Overview
This lecture covers the main parts of the cell, focusing on organelles and their roles in protein synthesis, energy production, storage, reproduction, and structure.
Cell Membrane & Cytoplasm
- The cell membrane is a phospholipid bilayer that encloses the cell and controls entry and exit of substances.
- Proteins are embedded in the membrane, serving as channels and receptors.
- Cytoplasm refers to the fluid inside the cell where organelles are suspended.
Protein Synthesis Process
- The nucleus contains DNA (genetic material) and is surrounded by the nuclear envelope.
- DNA in the nucleus is transcribed into mRNA, which carries instructions to build proteins.
- The nucleolus inside the nucleus produces ribosomes.
- Ribosomes read mRNA and assemble amino acids into proteins.
- The rough endoplasmic reticulum (rough ER), studded with ribosomes, modifies proteins (folding, quality control, glycosylation, destination tagging).
- Proteins are sent to the Golgi apparatus for further modification and packaging into vesicles.
- Vesicles transport proteins to their final destination: cell membrane, outside the cell, other organelles, or smooth ER.
- The smooth endoplasmic reticulum (smooth ER) synthesizes lipids and carbohydrates, often using protein enzymes.
Energy Production
- Mitochondria convert food (sugar) and oxygen into ATP through cellular respiration.
- ATP is the cell’s main energy currency.
- Mitochondria contain their own DNA, inherited from the mother.
Storage & Breakdown
- Lysosomes contain enzymes to break down waste, pathogens, or old organelles (lysis means to break apart).
- Peroxisomes detoxify harmful substances, like hydrogen peroxide.
- Vacuoles store various chemicals; they are large in plant cells, small in animal cells.
Cell Reproduction
- The nucleus holds genetic information needed for mitosis and meiosis.
- The cell membrane divides to create new cells.
- Centrosomes (containing centrioles) organize microtubules and help separate chromosomes during cell division.
Structure & Movement
- The cytoskeleton, made of microtubules and filaments, provides structural support and holds organelles in place.
- Microvilli increase cell surface area for absorption (e.g., in the intestine).
- Cilia are hair-like projections with microtubules enabling movement (e.g., in the lungs).
- Flagella are long, whip-like structures for movement (e.g., sperm cells).
Key Terms & Definitions
- Cell Membrane — Phospholipid bilayer that surrounds and protects the cell.
- Cytoplasm — Fluid inside the cell.
- Nucleus — Organelle containing DNA.
- Nucleolus — Structure in the nucleus that makes ribosomes.
- Ribosome — Organelle that assembles proteins from mRNA instructions.
- Rough Endoplasmic Reticulum (Rough ER) — Modifies and folds proteins; has ribosomes.
- Smooth Endoplasmic Reticulum (Smooth ER) — Synthesizes lipids and carbohydrates.
- Golgi Apparatus — Modifies, packages, and ships proteins.
- Mitochondria — Produces ATP energy through cellular respiration.
- Lysosome — Breaks down waste and cellular debris.
- Peroxisome — Detoxifies toxins.
- Vacuole — Stores substances.
- Centrosome/Centriole — Organizes microtubules during cell division.
- Cytoskeleton — Protein framework supporting cell shape and movement.
- Microvilli — Surface extensions that increase surface area.
- Cilia/Flagella — Structures for cell movement.
Action Items / Next Steps
- Practice identifying and naming all cell structures.
- Try to explain the protein synthesis process involving different organelles.
- Review diagrams and blank study sheets as practice.
- Read assigned material or unit guides as directed.