What are the three steps of cell signaling and what happens in each step?

Question 1

3 Stages of Cell Signaling

Answer 1

Signal Reception
Signal Transduction
Cellular Response

Question 2

signal reception

Answer 2

Signaling molecule (ligand) binds to receptor protein
(Peptides, proteins, amino acids, lipids, gases,)
Receptor protein changes shape

Question 3

signal transduction

Answer 3

Relay signals from receptor(s) to target molecule(s)
Protein phosphorylation and dephosphorylation
Signal transduction pathway

Question 4

Cellular response

Answer 4

Cell division
Regulation of transcription
Enzyme activation and inactivation

Question 5

signal reception (repeat)

Answer 5

Signaling molecule binds to a receptor,

causing conformational change in receptor

Question 6

Signal receptors in the plasma membrane

Answer 6

• G protein-coupled receptors (GPCRs)
• Receptor tyrosine kinases
• Ion channel receptors

Question 7

are there signal receptors else where

Answer 7

intracellular

In cytoplasm, nucleus, organelle

Question 8

Signal transduction (repeat)

Answer 8

Cascades of molecular interactions transmit signals from receptors to relay molecules in the cell

Question 9

What kind of pathway is transduction

Answer 9

Signal transduction pathways

Question 10

What kind of signal transduction is common

Answer 10

Protein-protein interactions

Protein phosphorylation and dephosphorylation

Question 11

What is happening in transduction pathway

Answer 11

Series of different proteins in a pathway are phosphorylated in turn, each adding a phosphate to next protein in line

Question 12

Phosphorylation cascade in transduction pathway

Answer 12

• Kinase phosphorylates protein (active form)

- Phosphatase dephosphorylates protein (inactive form)

Question 13

Cellular response

Answer 13

• Cell signaling leads to regulation of transcription
• Growth factor binds to receptor
• Phosphorylation cascade
• Last activated kinase enters nucleus
• Activates transcription factor (stimulates transcription)
• mRNA translated to protein

Question 14

cellular response simplified

Answer 14

transcription stimulated by growth factor

mRNA translated to protein

Question 15

What are some cellular responses to signal transduction

Answer 15

• activates succession of relay molecules including cAMP and 2 protein kinases
• cell proliferation, death, differentiation, and metabolism

Question 16

Which of the following is NOT a common second messenger in cell signaling? 
A.	Ca2+
B.	Cyclic adenosine monophosphate
C.	Diacylglycerol
D.	Tyrosine
E.	Inositol trisphosphate

Answer 16

D. Tyrosine

Question 17

A cell expresses a transmembrane protein that is cleaved at the plasma membrane to release an extracellular fragment.
The fragment binds to receptor proteins on nearby cells and activates signaling pathways resulting in altered gene expression patterns in the cells. What form of intercellular signaling does this represent?

A. Contact-dependent signaling
B. Paracrine signaling
C. Synaptic signaling
D. Endocrine signaling

Answer 17

B) Paracrine signaling acts on neighboring cells via local mediators.

Question 18

Sort the following events to reflect the normal order in which they occur in G-protein-coupled receptor signaling leading to transcription of genes with cAMP response elements.
(A) Binding of CREB to PKA
(B) Binding of cAMP to PKA
(C) Dissociation PKA into catalytic/regulatory subunits
(D) Activation of adenylyl cyclase

Answer 18

DBCA
Activation of adenylyl cyclase
Binding of cAMP to PKA
Dissociation of PKA into catalytic & regulatory subunits
Binding of CREB to PKA

Question 19

Which of the following events normally activates a GTP-binding protein?
A. GTP hydrolysis by the protein
B. Activation of upstream GTPase-activating protein
C. Activation of an upstream guanine nucleotide
exchange factor
D. Phosphorylation of a bound GDP molecule by an
upstream phosphorylase
E. Pi release after GTP hydrolysis

Answer 19

C) Activation of an upstream guanine nucleotide exchange factor