Receptors & Cell Signaling

Question 1

________ is the basis for maintaining homeostasis, cell growth, division and differentiation

Answer 1

Cell signaling

Question 2

What generic types of disease occur with errors in cellular signaling?

Answer 2

Cancer, diabetes, autoimmunity

Question 3

What hormone is produced by fat cells to tell the hypothalamus the body is satiated?

Answer 3

Leptin

Question 4

1) A ________ causes a signaling cell to synthesize and secrete a ________ molecule

Answer 4

Stimulus ; signaling

Question 5

2) The signal is transported to a __________, where it binds to a _____________ or infiltrates the membrane and binds to an ______________ (aka signal transduction)

Answer 5

Target cell ; receptor protein ; intracellular receptor

Question 6

3) Signaling molecule-receptor complex _______ or ________ intracellular signaling proteins in the cell

Answer 6

Activates ; inhibits

Question 7

4) __________ alter the activity of different components downstream and generate _______________

Answer 7

Effectors ; secondary messengers

Question 8

Type of signal that is transported via blood (think hormone)

Answer 8

Endocrine

Question 9

Epinephrine released by the adrenal medulla that acts on the heart muscle is an example of what type of signaling? (Think long-distance and long lasting - hours to days, freely diffusing signals)

Answer 9

Endocrine

Question 10

Type of signal that diffuses to a neighboring target cell of a different cell type

Answer 10

Paracrine

Question 11

What type of signal is at work when Leydig cells synthesize and secrete testosterone, which induces spermatogensis by acting on Sertoli and germ cells? (Think local signaling, short-lied signals)

Answer 11

Paracrine factor

Question 12

Neurotransmitters are often what type of signal?

A) Autocrine
B) Paracrine
C) Endocrine
D) Direct/Juxtacrine

Answer 12

B) Paracrine

Short-lived and close to target receptors

Question 13

Type of signal where secreting cells express surface receptors for the signal they produce

Answer 13

Autocrine

Question 14

Growth factors in cancer cells often involve what type of cell signaling?

Answer 14

Autocrine

Question 15

__________ signaling is common in chemokines: interleukin-1 produced by T-lymphocytes promote their own replication in immune response

Answer 15

Autocrine

Question 16

This type of signal binds to a signaling cell which then binds to a receptor on the target cell

Answer 16

Direct/Juxtacrine

Question 17

Which signals can can freely diffuse across the membrane?
A) large, uncharged, polar
B) Ions
C) Hydrophobic

Answer 17

C) Hydrophobic

Large, uncharged, polar signals require an active transport mechanism.
Ions: Ion channels
Small, uncharged, polar: gradient-dependent diffusion

Question 18

Lipophilic signals interact with receptors on the ________ of the cell and must be bound to _________ to be transported through the bloodstream. Lipophilic signals have ______ half lives.

Answer 18

inside ; carrier proteins ; long (hours to days)

Question 19

The two types of lipophilic receptors are:

Answer 19

Cytoplasmic receptors and Nuclear Receptors

Question 20

Cytoplasmic receptors

Answer 20

Form complexes w/ HSP. Dissociates from HSP upon signal binding and translocates to the nucleus and binds to a DNA sequence, altering the rate of transcription

Question 21

Nuclear receptors

Answer 21

Present in nucleus bound to DNA. Alters transcription of certain genes after signal binding.

Question 22

Signals that are water-soluble and cannot diffuse through cellular and nuclear membranes are _________ signals.

Answer 22

Hydrophilic

Question 23

Hydrophilic signals bind to __________, trigger activation of events ___________. They are generally small and derived from __________. Hydrophilic signals have ________ half-lives.

Answer 23

Surface receptors ; downstream ; amino acids ; short (seconds to minutes)

Question 24

What are the two types of hydrophobic receptors?

Answer 24

G protein-coupled receptors (GPCR)

Receptor tyrosine kinases

Question 25

GPCR involves:

Signaling mediated by ___________, effector proteins, second _________, and ___ (#) alpha helices

Answer 25

G proteins ; messengers ; 7

Question 26

Receptor Tyrosine Kinases are mediated by ________ G proteins and ____________
RTKs contain ___ alpha-helical transmembrane domain.

Answer 26

Monomeric ; protein kinases ; 1

Question 27

Lipophilic vs. hydrophilic medications

oral contraceptives contain ________ signaling molecules that have long half-lives (hours to days) and are hence, taken ________

Answer 27

Lipophilic ; daily

Question 28

Lipophilic vs. hydrophilic medications

________ signaling molecules had short half-lives (seconds to minutes) and are administered at the time they are needed. For example: epinephrine is used to combat acute allergic rxns

Answer 28

Hydrophilic

Question 29

Graves’ disease and other thyroid disease result in a(n) ________ in TSH and a(n) _________ in T3 and T4.

