Why are nucleic protein molecules. Which came first: nucleic acid or protein?

Question 1. What processes do scientists study at the molecular level?
Studied at the molecular level critical processes vital functions of the body: its growth and development, metabolism and energy conversion, storage and transmission hereditary information, variability. An elementary unit at the molecular level is a gene - a fragment of a nucleic acid molecule in which a certain amount of biological information is recorded in a qualitative and quantitative sense.

Question 2. What elements predominate in the composition of living organisms?
A living organism contains more than 70-80 chemical elements, but carbon, oxygen, hydrogen, nitrogen and phosphorus predominate.

Question 3. Why are molecules of proteins, nucleic acids, carbohydrates and lipids considered as biopolymers only in the cell?
Molecules of proteins, nucleic acids, carbohydrates and lipids are polymers because they consist of repeating monomers. But only in a living system (cell, organism) do these substances manifest their biological essence, having a number of specific properties and performing many essential functions. Therefore, in living systems such substances are called biopolymers. Outside the living system, these substances lose their biological properties properties and are not biopolymers.

Question 4. What is meant by the universality of biopolymer molecules?
Regardless of the level of complexity and functions performed in the cell, all biopolymers have the following features:
their molecules have few long branches, but many short ones;
polymer chains are strong and do not spontaneously break apart;
capable of carrying a variety of functional groups and molecular fragments that provide biochemical functional activity, i.e., the ability to carry out biochemical reactions and transformations necessary for the cell in the intracellular solution environment;
have flexibility sufficient to form very complex spatial structures necessary to perform biochemical functions, i.e., for the operation of proteins as molecular machines, nucleic acids as programming molecules, etc.;
S-N connections And C-C biopolymers, despite their strength, are also batteries of electronic energy.
The main property of biopolymers is the linearity of polymer chains, since only linear structures are easily encoded and “assembled” from monomers. In addition, if the polymer thread has flexibility, then it is quite easy to form the desired spatial structure from it, and after the molecular machine constructed in this way is depreciated and breaks, it can be easily disassembled into its component elements in order to use them again. The combination of these properties is found only in carbon-based polymers. All biopolymers in living systems are capable of performing certain properties and performing many important functions. The properties of biopolymers depend on the number, composition and order of arrangement of their constituent monomers. The ability to change the composition and sequence of monomers in the polymer structure allows the existence of a huge variety of biopolymer options, regardless of the species of the organism. In all living organisms, biopolymers are built according to a single plan.

American scientists managed to create a molecule that could be the ancestor of modern molecular carriers of hereditary information in a living cell - nucleic acids. It was called TNK because it contains the four-carbon sugar tetrose. It is assumed that in the process of evolution, the DNA and RNA we know came from it.

Until now, scientists involved in the reconstruction of events that occurred on Earth about four billion years ago cannot answer one simple and at the same time very important question - how did deoxyribo appear? nucleic acid, or, more simply, DNA?

After all, without this molecule, the first living cells (or their predecessors) could not store information about the structure of proteins, which is necessary for self-reproduction. That is, without DNA, life simply would not be able to spread across our planet, both in space and time.

Numerous experiments have shown that DNA itself cannot assemble, no matter what conditions you place all its “spare parts”. In order to create this molecule, the activity of several dozen enzyme proteins is required. And if so, then a vicious circle immediately arises in the reasoning of evolutionists, like the problem of the primacy of the chicken and the egg: where could enzymes come from if there is no DNA itself? After all, information about their structure is recorded precisely in this complex molecule.

True, in lately Some molecular biologists offer a way out of this impasse: they believe that hereditary information was previously stored in a “sister” DNA, ribonucleic acid, or RNA. Well, this molecule, under certain conditions, is capable of self-copying, and numerous experiments confirm this (you can read more about this in the article “In the beginning there was... ribonucleic acid”).

It seems that a solution was found - first, ribozymes (the so-called RNA molecules with enzymatic activity) copied themselves and, along the way, mutating, “acquired” information about new useful proteins. After some time, this information accumulated so much that RNA “understood” one simple thing- now you no longer need to do enough yourself difficult work by self-copying. And soon the next cycle of mutations turned RNA into more complex, but at the same time stable DNA, which no longer dealt with such “nonsense”.

However, a definitive answer to the question of how nucleic acids appeared has not been found. Because it still remained unclear how the very first RNA with the ability to copy itself appeared. After all, even it, as experiments have shown, is not capable of self-assembly - its molecule is also very complex for this.

