Unit 5

Question 1

Models of cell- cell signaling

Answer 1

Gap junctions, Contact dependent signaling, paracrine signaling, Synaptic signaling, autocrine signaling, endocrine signaling

Question 2

Gap junctions

Answer 2

Direct connections between adjacent cells allowing small molecules and ions to pass

Question 3

Example of Gap junctions

Answer 3

Cardiac muscle cells coordinating contraction

Question 4

Contact dependent signaling

Answer 4

Requires direct contact between membrane proteins of two cells

Question 5

Paracrine signaling

Answer 5

Short distance signaling where molecules diffuse to nearby target cells

Question 6

Paracrine signaling

Answer 6

Short distance signaling where molecules diffuse to nearby target cells

Question 7

Synaptic signaling

Answer 7

Specialized paracrine signaling in neurons using neurotransmitters at synapses

Question 8

Autocrine signaling

Answer 8

A cell signals itself, common in immune responses and cancer proliferation

Question 9

Endocrine signaling

Answer 9

Long distance communication using hormones transported via the bloodstream

Question 10

What are the three stages of cell signaling

Answer 10

Reception, transduction, response

Question 11

Reception stage of cell signaling

Answer 11

Target cell detects a signaling molecule (ligand) that binds to a receptor protein

Question 12

Transduction stage of cell signaling

Answer 12

The receptor converts the extracellular signal into an intracellular signal often involving a signal cascade

Question 13

Response stage of cell signaling

Answer 13

The cell produces a response such as activating genes opening ions channels or modifying metabolic pathways

Question 14

Types of receptors

Answer 14

GPCR (g protein coupled receptors), RTK (receptor tyrosine kinases), Ligand Gated ion channels, intracellular receptors

Question 15

GPCRs

Answer 15

Largest family of receptors, activate intracellular G proteins triggering downstream effects, ex: adrenaline signaling

Question 16

Receptor tyrosine kinases

Answer 16

Membrane receptors that dimerize union ligand binding, activating signaling pathway via phosphorylation cascades

Question 17

Ligand Gated ion channels

Answer 17

Open or close in response to ligand, allowing ion flow, ex: neurotransmitter receptors in neurons

Question 18

Intracellular receptors

Answer 18

Found inside the cell; bind small hydrophobic ligands like steroid hormones which directly regulate gene expression

Question 19

Intracellular signaling mechanisms

Answer 19

Molecular switches and second messengers

Question 20

Molecular switchers

Answer 20

Molecular switches and second messengers

Question 21

Molecular switches

Answer 21

Proteins that toggle between active and inactive states via phosphorylation or GTP binding

Question 22

Secondary messengers

Answer 22

Small molecules that amplify signals within the cell

Question 23

CAMP

Answer 23

Activates protein Kinase A PKA leading to metabolic effects

Question 24

IP3 and DAG

Answer 24

Generated from membrane phospholipids

Question 25

IP3 and DAG

Answer 25

Generated from membrane phospholipids

Question 26

IP3

Answer 26

Triggers Ca2+ release

Question 27

DAG

Answer 27

Activates protein kinase C PKC

Question 28

Calcium ions

Answer 28

Involved in exocytosis, muscle contraction and enzyme activation

Question 29

Nitric Oxide

Answer 29

A gas that diffuses across membranes and triggers vasodilation - Viagra enhances NO signaling

Question 30

Delta Notch signaling

Answer 30

Contact dependent signaling where Notch once cleaved acts as a transcription regulator - example neuron differentiation in drosophila

Question 31

Ras-MAP kinase pathway

Answer 31

Common receptor tyrosine kinase pathway involving the small G protein Ras which when muted is linked to many cancers

Question 32

Difference between GPCRs and RTKs

Answer 32

GPCRs use G proteins to transmit signals inside the cell leading to fast responses, RTKs phosphorylate themselves through auto phosphorylation to recruit signaling proteins leading to cell growth and division

Question 33

Why do secondary messengers matter

Answer 33

They amplify the signal meaning a smaller number of ligand molecules can cause a big cellular response

Question 34

How does cAMP work

Answer 34

cAMP is made from ATP by adenylyl cyclase then activates PKA which phosphorylates the target protein

Question 35

Why is calcium important in signaling

Answer 35

Ca2+ acts as universal signal its low concentration in cytoplasm but high in organelles like ER when released it triggers processes like muscle contraction and neurotransmitter release

Question 36

What are three main stages of cell signaling

Answer 36

Reception, transduction, response

Question 37

What is the difference between paracrine and endocrine signaling

Answer 37

The distance in which the signal travels, paracrine is short distance signaling where molecules go to nearby target cells Endocrine is long distance communication using hormones transported via the bloodstream

Question 38

What type of signaling uses neurotransmitters?

Answer 38

Synaptic signaling

Question 39

How do GPCRs activate intracellular signaling pathways

Answer 39

GPCR are membrane bound receptors that initiate signaling when they bind to extracellular ligands Steps of activation: 1. Ligand binds to extracellular domain of GPCR causing conformational change in receptor activating it 2. GPCR interacts w nearby G protein which is composed of three subunits, alpha which is either active (GPT) or inactive (GDP) and beta and gamma subunits which help regulate 3. The activates G protein subunits interact with intracellular effector proteins to generate cellular response

Question 40

Effectors for GPCRs (Adenylyl cyclase)

Answer 40

Andenylyl cyclase camp pathway is most common Alpha subunit binds and activates enzyme adenylyl cyclase which converts ATP to cAMP (secondary messenger), cAMP activates PKA which phosphorylates target proteins and starts signal cascade

Question 41

Effector for GPCR PLC

Answer 41

Alpha subunit actives phospholipase C, PLC cleaves pip2 into IP3 and DAG IP3 triggers calcium release from ER, DAG activates protein kinase C leading to phosphorylation cascade

Question 42

How do you inactivate GPCR

Answer 42

GTP hydrolyzed back to GDP