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By the end of this section, you will be able to:
  • Describe the structure of nucleic acids and define the two types of nucleic acids
  • Explain the structure and role of DNA
  • Explain the structure and roles of RNA

Nucleic acids are the most important macromolecules for the continuity of life. They carry the genetic blueprint of a cell and carry instructions for the functioning of the cell.

Dna and rna

The two main types of nucleic acids are deoxyribonucleic acid (DNA)    and ribonucleic acid (RNA)    . DNA is the genetic material found in all living organisms, ranging from single-celled bacteria to multicellular mammals. It is found in the nucleus of eukaryotes and in the organelles, chloroplasts, and mitochondria. In prokaryotes, the DNA is not enclosed in a membranous envelope.

The entire genetic content of a cell is known as its genome, and the study of genomes is genomics. In eukaryotic cells but not in prokaryotes, DNA forms a complex with histone proteins to form chromatin, the substance of eukaryotic chromosomes. A chromosome may contain tens of thousands of genes. Many genes contain the information to make protein products; other genes code for RNA products. DNA controls all of the cellular activities by turning the genes “on” or “off.”

The other type of nucleic acid, RNA, is mostly involved in protein synthesis. The DNA molecules never leave the nucleus but instead use an intermediary to communicate with the rest of the cell. This intermediary is the messenger RNA (mRNA)    . Other types of RNA—like rRNA, tRNA, and microRNA—are involved in protein synthesis and its regulation.

DNA and RNA are made up of monomers known as nucleotides . The nucleotides combine with each other to form a polynucleotide    , DNA or RNA. Each nucleotide is made up of three components: a nitrogenous base, a pentose (five-carbon) sugar, and a phosphate group ( [link] ). Each nitrogenous base in a nucleotide is attached to a sugar molecule, which is attached to one or more phosphate groups.

The molecular structure of a nucleotide is shown. The core of the nucleotide is a pentose whose carbon residues are numbered one prime through five prime. The base is attached to the one prime carbon, and the phosphate is attached to the five prime carbon. Two kinds of pentose are found in nucleotides: ribose and deoxyribose. Deoxyribose has an H instead of OH at the two prime position. Five kinds of base are found in nucleotides. Two of these, adenine and guanine, are purine bases with two rings fused together. The other three, cytosine, thymine and uracil, have one six-membered ring.
A nucleotide is made up of three components: a nitrogenous base, a pentose sugar, and one or more phosphate groups. Carbon residues in the pentose are numbered 1′ through 5′ (the prime distinguishes these residues from those in the base, which are numbered without using a prime notation). The base is attached to the 1′ position of the ribose, and the phosphate is attached to the 5′ position. When a polynucleotide is formed, the 5′ phosphate of the incoming nucleotide attaches to the 3′ hydroxyl group at the end of the growing chain. Two types of pentose are found in nucleotides, deoxyribose (found in DNA) and ribose (found in RNA). Deoxyribose is similar in structure to ribose, but it has an H instead of an OH at the 2′ position. Bases can be divided into two categories: purines and pyrimidines. Purines have a double ring structure, and pyrimidines have a single ring.

The nitrogenous bases, important components of nucleotides, are organic molecules and are so named because they contain carbon and nitrogen. They are bases because they contain an amino group that has the potential of binding an extra hydrogen, and thus, decreases the hydrogen ion concentration in its environment, making it more basic. Each nucleotide in DNA contains one of four possible nitrogenous bases: adenine (A), guanine (G) cytosine (C), and thymine (T).

Questions & Answers

what is ecology
Adeyemo Reply
what is zoology
Adeyemo
zoology branch of biology that study animals
Moses
A plant is a living thing that grows in the earth and has a stem, leaves, and roots
Bello Reply
what is a plant
dalitso Reply
A plant is a living thing that grows in the earth and has a stem, leaves, and roots
Bello
a plant is an is a living thing that is classified under autothrops because it makes its own food through the process of photosynthesis .
Joanne
what is plant
Odion Reply
Plants are autotrophic
Baramox
Then animal are heterotrophic
Iyiola
what are organisms
Godfred Reply
Living structures
Aryavarta
the diagram below show how the blood of a human embryo flows close to the mothers blood in the placenta . which substances are represent at x in higher concentrations than at y
Joyce Reply
what is ecology
Odion Reply
what is cell
Odion
what is cell
Odion
Is the basic unit of life
Agatha
What is a cell
Awal Reply
What are tissues
Awal
A cell is the smallest unit of living organisms.
hamidat
Tissues are group of similar cells performing a particular function.
hamidat
how to pronounce the word cyanobacteria
siva Reply
Cyano then bacteria. look that "cyano" is just like "ciyano".
hamidat
explain the term transpiration pull
Tank Reply
water is mainly " pulled" through the plant and that the driving force for this process is transpiration from the leaves .This is also referred to as the cohesion- tension -transpiration pull model transport.
Vanessa
explain TRANSIOCATION and GUTATION
Tank
what Is corona
INGIEBE Reply
My brother go and ask GOOGLE😷😷😷
hamidat
Google it for the right answer. Corona is a virus which causes Novel Covid-19 disease that has been declared by WHO as a global or world pandemic.
Katlholo
Why is it called Covid-19?
Katlholo
jjwhat is. condinative system
Odion
joy
Odion
condinative system is the system that harmonize all the. different. part. of. the. body and make. them function as a. specific unit
Odion
Describe the process of protein sythesis?
Kizito Reply
Ribosomes are responsible for protein synthesis in animals.
hamidat
What is a ploidy level
Francis Reply
Ploidy refers to the number of chromosomes. We have 23 pairs of chromosomes in somatic cells. Sex cells are haploid thus 23 chromosomes vs. 46 Chromosomes.
Eric
Evolution is evolvement according to one's environment. Let's use humidity as an example. A person from a very cold environment would not be used to hot humid weather. But over time their body would slowly, slowly adapt.
Eric
Give me (3) types of biodiversity
Jay
Hi guys 🇧🇪
Namutebi
hello boy
Tedi
hi
INGIEBE
yes
amani
what do you guys understand about evolution?
Kiana Reply
it's a process or analayzing some program
Fahamia
but am not sure if some know plz let share
Fahamia
is a study of
Sarah
unfolding or unrolling hence the process of development of growth
Sarah
is the periodic change of the structural features of an organism
Rahim
I think
Rahim
process of developing
Nikita
hi guiz
Mohammed
hello guys
Safuna
hi
Kaniki
Evolution ~ Is the gradual change of development over time in which a new species are formed
amani
Evolution is the sum total of adaptive changes that has existed before.
hamidat
odionjimoh
Odion
hi
Odion
why are diagrams not available
Evans Reply

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Source:  OpenStax, Biology. OpenStax CNX. Feb 29, 2016 Download for free at http://cnx.org/content/col11448/1.10
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