C2.1 Chemical Signalling Review

What is a ligand in chemical signaling?

• A type of enzyme that speeds up reactions
• A molecule that binds to a receptor to initiate a response
• A protein that transports signals through the blood
• A neurotransmitter that diffuses across a synapse

Answer explanation

Ligands bind to receptors to trigger a cellular response.

Receptors are proteins with specific binding sites for ligands.

• True
• False

Answer explanation

Receptors recognize and bind specific ligands to activate cell signaling.

Which of the following best describes quorum sensing in bacteria?

• Individual bacteria secreting toxins
• The use of signaling molecules to detect and respond to population density
• Bacteria competing for resources
• The process of bacteria undergoing mitosis

Answer explanation

Bacteria communicate using autoinducers to regulate gene expression collectively.

What happens when a ligand binds to its receptor?

• The receptor is destroyed
• The receptor changes shape and triggers a cellular response
• The receptor releases ATP
• The ligand is absorbed into the receptor

Answer explanation

Ligand binding causes conformational changes, activating signaling pathways.

Which of the following is an example of quorum sensing in bacteria?

• Vibrio fischeri producing bioluminescence.

• Escherichia coli sending neural impulses to each other.

• A macrophage phagocytosing Campylobacter jejuni.

• Lactobacillus spp. breaking down lactose in milk.

Answer explanation

Vibrio fischeri bacteria use quorum sensing to control light production.

Hormones, neurotransmitters, cytokines, and calcium ions are all functional categories of signaling molecules in animals.

• True
• False

Answer explanation

These signaling molecules regulate communication between cells in different ways.

Which category of signaling molecules is mainly involved in the immune response?

• Hormones
• Neurotransmitters
• Cytokines
• Calcium ions

Answer explanation

Cytokines help coordinate immune responses by signaling between immune cells.

What is the difference between a hormone and a neurotransmitter?

• Hormones act over long distances, neurotransmitters act locally
• Neurotransmitters only function in the immune system
• Hormones require direct cell contact
• Both function in the same way

Answer explanation

Hormones travel through the bloodstream, while neurotransmitters act across synapses.