Cell Communication

Page
4

When a signal molecule binds as a ligand to the receptor, the gate allows specific ions, such as Na+ or Ca2+, through a channel in the receptor

Slide 26

Fig. 11-7d

Signaling

molecule

(ligand)

Gate

closed

Ions

Ligand-gated

ion channel receptor

Plasma

membrane

Gate open

Cellular

response

Gate closed

3

2

1

Slide 27

Intracellular Receptors

Some receptor proteins are intracellular, found in the cytosol or nucleus of target cells

Small or hydrophobic chemical messengers can readily cross the membrane and activate receptors

Examples of hydrophobic messengers are the steroid and thyroid hormones of animals

An activated hormone-receptor complex can act as a transcription factor, turning on specific genes

Slide 28

Fig. 11-8-1

Hormone

(testosterone)

Receptor

protein

Plasma

membrane

EXTRACELLULAR

FLUID

DNA

NUCLEUS

CYTOPLASM

Slide 29

Fig. 11-8-2

Receptor

protein

Hormone

(testosterone)

EXTRACELLULAR

FLUID

Plasma

membrane

Hormone-

receptor

complex

DNA

NUCLEUS

CYTOPLASM

Slide 30

Fig. 11-8-3

Hormone

(testosterone)

EXTRACELLULAR

FLUID

Receptor

protein

Plasma

membrane

Hormone-

receptor

complex

DNA

NUCLEUS

CYTOPLASM

Slide 31

Fig. 11-8-4

Hormone

(testosterone)

EXTRACELLULAR

FLUID

Plasma

membrane

Receptor

protein

Hormone-

receptor

complex

DNA

mRNA

NUCLEUS

CYTOPLASM

Slide 32

Fig. 11-8-5

Hormone

(testosterone)

EXTRACELLULAR

FLUID

Receptor

protein

Plasma

membrane

Hormone-

receptor

complex

DNA

mRNA

NUCLEUS

New protein

CYTOPLASM

Slide 33

Concept 11.3: Transduction: Cascades of molecular interactions relay signals from receptors to target molecules in the cell

Signal transduction usually involves multiple steps

Multistep pathways can amplify a signal: A few molecules can produce a large cellular response

Multistep pathways provide more opportunities for coordination and regulation of the cellular response

Slide 34

Signal Transduction Pathways