Why do cells go through cell fluid for material exchange?

Because the cell fluid is the carrier.

Cell membranes

The cell membrane allows useful substances to enter the cell and keep other substances out of the cell, while also expelling the metabolic waste products produced in the cell to the outside of the cell.

There are three modes of transport through the cell membrane: active and passive assistance, as well as cytocytosis. Cell membranes are selectively permeable. The cell membrane separates the inside of the cell from the outside environment, so that the cell has a relatively stable internal environment

It can allow the substances needed for cell life to enter the cell, and block some substances from the outside of the cell, and at the same time, it can also discharge the waste produced in the cell to the outside of the cell The cell wall plays a protective and supporting role, the nucleus contains genetic material, and the cytoplasm is the place where various life activities are carried out.

There are three modes of transport through the cell membrane: active, passive, assisted, and cytocytosis. Cell membranes are selectively permeable.

Cell membranes are waste products of cellular metabolism.

Is it done by skimming?

Composition of the internal environment: Analysis: Extracellular fluid is also called internal environment, the internal environment is composed of plasma, interstitial fluid, and lymph, and the cells in the body can only exchange substances with the external environment through the internal environment Answer:

Solution: The cells in the body and the external environment do need the internal environment to exchange substances, but not only the internal environment The cells in the body exchange some substances with the external environment through the internal environment, but also need to go through the assistance of various systems and organs, such as the gas exchange of O 2 and CO2 needs to be completed with the help of the respiratory system and blood circulation, and the exchange of nutrients and metabolic wastes also needs to be completed with the help of the digestive system and the urinary system, so it is not only through the internal environment

Can cells in the body only exchange substances with the outside world through extracellular fluid, let me ask you. At present, the cells in the body can only exchange substances with the outside world through extracellular fluid, and this is his exchange method.

Intracellular and extracellular fluids are the parts of body fluids that are both separated from each other and interconnected through the internal environment where substances are exchanged.

Cells are immersed in interstitial fluid, and only the cell membrane is separated between the intracellular fluid, and water and all substances that can penetrate the cell membrane can be exchanged between the intracellular fluid and the interstitial fluid.

Only the capillary wall separates the tissue fluid from the plasma, and water and everything else that can pass through the capillary wall can be exchanged between the two.

Interstitial fluid can also penetrate into the capillary lymphatic vessels to form lymph.

Therefore, the cells in the human body can indirectly exchange substances with the external environment through the internal environment.

Specifically, the oxygen inhaled by the respiratory system and the nutrients absorbed by the digestive system first enter the bloodstream, and then enter the cells in the body through the tissue fluid;

At the same time, the waste products and carbon dioxide produced by cell metabolism in the body must first enter the interstitial fluid, and then enter the bloodstream to be transported to the urinary system and respiratory system for excretion. It can be seen that the cells in the body can only exchange substances with the external environment through the internal environment.

There are several ways in which substances are exchanged inside and outside the cell membrane.

OnePassive transport. When two solutions of the same substance and different concentrations are placed next to each other, the molecules of the solute will produce a net flow along the concentration difference or potential difference (the two are collectively called the electrochemical gradient), which is called passive transport. The driving force during passive transport is electrochemical potential energy.

There is no need for cell membranes or other forms of energy from the cells.

Passive transport can take two forms:

Pure diffusion: The way in which molecules or ions of a substance pass through the cell membrane along an electrochemical gradient is called simple diffusion.

Facilitated diffusion: Some substances that are insoluble in lipids, or have very little solubility, diffuse from the high-concentration side of the membrane to the low-concentration side of the membrane with the "help" of some special proteins in the membrane structure, and the mode of material transport is called facilitated diffusion.

IIActive transshipment. It refers to the process in which a cell moves a substance, molecule, or ion from one side of the membrane to the other through a certain energy-dissipating process of its own, against the electrochemical gradient. The energy required for active transport is provided by the cell membrane or the cell to which the cell membrane belongs.

Active transshipment also comes in two forms:

Primary active transport:In active transport, if the energy required is an active transport process that is directly provided by ATP, it is calledPrimary active transport:, also known as a "sodium pump".

Secondary active transport:Carrier proteins must bind to both the Na+ and the molecules of the species to be transported in order to transport their molecules against the concentration gradient in the direction of the Na+ concentration gradient into the cell. The energy for transport comes indirectly from ATP.

3. Exocytosis and exocytosis transport.

Endocytosis:It refers to the process of entering the cell by certain clumps of external substances, such as bacteria, viruses, foreign bodies, lipoproteins and macromolecular nutrients in plasma. If the ingested substance is solid, it can form larger vesicles, which is called phagocytosis.

If it is a tiny droplet-shaped liquid, smaller vesicles are formed, called pinocytosis.

Exocytosis:For endocrine glands secreting hormones, exocrine glands secreting prozymale granules or mucus, nerve cells secreting and releasing neurotransmitters, etc., the transmembrane potential changes or special chemical signals of the membrane cause the Ca2+ channel in the local membrane to open, and the induced substance bubble is transported to the inner surface of the cell membrane, and after fusing with the cell membrane, the outward opening ruptures and the contents are discharged at one time.

Direct exchange is in the capillaries, and the capillary walls consist of only one layer of epithelial cells.

composition, very thin, conducive to the exchange of substances, and capillaries are distributed throughout the body, surface area.

The sum is great, and it is also conducive to the exchange of matter. Other blood vessels, such as arteries and veins, have thick walls that prevent material exchange.

In addition, blood and interstitial fluid can be exchanged indirectly: the interstitial fluid can penetrate into the lymphatic vessels, and the lymphatic fluid in the capillary lymphatic vessels collects into the lymphatic vessels, and finally in the left and right clavicles.

The lower veins enter the bloodstream, which is also considered a route of material exchange.

Through blood circulation, its main function is to continuously transport oxygen and nutrients to various tissues and organs in the body, and transport the metabolites produced by the respiration of tissues and organs to the excretory organs and excrete them from the body.

A lot of it is not, the intracellular fluid is the fluid inside the cell, and the extracellular fluid is the fluid outside the cell, which is the environment in which the cells of the human body live, also called the internal environment. Plasma in the blood is a tissue fluid that can exchange substances with blood cells, so it can exchange substances with a part of the intracellular fluid.

The nutrients needed by human cells should enter the circulatory system through the digestion and absorption of the digestive system, and the oxygen should enter the circulatory system through the respiratory system, and also fit the nutrients to be transported to the tissues with the circulatory system, enter the interstitial fluid, and then be used by the tissue cells, and the metabolic waste produced by the tissue cells enters the interstitial fluid, and then enters the circulatory system, and through the transportation of the circulatory system, most of the water, urea, and inorganic salts are discharged through the urinary system with urine, and carbon dioxide and part of the water are discharged by the respiratory system. A small amount of inorganic salts are excreted with sweat through **, therefore, the exchange of substances between human cells and the external environment must pass through the digestive system, respiratory system, urinary system, circulatory system, etc