Lec. 9 Cell Communication

Question 1

Cell signaling stages

Answer 1

1. Reception- signaling molecule and receptor bind and induces a change in location/shape of receptor
2. Transduction- Relay molecules in intracellular signal transduction pathway
3. Response- Activation of cellular response

Activation of gene transcription, cytoskleton, change in metabolism, etc

Question 2

What are the 4 types of signals?

Answer 2

1. secreted signals act locally
2. secreted signals that act at distant sites
3. cell surface signals
4. intracellular signals

Question 3

Examples of local signal

Explain how they work

Answer 3

1. paracrine signaling (growth factors)
2. Synaptic signaling (neurotransmitters)

Paracrine signaling- Secretory cells make growth factor that releases to extracellular space (exocytosis) and reaches nearby (local) cells
Synaptic- Neurotransmitters are released and diffuse to target cell once signal reaches receptors (more specific)

Question 4

Distant signaling

Answer 4

aka Hormonal signaling
Animal cells: travel in circulatory
Plant cells: travel in vessels, cell to cell, diffusion in air
- An endocrine cell making and releasing hormones that travel to the circulatory system

Insulin is a hormone that is secreted by the pancreas and target cells at distant locations (with insulin receptors) in the blood

Question 5

Intracellular signaling

Answer 5

-Signals that travel from cytoplasm in one cell to another
- Gap junction in animalss, plasmodesmata in plants

Question 6

Cell surface signaling

Answer 6

• A signal molecule binds to receptors and proteins on the surface to travel within the cell
• Important dutring development and for immune response

FC receptors on white blood cells bind to antibodies that have bound to surface molecules in the surface of the bacterium and stimulates phagocytosis

Question 7

What are the types of receptors that aren’t on the cell surface? What are they called?

Answer 7

Ligands can also directly cross the membrane bilayer called intracellular receptors (in the cytosol or nucleus)
1. steroid hormones, thyroid hormes, Nitric Oxide

LIGANDS MUST BE HYDROPHOBIC

Question 8

What are the types of plasma membrane (cell surface) receptors

Answer 8

• Plasma membrane receptors
  1. G-Protein coupled receptor
  2. Tyrosine kinase receptor
  3. ligand-gated ion channels

ligands are hydrophillic

Question 9

G protein coupled receptor

Answer 9

1. Inactive G protein
2. Signaling molecule binds to receptor and GDP is replaced by GTP and activates to receptor
3. G protein is released and binds to enzyme which activates cell response
4. System comes to rest and GTP is dephosphorylated to GDP (which can restart process)

Ligands include hormones, neurotransmitters (important in sensory reception)

Question 10

Tyrosine kinase receptors

Answer 10

1. 2 different tyosine subunits
2. 2 Signalling molecules bind to the tyrosine receptors which dimerize it (come together)
3. When the subunits join, receptor is activated and phosphorylates each other (replacing ATP with ADP)
4. Relay proteins bind to receptors and become active which activates cellular response

Ligands are generally growth factors
Can trigger multiple cellualr response simulaneously
Abornmal TKR involved in cancer (growth factors trigger unregulated division)

Question 11

What receptor are targeted by 60% of medicines

Answer 11

GPCR pathways since most toxins interfere with GPCR dunction

Question 12

Ligand gated ion channels

Answer 12

1. Signalling molecule (such as neurotransmitter) binds to recepetor
2. Receptor opens the channel allowing ions to flow down gradient in/out of cell
3. Cellular respose and channel closes

Ligands are Neurotransmitters (important in nerve cells), Ions flow in or out of cell

Question 13

What are the 2 types of ion channels

Answer 13

1. voltage gated ion channels- activated by electrical signals
2. stretch activated ion channels- activated by mechanical change in cell membrane

Question 14

Mechanisms of transduction:

Answer 14

Protein phosphorylation cascades and second messengers (calcium, IP3, cAMP)