AP Biology Unit 4 Review

Overview

• Focus on cell communication, feedback/homeostasis, cell division, and cell cycle regulation.
• Presented by Glenn Wolkenfeld, experienced AP Biology teacher.
• Emphasis on interaction with material and feedback for exam success.
• Learn-biology.com and BiomMania AP Bio App recommended for further study.

Cell Communication

Key Concepts

• Cell Signaling: Cells communicate via direct contact or through signaling molecules, known as ligands.
  • Hormones: Long-distance signals traveling through bloodstream.
  • Local Regulators: Short-distance communication.
• Quorum Sensing: Bacterial communication through biofilm formation; cells release signaling molecules to activate gene expression.

Phases of Cell Signaling

1. Reception: Ligand binds to receptor based on complementary shape.
2. Signal Transduction: Message is relayed and amplified, often involving a second messenger.
3. Response: Activation of cellular response or gene expression.

Mechanisms of Hormone Action

• Steroid Hormones: Nonpolar, diffuse through membranes, bind to cytoplasmic receptors, and act as transcription factors.
• Water-Soluble Hormones: Bind to membrane receptors, use second messengers, often result in faster but shorter responses.

Feedback and Homeostasis

Homeostasis

• Maintenance of internal conditions at optimal levels, such as body temperature.
• Feedback Mechanisms: Outputs act as inputs to regulate processes.
  • Negative Feedback: Promotes homeostasis by returning systems to set points.
  • Positive Feedback: Drives processes to completion, such as childbirth.

Examples

• Blood Glucose Regulation: Insulin and glucagon maintain blood sugar levels through antagonistic feedback loops.
• Type 1 and Type 2 Diabetes: Differences in insulin production and cellular response.
• Childbirth and Fruit Ripening: Examples of positive feedback mechanisms.

Cell Cycle

Mitosis

• Functions: Growth, repair, and reproduction in eukaryotes.
• Phases:
  • Interphase: Cell growth and DNA replication.
  • Prophase: Chromosomes condense, spindle formation.
  • Metaphase: Chromosomes align at cell equator.
  • Anaphase: Sister chromatids separate.
  • Telophase: Nuclear membranes reform.
  • Cytokinesis: Cell splits into two daughter cells.

Control of the Cell Cycle

• Checkpoints: Ensure proper division and can trigger apoptosis if conditions are not met.
• Cyclins and CDKs: Regulate cell cycle progression through concentration changes and interactions.

Cell Cycle Regulation and Cancer

Signaling and Genetic Regulation

• Proto-oncogenes and Tumor Suppressors: Mutations can lead to uncontrolled cell division.
• Examples:
  • Ras Proto-oncogene: Constitutive activation leads to excessive growth signals.
  • p53 Tumor Suppressor: Loss of function prevents DNA repair and apoptosis.

Resources for Success

• Learn-biology.com: Interactive resources and guarantees to support AP Bio exam preparation.
• Next Steps: Engage with the curriculum to ensure understanding and readiness for the exam.