Unit 4: Cell Communication and The Cell Cycle

What are the two main types of cell signaling based on distance?

Local signaling (paracrine and synaptic) and long-distance signaling (endocrine).

What are the three stages of cell signaling?

Reception, Transduction, and Response.

What is a ligand?

A molecule that binds to a specific receptor on a target cell.

What is the role of G protein-coupled receptors in cell signaling?

They activate G proteins that then bind to enzymes to trigger a response.

Describe the function of ligand-gated ion channels.

They open or close in response to a ligand binding, allowing or blocking ion diffusion.

What is phosphorylation, and why is it important in cell signaling?

Phosphorylation is the addition of a phosphate group to a protein, which can activate it and propagate a signal.

What are second messengers? Give an example.

Small molecules that spread the signal within the cell; an example is cyclic AMP (cAMP).

What is negative feedback?

A mechanism that reduces or stops a response to return to a stable state, like insulin lowering blood glucose.

What is positive feedback?

A mechanism that reinforces a response, increasing it, like oxytocin in childbirth.

What is the function of endocrine glands?

They release hormones into the bloodstream to regulate various body functions.

Distinguish between peptide and steroid hormones.

Peptide hormones are water-soluble and bind to cell membrane receptors, while steroid hormones are lipid-soluble and pass into cells to bind to internal receptors.

Give an example of a hormone cascade.

Thyroid hormone release controlled by the pituitary gland.

How does an action potential propagate along a neuron?

It travels from dendrite → cell body → axon, jumping at nodes of Ranvier (saltatory conduction).

What happens at a synapse?

Neurotransmitters are released and bind to receptors on the next neuron, triggering a response.

What are the three lines of defense in the immune system?

1. Barrier defenses, 2. Non-specific (innate) immunity, 3. Specific (adaptive) immunity.

What are B cells and T cells, and how do they function in immunity?

B cells produce antibodies in humoral immunity, while T cells destroy infected cells in cell-mediated immunity.

What is the cell cycle?

The life cycle of a cell from its formation to division into two daughter cells.

Why is the cell cycle important?

It enables growth, repair, and the production of identical cells.

What are the phases of interphase?

G1 phase (growth), S phase (DNA replication), and G2 phase (preparation for mitosis).

List the stages of mitosis.

Prophase, Prometaphase, Metaphase, Anaphase, Telophase.

What happens during metaphase in mitosis?

Chromosomes align at the metaphase plate.

What is cytokinesis?

The division of the cytoplasm, completing cell division.

How is cytokinesis different in plant and animal cells?

In animal cells, it occurs through cleavage, and in plant cells, through the formation of a cell plate.