What are the ways in which cells transport substances across membranes?

There are five forms of transmembrane material transport in cell membranes: (1) simple diffusion: transmembrane transport of fat-soluble substances such as O2, CO2, NH3, etc.; (b).

Facilitated diffusion: It is further divided into two types:1

Carrier-mediated facilitated diffusion, e.g., glucose from the blood into red blood cells; 2.channel-mediated facilitated diffusion, such as K+, Na+, Ca2+ compliant gradient transmembrane transport; (3) Active operation (primary) such as K+, Na+, Ca2+ inverted concentration gradient or potential gradient transmembrane transport; (iv).

Secondary active transport.

Such as the active transport across the luminal membrane when glucose is absorbed and reabsorbed by intestinal mucosal and renal tubular epithelial cells: (5).

Transport of outgoing and inbound substances.

For example, the process of leukocytes, phagocytes, and foreign bodies is cytokinesis; The secretion of glandular cells and the release of neurotransmitters are cytokinesis.

There are three modes of cell transmembrane material transport: filtration (water-soluble diffusion), simple diffusion (fat-soluble diffusion), and vector transport (including active transport and facilitated diffusion).

1) Filtration (water-soluble diffusion): Molecules of a substance are subjected to hydrostatic or osmotic pressure.

It follows the body fluid through the cell membrane.

The aqueous channel travels from one side of the cell membrane to the other, which is a passive transport mode.

2) Simple diffusion (fat-soluble diffusion): Non-polar molecules are lipids that dissolve in cell membranes with their fat-soluble properties.

The passage of the cell membrane through the cell membrane is called simple diffusion and is also a passive transport modality, also known as passive diffusion.

Vector transport (including active transport and facilitated diffusion): Many cell membranes have special transmembrane proteins that control some important endogenous physiological substances in the body (e.g., sugars, amino acids, neurotransmitters).

metal ions) in and out fine.

Womb. After transmembrane proteins bind to substance molecules or physiological substances on one side of the cell membrane, they undergo a conformational change and release the bound substance on the other side of the cell membrane. This mode of transport is called carrier transport.

Among them, active transport requires energy consumption, while facilitative diffusion does not require energy, and transport is achieved through electrochemical difference, which is also a kind of passive transport.

1. Free diffusion.

The diffusion of a substance from the high-concentration side through the plasma membrane to the low-concentration side does not require a carrier and does not consume energy. The free diffusion rate of a substance is related to the degree of fat solubility of the substance, the difference in solute concentration between the two sides of the membrane, the size of the solute molecule and the properties of the charge.

2. Assist in diffusion.

The substance must be assisted by a carrier protein in order to diffuse from the high-concentration side through the plasma membrane to the low-concentration side, but this method does not consume metabolic energy.

3. Active transportation.

It is the way in which carrier proteins on the plasma membrane consume energy and assist in the transport of substances against the concentration gradient. Substances are transported against the concentration gradient with the assistance of carrier proteins, which consume the energy provided by ATP.

4. Cytocytosis.

The transport of biological macromolecules and particulate matter inside and outside the cell is completed through a series of processes such as membrane bubble formation, displacement, and fusion, so it is called membrane bubble transport, which does not require the assistance of carrier proteins in the transport process, but needs to consume cellular metabolic energy. According to the direction of transport, it can be divided into two ways: endocytosis and exocytosis.

5. Through-cell transportation.

A pinocytotic vesicle is formed on one side of the cell to cross the cytoplasm and the other side releases the material in the vesicle.

6. Intracellular membrane vesicle transport.

The transport of substances between the various parts of the intracellular membrane system also takes place through the membrane vesicle transport mode.

(1) Simple diffusion: transmembrane transport of fat-soluble substances such as O2, CO2, NH3, etc.;

ii) Facilitated diffusion: It is further divided into two types: 1Carrier-mediated facilitated diffusion, e.g., glucose from the blood into red blood cells; 2.channel-mediated facilitated diffusion, such as K+, Na+, Ca2+ transmembrane transport along concentration gradients;

iii) active transport (primary) such as K+, Na+, Ca2+ transmembrane transport against concentration gradients or potential gradients;

iv) Secondary active transport.

