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Learning objectives

  • Describe the biochemical structure of deoxyribonucleotides
  • Identify the base pairs used in the synthesis of deoxyribonucleotides
  • Explain why the double helix of DNA is described as antiparallel

In Microbial Metabolism , we discussed three classes of macromolecules: proteins, lipids, and carbohydrates. In this chapter, we will discuss a fourth class of macromolecules: nucleic acids. Like other macromolecules, nucleic acid s are composed of monomers, called nucleotide s, which are polymerized to form large strands. Each nucleic acid strand contains certain nucleotides that appear in a certain order within the strand, called its base sequence . The base sequence of deoxyribonucleic acid (DNA) is responsible for carrying and retaining the hereditary information in a cell. In Mechanisms of Microbial Genetics , we will discuss in detail the ways in which DNA uses its own base sequence to direct its own synthesis, as well as the synthesis of RNA and proteins, which, in turn, gives rise to products with diverse structure and function. In this section, we will discuss the basic structure and function of DNA.

Dna nucleotides

The building blocks of nucleic acids are nucleotides. Nucleotides that compose DNA are called deoxyribonucleotides . The three components of a deoxyribonucleotide are a five-carbon sugar called deoxyribose , a phosphate group, and a nitrogenous base , a nitrogen-containing ring structure that is responsible for complementary base pairing between nucleic acid strands ( [link] ). The carbon atoms of the five-carbon deoxyribose are numbered 1ʹ, 2ʹ, 3ʹ, 4ʹ, and 5ʹ (1ʹ is read as “one prime”). A nucleoside comprises the five-carbon sugar and nitrogenous base.

a) At the center of a deoxyribonucleotide is a deoxyribose sugar. This is a pentagon shape with O at the top and H attached to the bottom right Carbon and OH attached to the bottom right Carbon. Attached to the upper left carbon is a phosphate group which consists of a Phosphate attached to 4 oxygens. Attached to the upper right carbon of the sugar is a base which consists of 1 or 2 rings that contain both carbon and nitrogen. B) A more detailed drawing of deoxyribose. This is a pentagon shaped structure with oxygen at the top corner.  Moving clockwise, the upper right corner has a carbon labeled 1-prime. There is an OH attached to this carbon. The bottom right carbon is labeled 2-prime and has an H attached to it. The bottom left carbon is labeled 3-prime and has an OH group attached to it. The upper left carbon is labeled 4-prime and has CH2OH attached. This last carbon is labeled 5-prime.
(a) Each deoxyribonucleotide is made up of a sugar called deoxyribose, a phosphate group, and a nitrogenous base—in this case, adenine. (b) The five carbons within deoxyribose are designated as 1ʹ, 2ʹ, 3ʹ, 4ʹ, and 5ʹ.

The deoxyribonucleotide is named according to the nitrogenous bases ( [link] ). The nitrogenous bases adenine (A) and guanine (G) are the purines ; they have a double-ring structure with a six-carbon ring fused to a five-carbon ring. The pyrimidines , cytosine (C) and thymine (T), are smaller nitrogenous bases that have only a six-carbon ring structure.

Pyrimidines have 1 ring containing both carbon and nitrogen in the ring. Cytosine and thymine are both pyrimidines. Their rings are the same but have different functional groups attached. Purines have 2 rings containing carbon and nitrogen. Adenine and Guanine are both purines but have different arrangement of atoms as part of and attached to their rings.
Nitrogenous bases within DNA are categorized into the two-ringed purines adenine and guanine and the single-ringed pyrimidines cytosine and thymine. Thymine is unique to DNA.

Individual nucleoside triphosphates combine with each other by covalent bonds known as 5ʹ-3ʹ phosphodiester bonds , or linkages whereby the phosphate group attached to the 5ʹ carbon of the sugar of one nucleotide bonds to the hydroxyl group of the 3ʹ carbon of the sugar of the next nucleotide. Phosphodiester bonding between nucleotides forms the sugar-phosphate backbone , the alternating sugar-phosphate structure composing the framework of a nucleic acid strand ( [link] ). During the polymerization process, deoxynucleotide triphosphates (dNTP) are used. To construct the sugar-phosphate backbone, the two terminal phosphates are released from the dNTP as a pyrophosphate. The resulting strand of nucleic acid has a free phosphate group at the 5ʹ carbon end and a free hydroxyl group at the 3ʹ carbon end. The two unused phosphate groups from the nucleotide triphosphate are released as pyrophosphate during phosphodiester bond formation. Pyrophosphate is subsequently hydrolyzed, releasing the energy used to drive nucleotide polymerization.

