Cell surface or membrane is made of phospholipid bilayer with embedded proteins and sugars. Cell membrane acts as a barrier between cell and its external environment but it is also responsible for the communication with other cells and transport of molecules inside and outside the cell. It is selectively permeable to ions and molecules (some of them pass through the membrane easily, while others require transport proteins or channels). There are 4 ways of molecule transport:
1. Diffusion – no energy required
2. Facilitated transport – transport proteins included
3. Active and co-transport – energy required
4. Vesicle transport (exocytosis and endocytosis)
Microvilli are extensions of cell membrane that increase its surface for diffusion.
Different types of cell junctions have a different influence on the membrane transport. For example, tight junctions are a barrier and the molecules are unable to pass through.
Answer:
Tiaga
Explanation:
A Tiaga is generally described as a snowy forest.
Polarity of a Water Molecule. Water (H2O) is polar because of the bent shape of the molecule. The shape means most of the negative charge from the oxygen on side of the molecule and the positive charge of the hydrogen atoms is on the other side of the molecule. This is an example of polar covalent chemical bonding.
<span>A dichotomous key is very easy to use because it provides only two choices. </span>
