonds stabilize but do not change a proteinâs final conformation.

(d)Agents such as mercaptoethanol can break disulfide bonds through oxidation.

19.Proteins bind selectively to small molecule targets called ligands. The selection of one ligand out of a mixture of

possible ligands depends on the number of weak, noncovalent interactions in the proteinâs ligand-binding site. Where

is the binding site typically located in the protein structure?

(a)on the surface of the protein (b)inside a cavity on the protein surface

(c)buried in the interior of the protein (d)forms on the surface of the protein in the presence of ligand

thanks

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

viridiangoat964

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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BISC401 Lecture Notes - Lecture 5: Heme, Cell Membrane, Guanosine Triphosphate

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