Bio117 Chapter 7: Chemical Signals

Nervous System: Working Cell

Neuron

Nervous System: Distance from Target Cells

Near Zero

Nervous System: Type of Signal

Electrical (nerve impulse)

Nervous System: Speed of Signal

Fast

Nervous System: Duration of Signal

Brief

Nervous System: Specificity of Signal

Very specific

Nervous System: Coordinated Signals?

Very Coordinated

Endocrine System: Working Cell

Endocrine Cell

Endocrine System: Distance from Target Cells

Very far

Endocrine System: Type of Signal

Chemical (hormones)

Endocrine System: Speed of Signal

Very slow

Endocrine System: Duration of Signal

Long

Endocrine System: Specificity of Signal

Not very specific

Endocrine System: Coordinated Signals?

Not very coordinated

Neural Signaling

Neurotransmitters, short distance

Autocrine Signaling (Autocrines)

Self signaling

Paracrine Signaling (Paracrines)

Alongside(intermediate) signaling, cell to cell

Endocrine Signaling

Long distance via bloodstream, hormones and neurohormones

Pheromones: Prison/Dorm Effect

Menstral cycle syncing

Pheromones: Parental Bonding/Nursing Effect

Babies recognize mother’s odor

Pheromones: “S3X” (Social) Pheromones

Activates brain chemical Oxytocin correlating with affiliation or familiarity

First Messengers

extracellular, neurotransmitters (autocrines, paracrines), hormones (autocrines, paracrines), cytokines

Second Messengers

intracellular, calcium, cAMP

Types of ion channels

ligand gated (chemically gated), voltage gated

cAMP/PK Signal Transduction

Receptor binding activates G-Protein (3 subunits), G-Protein activates Adenylyl Cyclase to turn ATP into cAMP, cAMP activates cAMP-dependent protein kinase, cAMP-dependent protein kinase phosphorylates proteins for cell response

Signal Amplication

1 recepter binding first messenger can lead to a cascading effect: 100 cAMP, 100 PKA (protein kinase A), 10,000 phosphorylated enzymes, 1,000,000 phosphorylated enzymes

Gs(+) Protein

Stimulatory Chemical Signal binds to receptor, receptor activates stimulatory G-protein, sends stimulatory G-protein alpha subunit to enhance adenylate cyclase activity

Gi(-) Protein

Inhibitory Chemical Signal binds to receptor, receptor activates inhibitory G-protein, sends inhibitory G-protein alpha subunit to inhibit adenylate cyclase activity

PLC (Phospholipase C)

converts PIP2 into IP3 and DAG

PIP2 (Phosphoinositol biphosphate)

substrate for PLC, contain 1 glycerol and 2 fatty acids

IP3 (Inositol triphosphate)

created from PIP2, goes to smooth ER, smooth ER transfers stored calcium into cytosol for cell response

DAG (Diacylglycerol)

created from PIP2, activates Protein Kinase C (PKC), PKC phosphorylates calcium channel which then opens for calcium to get into cell

Calcium from Calcium Channel

Activates Calmodulin, Calmodulin activates Calmodulin-dependent protein kinases, which phosphorylates proteins for cell response

Second messengers of IP3 and DAG Signal Transduction

IP3, DAG, Ca²+, Ca²+ activated Calmodulin

cAMP vs cGMP

cAMP: activates cAMP-dependent PKs → Protein Phosporylation → Cellular Responses (ex. Muscle Contractions)

cGMP: activates cGMP-dependent PKs → Protein Phosporylation → Cellular Responses (ex. Muscle Relaxations)

Nitric Oxide (NO) gas

chemical messenger, L-argenine activates nitric acid synthase → NO → Guanylyl Synthase → converts GTP into cGMP → Biological effects

Built-in Tyrosine Kinase

TK built into receptor, when receptor binds, TK phosphorylates docking protein

JAK Kinase (Janus Kinase)

attached to receptor, phosphorylates proteins for cell response

Eicosanoids

2nd messengers derived from fatty acids

Signal Transduction Using Eicosanoids

Receptor → PLA (Phospholipase A) → converts phospholipids into arachidonic acid → either splits into cycloocygenase pathway or lipoxygenase pathway (both use eicosanoids)

Difference Between PLC and PLA

PLC is used in the signal transduction of TP3 and DAG

PLA is used in the signal transduction of Eicosanoids

Steroid hormones

cytosolic, nuclear (reaches nucleus)

Thyroid hormones

Mitochondrial, nuclear (reaches nucleus)

Hormones

Organic (not carbon dioxide)

Living Cells (not chemicals from dead cells)

Localized (not glucose needed in every cell)

Distance (not neurotransmitters)

Target Cells with Specific Receptors (not nutrients)