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AP Biology Unit 4 Key Concepts

Nov 21, 2024

Lecture: AP Biology Unit 4 Review

Overview

  • Topics Reviewed: Unit 4
    1. Cell Communication & Signaling
    2. Feedback Mechanisms & Homeostasis
    3. Cell Division & Cycle
    4. Cell Cycle Regulation, Cancer & Apoptosis
  • Presenter: Glenn Wolkenfeld (Mr. W)

Part 1: Cell Signaling

The Big Picture

  • Cells constantly communicate; essential for life.
  • Types of cell communication:
    • Direct Cell-to-Cell Communication: Molecules pass through junctions between adjacent cells.
    • Signal Communication: Cells secrete signaling molecules (ligands) that target cells pick up.
    • Types of Ligands:
      • Hormones: Long-distance travel through bloodstream.
      • Local Regulators: Short-distance communication.

Quorum Sensing in Bacteria

  • Involves biofilm formation (e.g., dental plaque).
  • Bacteria release signaling molecules that activate gene expression for biofilm production.

Phases of Cell Signaling

  1. Reception: Ligand binds to receptor.
  2. Signal Transduction: Message transformed and amplified.
  3. Cellular Response: Activation of cellular functions.

Hormones

  • Steroid Hormones: Nonpolar, diffuse through membranes.
  • Water Soluble Hormones: Require receptors; work through second messengers.

Part 2: Epinephrine & G Protein Coupled Receptors

Fight or Flight Response

  • Epinephrine (Adrenaline): Polar hormone affecting liver, heart, etc.
  • Response Examples: Increase heart rate, glucose production.

Mechanism

  • Epinephrine binds to G Protein Coupled Receptor, activating G proteins and leading to cellular response.
  • Signal Amplification: Small initial signal results in large-scale response.
    • Enzymes Activated: Glycogen phosphorylase converts glycogen to glucose.

Deactivation

  • Process shuts down quickly once the threat is gone.

Part 3: Feedback & Homeostasis

Homeostasis

  • Definition: Maintaining stable internal conditions.
  • Feedback Systems:
    • Negative Feedback: Stabilizes system by reducing output.
    • Positive Feedback: Enhances and accelerates changes.

Examples

  • Blood Sugar Regulation: Insulin and glucagon maintain glucose levels.
    • Type 1 & 2 Diabetes: Result from breakdown in feedback mechanisms.
  • Childbirth & Fruit Ripening: Positive feedback accelerates process to conclusion.

Part 4: The Cell Cycle

Mitosis

  • Purpose: Duplicate chromosomes and divide cells for growth, repair, and reproduction.
  • Phases: Interphase (G1, S, G2), M Phase (Mitosis & Cytokinesis).

Phases of Mitosis

  1. Interphase: Cell grows and duplicates DNA.
  2. Prophase: Chromosomes condense; spindle fibers form.
  3. Metaphase: Chromosomes align at cell equator.
  4. Anaphase: Sister chromatids separate.
  5. Telophase: Nuclear membranes form.
  6. Cytokinesis: Cell splits into two.

Importance of G0 Phase

  • Non-dividing phase for specialized cells like neurons.

Part 5: Regulation of the Cell Cycle

Checkpoints

  • Internal mechanisms ensure proper cell cycle progression.
  • Key Checkpoints: G1, G2, M.

Apoptosis

  • Programmed cell death; prevents damaged cells from dividing.

Cyclin & Cyclin-Dependent Kinases

  • Regulate cell cycle progression through cycles of concentration.

Cancer and Cell Cycle Disregulation

  • Proto-oncogenes & Tumor Suppressors: Mutations here lead to cancer.
  • Example: Mutations in Ras and p53 disrupt normal cell cycle control.

Resources

  • LearnBiology.com: Offers quizzes, flashcards, and tutorials for AP Bio preparation.
  • Free trials available for comprehensive exam review.

Full transcript