Submitted by:

Aldrin J. Corañez

4BIO4

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1

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2. The G protein α subunit

activates adenylate cyclase.

Epinephrine/

norepinephrine

receptor

Epinephrine or

Norepinephrine

molecules

Adenylate

cyclase

G

Protein

Inactive

protein

kinase

Active

protein

kinase

Ca2+

ATPase

cAMP

Ca2+

ions

1. Binding of norepinephrine

or epinephrine changes the

shape of the β1 adrenergic

receptor, which activates the

associated G protein.

3. Adenylate cyclase

catalyzes the conversion

of ATP to cAMP.

4. The cAMP activates

protein kinase A.

5. The protein kinase

phosphorylates L-type Ca2+

channels, allowing Ca2+ to

enter the cell, which

stimulates contraction.

6. The protein kinase

phosphorylates Ca2+ channels

on the sarcoplasmic

reticulum, allowing Ca2+ to

move to the cytoplasm, which

stimulates contraction.

7. The protein kinase

phosphorylates myosin,

stimulating contraction.

8. The protein kinase

phosporylates the

sarcoplasmic Ca2+ ATPase,

speeding the removal of Ca2+

from the cytoplasm during

relaxation, which decreases

relaxation time.

P

P

PP

P

P

P

P