unit 4 bio vocab

Important Vocabulary for Unit 4: Cell Communication and Cell Cycle (AP Biology)

I. Cell Communication

Ligand – A signaling molecule that binds to a receptor to initiate a cellular response.
Receptor – A protein that detects a specific ligand and initiates signal transduction.
Signal Transduction Pathway – A series of molecular events that relay and amplify a signal to elicit a response.
Juxtacrine Signaling – Direct communication between adjacent cells via membrane-bound molecules or cell junctions.
Paracrine Signaling – Local signaling where cells release molecules that affect nearby target cells.
Autocrine Signaling – A cell produces a signal that it also responds to.
Endocrine Signaling – Long-distance signaling where hormones travel through the bloodstream to reach target cells.
G-Protein Coupled Receptor (GPCR) – A membrane receptor that activates a G-protein, triggering a signal cascade.
Receptor Tyrosine Kinase (RTK) – A membrane receptor that phosphorylates proteins to relay signals.
Ion Channel Receptor – A receptor that opens or closes an ion channel in response to ligand binding.

II. Signal Transduction

Second Messenger – Small molecules (e.g., cAMP, Ca²⁺) that amplify signals inside the cell.
Phosphorylation Cascade – A series of protein activations through phosphorylation, amplifying the signal.
cAMP (Cyclic AMP) – A common second messenger that activates protein kinases.
Protein Kinase – An enzyme that transfers phosphate groups to proteins, activating them.
Protein Phosphatase – An enzyme that removes phosphate groups from proteins, deactivating them.

III. Changes in Signal Transduction Pathways

Mutation – A change in DNA that may affect signal transduction (e.g., cancer-causing mutations).
Inhibitor – A molecule that blocks receptor function or signal transduction (e.g., drugs, toxins).
Apoptosis – Programmed cell death, often triggered by signal transduction pathways.

IV. Feedback Mechanisms

Homeostasis – The maintenance of stable internal conditions through feedback mechanisms.
Negative Feedback – A process that counteracts change to maintain balance (e.g., insulin regulation of blood sugar).
Positive Feedback – A process that amplifies change until a specific outcome is reached (e.g., childbirth contractions).

V. The Cell Cycle

Cell Cycle – The sequence of events in a cell’s life, including growth and division.
Interphase – The longest phase of the cell cycle, where the cell grows and prepares for division.
G1 Phase – The first growth phase; the cell increases in size and prepares for DNA replication.
S Phase – DNA replication occurs, doubling the genetic material.
G2 Phase – The second growth phase; the cell prepares for mitosis.
Mitosis – The division of a cell’s nucleus into two identical nuclei.
Cytokinesis – The division of the cytoplasm to form two daughter cells.

VI. Regulation of the Cell Cycle

Cell Cycle Checkpoints – Control points that regulate the cycle and prevent errors.
G1 Checkpoint – The main checkpoint; determines if a cell will divide or enter G0.
G2 Checkpoint – Ensures DNA replication was completed correctly before mitosis.
M Checkpoint – Ensures chromosomes are correctly attached to spindle fibers before separation.
Cyclin – A regulatory protein whose levels fluctuate to control the cell cycle.
Cyclin-Dependent Kinase (CDK) – An enzyme that, when bound to cyclin, regulates cell cycle progression.
Maturation Promoting Factor (MPF) – A complex of cyclin and CDK that promotes mitosis.
Growth Factor – A signaling molecule that stimulates cell division.
Density-Dependent Inhibition – A phenomenon where crowded cells stop dividing.
Anchorage Dependence – The requirement that cells must be attached to a surface to divide.

VII. Cancer and Uncontrolled Cell Growth

Cancer – Uncontrolled cell growth due to mutations in regulatory genes.
Tumor-Suppressor Gene – A gene that inhibits cell division; mutations can lead to cancer (e.g., p53).
p53 Gene – A tumor suppressor that halts the cell cycle if DNA damage is detected.
Proto-Oncogene – A normal gene that promotes cell division; when mutated, it becomes an oncogene, leading to uncontrolled growth.
Oncogene – A mutated gene that drives uncontrolled cell division, leading to cancer.
Metastasis – The spread of cancer cells to other parts of the body.
Benign Tumor – A non-cancerous mass of cells that do not spread.
Malignant Tumor – A cancerous mass that invades surrounding tissues.

This list covers the essential vocabulary for Unit 4: Cell Communication and Cell Cycle in AP Biology. Let me know if you need study guides, practice questions, or review activities! 😊📚

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