Some molecular biologists, however, suggested that perhaps in those distant times there could have been another nucleic acid, more simple in structure than DNA and RNA. And it was she who was at first the molecule that stored information.

However, it is quite difficult to verify such an assumption, since at present there are no other “keepers” of information from the group of these acids, except DNA and RNA. Nevertheless, modern methods biochemistry makes it possible to recreate such a compound, and then experimentally test whether it is suitable for the role of the “main molecule of life” or not.

And recently, scientists from the University of Arizona (USA) suggested that the common ancestor of DNA and RNA could be TNA, or tetrosonucleic acid. It differs from its descendants in that the “sugar-phosphate bridge” of this substance, which holds together nitrogenous bases (or nucleotides), contains not pentose - a sugar of five carbon atoms, but a four-carbon tetrose. And this type of sugar is much simpler than the five-carbon rings of DNA and RNA. And, most importantly, they can be assembled themselves - from two identical two-carbon pieces.

American biochemists tried to create several short molecules of tetrose and in the process found out that this did not require the use of a massive and complex enzymatic apparatus - under certain conditions, the acid was collected in a saturated solution from “spare parts” using only two enzymes.

That is, it really could have appeared at the very beginning of the formation of life. And until the first living organisms were able to acquire an enzymatic apparatus capable of synthesizing RNA and DNA, it was the TNC that was the custodian of hereditary information.

But could this molecule, in principle, play such an important role? Now it is impossible to directly test this, since there are no proteins capable of reading information from TNCs. However, Arizona molecular biologists decided to take a different route. They conducted an interesting experiment - they tried to connect DNA and TNC strands with each other. The result was a hybrid molecule - in the middle of the DNA chain there was a fragment of TNA 70 nucleotides long. Interestingly, this molecule was capable of replication, that is, self-copying. And this property is the most important for any molecular information carrier.

Moreover, scientists have shown that the TNA molecule can easily combine with a protein and, accordingly, obtain enzymatic properties. The researchers conducted a series of experiments that demonstrated that TNC could produce a structure that specifically binds to the protein thrombin: a TNC chain was formed on a DNA chain, but after the DNA left, it did not lose the features of its structure and continued to specifically hold the protein.

The TNK fragment was 70 nucleotides long, which is enough to create unique “seats” for enzyme proteins. That is, something like a ribozyme could also be obtained from TNCs (let me remind you that it consists of RNA associated with a protein).

So, experiments have shown that TNK could well be the ancestor of DNA and RNA. The latter may have formed somewhat earlier as a result of a series of mutations that led to the replacement of tetrose by pentose. And then, with the help of natural selection, it turned out that ribonucleic acid is more stable and stable than its tetrose predecessor (tetroses are indeed very unstable to a number of chemical influences). And thus the descendant competitively ousted its ancestor from the niche of a molecular information carrier.

The question arises: could TNCs have had some ancestor that contained a simpler sugar than tetrose? Most likely not, and here's why. Only starting with four carbon atoms, sugars can form cyclic structures; three-carbon carbohydrates are unable to do this. Well, without this, nucleic acid is not formed - only cyclic sugar molecules are able to hold all the other components of this substance. So it seems that TNK was indeed the first.

It should be noted that the authors of the work do not at all claim that “this is exactly how it happened.” Strictly speaking, they only proved the possibility of the existence of an ancestral form of ribonucleic acids, such as TNA (which, by the way, is in modern world V natural environment does not occur). The value of the discovery lies in the fact that one of the probable paths of evolution of molecular carriers of hereditary information was shown. Well, and, finally, the old dispute about what appeared first - nucleic acid or protein has been resolved...

What elements predominate in living organisms?
Why are molecules of proteins, nucleic acids, carbohydrates and lipids considered as biopolymers only in the cell?
What is meant by the word universality of biopolymer molecules?

1.Which substance is highly soluble in water? a) fiber b) protein c) glucose d) lipids 2. Protein molecules differ from each other

