AP Biology Unit 4 Review

Introduction

• Focus on preparing for AP Bio exams and Unit 4 test.
• Topics include Cell Communication, Feedback/Homeostasis, Cell Cycle, and its Regulation.
• Presented by Glenn Wolkenfeld, an experienced AP Biology teacher.
• Emphasis on interacting with material and getting feedback.

Cell Communication and Signaling

Overview

• Cells communicate constantly, essential for multicellular organisms.
• Two main types of signals: local and long-distance.

Types of Communication

• Direct Cell-to-cell Communication: via physical junctions.
• Signal molecules (ligands): include hormones for long-distance and local regulators for short-distance.

Ligand and Receptor Interaction

• Ligands bind to receptors via complementary shapes.
• Leads to cellular responses.

Cell Signaling Phases

1. Reception: Ligand binding to receptor.
2. Signal Transduction: Message conversion often involving signal amplification.
3. Response: Activation of cellular processes.

Mechanism Differences

• Water-soluble hormones: Bind with membrane receptors, use second messengers.
• Steroid hormones: Diffuse through membranes, act as transcription factors.

Example: Epinephrine and G-protein

• Epinephrine triggers a fight-or-flight response.
• Binds to G-protein coupled receptors, starting a phosphorylation cascade.
• Amplifies the signal, leading to liver cells converting glycogen to glucose.

Feedback Mechanisms and Homeostasis

Homeostasis

• Maintenance of stable internal conditions.
• Example: body temperature regulation.

Feedback Types

• Negative Feedback: Returns system to set point (e.g., blood sugar regulation with insulin).
• Positive Feedback: Accelerates processes to a conclusion (e.g., childbirth with oxytocin).

Diabetes and Feedback Disruption

• Type 1 Diabetes: Autoimmune, no insulin produced.
• Type 2 Diabetes: Insulin resistance, ineffective insulin signaling.

The Cell Cycle

Mitosis and Its Functions

• Mitosis duplicates chromosomes, essential for growth, repair, and reproduction.

Cell Cycle Phases

1. Interphase: G1 (growth), S (DNA replication), G2 (preparation for mitosis).
2. Mitosis (M phase): Chromosome segregation and cytokinesis.

Phases of Mitosis

• Prophase: Chromosomes condense, spindle forms.
• Metaphase: Chromosomes align at equator.
• Anaphase: Sister chromatids separate.
• Telophase and Cytokinesis: Daughter cells form.

G0 Phase

• Non-dividing state for specialized cells.

Regulation of the Cell Cycle

Checkpoints

• Critical points to assess and control cell progression.
• Include G1, G2, and M checkpoints.

Apoptosis

• Programmed cell death, essential for removing damaged cells.

Cyclins and CDKs

• Cyclins regulate the cell cycle with fluctuating concentrations.
• Cyclin-dependent kinases (CDKs) activate cellular processes.

Dysregulation and Cancer

Cancer and Cell Cycle

• Cancer involves unregulated cell division.
• Proto-oncogenes and tumor suppressor genes play key roles.

Genetic Mutations

• RAS Proto-oncogene: Can become overactive, leading to increased cell division.
• p53 Tumor Suppressor: Mutation can prevent cell cycle arrest, leading to cancer.

Conclusion

• Cell cycle regulation is crucial to prevent dysregulation and cancer development.

Resources for AP Bio Success

• Utilize Learn-Biology.com for interactive learning and guaranteed exam success.