Overview
This lecture explains the structure and function of animal cells, highlighting key organelles and comparing animal and plant cells.
Animal Cells: Basic Structure
- Animal cells are eukaryotic, meaning they contain a true nucleus and various organelles.
- Eukaryotic cells are surrounded by a flexible cell membrane, not a rigid cell wall.
- The flexibility of the membrane allows animals to have diverse cell, tissue, and organ types.
Comparison: Animal vs. Plant Cells
- Both animal and plant cells are eukaryotic with organelles.
- Plant cells have rigid cell walls made of cellulose, while animal cells have flexible membranes.
- Plant cells contain organelles that make food (like chloroplasts), which animal cells lack.
- Rigid walls prevent plants from developing complex nerve and muscle cells.
Specialized Animal Cell Features
- Only animals have specialized muscle tissue for movement.
- Animal flexibility enables advanced organ systems and behaviors.
Discovery & Analogy
- Robert Hooke discovered cells in 1665, naming them after monks' cells.
- The cell is compared to a city with different organelles acting as city parts.
Cell Membrane & Movement
- Some animal cells have cilia (tiny arms) or flagella (whip-like tails) for movement.
- Cilia and flagella have a 9+2 microtubule structure.
- The cell membrane controls entry/exit of substances (selective permeability).
Internal Environment & Support
- The cytoplasm is a watery solution that fills the cell.
- The cytoskeleton, made of protein strands, reinforces the cell.
- Centrosomes create microtubules for structural support.
Organelles and Their Functions
- Endoplasmic Reticulum (ER): Network of membranes; rough ER synthesizes proteins, smooth ER makes lipids, detoxifies, and stores ions.
- Ribosomes: Assemble amino acids into polypeptides; found in cytoplasm or attached to ER/nuclear envelope.
- Golgi Apparatus: Modifies, packages, and ships proteins; forms vesicles for transport.
- Lysosomes: Contain enzymes to break down waste and recycle materials.
The Nucleus & Genetic Material
- The nucleus stores DNA, directs cell functions, and is surrounded by a double membrane.
- Chromatin holds DNA; condenses into chromosomes during cell division.
- The nucleolus inside the nucleus makes ribosomal RNA (rRNA) for ribosome assembly.
- Messenger RNA (mRNA) carries instructions from the nucleus to ribosomes.
Mitochondria: The Powerhouse
- Mitochondria perform cellular respiration, converting food into ATP (energy).
- Mitochondria have their own DNA, inherited only from the mother.
- The endosymbiotic theory suggests mitochondria were once separate bacteria.
Key Terms & Definitions
- Eukaryotic cell — cell with a nucleus and membrane-bound organelles.
- Organelles — specialized cell structures with particular functions.
- Cell membrane — flexible barrier controlling substance movement in/out.
- Cilia/Flagella — structures for movement, made of microtubules.
- Cytoplasm — fluid filling the cell, containing organelles.
- Cytoskeleton — protein network for cell shape and structure.
- Endoplasmic Reticulum (ER) — organelle for protein and lipid synthesis.
- Ribosome — structure that builds proteins from amino acids.
- Golgi Apparatus — packages and ships proteins.
- Lysosome — digests and recycles cellular waste.
- Nucleus — stores DNA and regulates cell processes.
- Chromatin — DNA/protein complex inside the nucleus.
- Nucleolus — makes rRNA for ribosome formation.
- mRNA — messenger RNA, carries genetic instructions.
- Mitochondria — site of energy production (ATP).
Action Items / Next Steps
- Review details of protein synthesis and cellular respiration in related episodes, if needed.
- Prepare questions for clarification on organelle functions.