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Answer:
1.The cell membranes main trait is its selective permeability, which means that it allows more substances to cross it easily, but not others. small molecules that are nonpolar (have no charge) can cross the membrane easily through diffusion but ions (charged molecules) and larger molecules typically cannot.
2. The structure is called a lipid bilayer because it is composed of two layers of fat cells organized in two sheets. the lipid bilayer is typically about five nanometers thick and surrounds all cells providing the cell membrane structure.
3. Osmosis.osmosis is the movement of water across a membrane from an area of low solute concentration to an area of high solute concentration.
4. Active transport. during active transport substances move against the concentration gradient, from an area of low concentration to an area of high concentration. this process is active because it requires the use of energy (usually in the form of ATP). it is the opposite of passive transport.
Explanation:
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Semipermeability is the property of the cell membrane to allow some molecules to pass easily through, but not all. The cell membrane is a lipidic bilayer because it is composed of two layers of lipids. Water molecules can cross the membrane through the osmosis process. Active transport moves materials against the concentration gradient.
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1. What property of the cell membrane allows some molecules to pass easily through, but not all? SEMIPERMEABILITY
A semipermeable membrane -or selectively permeable membrane- allows the passage of only certain molecules and ions through diffusion.
Permeability depends on the molecule or ion size, charge, and concentration, among others.
For instance, small nonpolar molecules or ions can pass through the membrane by simple diffusion. Water can do it by osmosis. Proteins instead, are macromolecules that need to be assisted by a membrane protein (carrier or channel) to make it to the other side of the membrane.
2. Because the cell membrane is made of 2 layers of lipids it is called a LIPIDIC BILAYER
Lipids that compose the membrane are amphipathic, meaning that they have hydrophilic heads and hydrophobic tails. Since membranes are composed mostly of lipids, they need to be arranged as a bilayer. This structure allows lipids to hide their hydrophobic tails, leaving only heads on the surface to interact with water, inside and outside the cell.
3. What is the transport of water across the cell membrane called? OSMOSIS
Osmosis is the phenomenon that occurs when two dilutions of different concentrations -for instance, the interior of the cell and another solution- are separated by a semipermeable membrane.
The membrane allows the pass of water but not solute. Hence, water can move from the most diluted side to the less diluted one.
Water tends to go from the hypotonic solution to the hypertonic one and keeps doing so until concentrations on both sides get equal.
4. Transport that moves materials against the concentration gradient is said to be ACTIVE TRANSPORT
Active transport occurs against the electrochemical gradient, so it needs energy to happen. It carries molecules from a low concentration side to a high concentration side. Carrier proteins are involved in active transport.
There are two types of active transport:
- Primary active transport uses energy from the ATP molecule. An example is Na-K bomb.
- Secondary active transport uses energy from the electric membrane potential. Examples are the carriage of Na, K, Mg metallic ions.
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