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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

the largest structure in a cell
Wodada Reply
chemical cell tissue organ organ systems organism
Oti Reply
a cell is a smallest functional unit of the human body
Wodada
essay of urinary formation
Abubakar Reply
what is condom
Saurav Reply
what are organelles?
Leona Reply
Organelles are membrane bound structures found in the cytoplasm of a cell each performing a specific role in the cell.
Yasir
little organs (structure) that perform specific functions inside a cell e.g. mitochondria (power house of the cell) provides enegy for the cell in the form of ATP (adenosine triphosphate)
Reverian
organelle are bound structure found within the cells and which perform a specific function in a cell eg: Golgi Apparatus, cell membrane
Andrews
Besides the nucleus,the eukaryotic cell have other membrane bound distinct structure called organelles.e.g-endoplasmic reticulum, golgicomlex,lysosome mitochondria.etc
Ajay
A structure within a cell that specialized for a particular function. e.g Golgi apparatus,mitochondria etc
Abbas
The organic and inorganic molecules that perform various function of cell
Muhammad
Organelles are organic and inorganic molecules that help in the formation of a cell
Jude
They are specialised structures or bodies found in the cytoplasm of a cell. E.g mitochondria, lysosomes, Golgi body or apparatus and so on
Quadri
what is Anatomy?
Leona Reply
Biology that mainly deals with the structure and parts of an organism
Reverian
oh..thank you.
Leona
tanks
Sani
Anatomy is the study of internal structure of living organisms.
Muhammad
correct muhammad
Jasper
what is a cell?
Leona Reply
the most basic part of living creature (?)
Hasianna
the basic unit of all living things
Reverian
controlled by a nucleus with small organelles (little organs) inside the cell.
Reverian
thanks.
Leona
Basic unit of life defines a cell
keboetswe
Oh.ok.thnx
keboetswe
cell are tiny living organism from which all others living arose popularly difined as the basic building block of all lives or living things
Quadri
information for blood vessels
Sumit Reply
helps pump blood through body
scott
arteries carry blood away from the heart while veins return it to the heart
Reverian
veins have thinner outer walls because blood pressure in them is very low compared to arteries with thicker outer walls to withstand the higher blood pressure.
Oliver
Are tube or route through which blood and other materials go round the body
Quadri
moist surface, large surface area, well ventilated surface, tiny wall.
Quadri
cell, tissue, organ, organism, organ system,
Gheida Reply
please what are the characteristics of a good respiratory system?
Salomon Reply
thin wall ,a moist inner surface ,a huge combined surface area and a rich blood supply.
Nchimunya
Help me am confused what is the cell membrane as a partially permeable membrane
Janelle Reply
it is the ability of a molecules to cross a cell membrane depending on their both size and chemical properties.
Andrews
Based on my previous understanding of biological systems, a cell membrane is a semi-permeable membrane made up of a phospholipids bi-layer. The polar head consisting of phosphate and the hydrophobic end made up of lipids.
Abayomi
human largest bond
Hifzu
sorry
Hifzu
largent
Hifzu
Smallest bone of rabbit is
Sahrukh Reply
difference between catebolism and anebolism
Anthvanath Reply
energy consuming and transforming respectively
Quadri
identify the causes of infertility in human beings
Rodrick Reply
Describe how a healthy pregnancy could be maintained
Rodrick
Huaman largest bone
Sahrukh
How I can test DNY
Salamin Reply
Samllest bone
Sahrukh

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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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