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Transcript
The plant cell. The flow of energy vacuoles Vacuoles have a single membrane: The tonoplast Expansion of plant cells occurs mainly in the vacuole so that this is the largest compartment of most mature cells. Main functions of the vacuole • Isolating materials that might be harmful or a threat to the cell • Containing waste products • Maintaining internal hydrostatic pressure or turgor within the cell • Maintaining an acidic internal pH • Containing small molecules (anthocyanins for color) • Exporting unwanted substances from the cell • Allows plants to support structures such as leaves and flowers due to the pressure of the central vacuole Plamolysis Others components of the cell wall The cell wall is a cross-linked matrix of: Cellulose Lignine Hemicelluloses: regulate the cell enlargement Pectins: attract water to the walls and form the middle lamella Glycoproteins: structural proteins The arrow indicates the middle lamella (ML) holding the cell walls together. Primary cell walls Cellular undifferentiation Support Primary cell walls Unevenly thickened walls. Primary pit fields and plasmodesmate Secondary wall Alkaloids Collenchyma elongated cells with unevenly thickened walls. Simple pits and pit-pairs structural support for shoots and leaves cellulose and pectin. Sclerenchyma Tissues that have ceased elongation. Mature sclerenchyma is composed of dead cells Cellulose, hemicellulose, and lignin. Fibres and sclereids Secondary wall Sclereids are small bundles of sclerenchyma tissue in plants that form durable layers, such as the cores of apples and the gritty texture of pears. astrosclereids Cell wall In a secondary wall commonly we can find S1 Outer layer S2 Middle layer S3 Inner layer In order to increase the thickness and the surface area new cellulose microfibrils are placed on top of those previously formed Cellulose synthase expansines Flow of energy The laws of thermodynamics 1st “energy change” 2nd potential energy at the final state < potential energy of the initial state Exergonic reactions Endergonic reactions Solar radiation and photosynthesis are the better examples of thermodynamic laws and exergonic reactions. Flow of energy Difussion, osmosis, turger Redox reactions Photosynthesis Cellular respira1on Energy of activation An enzyme speeds up a chemical reac4on by lowering its energy of ac4va4on, the energy that must be supplied in order for molecules to react with one another. Temperature and ph and enzymes Temperature and ph and enzymes Define tonoplast What is plasmolysis? Why are pec4nes important? What is the difference between primary pit fields and plasmodesmata? What are sclereids? Draw the structure of the complete cell wall What is the difference between endergonic and exergonic reactions? Define energy of ac4va4on