Answer 29

Decrease ; increase

Question 30

Graves’ disease : list symptoms and treatment options

Answer 30

Most common amongst women, presents by 40s

Present with weight loss, tachycardia, insomnia, pretibial myxedema, ophtalmopathy (exophthalmos), thyroid goiter

Treatment: surgical resection of the thyroid gland, radioactive iodine, pharmacological intervention

Question 31

GPCRs have an _____-cellular domain that binds to a signal, a _________ domain composed of ___ helices, and an _____cellular domain that interacts with trimeric _________.

Answer 31

Extra- ; trans- ; 7 ; intra ; G proteins

Question 32

GPCRS are arranged in a _________ pathway within the membranes. They include an extra cellular _______ bond. Have a C-terminus tethered to the ______.

Answer 32

Circular ; disulfide ; membrane

Question 33

Binding epinephrine to B-adrenergic repceptor causes __________ in bronchial and intestinal smooth muscles
BUT causes ________ in the heart.
Binding produces the same secondary messenger ________ in both tissues but the downstream signaling pathways diverge resulting in different physiological pathways.

Answer 33

Relaxation ; contraction ; cAMP

Epinephrine can be administered to relieve bronchospasms during an asthma attack or to restore cardiac rhythms after arrest. Side effect of albuterol - can cause tachycardia.

Question 34

Trimeric G proteins contain ____ distinct subunits with _____ase activity. They act as a molecular _________.

Answer 34

3 (alpha, beta, gamma) ; GTPase ; on-off switch

Question 35

T or F:

Trimeric G proteins are active when alpha subunit is bound to GDP.

Answer 35

False. Trimeric G proteins are active when alpha subunit is bound to GTP and inactive when bound to GDP.

Question 36

GEF (guanine nucleotide exchange factors) are proteins that ________ G-proteins by promoting exchange of GDP for GTP.

Answer 36

Activate

Question 37

GAP (GTPase-activating proteins) _______ G proteins by promoting GTPase activity

Answer 37

Inactivate, or speed up the inactivation of G proteins as GTPase activity hydrolyzes GTP to GDP and Phosphate (Pi)

Question 38

A(n) ___________ is typically a embrace-bound enzyme that catalyze rxns that produce _________ messengers.

Answer 38

Effector protein ; second

Question 39

CAMP,cGMP, DAG, IP3 and Ca2+ are all examples of _________

Answer 39

Secondary messengers

Question 40

Slide 27-30

Answer 40

Finish

Question 41

Gs activation ________ adenylate Cyclase

Answer 41

Activates

Question 42

Adenylyl Cyclades generates _______ from ATP, which activates ____

Answer 42

cAMP ; PKA

PKA directly regulates many pathways via phosphorylation

Question 43

Gi activation _______ adenylate cyclase

Answer 43

Inhibits

With Gi, cAMP is not produced and PKA is not activated

Question 44

Gt activation by _______ activates cGMP PDE

Answer 44

Light

cGMP PDE catalyze the hydrolysis of cGMP to 5’-GMP

Lower concentration of cGMP causes hyperpolarization of visual cells

Question 45

Gq activation by phospholipase C ________ PLC

Answer 45

Activates

Question 46

PLC cleaves PIP2 into _____ and ______, which translocates to ER and opens ligand-gated ______ channels, increasing _____ concentration, which causes translocation of PKC to plasma membrane where it is activated by DAG.

Answer 46

DAG ; IP3 ; Ca2+

Question 47

T or F
Activators of cGMP PDE increases concentration of cellular cGMP, leading to smooth muscle relaxation and vasodilation (think Viagra, levitate, cialis).

Answer 47

False. Inhibitors of cFMP PDE increases concentration of cellular cGMP that leads to smooth uncle relaxation and vasodilation.

Question 48

Patients may take nitrates (NO) to ______ blood pressure.

Should patients on nitrates take drugs like cialis or viagra?

Answer 48

Lower ; NO - the combo can lead to extreme vasodilation and fatal drops in blood pressure

Question 49

Albuterol is a ________ and _____-Philip molecule that binds to and activate __________ receptors

Answer 49

B-against ; hydro- ; b-andrenergic

Used to treat asthma, bronchitis, COPD. Unresponsive pts can be given epinephrine.

Question 50

Histamines (derived from histidine) bind to 4-histidine in ________. So antihistamines block histamine binding to _________ which prevents the allergic response.

Answer 50

GPCR ; GPCR

Common antihistamines: cetirizine (zyrtec), loratadine (Claritin), diphenhydramine (Benadryl)

Question 51

Cholera toxin prevents the _______ of Gsa and pertussis toxin prevents the ________ of Gia

Answer 51

Inactivation ; activation