Cell Communication

Page
6

Further regulation of cell metabolism is provided by G-protein systems that inhibit adenylyl cyclase

Slide 42

First messenger

Fig. 11-11

G protein

Adenylyl

cyclase

GTP

ATP

cAMP

Second

messenger

Protein

kinase A

G protein-coupled

receptor

Cellular responses

Slide 43

Calcium Ions and Inositol Triphosphate (IP3)

Calcium ions (Ca2+) act as a second messenger in many pathways

Calcium is an important second messenger because cells can regulate its concentration

Slide 44

EXTRACELLULAR

FLUID

Fig. 11-12

ATP

Nucleus

Mitochondrion

Ca2+ pump

Plasma

membrane

CYTOSOL

Ca2+

pump

Endoplasmic

reticulum (ER)

Ca2+

pump

ATP

Key

High [Ca2+]

Low [Ca2+]

Slide 45

A signal relayed by a signal transduction pathway may trigger an increase in calcium in the cytosol

Pathways leading to the release of calcium involve inositol triphosphate (IP3) and diacylglycerol (DAG) as additional second messengers

Animation: Signal Transduction Pathways

Slide 46

Fig. 11-13-1

EXTRA-

CELLULAR

FLUID

Signaling molecule

(first messenger)

G protein

GTP

G protein-coupled

receptor

Phospholipase C

PIP2

IP3

DAG

(second messenger)

IP3-gated

calcium channel

Endoplasmic

reticulum (ER)

Ca2+

CYTOSOL

Slide 47

Fig. 11-13-2

G protein

EXTRA-

CELLULAR

FLUID

Signaling molecule

(first messenger)

G protein-coupled

receptor

Phospholipase C

PIP2

DAG

IP3

(second messenger)

IP3-gated

calcium channel

Endoplasmic

reticulum (ER)

Ca2+

CYTOSOL

Ca2+

(second

messenger)

GTP

Slide 48

Fig. 11-13-3

G protein

EXTRA-

CELLULAR

FLUID

Signaling molecule

(first messenger)

G protein-coupled

receptor

Phospholipase C

PIP2

DAG

IP3

(second messenger)

IP3-gated

calcium channel

Endoplasmic

reticulum (ER)

Ca2+

CYTOSOL

Various

proteins

activated

Cellular

responses

Ca2+

(second

messenger)

GTP

Slide 49

Concept 11.4: Response: Cell signaling leads to regulation of transcription or cytoplasmic activities