Overview
This lecture continues the discussion on cells, emphasizing the structure, function, and main components of both eukaryotic and prokaryotic cells. It explores how these cell types differ and the roles of their various parts.
Cell Types
- All living things are made up of cells, which are categorized as either prokaryotic or eukaryotic.
- Prokaryotic cells do not have a nucleus or membrane-bound organelles; examples include bacteria and archaea.
- Eukaryotic cells contain a nucleus and several membrane-bound organelles; these cells are found in plants, animals, fungi, and protists.
Prokaryotic Cell Structure
- Prokaryotes have a plasma membrane that surrounds the cell and controls what enters and exits.
- The cytoplasm fills the cell and contains ribosomes for protein synthesis.
- Genetic material (DNA) is located in the nucleoid region, not enclosed by a membrane.
- Most prokaryotes have a cell wall that provides structure and protection.
- Some possess external features such as flagella for movement and pili for attachment to surfaces or other cells.
Eukaryotic Cell Structure
- Eukaryotic cells have a plasma membrane and cytoplasm, like prokaryotes, but also contain complex organelles.
- The nucleus, surrounded by a nuclear envelope, stores the cell’s DNA and controls cellular activities.
- Key organelles include:
- Mitochondria, which generate energy for the cell.
- Endoplasmic reticulum, involved in protein and lipid synthesis.
- Golgi apparatus, which modifies, sorts, and packages proteins.
- Lysosomes, responsible for digestion and waste removal.
- Plant cells, a type of eukaryote, have additional structures:
- A rigid cell wall for support.
- Chloroplasts for photosynthesis.
- A large central vacuole for storage and maintaining cell shape.
Differences Between Cell Types
- Eukaryotic cells are typically larger and more complex than prokaryotic cells.
- Only eukaryotic cells have a defined nucleus and membrane-bound organelles.
- Prokaryotic cells are simpler, lacking these internal compartments.
Key Terms & Definitions
- Prokaryote: A single-celled organism without a nucleus or membrane-bound organelles.
- Eukaryote: A cell that contains a nucleus and membrane-bound organelles.
- Organelle: A specialized structure within a cell that performs a specific function.
- Nucleus: The membrane-bound compartment in eukaryotic cells that contains genetic material.
- Plasma membrane: The outer boundary of the cell that controls the movement of substances in and out.
- Cytoplasm: The jellylike fluid inside the cell where organelles are suspended.
Action Items / Next Steps
- Study diagrams of both prokaryotic and eukaryotic cells to recognize their structures.
- Practice identifying major organelles and understanding their functions in preparation for upcoming quizzes.
- Review the differences between cell types to reinforce understanding of their unique features.