Overview
This lecture explains the parts of the cell, connecting the roles of organelles to key functions like protein synthesis, energy production, and cell structure.
Cell Membrane & Cytoplasm
- The cell membrane is a phospholipid bilayer that encloses cell contents and contains embedded proteins.
- Cytoplasm is the fluid inside the cell where organelles are suspended (cyto = cell, plasm = fluid).
Nucleus and Genetic Information
- The nucleus contains DNA in the form of chromatin and is surrounded by a nuclear envelope.
- DNA in the nucleus is transcribed into mRNA, which carries instructions for building proteins.
- The nucleolus inside the nucleus produces ribosomes.
Protein Synthesis Pathway
- Ribosomes read mRNA instructions and assemble proteins from amino acids.
- Rough Endoplasmic Reticulum (Rough ER) has ribosomes, modifies new proteins (folding, quality control, glycosylation, tagging for destination).
- The Golgi apparatus further modifies proteins, packages them in vesicles, and directs them to their final destinations.
- Smooth Endoplasmic Reticulum (Smooth ER) synthesizes lipids and carbohydrates, often with the help of enzymes (proteins).
Energy Production: Mitochondria
- Mitochondria convert food (sugar) and oxygen into ATP via cellular respiration, releasing CO₂ and water.
- Mitochondria have their own DNA, inherited maternally.
Storage & Breakdown Organelles
- Lysosomes contain enzymes that digest unwanted materials or pathogens.
- Peroxisomes detoxify harmful substances, like hydrogen peroxide.
- Vacuoles store various substances; large in plant cells, small in animal cells (large in fat cells).
Cell Reproduction: Mitosis and Meiosis
- The nucleus provides genetic material for new cells.
- Centrosomes (with two centrioles) help separate chromosomes during cell division.
- The cell membrane divides to form two new cells.
Structure and Movement
- The cytoskeleton (microtubules and filaments) maintains cell shape and organelle placement.
- Microvilli increase cell surface area for absorption (e.g., in the intestines).
- Cilia and flagella (contain microtubules) provide movement; flagella propel sperm cells.
Key Terms & Definitions
- Organelle — Specialized structure within a cell with specific functions.
- Phospholipid Bilayer — Double-layered membrane structure forming the cell boundary.
- Chromatin — DNA in a loose, thread-like form in the nucleus.
- mRNA (Messenger RNA) — RNA copy of DNA that carries protein-building instructions.
- Ribosome — Organelle that assembles amino acids into proteins using mRNA.
- Rough ER — Endoplasmic reticulum with ribosomes, modifies proteins.
- Golgi Apparatus — Packages and ships proteins.
- Smooth ER — Synthesizes lipids and carbohydrates.
- Mitochondria — Organelle that produces ATP, the cell’s energy currency.
- Lysosome — Contains enzymes to break down waste.
- Peroxisome — Detoxifies chemicals.
- Vacuole — Stores substances inside the cell.
- Cytoskeleton — Protein framework providing structure to the cell.
- Microvilli — Cell membrane projections increasing surface area.
- Cilia/Flagella — Structures for cell movement.
- Centrosome/Centriole — Organizes chromosomes during cell division.
Action Items / Next Steps
- Practice naming and explaining functions of cell organelles.
- Review the process of protein synthesis and organelle roles.
- Complete any assigned readings or study diagrams for cell structures.