Ce|wal(细胞壁) While the M L is made up of pectic substances(果胶物质), the primary wall also contains hemicelluloses and cellulose pectins(果胶质)α re based on branched chains of a sugar polymer madeψ p of galacturonic acid(半乳糖醛 酸). This is galactose(半乳糖) in which the alcoholic group(崞羟基)atC6is replaced by a carboxyl group(羰基)
• While the M.L. is made up of pectic substances(果胶物质), the primary wall also contains hemicelluloses and cellulose. Pectins(果胶质) are based on branched chains of a sugar polymer made up of galacturonic acid(半乳糖醛 酸). This is galactose (半乳糖)in which the alcoholic group(醇羟基) at C6 is replaced by a carboxyl group(羰基). Cell wall(细胞壁）
Free space Clearly, ionization of carboxyl groups creates a negative charge which makes the cell wall a cation exchange resin. Indeed much Ca2+ is associated with the pectins. In soils with high quantities of free al3+ this toxic ion is bound in large quantities to the cell wall
Free space • Clearly, ionization of carboxyl groups creates a negative charge which makes the cell wall a cation exchange resin. Indeed much Ca2+ is associated with the pectins. In soils with high quantities of free Al3+, this toxic ion is bound in large quantities to the cell wall
ree space Thus when ions enter the cell wal cations can exchange with the cell wal according to their binding affinity typically trivalents>divalents>monovalents Cation exchange capacity(CEC) Anions should not be bound at all
Free space • Thus when ions enter the cell wall, cations can exchange with the cell wall according to their binding affinity :typically • trivalents>divalents>monovalents. • Cation exchange capacity (CEC) • Anions should not be bound at all
cel! membranes(生物膜) Allow for controlled intracellular environment Overton in 1890 demonstrated that penetration of many solutes across the membrane was a function of their lipid solubility. He proposed therefore that the membrane itself was lipid(脂质)
Cell membranes(生物膜) • Allow for controlled intracellular environment • Overton in 1890 demonstrated that penetration of many solutes across the membrane was a function of their lipid solubility. He proposed therefore, that the membrane itself was lipid（脂质）
cel! membranes(生物膜) Unfortunately scientists inferred from this that the permeability(通透性)and diffusion gradient of a substance determined its penetration of the p Most biologically important molecules are not lipid soluble and must penetrate the plasma membrane through proteinaceous transport systems
Cell membranes(生物膜) • Unfortunately scientists inferred from this that the permeability（通透性） and diffusion gradient of a substance determined its penetration of the p.m. • Most biologically important molecules are not lipid soluble and must penetrate the plasma membrane through proteinaceous transport systems