What is the permeability of the cell membrane and what is the reason for the choice of permeability

It is the ease with which a substance passes through a biosemipermeable membrane.

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.

Permeability is the ease with which a substance passes through a biosemi-permeable membrane.

The permeability of biosemipermeable membranes to certain molecules in the body can be roughly divided into the following three situations:

There are water molecules that permeate freely; It can be permeable to glucose, amino acids, urea, chloride ions, etc.; Proteins, sodium, potassium, etc., which are not easily permeable.

The existence of permeability has important physiological significance for the movement of water inside and outside the cell, the exchange of various substances, and the maintenance of pH and osmotic pressure. In some pathological situations (such as allergies, trauma, burns, hypoxia, etc.), reactions such as tissue edema occur due to the destruction of the normal structure and function of the biosemipermeable membrane, which increases its permeability.

1. The essence of the two is different:

1. The essence of cell membrane fluidity: The cell membrane phospholipid constitutes the basic scaffold of the membrane by molecular layers, and this scaffold is not static.

2. The essence of cell membrane selective permeability: the membrane can only allow some substances (such as glucose, carbon dioxide, etc.) to pass through, and cannot let other substances (such as proteins) pass through.

Second, the nature of the two is different:

1. The nature of cell membrane fluidity: The phospholipid bilayer of the cell membrane is a light oil-like liquid with fluidity. Some protein molecules are embedded on the surface of the phospholipid molecular layer, some are partially or completely embedded in the phospholipid bilayer, and some span the entire phospholipid bilayer.

Most protein molecules are also motile.

2. The nature of cell membrane selective permeability: selective permeability is a kind of semi-permeability, and only bioactive membranes have selective permeability.

The fluidity of the cell membrane refers to the fluidity of its phospholipid bilayer, which is a structural property; Selective permeability refers to the selectivity of proteins in its structure to some substances that can permeate the membrane, which is a functional property.

Fluidity refers to the structural feature, and selective passability is a functional feature that refers to the selective absorption of the cell membrane when it absorbs substances.

The fluidity of the cell membrane is caused by the lateral sliding and longitudinal expansion of the phospholipid bilayer, the scaffold of the membrane, and the movement of membrane proteins, such as endocytosis and cytocytosis of amoebae, and the change of membrane thickness when heated. This is a structural feature of the membrane.

Selective permeability mainly refers to the ability of carrier proteins on the membrane to selectively allow small molecule substances to enter and exit the cell, such as amino acids, inorganic salts, etc. This is a functional feature of the membrane.

Differences: 1. Different definitions.

Selective permeability: The cell membrane of a living cell has the property of only allowing some substances to pass through and not others. It is more emphasized that this is a property (a property of the cell membrane of a living cell, and this is one way to tell if a cell is a living cell).

Permeability: The property of a membrane that allows ions or molecules to pass through. Although this is also a property, the actual use is a numerical value, and permeability can be measured using qualitative and quantitative methods.

Second, the dispersion is greater than the structure is different.

Cell membrane permeability vertical refers to the structure of the cell membrane with the nature of a semi-permeable membrane. For example, grease and water can be permeable but macromolecules cannot.

Selective permeability refers to the selective permeability of membrane proteins on the cell membrane. For example, K+ and N+ are selected to enter the cells.

The selective permeability of the cell membrane is related to the type of molecule that passes through. The smaller and more hydrophobic or non-polar the molecule, the easier it is to pass through the membrane, such as; O2, CO2, N2, benzene, uncharged polar small molecules can also quickly diffuse through the membrane, such as: H2O and glycerol, for some uncharged polar macromolecules (such as glucose, sucrose) and some ions (such as H+, Na+, HCO3-), impermeable.

1.Specific transporters (including carrier proteins, channel proteins) with different structures and functions in the cell membrane, and they differ in type, quantity, and activity on the plasma membrane of different cells.

2.The hydrophobic characteristics of the phospholipid bilayer of the cell membrane that is invisible.

3.Vitality of cells. The above aspects have a direct role in determining the selection and permeability of cell membranes.

The cell grandchild membrane isolates each cell from its surroundings and maintains a relatively stable environment inside the cell. At the same time, the cell membrane also has important functions such as material exchange, cell recognition, secretion, excretion, and immunity.

The ways in which substances move in and out of the cell include free diffusion (transport from the side with a high concentration of a substance to a measure with a low concentration without consuming energy and carriers), active transport (transporting from the side with a low concentration of a substance to the side with a high concentration of energy and carriers), and endocytosis and efflux (macromolecules and particulate matter).

In the process of active transport, due to the different number of carriers of different substances on the cell membrane, the number, speed and difficulty of different substances entering and leaving the cell are different, which reflects the functional characteristics of the cell membrane - selective permeability.