Structure of ATP and biological role. Functions of ATP

In any cell of our body millions of biochemical reactions take place. They are catalyzed by a variety of enzymes that often require energy. Where does the cell take it? This question can be answered if one considers the structure of the ATP molecule, one of the main sources of energy.

ATP is a universal source of energy

ATP is decoded as adenosine triphosphate, or adenosine triphosphoric acid. The substance is one of the two most important sources of energy in any cell. The structure of ATP and the biological role are closely related. Most biochemical reactions can occur only with the participation of molecules of matter, especially with regard to plastic metabolism. However, ATP is rarely directly involved in the reaction: for the flow of any process, energy is needed, which is contained precisely in the chemical bonds of adenosine triphosphate.

The structure of the molecules of the substance is such that the resulting bonds between the phosphate groups carry a huge amount of energy. Therefore, such relationships are also called macroergic, or macro-energetic (macro = large, large number). The term macroergic bonds was first introduced by the scientist F. Lipman, and he also suggested using the значок symbol for their designation.

It is very important for the cell to maintain a constant level of adenosine triphosphate. This is especially true for cells of muscle tissue and nerve fibers, because they are the most volatile and require high content of adenosine triphosphate to perform their functions.

The structure of the ATP molecule

Adenosine triphosphate consists of three elements: ribose, adenine and phosphoric acid residues.

Ribose is a carbohydrate that belongs to the pentose group. This means that in the ribose composition there are 5 carbon atoms that are enclosed in a cycle. Ribose binds to the adenine of the β-N-glycosidic bond on the 1-st carbon atom. Also, the residues of phosphoric acid on the 5-th carbon atom are added to the pentose.

Adenine is a nitrogenous base. Depending on which nitrogenous base is attached to the ribose, GTP (guanosine triphosphate), TTP (thymidine triphosphate), TCC (cytidine triphosphate) and UTP (uridine triphosphate) are also isolated. All these substances are similar in structure to adenosine triphosphate and perform approximately the same functions, but they are much less common in the cell.

Remains of phosphoric acid . Ribose can be joined as much as possible by three residues of phosphoric acid. If there are two or only one, then the substance is called ADP (diphosphate) or AMP (monophosphate), respectively. It is precisely between the phosphorus residues that macro-energetic bonds are made, after the rupture of which is released from 40 to 60 kJ of energy. If two bonds break, 80 are allocated, and less often - 120 kJ of energy. If the bond between the ribose and the phosphorus residue is broken, only 13.8 kJ are released, so in the triphosphate molecule there are only two macroergic bonds (P ̴ P ̴ P), and one (P ̴ P) in the ADP molecule.

Here are the features of the structure of ATP. Due to the fact that a macron-energy bond is formed between the phosphoric acid residues, the structure and functions of ATP are interrelated.

The structure of ATP and the biological role of the molecule. Additional functions of adenosine triphosphate

In addition to energy, ATP can perform many other functions in the cell. Along with other nucleotide triphosphates, triphosphate is involved in the construction of nucleic acids. In this case, ATP, GTP, TTF, CTF and UTP are suppliers of nitrogenous bases. This property is used in the processes of DNA replication and transcription.

Also, ATP is necessary for the operation of ion channels. For example, the Na-K channel pumps 3 sodium molecules out of the cell and pumps 2 potassium molecules into the cell. This ion current is needed to maintain a positive charge on the outer surface of the membrane, and only through adenosine triphosphate can the channel function. The same applies to proton and calcium channels.

ATP is the precursor of the secondary messenger cAMP (cyclic adenosine monophosphate) - cAMP not only transmits the signal obtained by the cell membrane receptors, but is an allosteric effector. Allosteric effectors are substances that accelerate or slow down enzymatic reactions. Thus, cyclic adenosine triphosphate inhibits the synthesis of an enzyme that catalyzes the cleavage of lactose in bacterial cells.

The very molecule of adenosine triphosphate can also be an allosteric effector. And in similar processes ATP antagonist is ADP: if triphosphate accelerates the reaction, then diphosphate inhibits, and vice versa. Such are the functions and structure of ATP.

How is ATP formed in a cell

The functions and structure of ATP are such that the molecules of the substance are rapidly used and destroyed. Therefore, the synthesis of triphosphate is an important process of energy generation in the cell.

There are three most important ways of synthesis of adenosine triphosphate:

1. Substrate phosphorylation.

2. Oxidative phosphorylation.

3. Photophosphorylation.

Substrate phosphorylation is based on multiple reactions occurring in the cytoplasm of the cell. These reactions are called glycolysis - the anaerobic stage of aerobic respiration. As a result of 1 cycle of glycolysis from 1 molecule of glucose, two molecules of pyruvic acid are synthesized, which are further used to generate energy, and two ATPs are also synthesized.

• C ₆ H ₁₂ O ₆ + 2 ADP + 2 FN -> 2 C ₃ H ₄ O ₃ + 2 ATP + 4H.

Oxidative phosphorylation. Breathing cells

Oxidative phosphorylation is the formation of adenosine triphosphate by electron transfer via the electron transport chain of the membrane. As a result of this transfer, a proton gradient is formed on one side of the membrane and a molecule is built by means of the protein integral ATP synthase complex. The process proceeds on the mitochondrial membrane.

The sequence of stages of glycolysis and oxidative phosphorylation in mitochondria constitutes a general process called respiration. After a complete cycle of 1 molecule of glucose, 36 ATP molecules are formed in the cell.

Photophosphorylation

The process of photophosphorylation is the same oxidative phosphorylation with only one difference: the photophosphorylation reactions take place in the chloroplasts of the cell under the influence of light. ATP is formed during the light stage of photosynthesis - the main process of obtaining energy from green plants, algae and some bacteria.

In the process of photosynthesis, electrons pass through the same electron transport chain, as a result of which a proton gradient is formed. The concentration of protons on one side of the membrane is a source of ATP synthesis. The molecules are assembled by means of an ATP synthase enzyme.

Interesting facts about ATP

- The average cell contains 0.04% adenosine triphosphate from the whole mass. However, the greatest value is observed in muscle cells: 0.2-0.5%.

- There are about 1 billion ATP molecules in the cell.

- Each molecule lives no more than 1 minute.

- One molecule of adenosine triphosphate is renewed per day 2000-3000 times.

- In total for a day the human body synthesizes 40 kg of adenosine triphosphate, and at each moment the ATP stock is 250 g.

Conclusion

The structure of ATP and the biological role of its molecules are closely related. The substance plays a key role in life processes, because the macroergic bonds between the phosphate residues contain a huge amount of energy. Adenosine triphosphate performs many functions in the cell, and therefore it is important to maintain a constant concentration of the substance. Disintegration and synthesis proceed at high speed, since the binding energy is constantly used in biochemical reactions. It is an indispensable substance of any cell of the body. Here, perhaps, and all that can be said about what structure ATP has.