AP Biology Unit 4 – Cell Communication and Cell Cycle: Ultimate Study Notes (CED aligned)

What is a primary purpose of cell communication?

To coordinate cellular activities

Why can only certain cells respond to a signal?

They have the correct receptor

Why can the same signal produce different responses in different cells?

Cells have different proteins and receptors

In autocrine signaling, the signal:

Acts on the same cell that released it

Paracrine signaling is best described as:

Local signaling to nearby cells

Which is a characteristic of endocrine signaling?

Travels through bloodstream to distant cells

Hydrophilic ligands typically:

Bind to membrane receptors

Hydrophobic ligands usually:

Cross the membrane and bind intracellular receptors

What happens when a ligand binds to a receptor?

The receptor changes shape

What occurs during signal transduction?

Signal is relayed and amplified inside the cell

What is signal amplification?

One signal causing a large cellular response

Which is an example of a second messenger?

cAMP

What is the correct order in a GPCR pathway?

Ligand → receptor → G protein → enzyme

Receptor tyrosine kinases are important because they:

Trigger phosphorylation cascades and cell division

What happens when a ligand binds a ligand-gated ion channel?

Channel opens and ions flow across membrane

Intracellular receptors are activated by signals that:

Can cross the membrane (lipid-soluble)

Many signaling pathways result in:

Changes in gene expression

What is negative feedback?

Reduces pathway activity to maintain balance

What occurs during S phase?

DNA replication

What is the result of mitosis?

Two identical daughter cells

During metaphase:

Chromosomes align in the middle of the cell

What happens in anaphase?

Sister chromatids separate

What is checked at the G1 checkpoint?

Cell size and DNA damage

What is the role of cyclins?

Activate CDKs to regulate the cell cycle

Cancer is best described as:

Uncontrolled division due to mutations

Oncogenes result from:

Mutated proto-oncogenes that promote excessive growth

Tumor suppressor genes normally:

Stop or slow the cell cycle

What happens in density-dependent inhibition?

Cells stop dividing when crowded