Scienze in inglese

Materie:	Appunti
Categoria:	Inglese
Download:	114
Data:	12.01.2006
Numero di pagine:	3
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Osmosis: is the movement of water molecules to an area of high water concentration to an area of low water concentration through a semi permeable membrane.
Hypertonic solution: contains a high concentration of solute relative to another solution. The water diffuses out of the cell causing the cell to shrivel.
Hypotonic solution: contains a low concentration of solute relative to another solution. The water diffuses into of the cell causing the cell to swell and possibly explode.
Isotonic solution: contains the same concentration of solute as another solution. The water diffuses into and out of the cell has at the same rate.
Osmotic pressure: is force per area that prevents water from passing through membrane.
Diffusion: is the net movement of molecules from a region of high concentration to an area of lower concentration. In a solution with equal concentration, some molecules will be moving out of the region and other molecules are moving into that area.
Semi-permeable membrane: bilayer nature of biological membrane. Water can go through. Many solutes won’t go through the membrane fast enough because they are too big. They are very thin layers of materials which allow some things to pass through them.

A region of high concentration: of water is either a very dilute solution of something like sucrose or pure water
. A region of low concentration: of water is a concentration of solution of something like sucrose.

If the medium surrounding the cell has a higher water concentration than the cell; it will again water by osmosis. The cell swells up. If the medium surrounding the cell has a lower water concentration than the cell, it loses water by osmosis. The cell will shrink .If the medium is the same water concentration as the cell there will be no net movement of water. The cell will stay the same rate.
Isotonic: the cells were diluted in serum hey have a biconcave shape. Hypotonic: The cells in serum were diluted in water: the cells are swollen and they have lost their biconcave shape. Hypertonic: a concentrated solution of NaCl was mixed with the cell and serum: the cell assume the spiky shape.

Cell membrane: the most common molecules are the phospholipids. This has a polar head and 2 no polar tails. The phospholipids are aligned tail to tail. Phospholipids and glycolipids are 2 important structural components of cell membrane. Cholesterol is another important component of cell membrane. Proteins are suspended in the inner layer.
Passive transport: requires no energy from the cell. Active transport: requires the cell to spend energy in form of ATP. (1) Proteins-> pumps. (2) Movement->low conc->high conc. (3) energy->ATP. (4) Saturates-> high conc->due to lack of available protein. (5) Pumps->Ca-ATPase / H-ATPase.
Facilitated diffusion: protein act as carriers. Movement is from high concentration to low. Occurs across cell membrane. Saturates when substance reaches high concentration due to lack of available protein.
Secondary active transport: uses proteins for facilitated diffusion. Saturates when substance reaches high concentration due to lack of available protein.
Cotransport→moves more molecules in the same direction. Counter transport moves more molecules in opposite direction.
Lipid bilayer: Is permeable to water oxygen and carbon dioxide. Isn’t permeable to: ions, small hydrophilic molecules and macromolecules.
The Na+/K+ ATPase. The cytosol of animal cell contains a concentration of K+ ions as much as 20times higher than the extracellular fluid. The extracellular fluid contains a concentration of Na+ ions 10times higher than within the cell. Actively transport 3Na+ ions out of the cell for each 2K+ions pumped into the cell.
Power: is the rate at which work is dome. The unit of power is WATT. The kilowatt is used to measure power. A non-SI unit of power is the horsepower. It’s equivalent to 746 watts.
Kinetic energy is the energy of motion. An object which has motion has kinetic energy. It distinguishes the k.e. of an object on a macroscopic level and the k.e. of individual molecules on the molecular level. An elastic collision is one in which isn’t change in kinetic energy after a collision has occurred. An inelastic collision: some energy is dissipated when colliding objects are in contact. The result is the production of heat, sound, light or other form of energy.