Such as the active transport across the luminal membrane when glucose is absorbed and reabsorbed by intestinal mucosal and renal tubular epithelial cells

5) Transporting substances in the form of cells and cells.

For example, the process of white blood cells engulfing bacteria and foreign bodies is cytoenter; The secretion of glandular cells and the release of neurotransmitters are cytokinesis.

Active transport: to ATP and carrier proteins e.g. K+ ions into the cell.

Passive transport: It is also divided into free diffusion and assisted transport.

Free diffusion: Do not enter the cells with ATP and carrier proteins e.g. O2.

Assist in transport: To carrier proteins do not ATP e.g. glucose into red blood cells.

Endocytosis and exocytosis: Depends on the fluidity of the cell membrane to ATP e.g., secreted proteins.

Active transport – ions enter the cell.

Passive transport includes assisting in transport—glucose into red blood cells and free diffusion—water into cells.

Efflux or exocytosis Example: Proteins enter the cell.

Simple diffusion (free diffusion): oxygen, carbon dioxide, nitrogen, ammonia, urea, alcohol and sterol (steroid) hormones, etc.

Facilitated diffusion (assisted diffusion): Channel-mediated transport of glucose, amino acids, nucleotides, sodium ions, potassium ions, etc.

Active transport (active transport): ionics.

Among the corrective recommended answers in water can be facilitated diffusion!!

In addition, there are exotic and inbound effects.

Hello, I am Xiaoli teacher, and I have provided consulting services to nearly 4,000 people, with a cumulative service time of more than 1,000 hours! I've seen your question, and I'm sorting out the answer now, it will take about three minutes, so please wait a little bit Thank you

There are five forms of transmembrane material transport in cell membranes: (1) simple diffusion: transmembrane transport of fat-soluble substances such as O2, CO2, NH3, etc.; (ii) Facilitated diffusion:

It is further divided into two types:1Carrier-mediated facilitated diffusion, e.g., glucose from the blood into red blood cells; 2.

channel-mediated facilitated diffusion, such as K+, Na+, Ca2+ transmembrane transport along concentration gradients; iii) active transport (primary) such as K+, Na+, Ca2+ transmembrane transport against concentration gradients or potential gradients; (4) Secondary active transport, such as active transport across the luminal membrane when glucose is absorbed and reabsorbed by intestinal mucosa and renal tubular epithelial cells: (5) Cytokinesis and cytokinesis material transport, such as the process of leukocyte phagocytosis of bacteria and foreign bodies; The secretion of glandular cells and the release of neurotransmitters are cytokinesis.

The transport mode and characteristics of cell transmembrane substances are as follows:

First, the mode of transshipment:

1. Simple diffusion, differential concentration, no carrier, no energy.

2. Facilitation diffusion, differential concentration, need carrier, no energy, active transport, reverse concentration difference, need carrier, need energy, enter the cell: phagocytosis, swallowing, cytosis, exocytosis.

2. Features: 1. Inverse concentration gradient and inverse chemical gradient transport.

2. The energy needs to be directly supplied by ATP or coupled with the process of releasing energy, and it is sensitive to metabolic toxicity. Pei Fan Silver.

3. All have carrier proteins and depend on membrane transport proteins.

4. It is selective and specific.

Composition of the cell membrane:

It is composed of lipid bilayers, only fat-soluble substances can pass through it, and there are constantly a variety of substances, from ions and small molecules to macromolecules such as proteins, as well as clumpy solids or droplets in and out of cells, including various energy-supplying substances, raw materials for the synthesis of new cellular substances, intermediate metabolites and end products, vitamins, oxygen and carbon dioxide, as well as Na+, K+, Ca2+ ions, etc., their physical and chemical properties are different, and most of them are insoluble in lipids or their water solubility is greater than their fat solubility. Banquet <>

(1) Simple diffusion: The phenomenon of fat-soluble small molecule substances or ions moving from the high-concentration side of the membrane to the low-concentration side is called simple diffusion. Factors influencing simple diffusion:

1.concentration difference on both sides of the membrane; 2.Permeability of the membrane.

