What is the selection permeability of cells, kneel and beg for details!

To be precise, the biofilm is selectively permeable: it means that small molecule substances, a small number of ions and water molecules needed by cells can freely pass through the biofilm structure (for example, the cell membrane is one of them), while other biological macromolecules such as proteins, starch, etc., as well as some ions and other substances that are not needed by the cell cannot enter and exit the cell freely. (That's it, that's it).

The biggest difference between semi-permeable membranes and biofilms is that semi-permeable membranes are not biologically active.

As long as the size of the molecule of the substance is smaller than the pores on the semi-permeable membrane, then it can pass through the semi-permeable membrane; However, biological touch is different, even if the molecule is small, it depends on whether the cell needs it or not, and it is ultimately controlled by the nucleus, and it needs to be allowed to pass through...

The cell membrane is mainly composed of lipid bilayer and membrane protein, and the selective permeability of the cell membrane is mainly determined by the membrane protein (carrier protein, channel protein), and the simple lipid bilayer membrane is highly impermeable to charged ions such as potassium and sodium, while it is permeable to fat-soluble substances, and of course, the size of the molecule is also required; The same is true for different carrier proteins in the cell membrane to transport different ions, and in general, the factors that affect the passage of substances through the cell membrane are, whether they are fat-soluble, the size of the molecule, and the chargeability.

The so-called selective permeability is selective passing, that is, selecting some substances for absorption according to the needs of the cell.

No points, forget it to be a good person, cell selection permeability means that because it is a semi-permeable membrane, some things can pass through, some can't, and some can be recognized and let it pass.

According to the needs of the cell itself, it is a little conscious that it wants to go in.

on the cell membrane. The following three points are decisive in the choice of permeability:

1. Specific transporters with different structures and functions in cell membranes (including carrier proteins.

channel proteins), which differ in type, number, and activity on the plasma membrane of different cells.

2. The phospholipid bilayer of the cell membrane itself.

hydrophobicity.

Features. 3. Cell viability.

Selective permeability means that the membrane can only allow some substances (e.g., glucose, carbon dioxide.

etc.), the property of not allowing other substances (such as proteins) to pass through. Selective permeability is a type of semi-permeability, and only bioactive membranes have selective permeability.

The cell wall is not selectively permeable. The cell wall (main components: cellulose and pectin) is not a membrane structure (main components: phospholipids and proteins) and is fully permeable, allowing the free passage of any substance. Therefore, it is not a permeable membrane or a semi-permeable membrane.

1. Maintain the shape of the cell, control the cell growth, increase the mechanical strength of the cell, 2. The cell wall allows small molecules and low molecular weight proteins such as ions and polysaccharides to pass through, while blocking macromolecules or microorganisms.

3. Some oligosaccharide fragments in the defense and resistance cell wall can induce the formation of phytoalexin, and they also have a regulatory effect on other physiological processes.

4. Enzymes in the cell wall of other functions are widely involved in the synthesis, transfer, hydrolysis, transport of extracellular substances to the cell, and defense of cell wall polymers.

5. Participate in the mutual adhesion between cells, that is, "plasmodesmata".

The cell membrane, also known as the plasma membrane, is a membrane structure located on the periphery of the protoplast, close to the cell wall, and its role is to protect the inside. The main substances that make up the plasma membrane are proteins and lipids, as well as a small amount of polysaccharides, trace amounts of nucleic acids, metal ions and water, which are old under the electron microscope, and the cell membrane fixed with osmium tetroxide has obvious "dark-light-dark" three parallel bands, the inner and outer two dark bands are composed of protein molecules, and the middle layer of bright bands is composed of double layers of lipid molecules, and the thickness of the three is about and, such a membrane is called a unit hand membrane or biofilm.

The selective permeability of the cell membrane means that the cell membrane allows water molecules to pass freely, and the ions and small molecules that the cell chooses to absorb can also pass through, while other ions, small molecules and macromolecules cannot pass through. Selective permeability is an important property of cell membranes in terms of function.