Overview
This lecture introduces the modern cell theory, explains differences between prokaryotic and eukaryotic cells, and describes key organelles and their functions in animal and plant cells.
Modern Cell Theory
- The cell is the smallest living unit in all organisms.
- All living things are made of one or more cells.
- All cells come from pre-existing cells.
Types of Cells
- Unicellular organisms consist of a single cell (e.g., amoeba); multicellular organisms have many cells (e.g., humans).
- Prokaryotes (bacteria, archaea) lack a nucleus and membrane-bound organelles.
- Eukaryotes (plants, animals, fungi, protists) have a nucleus and membrane-bound organelles.
Similarities and Differences: Prokaryotes vs. Eukaryotes
- Both have genetic material, cytoplasm, ribosomes, and a cell membrane.
- Prokaryotes have no nucleus or membrane-bound organelles.
- Eukaryotes contain a nucleus and membrane-bound organelles like mitochondria.
Cell Structures and Functions
- The cell membrane (plasma membrane) is selectively permeable and maintains homeostasis.
- Cytoplasm is the jelly-like material inside cells that surrounds internal structures.
- The cytoskeleton supports the cell and helps with movement.
Organelles in Eukaryotic Cells
- Ribosomes make proteins and are found in all cells (not membrane-bound).
- The nucleus houses genetic material and controls cell activities; contains nucleolus for ribosome production.
- Endoplasmic reticulum (ER) processes and transports molecules; rough ER has ribosomes and is involved in protein production, while smooth ER detoxifies and makes lipids.
- Golgi apparatus modifies, sorts, and packages molecules for transport or secretion.
- Mitochondria generate ATP energy via cellular respiration using glucose and oxygen.
Plant Cell Specific Organelles
- Chloroplasts perform photosynthesis, making glucose from light energy; contain green pigment.
- Vacuoles store materials; plant cells usually have a large central vacuole.
- Plant cells have a cell wall for extra protection and shape.
Protein Pathway in Eukaryotic Cells
- DNA instructions in the nucleus guide ribosome-made protein production.
- Proteins travel through rough ER in vesicles to Golgi apparatus for sorting.
- Sorted proteins may be secreted out of the cell via vesicles.
Key Terms & Definitions
- Cell Membrane — selectively permeable barrier controlling entry and exit in the cell.
- Cytoplasm — jelly-like substance inside all cells.
- Ribosome — organelle that synthesizes proteins.
- Nucleus — membrane-bound structure holding genetic material in eukaryotes.
- Endoplasmic Reticulum (ER) — organelle for processing, folding, and transport of molecules.
- Golgi Apparatus — organelle for modifying, sorting, and packaging molecules.
- Mitochondria — power-producing organelle generating ATP.
- Chloroplast — plant organelle for photosynthesis.
- Vacuole — storage organelle in cells.
- Cell Wall — rigid layer in plant cells for protection/shape.
- Prokaryote — cell without nucleus or membrane-bound organelles.
- Eukaryote — cell with nucleus and membrane-bound organelles.
Action Items / Next Steps
- Watch additional videos on the cell membrane and cytoskeleton for more detail.
- Research more organelles in eukaryotic cells online.