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Nucleic acids

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

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.

The other type of nucleic acid, RNA, is mostly involved in protein synthesis. The DNA molecules never leave the nucleus, but instead use an RNA intermediary to communicate with the rest of the cell. Other types of RNA are also 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 a phosphate group. DNA nucleotides contain the sugar deoxyribose and one of the four bases adenine (A),thymine (T),guanine (G), or cytosine (C). RNA nucleotides contain the sugar ribose and one of the four bases A,uracil (U),G,or C.

Structure of a nucleotide.
A nucleotide is made up of three components: a nitrogenous base, a pentose sugar, and a phosphate group.

Dna double-helical structure

DNA has a double-helical structure ( [link] ). It is composed of two strands, or polymers, of nucleotides. Each strand is formed with bonds between phosphate and sugar groups of adjacent nucleotides (called a phosphodiester bond). The two strands are bonded to each other at their bases with hydrogen bonds, and the strands coil about each other along their length, hence the “double helix” description, which means a double spiral.

Double helix of DNA.
The double-helix model shows DNA as two parallel strands of intertwining molecules. (credit: Jerome Walker, Dennis Myts)

The alternating sugar and phosphate groups lie on the outside of each strand, forming the backbone of the DNA. The nitrogenous bases are stacked in the interior, like the steps of a staircase, and these bases pair; the pairs are bound to each other by hydrogen bonds. The bases pair in such a way that the distance between the backbones of the two strands is the same all along the molecule.

Section summary

Living things are carbon-based because carbon plays such a prominent role in the chemistry of living things. The four covalent bonding positions of the carbon atom can give rise to a wide diversity of compounds with many functions, accounting for the importance of carbon in living things. Carbohydrates are a group of macromolecules that are a vital energy source for the cell, provide structural support to many organisms, and can be found on the surface of the cell as receptors or for cell recognition. Carbohydrates are classified as monosaccharides, disaccharides, and polysaccharides, depending on the number of monomers in the molecule.

Lipids are a class of macromolecules that are nonpolar and hydrophobic in nature. Major types include fats and oils, waxes, phospholipids, and steroids. Fats and oils are a stored form of energy and can include triglycerides. Fats and oils are usually made up of fatty acids and glycerol.

Proteins are a class of macromolecules that can perform a diverse range of functions for the cell. They help in metabolism by providing structural support and by acting as enzymes, carriers or as hormones. The building blocks of proteins are amino acids. Proteins are organized at four levels: primary, secondary, tertiary, and quaternary. Protein shape and function are intricately linked; any change in shape caused by changes in temperature, pH, or chemical exposure may lead to protein denaturation and a loss of function.

Nucleic acids are molecules made up of repeating units of nucleotides that direct cellular activities such as cell division and protein synthesis. Each nucleotide is made up of a pentose sugar, a nitrogenous base, and a phosphate group. There are two types of nucleic acids: DNA and RNA.

Questions & Answers

what is the meaning of extended family
Shellyann Reply
extended family is two are more nuclear family living together under one roof
Nordalee
what is genetic engineering
Ebot Reply
good day please what is a cell?
Colota Reply
cell is the basic unit of all living things/organism
Hassan
differenciate b/w cilia and flagellum
Abshira
Cilia: 1. They are smaller in number. 2. Cilia usually occur throughout or major part of the surface of a cell. 3. They beat oar like and in a co-ordinated rhythm 4. Cilia help in locomotion, feeding, circulation, etc.. 5. Example: Paramecium
iti
Flagella: 1. They are larger in size. ADVERTISEMENTS: 2. Flagella are commonly found at one end of the cell. 3. The flagella beat whip-like and independently. 4. Flagella help in locomotion. 5. Example: Euglena
iti
smallest structural and functional unit of an organism!
zidane
cell is the basic unit of all living things
Lukman
what is homeostasis
alex Reply
the ability of an organism to maintain stable internal environment, even when the external environment changes
Bee
what's the function of the hypothalamus
Agyekum
what is homeostasis
Edward Reply
constant maintenance of internal body temperature
Agyekum
What is the function of the Pituitary Gland?
WeNdlovu
how can homeostasis be maintained?
alex
pituitary gland also known as the master gland secretes hormones which triggers other gland to secretes their hormones
Agyekum
what's the full meaning of DNA and RNA
Deborah Reply
DNA is Deoxyribonucleic acid and RNA means Ribonucleic acid
Christian
sha is mitochondria?
Sparrow Reply
what is biology
Femi Reply
biology is the study which deals with the study of the biological components or animal and plants.
Juhi
biology is the study of life.
Roger
biology is the branch of science which deals with study of two parts 1.botany&2zoology these is known as biology....
Chetan
biology is the study of human beings ...
Chetan
Biology is a branch of science that deals with the study of nature
Agyekum
biology is the science of living organism
Abshira
biology is the branch of science that deals with study of living organisms
Lukman
what is neculer cell?
is it nuclear cell?
iti
asthma occur in which part of the body organ?
Festus Reply
what is hemoglobin
Lucky Reply
a protein that carries oxygen, it is found within red blood cells
EmmyOrangePeel
Apart from endocrinology, what other alternative should be done to a D/m client
Deborah Reply
good day please what is excretion
Blaise Reply
excretion is the process by which metabolic wastes and other none-useful materials are eliminated from an organism.
Petrene
its the process of eliminating or removal of metabolic waste and non useful materials from an organ.
eyong
Its the removal of metabolic waste product from the body
Boo
it is the removal from the body of living organisms, toxic waste products of metabolism which if allowed to accurate can cost harm to the body..
Renzo
how are protons formed?
Brian Reply
What is isotopes?
Brian
isotopes is a phenomenon in which atoms of the same element has the same atomic number but different mass number due to a difference in their neutron number or relative abundance in the earth crust
Efosa
give me more mcqs there r just two mcqs
Salma Reply
Define the term Disease in one paragraph.
Sutanya Reply
Disease is any disorders that counteract with the normal performance of the immune system.
Agyekum
what is cell?
Colota
Cell is the basic unit of life It is the building block of an organism
Agyekum
do agree with me that if someone needs to truely be a biologist he should be mathematician physicist & chemist in oreder to acheive the level #biologist
Assila
what is a protoplasm?
Colota
colourless living part of the cell
Jenny
what is protoplasm made up of?
Jack

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Source:  OpenStax, Human biology. OpenStax CNX. Dec 01, 2015 Download for free at http://legacy.cnx.org/content/col11903/1.3
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