Chapter 15 - Cell Communication Part 1: Nuclear Receptors & GPCRs

Question 1

What are intracellular signals?

Answer 1

Signals originating within the cell for rapid metabolic regulation.

Question 2

What are extracellular signals?

Answer 2

Signals between cells, such as hormones, for metabolic integration.

Question 3

Give examples of intracellular signals.

Answer 3

Fe metabolism, substrate availability, misfolded proteins.

Question 4

Name examples of extracellular signals.

Answer 4

Hormones, neurotransmitters, growth factors.

Question 5

What is autocrine signaling?

Answer 5

Cells responding to signals they release themselves.

Question 6

Define paracrine signaling.

Answer 6

Signals acting locally between nearby cells.

Question 7

What is endocrine signaling?

Answer 7

Hormones traveling through the bloodstream to distant cells.

Question 8

How is signal specificity achieved in cell signaling?

Answer 8

Through ligand-receptor interactions.

Question 9

Name three families of cell surface receptors.

Answer 9

GPCRs, receptor tyrosine kinases, ligand-gated ion channels.

Question 10

Describe G-protein coupled receptors (GPCRs).

Answer 10

Receptors with seven transmembrane domains activating G proteins.

Question 11

What is the role of receptor tyrosine kinases (RTKs)?

Answer 11

They phosphorylate tyrosine residues on signaling proteins.

Question 12

What are nuclear receptors?

Answer 12

Intracellular receptors acting as transcription factors.

Question 13

How does GPCR activation affect intracellular pathways?

Answer 13

It activates G proteins, triggering secondary messengers.

Question 14

Name a second messenger produced by GPCRs.

Answer 14

Cyclic AMP (cAMP).

Question 15

How is cAMP generated?

Answer 15

By adenylyl cyclase activated by G-proteins.

Question 16

What is IP₃ and what does it do?

Answer 16

A second messenger that releases Ca²⁺ from the ER.

Question 17

Describe the role of diacylglycerol (DAG) in signaling.

Answer 17

It activates protein kinase C (PKC).

Question 18

What enzyme produces IP₃ and DAG?

Answer 18

Phospholipase C (PLC).

Question 19

What role does Ca²⁺ play in signal transduction?

Answer 19

It acts as a messenger activating various kinases.

Question 20

Define calmodulin.

Answer 20

A Ca²⁺-binding protein activating enzymes like CaM-kinase.

Question 21

What is the function of CaM-kinase?

Answer 21

It mediates Ca²⁺-dependent signaling, critical for learning and memory.

Question 22

Explain positive feedback in cell signaling.

Answer 22

It amplifies the response, leading to an all-or-none effect.

Question 23

What is negative feedback in signaling?

Answer 23

A mechanism that reduces the response, aiding in signal desensitization.

Question 24

What is receptor desensitization?

Answer 24

Reduction of receptor response after prolonged stimulation.

Question 25

Give an example of a disease caused by disrupted RTK signaling.

Answer 25

Cancer, due to overactive receptor tyrosine kinases.

Question 26

Name a drug class that targets GPCRs.

Answer 26

Beta-blockers, used in heart disease treatment.

Question 27

How does receptor internalization affect signaling?

Answer 27

It removes receptors from the surface, reducing sensitivity.

Question 28

What is adenylyl cyclase's role in the cAMP pathway?

Answer 28

It converts ATP to cAMP, initiating signal transduction.

Question 29

How does Ca²⁺ signaling affect muscle contraction?

Answer 29

It triggers contractions by activating contractile proteins.

Question 30

Explain the fight-or-flight response at the molecular level.

Answer 30

Adrenaline activates GPCRs, raising cAMP, and triggering responses.

Question 31

What does cholera toxin do to G-protein signaling?

Answer 31

Locks G-protein in active state, causing excessive cAMP production.

Question 32

How do GPCRs influence heart rate?

Answer 32

They regulate K⁺ channels, altering the pace of cardiac contraction.

Question 33

What type of receptor is the glucocorticoid receptor?

Answer 33

A nuclear receptor that binds cortisol and regulates gene transcription.

Question 34

Define signal transduction.

Answer 34

The process by which a cell responds to extracellular signals via receptors.

Question 35

What is the role of CREB in the cAMP pathway?

Answer 35

A transcription factor activated by PKA to regulate gene expression.

Question 36

How does phosphorylation affect signaling proteins?

Answer 36

It activates or inactivates proteins, modifying cellular responses.

Question 37

What is a 'second messenger' in cellular signaling?

Answer 37

A small molecule that relays signals inside the cell.

Question 38

Why is Ca²⁺ considered a ubiquitous messenger?

Answer 38

It participates in numerous cellular processes across cell types.

Question 39

What is the effect of IP₃ binding to its receptor?

Answer 39

It releases Ca²⁺ from intracellular stores, modulating cellular activities.

Question 40

Describe the importance of signal amplification.

Answer 40

Ensures a strong response from a small signal input.

Question 41

How does nitric oxide (NO) act as a signaling molecule?

Answer 41

It diffuses across membranes to activate guanylyl cyclase.

Question 42

How do muscarinic Ach receptors affect cardiac cells?

Answer 42

They reduce heart rate by opening K⁺ channels via GPCR signaling.

Question 43

What is the Wnt signaling pathway's role in cell fate?

Answer 43

Regulates cell proliferation and differentiation through gene expression.

Question 44

Name the three major classes of secondary messengers.

Answer 44

Cyclic nucleotides, IP₃/DAG, and Ca²⁺ ions.

Question 45

How is cGMP different from cAMP in signaling?

Answer 45

cGMP often mediates visual and smooth muscle responses.

Question 46

What is the function of arrestins in GPCR signaling?

Answer 46

They desensitize GPCRs, facilitating receptor internalization.

Question 47

Describe Ras protein's role in cell signaling.

Answer 47

A GTPase involved in cell growth signaling via RTKs.

Question 48

How does receptor clustering influence signaling?

Answer 48

Increases the efficiency of signal transduction.

Question 49

What are coincidence detectors in signaling?

Answer 49

Proteins that require two signals to initiate a response.

Question 50

What is the physiological significance of GPCR diversity?

Answer 50

Allows cells to respond to a variety of ligands and signals.