Lecture on Cell Biology

Introduction

• Feeling overwhelmed with cell biology?
  • This lecture will cover:
    • Introduction to cells
    • Why cells are small
    • Internal organization of cells (compartmentalization and endomembrane system)
    • Cell parts and functions
    • Membrane structure and transport
    • Osmosis
• Presenter: Glenn Wolkenfeld (Mr. W), retired AP Biology teacher
• Resources: Checklist available at AP Bio Success / Checklist

Cells: The Basics

• Basic Cell Structure
  • Cells are the basic unit of life.
  • Structure: Membrane separating cytoplasm from cell exterior, DNA, and systems for maintaining and replicating cells.
  • Importance of proteins (especially enzymes) in cell functions.

Prokaryotic vs. Eukaryotic Cells

• Prokaryotic Cells
  • Small, simple, no nucleus, circular chromosome, plasmids.
  • Found in Archaea and Bacteria domains.
• Eukaryotic Cells
  • Larger, complex, with nucleus, multiple linear chromosomes, mitochondrial presence.
  • Found in the Eukarya domain.

Cell Size and Surface Area

• Importance of surface area for diffusion of substances.
• Small cells have a higher surface area to volume ratio.
• Larger cells are less efficient in nutrient and waste diffusion.
• Example: Elephant ears and fish gills increase surface area for diffusion.

Cellular Compartmentalization

• Advantages
  • Allows distinct internal chemistry.
  • Increases internal surface area for enzyme activity.
• Comparison
  • Prokaryotic: Fewer compartments.
  • Eukaryotic: Highly compartmentalized, with structures like lysosomes, ER, Golgi apparatus, vacuoles.

Endomembrane System

• Dynamic, interconnected internal membranes and compartments including:
  • Nuclear membrane
  • Rough and smooth ER
  • Golgi apparatus
  • Lysosomes

Origin of Eukaryotic Cells

• Endosymbiosis Theory
  • Mitochondria and chloroplasts originated from free-living bacterial cells.
  • Evidence: Own DNA, binary fission, ribosome similarity, double membranes.

Eukaryotic Cell Parts and Functions

• Nucleus: Stores DNA, site of ribosome assembly.
• Ribosomes: Translate mRNA into proteins, found free or bound to ER.
• Mitochondria: Convert food energy to ATP.
• Endoplasmic Reticulum (ER)
  • Rough: Protein synthesis.
  • Smooth: Lipid synthesis, detoxification.
• Golgi Apparatus: Modifies, packages proteins for transport.
• Lysosomes: Digestive enzymes for intracellular digestion.
• Cytoskeleton: Protein fibers, enable cell movement.

Membrane Structure and Function

• Phospholipids
  • Hydrophobic tails, hydrophilic heads form bilayer.
• Fluid Mosaic Model
  • Membrane composed of phospholipids, proteins, cholesterol in motion.

Membrane Transport

• Diffusion: Molecules move from high to low concentration.
• Passive Transport: No energy, includes simple and facilitated diffusion.
• Active Transport: Requires energy, moves substances against gradient.
• Bulk Transport
  • Endocytosis: Membrane engulfs substances.
  • Exocytosis: Vesicle contents released outside cell.

Osmosis

• Definition: Water diffusion from high to low concentration.
• Effects on cells:
  • Hypotonic: Cell swells as water enters.
  • Hypertonic: Cell shrinks as water leaves.
  • Isotonic: Water movement balanced.

Plant Structures

• Stomata: Pores for gas exchange, regulated by guard cells.
• Cell Wall: Provides support, prevents overexpansion.

Water Potential

• Concept: Tendency of water to move from areas of high to low potential.
• Formula: Ψ = Ψs + Ψp

Conclusion

• Encouragement to use learn-biology.com for study resources.
• Mention of upcoming video series and additional learning materials.