1. Diffusion
Diffusion is the movement of molecules from an area with a high concentration to other areas with a lower concentration caused by the kinetic energy of the molecules. The rate of diffusion through the cell membrane depends on the difference in concentration, molecular size, charge, solubility in lipid particles and temperature. In general, substances that dissolve in lipids, the hydrophobic molecules diffuse through the membrane more easily than hydrophilic molecules. In addition, the cell membrane is also permeable to small molecules that are not charged as H2O, CO2, and O2. In the same circumstances, small molecules more rapidly diffuses through the cell membrane than large molecules. Simple diffusion of hydrophilic molecules is higher than 7-8 Å (Å = angstrom = 10-10 m) can hardly take place because it was blocked by a cell membrane, but such molecules can enter the cell by diffusion assisted or facilitated diffusion. Assisted diffusion depends on a special transport mechanism of the cell membrane like permease. Permease is a protein (enzyme) cell membrane that would give way to ions and uncharged polar molecules that can cross two hydrophobic lipid layer of the cell membrane. ADP diffusion into and out of the mitochondrial ATP also requires diffusion helped. In all helped the diffusion process, the molecules move in the direction of the concentration gradient.
2. Osmosis
In essence, osmosis is a process of diffusion. Osmosis is the diffusion of each solvent through a differentially permeable membrane. Universal solvent is water. Thus, it can be said that osmosis is the diffusion of water through a differentially permeable membrane of high concentration of solvent (water) to the solvent concentration is low (less water). Osmosis process will stop if the concentration inside and outside the cell has been balanced. When the cells have a higher concentration of dissolved substances (less water, or hypertonic) than outside the cell, then the water outside the cell to enter the cell. Events entry of water into the cell can result in rupture of cells in animal cells (hemolysis). Whereas, in the plant cells, the cells will only be inflated because retained by the cell wall. High concentration of water outside the cell called hypotonic. Meanwhile, when the cell has a lower concentration of solute (water) than outside the cell, then the water is inside the cells out of the cell. The discharge of water from the cell causes the cell to shrink. In animal cells, these cells are called Crenation contractionary, while in plant cells called plasmolysis.
3. Transport Active
Active transport is the movement of ions and molecules against a concentration gradient by using the energy to get in or out of the cell through the cell membrane. In addition to requiring energy in the form of ATP, active transport also needs an enzyme to move molecules and ions from a low concentration to a high concentration. In order for the enzyme to function as a pump, then the enzyme has to be able to bind ions and transport ions from one side of the membrane to the other side. Sugar molecules and amino acids are actively transported into the cell uses energy. This energy is obtained from Na + concentration gradient that occurs in the transport of sodium-potassium. With the help of a special transport proteins, the molecules of glucose and sodium ions into the cell together. Then, sodium is released again by the sodium-potassium pump. Thus, the sodium-potassium pump is not only active transport of Na + and K +, but it does not directly provide the energy for the transport process to another. Endocytosis is a material transport mechanism, such as macromolecular proteins from the fluid outside the cell to inside the cell by wrapping macromolecules such a way dent portion of the cell membrane to the inside. Sac formed then escape from the outside of the membrane and formed vacuoles in the cytoplasm. Then, fused with lysosomes and vacuoles endositik the contents of the organelles together to form secondary lysosomes. Lysosomal enzymes will digest macromolecules into soluble ingredients (amino acids, sugars, and nucleotides).
4. Endocytosis and Exocytosis
Endocytosis is a material transport mechanism, such as macromolecular proteins from the fluid outside the cell to inside the cell by wrapping macromolecules such a way dent portion of the cell membrane to the inside. Sac formed then escape from the outside of the membrane and formed vacuoles in the cytoplasm. Then, fused with lysosomes and vacuoles endositik the contents of the organelles together to form secondary lysosomes. Lysosomal enzymes will digest macromolecules into soluble ingredients (amino acids, sugars, and nucleotides). Exocytosis is the opposite of endocytosis. In the cells that secrete large amounts of protein, the protein is first gathered in a bag coated membrane in the Golgi apparatus, then moves to the cell surface, and closer to the cell membrane and emptied it out.
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