Overview
This lecture explains the structure and function of vacuoles in both animal and plant cells, highlighting key differences and their biological importance.
Vesicles and Vacuoles in Cells
- Vesicles are small sacs of fluid enclosed by a membrane, used to transport substances within cells.
- Examples include vesicles moving proteins from the rough endoplasmic reticulum to the Golgi apparatus and from the Golgi to the cell membrane.
- Vacuoles are larger, longer-lived membrane sacs compared to vesicles.
Vacuoles in Animal Cells
- Animal cell vacuoles are temporary structures.
- They can form during phagocytosis, where pathogens are engulfed into phagocytic vacuoles by white blood cells.
- Lysosomes fuse with phagocytic vacuoles to destroy the engulfed pathogens.
- Animal cell vacuoles also help to remove waste materials.
Vacuoles in Plant Cells
- Plant cells have a large, permanent vacuole surrounded by a membrane called the tonoplast.
- The tonoplast regulates which chemicals enter and exit the vacuole.
- The vacuole contains cell sap, a fluid with dissolved sugars, mineral salts, amino acids, and sometimes poisons or pigments.
- Poisons in vacuoles deter herbivores; pigments attract pollinators.
- Vacuoles can store waste chemicals produced by the plant cell.
Role of Vacuoles in Plant Support
- The cell sap’s low water potential causes water to enter the vacuole by osmosis.
- Water entering the vacuole creates hydrostatic (turgor) pressure against the cell wall.
- This turgidity helps support the plant, especially those without a woody stem.
Key Terms & Definitions
- Vesicle — Small membrane-bound sac that transports substances within a cell.
- Vacuole — Larger, often longer-lived membrane-bound sac; stores substances and maintains cellular conditions.
- Phagocytosis — Process where a cell engulfs particles or pathogens.
- Phagocytic vacuole — Vacuole formed during phagocytosis containing the engulfed material.
- Lysosome — Organelle containing digestive enzymes that break down waste or engulfed materials.
- Tonoplast — Membrane surrounding the vacuole in plant cells.
- Cell sap — Fluid inside plant cell vacuoles, containing dissolved substances.
- Turgid — Condition where plant cells are swollen with water, providing structural support.
Action Items / Next Steps
- Review the differences between animal and plant vacuoles.
- Prepare to describe the structure and function of vacuoles for exam questions.