Lecture 9

Question 1

Secreted Cells that Act Locally

Answer 1

Paracrine signaling: secreted signals, between cells, close to each other, not touching, ie: growth factors
Synaptic signaling: local signaling that occurs in animal nervous system, molecules diffuse across synapse, Neurotransmitters

Question 2

Secreted signals that act at distant sites: Hormones

Answer 2

Travel to target cells at distant sites
Animal cells: travel in circulatory system (blood vessels)
Plant cells: travels in vessels, cell to cell, or diffusion in air
ie: endocrine signaling

Question 3

Intracellular signals

Answer 3

Communication WITHIN a cell

Question 4

Intracellular Receptors

Answer 4

Ligands can move directly across membrane bilayer (ie: steroid hormones, thyroid hormones, and nitric oxide)
Receptor in cytosol or nucleus
Hormone-receptor complex acts as “transcription factor” (control rate of transcription)

Question 5

Cell surface signals

Answer 5

Important during development and for immune response
ie: when bacteria enter an organism, it will develop antibodies that white blood cells will detect and bind to, triggering phagocytosis

Question 6

Step 1: Signal Reception

Answer 6

Target cell’s detection of signaling molecule, signal (ligand) bind to receptor, changing the shape of the receptor
Receptors:
- Plasma membrane proteins (ligands: secreted, hydrophilic, water-soluble, or membrane-bound)
- Cytoplasmic or nuclear proteins (ligands: hydrophobic, lipid soluble)

Question 7

Plasma Membrane Receptors: GPCR

Answer 7

G-protein-coupled receptor
Ligands include hormones, neurotransmitters
Important in sensory reception

Question 8

Plasma Membrane Receptors: TKR

Answer 8

Tyrosine kinase receptors
Ligands known as growth factors
Can activate multiple cellular responses (different than G-proteins)
Enzymes that catalyze (speed up) transfer of phosphate group
Abnormal TKR activation are involved in different types of cancer while antibodies that block TKRs and being used to fight it

Question 9

Ligand-gated ion channels

Answer 9

Ligands: neurotransmitters
Ions such as Na+ or Ca+ flow in or out of cell
Important for communication between nerve cells
Some are present in membrane of organelles (sER)
Some of voltage-gated and some are stretch-activated (change in cell membrane)

Question 10

Step 2: Transduction

Answer 10

Converts signal to a form that can bring a specific cellular response
Occurs in steps called the SIGNAL TRANSDUCTION PATHWAY

Question 11

Step 3: Cellular Response

Answer 11

Transduced signal triggers specific cellular response
Almost any cellular activity