CELL CYCLE & COMMUNICATION - UNIT GUIDE

Direct contact vs. chemical signaling

The two primary ways cells communicate with one another.

Short-distance cell communication

Communication using local regulators that target cells in the immediate vicinity.

Long-distance cell communication

Communication where signals travel long distances, often via hormones in the bloodstream.

Signal transduction pathway

A sequence linking signal reception with a cellular response, often involving phosphorylation cascades.

Ligand

A chemical messenger that initiates signaling by binding to a specific receptor protein.

G protein-coupled receptors (GPCRs)

An example of a receptor protein commonly found in eukaryotes.

Receptor locations

Receptors may be located on the cell surface, in the cytoplasm, or in the nucleus.

Role of signaling cascades

To relay and amplify incoming signals from receptors, resulting in appropriate cellular responses.

Receptor conformational change

When a ligand binds, the intracellular domain changes shape to initiate signal transduction.

Second messengers

Molecules like cyclic AMP (cAMP) and enzymes that relay and amplify intracellular signals.

Ligand-gated channels

Ion channels that open or close in response to the binding of specific ligands.

Outcomes of signal transduction

Changes in gene expression, altered cell function, modified phenotype, or apoptosis.

Effect of mutations in signaling pathways

Mutations in receptor domains or pathway components can alter downstream signaling and cellular responses.

Chemical inhibitors and activators

Chemicals that interact with signaling components to either activate or inhibit the pathway.

Negative feedback mechanisms

Homeostatic mechanisms that reduce an initial stimulus to return a perturbed system to its target set point.

Positive feedback mechanisms

Mechanisms that amplify responses, moving a variable further away from the initial set point.

Stages of the cell cycle

Sequential stages consisting of interphase (G1, S, G2), mitosis, and cytokinesis.

G1 phase

A phase where the cell is metabolically active, duplicating organelles and cytosolic components.

S phase

The phase where DNA replicates in chromatin form to form two sister chromatids at a centromere.

G2 phase

A phase involving protein synthesis, large-scale ATP production, and centrosome replication.

G0 phase

A nondividing stage where cells can exit the cycle, but may reenter in response to appropriate cues.

Purpose of mitosis

Ensures the transfer of a complete genome into two identical daughter cells for growth and repair.

Prophase (Mitosis)

Sister chromatids condense, mitotic spindle forms, and centrosomes move to opposite poles.

Metaphase (Mitosis)

Spindle fibers align chromosomes along the equator of the cell.

Anaphase (Mitosis)

Paired sister chromatids separate as spindle fibers pull them toward opposite poles.

Telophase (Mitosis)

Mitotic spindle breaks down, a new nuclear envelope develops, and cytoplasm divides.

Cytokinesis

Division of cytoplasm via cleavage furrow in animals or cell plate in plants, producing two cells.

Cell cycle checkpoints

Internal controls that regulate progression through the cell cycle.

Cyclins and Cdks

Protein interactions between cyclins and cyclin-dependent kinases that control the cell cycle.

Consequences of cell cycle disruptions

Disruptions to the cell cycle regulation may result in cancer or apoptosis.