a) sequence of alternation of amino acids

b) the number of amino acids in the molecule

c) the form of the tertiary structure

d) all the specified features

3. In what case is the composition of a DNA nucleotide correctly indicated?

a) ribose, phosphoric acid residue, thymine

b) phosphoric acid, uracil, deoxyribose

c) phosphoric acid residue, deoxyribose, adenine

d) phosphoric acid, ribose, guanine

4. Monomers of nucleic acids are:

a) nitrogenous bases

b) ribose or deoxyribose

c) deoxyribose and phosphate groups

d) nucleotides

5. Amino acids in a protein molecule are connected through:

a) ionic bond

b) peptide bond

V) hydrogen bond

G) covalent bond

6. What is the function of transfer RNA?

a) transfers amino acids to ribosomes

b) transfers information from DNA

c) forms ribosomes

d) all listed functions

7. Enzymes are biocatalysts consisting of:

a) proteins b) nucleotides c) lipids c) fats

8. Polysaccharides include:

a) starch, ribose

b) glycogen, glucose

c) cellulose, starch

d) starch, sucrose

9. Carbon as an element is included in:

a) proteins and carbohydrates

b) carbohydrates and lipids

c) carbohydrates and nucleic acids

d) everyone organic compounds cells

10. The cell contains DNA:

a) in the nucleus and mitochondria

b) in the nucleus, cytoplasm and various organelles

c) in the nucleus, mitochondria and cytoplasm

d) in the nucleus, mitochondria, chloroplasts

WHAT IS A NUCLEIC ACIDS MONOMETER? OPTIONS (AMINO ACID, NUCLEOTIDE, PROTEIN MOLECULE?) WHAT IS INCLUDED

NUCLEOTIDE COMPOSITION

OPTIONS: (AMINO ACID, NITROGEN BASE, PHOSPHORIC ACID RESIDUE, CARBOHYDRATE?)

Help please!

1.The science that studies cells is called:
A) Genetics;
B) Selection;
B) ecology;
B) Cytology.
2. Organic substances of the cell:
A) Water, minerals, fats;
B) Carbohydrates, lipids, proteins, nucleic acids;
C) Carbohydrates, minerals, fats;
D) Water, minerals, proteins.
3. Of all organic matter The bulk of the cell consists of:
A) Proteins.
B) Carbohydrates
B) Fats
D) Water.
4. Replace the highlighted words with one word:
A) Small molecules of organic substances form complex molecules in the cell.
B) Constant structural components cells perform functions vital to the cell.
B) Highly ordered, semi-liquid internal environment cells ensures the chemical interaction of all cellular structures.
D) The main photosynthetic pigment gives the green color to chloroplasts.
5. Accumulation and packaging chemical compounds in the cage they carry out:
A) Mitochondria;
B) Ribosomes;
B) Lysosomes;
D) Golgi complex.
6. The functions of intracellular digestion are performed by:
A) Mitochondria;
B) Ribosomes;
B) Lysosomes;
D) Golgi complex.
7. The “assembly” of a polymeric protein molecule is carried out:
A) Mitochondria;
B) Ribosomes;
B) Lysosomes;
D) Golgi complex.
8. Totality chemical reactions as a result of which the breakdown of organic substances occurs and the release of energy is called:
A) Catabolism;
B) anabolism;
B) Metabolism;
D) Assimilation
9. "Cheating" genetic information from a DNA molecule by creating mRNA is called:
A) Broadcast;
B) Transcription;
B) Biosynthesis;
D) Glycolysis.
10. The process of formation of organic substances in light in chloroplasts using water and carbon dioxide called:
A) Photosynthesis;
B) Transcription;
B) Biosynthesis;
D) Glycolysis.
11. The enzymatic and oxygen-free process of decomposition of organic substances is called:
A) Photosynthesis;
B) Transcription;
B) Biosynthesis;
D) Glycolysis.
12. Name the main provisions of the cell theory.

Question 1. What processes do scientists study at the molecular level?

The most important life processes of the organism are studied at the molecular level: its growth and development, metabolism and energy conversion, storage and transmission of hereditary information, variability.

Question 2. What elements predominate in the composition of living organisms?

A living organism contains more than 70-80 chemical elements, but carbon, oxygen, hydrogen and nitrogen predominate.

Question 3. Why are molecules of proteins, nucleic acids, carbohydrates and lipids considered as biopolymers only in the cell?

Molecules of proteins, nucleic acids, carbohydrates and lipids are polymers because they consist of repeating monomers. But only in a living system (cell, organism) do these substances manifest their biological essence, possessing a number of specific properties and performing many important functions. Therefore, in living systems such substances are called biopolymers. Outside a living system, these substances lose their biological properties and are not biopolymers.

Question 4. What is meant by the universality of biopolymer molecules?

The properties of biopolymers depend on the number, composition and order of arrangement of their constituent monomers. The ability to change the composition and sequence of monomers in the polymer structure allows the existence of a huge variety of biopolymer options, regardless of the species of the organism. In all living organisms, biopolymers are built according to a single plan.

1.1. Molecular level: general characteristics

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