What provides the energy for the polymerization reactions in DNA synthesis?

Do you know what provides the energy for the polymerization reactions in DNA synthesis?

Today, we will talk about where does the energy for the polymerization reactions in DNA synthesis comes from? We collected this biology into the biology part of the MCAT practice test.

What provides the energy for the polymerization reactions in DNA synthesis?

1. ATP
2. DNA polymerase
3. breaking the hydrogen bonds between complementary DNA strands
4. the deoxyribonucleotide triphosphate substrates

What is DNA polymerase?

DNA polymerase, also known as DNA-dependent DNA polymerase (DNA pol). It is a class of enzymes that uses parental DNA as a template to catalyze the polymerization of substrate dNTP molecules to form daughter DNA.

DNA polymerase was first discovered in 1957 by American scientist Arthur Komberg in Escherichia coli and was called DNA polymerase Ⅰ. Later, a variety of DNA polymerases were found in other prokaryotes and eukaryotes one after another.

The discovery of DNA polymerase I is of great importance to the study of biology. Because it plays a central role in the life process. It has enabled us to understand how DNA is replicated and repaired.

Before a cell divides, pol I copies all the components of the cell’s DNA. The mother cell then passes a copy of its DNA to each daughter cell, thus passing on genetic information from generation to generation.

Kornberg discovered that pol I can read the complete DNA strand and use it as a template to synthesize a new strand. The latter is identical to the original DNA strand – a process that is no different than a photocopier copying a document.

However, a photocopier is mechanical in copying a document; it does not care about the content of the document. In contrast, some members of the seven subclasses of DNA polymerases are able to proofread the original DNA template, detecting, removing, and correcting errors to produce a new, error-free DNA strand. This includes DNA polymerase I.

Other DNA polymerases can only copy and not repair, so they can either preserve mutations in the genome or cause cell death.

Properties of DNA polymerases

There are several DNA polymerases, three for E. coli. Usually, DNA polymerases have the following common characteristics.

• DNA template is required. Therefore these enzymes are also called DNA-dependent DNA polymerases.
• (ii) Require RNA or DNA as a primer (primer), i.e. DNA polymerases cannot catalyze ab initio.
• Catalyzes the addition of dNTP to the 3′-OH end of the primer at a rate of 1000 nt/min. thus the direction of DNA synthesis is 5′ to 3′.
• All three DNA polymerases are multifunctional enzymes. They function at different stages of the DNA replication and repair process.

DNA polymerase II

DNA polymerase II is a multi-enzyme complex. It has a 5′-3′ polymerase active center and a 3′-5 ‘ exonuclease active center, but no 5 ‘ -3’ exonuclease active center.

Its activity to catalyze the 5′-3′ directional synthesis reaction was only 5% of that of DNA polymerase I. DNA replication was normal in all E. coli mutant strains defective for this enzyme. So it is also not the main polymerase for DNA replication but may play a role in DNA damage repair.

DNA polymerase III

DNA polymerase III is a multi-enzyme complex. The full enzyme consists of a total of 10 subunits in α, β, γ, δ, ε, θ, τ, χ and ψ.

The α, ε, and θ subunits form the core of the enzyme. α subunit contains the 5′-3′ polymerase active center, ε subunit contains the 3′-5′ exonuclease active center, θ subunit may play an assembly role, and other subunits have different roles. The other subunits have different roles.

DNA polymerase III has the highest activity and plays a leading role in the extension of the DNA replication strand and is the main enzyme catalyzing the synthesis of DNA replication.

Eukaryotic DNA polymerases More than a dozen DNA polymerases have been identified in eukaryotes. The five common ones are α, β, γ, δ and ε, all with 5′-3′ polymerase activity.

DNAα polymerase is responsible for synthesizing primers only, and DNAδ polymerase is used for synthesizing cytosolic DNA. DNA polymerase β and DNA polymerase ε are mainly involved in DNA damage repair, and DNA polymerase τ is used for the synthesis of mitochondrial DNA.

DNA double helix structure

The DNA double helix structure is very stable. There are three main forces that keep the DNA double helix structure stable.

The first force is the hydrogen bonding of complementary bases.

And the second force is the accumulation of layers in the DNA molecule, forming a base stacking forces. A hydrophobic core is formed inside the DNA. This means that there are almost no free water molecules in the hydrophobic core, which facilitates the formation of hydrogen bonds between complementary bases.

The third is the negative charge of the phosphate base, and the media cations to form ionic bonds, the DNA double helix structure also has a certain stabilizing effect.

But the hydrogen bond is not the main force in the stability of the DNA double helix structure. Because the energy of hydrogen bonding is very small.

The accumulation of bases in the DNA molecule can make the bases join, this force is called base stacking force, is the main force to stabilize the DNA double helix structure.

It is composed of deoxyribose and phosphate groups alternately connected by ester bonds. There are two main chains, which are “twist-like” and coiled around a common axis in a right-handed direction, parallel to each other and in opposite directions to form a double helix configuration.

The main strand is on the outside of the helix, which explains the hydrophilicity of the main strand, which is composed of sugar and phosphate.

The outer side of the DNA is a backbone of alternating deoxyribose and phosphate. The so-called double helix is the shape of the two main strands.

Correct Answer

This is the correct answer to what provides the energy for the polymerization reactions in DNA synthesis?

The deoxyribonucleotide triphosphate substrates provide the energy for the polymerization reactions in DNA synthesis.

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