A Tour of the Cell - Chapter 6 (Biology Campbell 12th Edition)

Introduction

• Living Cell: Basic unit of life; cannot be simpler than a cell.
• Domains of Life: Archaea, Bacteria, Eukarya (all based on at least one cell).
• Microscopy: Cells too small to see with naked eye; require light microscopes (LM).

Basic Features of All Cells

• Plasma Membrane: Cytoplasmic membrane/cell membrane.
• Cytosol: Fluid portion of the cytoplasm.
• Chromosomes: Carry genes; archaea/bacteria have one, eukaryotes have multiple.
• Ribosomes: Protein synthesis; all cells have them.

Prokaryotic Cells

• Domains: Archaea and Bacteria.
• Structure: Lack a nucleus; DNA in nucleoid region.
• Organelles: No membrane-bound organelles; have ribosomes.

Eukaryotic Cells

• Nucleus: Contains DNA; bounded by double membrane.
• Membrane-Bound Organelles: Include mitochondria, chloroplasts, ER, Golgi apparatus.
• Cytoplasm: Fluid portion, ribosomes present.

Cell Size

• Surface Area to Volume Ratio: Critical for cell function; limits cell size.
• Plasma Membrane Function: Selectively permeable, allows material exchange.

Eukaryotic Cell Components

• Nucleus: Contains most DNA; separated by nuclear envelope.
• Rough ER: Studded with ribosomes; synthesizes proteins.
• Smooth ER: Synthesizes lipids; detoxifies, stores calcium.
• Golgi Apparatus: Modifies, sorts, packages proteins.
• Lysosomes: Digestive organelle; breaks down macromolecules.
• Vacuoles: Large vesicles; varied functions (e.g., central vacuole in plants).

Mitochondria and Chloroplasts

• Mitochondria: Site of cellular respiration; ATP generation.
• Chloroplasts: Site of photosynthesis; found in plants/algae.
• Endosymbiont Theory: Origin from engulfed prokaryotic cells.

Cytoskeleton

• Function: Support, shape, and movement.
• Components:
  • Microtubules: Thickest; involved in cell shape, organelle movement.
  • Microfilaments: Actin; thinnest, muscle contraction, cell shape.
  • Intermediate Filaments: More permanent, provide structural support.

Extracellular Structures

• Cell Walls: Rigidity and protection in plants, fungi, some protists.
• Extracellular Matrix (ECM): Found in animal cells; structural support, cell communication.

Cell Junctions

• Tight Junctions: Make cells watertight.
• Desmosomes: Fasten cells together.
• Gap Junctions: Allow for communication between cells.

Summary

• Key Takeaways: Understanding cell structure and function; differences between prokaryotic and eukaryotic cells; significance of cell size and structure; role of the cytoskeleton and extracellular components.