Overview
This lecture covers the structure and functions of plant cells, focusing on their key organelles and their roles in cell processes.
Plant Cell Structure
- Plant cells have an outer cell wall that provides rigidity and support.
- The cell membrane lies inside the cell wall and controls selective movement of substances in and out of the cell.
- The cytoplasm contains a network of fibers and filaments forming the cytoskeleton, which connects organelles.
Major Organelles and Their Functions
- The central vacuole stores water, sugars, amino acids, and other useful substances.
- Chloroplasts are green organelles that absorb sunlight for photosynthesis, enabling the plant to produce food.
- Mitochondria are the "powerhouse" of the cell, producing energy-rich ATP molecules.
- The nucleus controls all cell functions and contains the hereditary material (DNA).
- The nuclear membrane surrounds the nucleus and has nuclear pores for material exchange.
- The nucleolus inside the nucleus is dense and spherical, involved in ribosome production.
- Chromatin fibers in the nucleus are made of DNA.
Endoplasmic Reticulum & Protein Synthesis
- The endoplasmic reticulum (ER) is a network of interconnected tubules near the nucleus.
- Smooth ER (SER) lacks ribosomes and has a smooth appearance.
- Rough ER (RER) is studded with ribosomes, giving it a rough texture and is involved in protein synthesis.
- Ribosomes, either attached to RER or free in the cytoplasm, are responsible for synthesizing amino acid chains (proteins).
Golgi Body & Secretion
- The Golgi body receives proteins from the ER, packages them into vesicles, and transports them outside the cell.
Key Terms & Definitions
- Cell wall — rigid outer layer providing support to plant cells.
- Cell membrane — flexible boundary controlling movement of substances in/out of the cell.
- Cytoplasm — gel-like fluid inside the cell containing organelles.
- Cytoskeleton — network of fibers providing structure and support.
- Vacuole — large fluid-filled organelle for storage.
- Chloroplast — organelle for photosynthesis containing green pigment.
- Mitochondria — organelle producing ATP energy.
- Nucleus — control center of the cell holding DNA.
- Nucleolus — dense body inside the nucleus producing ribosomes.
- Chromatin — threadlike DNA-protein fibers in the nucleus.
- Endoplasmic reticulum (ER) — network for protein and lipid synthesis.
- Ribosome — organelle that synthesizes proteins.
- Golgi body — organelle that packages and exports proteins.
Action Items / Next Steps
- Review diagrams of plant cell structure and label all key organelles.
- Prepare a summary table comparing the functions of each organelle.