The characteristics of simple diffusion are: it does not need the help of membrane proteins, does not consume the cell's own metabolic energy, and proceeds along the concentration difference. Substances transported by simple diffusion:

Fat-soluble small molecule substances, such as CO2, O2, N2, NO, etc.

2) Facilitated diffusion: refers to the transport mode in which water-soluble small molecule substances or ions move from the high-concentration side of the membrane to the low-concentration side of the membrane with the help of membrane proteins. Types of Facilitated Diffusion:

1) Carrier transport: refers to the facilitation diffusion completed with the help of carrier proteins. Features of vector transport:

1.specificity; 2.saturation; 3.

Competitive inhibition. Carriers transport and transport substances: mainly water-soluble small molecule organic substances, such as glucose and amino acids.

2) Channel transport: refers to the facilitation diffusion completed with the help of channel proteins. Classification of channels:

voltage-gated channels; chemically gated channels; Mechanically gated access. Substances transported by channels: mainly inorganic salt ion substances, such as Na+, K+

Factors influencing facilitated diffusion:1concentration or potential difference between the two sides of the membrane; 2.

Number of vectors and functional status of channels. The characteristics of facilitated transport: it needs the help of membrane proteins, does not consume the cell's own metabolic energy, and proceeds along the concentration difference.

3) Active transport: refers to the transport of substances from the low-concentration side of the membrane to the high-concentration through the energy dissipation of the cell itself under the action of the biological pump on the cell membrane. Active Transporting Substances in Transshipment:

Mainly ionic substances such as Na+, K+, Ca2+Characteristics of active transport: it requires the action of a biological pump to digest the cell's own metabolic energy, and proceed against the concentration difference.

Factors influencing active transport:1the functional status of the biological pump; 2.

The metabolic level of the cell.

4) Expulsion and induction: The migration of macromolecular substances from the inside of the cell to the outside of the cell is called expulsion. The migration of macromolecular substances from the outside of the cell to the inside of the cell is called cell entry.

Substances transported in and out of cells: macromolecular substances such as transmitters, hormones, digestive enzymes, bacteria, tissue necrotic fragments, senescent red blood cells. Characteristics of outgoing and incoming:

The movement of the cell membrane is required, which consumes the cell's own metabolic energy.

There are four modes of cell transmembrane material transport: from the perspective of energy consumption, it can be divided into active transport and passive transport.

Free diffusion: refers to the diffusion process of fat-soluble small molecules through the cell membrane along the concentration difference. (Passive).

Transport: CO2, O2, N2, ethanol, urea, etc.

Characteristics: High concentration Low concentration.

No energy consumption. Assisted diffusion: refers to the diffusion of some non-fat-soluble or small fat-soluble small molecule substances from the high-concentration side to the low-concentration side with the help of carrier proteins and channel proteins on the membrane. (Passive).

Characteristics: High concentration Low concentration.

No energy required. Selective.

Permeability can be changed.

Active transport (or active transport): It is the transmembrane transport process in which cells transport substances against a concentration gradient or potential gradient through an energy-consuming process.

Features: High concentration, low concentration, inverse concentration gradient (inverse chemical gradient) transport;

requires energy (directly powered by ATP) or is coupled to a process that releases energy (co-transport) and is sensitive to metabolic toxicity;

all have carrier proteins and are dependent on membrane transport proteins;

Selective and specific.

Membrane vesicle transport (exit and entry): Exit refers to the process by which macromolecular substances in the cytoplasm are expelled from the cell in the form of secretory vesicles. Endocytosis refers to the process by which macromolecular substances or clumps of substances (such as bacteria, viruses, foreign substances, lipids, etc.) enter the cell.

Features: Directional transshipment.

Energy is needed. Depends on a variety of proteins and coupling mechanisms.

It can transport macromolecular substances.