Which statement describes a characteristic of a plant cell but is not true for an animal cell? 1. The cell has a nucleus to cont
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Answer:
Active transport:
- requires energy
- molecules move from low to high concentration sides
- Na+ and K+ move by active transport
Simple diffusion:
- molecules move from high to low concentration sides
- molecules pass between lipids
- small non-polar and polar molecules
Facilitated diffusion:
- molecules move from high to low concentration sides
- involves channel proteins
- move large molecules
Explanation:
- Simple Diffusion is the pathway of only small molecules that freely move through the membrane by momentary openings produced by the lipids' movements. Diffusion is a slow process that requires short distances and pronounced concentration gradients to be efficient. An example of diffusion is osmosis by which water is the transported molecule.
- Facilitated diffusion is the transport of hydrophilic molecules that can not freely cross the membrane. Channel protein and many carrier proteins are in charge of this transport. When uncharged molecules cross the membrane, they do it according to their concentration gradients, going from the more concentrated side to the lower concentrated one. When ions need to cross the membrane, the process depends on an electrochemical gradient. Glucose is an example of a hydrophilic protein that gets into the cell by facilitated diffusion.
Simple diffusion and facilitated diffusion are both passive transport processes because they only depend on electrochemical gradients, so they do not need any energy to occur.
- Active transport is the transport of molecules that move against the electrochemical gradient, so it does need energy to happen. Molecules move from the lower concentration side to the higher concentration side of the membrane. Carrier proteins are in charge of active transport. The needed energy might proceed from the ATP molecules or the membrane's electric potential. An example of molecules moved by active transport are the Na and K.
