Biology 9 Cell communication

What is quorum sensing?

Allows bacteria to determine density of cells by detecting signal molecules released by neighbors

what would happen if quorum sensing were blocked?

Cannot detect when large number of cells, less likely to attack with toxins

How do unicellular eukaryotes communicate?

Unicellular fungi can detect and extend projections towards mates, the protozoan Blepharisma uses a serotonin-like molecule as a mating pheromone

How do multicellular organism cells communicate?

1. Electrically: nerves, gap junctions between animal cells or plasmodesmata between plant cells

2. Chemical: paracrine signaling secretes regulators to communicate in close distance, neurotransmitters are diffused across the synapse in close distance.

How does long distance chemical signaling work?

This is the work of the endocrine system. Hormones are circulated in the body through the blood. They can also be circulated by plant vascular systems.

What happens when the signal reaches the target cell?

1. Reception: signaling molecules bind to receptor protein, usually in plasma membrane, intracellular for small or hydrophobic signals

2. Transduction: changes in receptor, activation of relay molecules, signal conversion to usable form

3. Response: change in the cell

What happens when a signal molecule binds to intracellular receptors?

Signal molecules that are hydrophobic or very small can cross the plasma membrane and the signal-receptor complex can trigger downstream events

Discuss the role of scaffolding proteins

G-protein coupled receptors aid in reception. Protein kinases transfer P from ATP to proteins in transduction

Discuss the role of G-protein coupled receptors

They are cell surface receptors that detect molecules outside the cell and activate cellular responses. They control key physiological functions. They can bind with signal molecules. Many modern medicines impact G-protein pathways. When a signal molecule is bound, the receptor activates the G-protein.

What is the role of receptor tyrosine kinases?

These molecules bind a signal and pass the message through various molecules. Phosphorylated tyrosine can activate relay proteins which trigger cellular responses.

What does signal amplification do?

It helps to generate stronger responses.