Questions & Answers

thilosysis beta oxidation us catalysed by
Tirupati Reply
Explain about enzyme transportation
Shahla Reply
Enzyme transportation
Shahla
it looks reallllyyyyy coooooooollll. i love enzymes theyre so cooll and i also like protein transportation so i think it would be really cool so an enzyme transport something so ill do some research and come back to ya in that
maxo
they be ridin' dirty
Bethany
what is the infectious disease process
Patience Reply
what are differences between endotoxins and exotoxins
sabote Reply
endo toxins work in the nuceus. i think
maxo
tell me if im right tho
maxo
Exotoxins are toxic substances secreted by bacteria and released outside the cell. Both gram positive and gram negative bacteria can produce and secrete exotoxins. Whereas Endotoxins are bacterial toxins consisting of lipids that are located within a cell. Only lysed gram negatives.
Abdi
Remebr the Lipid A portion of LPS is what's toxic.
Abdi
oh yeah. thanks
maxo
Your welcome :)
Abdi
How did you learn this?
maxo
For me personally the best book is 'microbiology made ridiculously simple'
Abdi
I got my basics from there and slowly added information from other sources.
Abdi
thats cool! yeah i like microbiology too! especially the molecular proteins theyre sooooooooooo cool!
maxo
what are the prokaryotic
Lungu Reply
prokaraytotic is a unicellular organizm that lacks membrane bound nucleus
Zaajid
and whats eukaryotic
abdiqani
eukaryotic cell are cell which contain anuclues and organells
Zaajid
eukaryotes are the cells that have organells which are protected by membranes
maxo
eukaryotic is are multicellular organisms which are open nucleus.
Serah
Explain on the Francisco reddi did to prove the theory of spontaneous generation
Diana Reply
what is parasite
Abdirizack Reply
parasite are organisms feeds on a host for food and survival.e.g round worm for animal, Dodder for plant parasites.
Serah
parasite are organisms that feeds on a host for food and survival.e.g round worm for animal and mistletoe for plant parasites.
Serah
parasite are organisms that feed on their host
Cylla
designing of aseptic area
Aashish Reply
I don't know
Abdirizack
what is rickettsia
DENNIS Reply
what is microbiology
Erasto
Is the science that works with microorganisms.
Rose
richettsa is small microorganisms that cause disease in human like typhus; they are like viruses that can grow only inside living cells, they're transmitted by mites, ticks or lices.
Rose
what is plasmid?
mavis
plasmid is extra chromosomal body present in bacteria...which have additional genetic functions example... antibiotic resistance genes....etc etc
Chaitanya
state the theory of spontaneous generation of micro oranisms and germ theory of disease
UKAMAKA Reply
what are the advantages of high note numerical aperture
Genius Reply
list if non flagellated pritozoa
Mepung Reply
Can someone that's understanding of the Kreb Cycle please explain & breakdown it down to me in the simplest way without giving me the dictionary version or Google version. Basically in there own words of knowledge....!
Kisha
ok
lucas
please can someone help explain positive and negative feedback in simple term
Gum
negative feedback is the arresting of reaction or reverse of the reaction according to the response and postive feed back is the direct response without reversing or arresting a reaction.
Greet
OK
umar
pls can someone explained Kinney stone in memorising in shot time
umar
what tyoebif microorganism will be killed by antibiotic trwatmeant
Mary Reply
I don't really don't understand aerobic respiration anaerobic respiration and fermentation. Can someone explain & breakdown this in the simplest way please.
Kisha
Anaerobic Respiration in which foodstuffs are partially oxidized, with the release of chemical energy, in a process not involving atmospheric oxygen, such as alcoholic fermentation, in which one of the end products is ethanol.
Muhammad
aerobic respiration A type of respiration in which foodstuffs are completely oxidized to carbon dioxide and water, with the release of chemical energy, in a process requiring atmospheric oxygen.
Muhammad
please can someone explain what pseudomonas species and biofilm is?
uju
Fermentation is the growth of cells or microorganisms in bioreactors (fermenters) to synthesize special products. Fermentation in biochemistry refers to the biodegradation of carbon compounds by cells or organisms under anaerobic (lack of oxygen) conditions.
Muhammad
Please under which conditions does pathogens become established in the human tissues and can cause diseases
Atambilla
please the life cycle of plasmodium parasite
mavis
who is John Needham
Mary Reply
John Needham is one of the researcher in microbiology. He also experimented when scientists did not believe animals could arise spontaneously ,but did believe microbes could.
Gum
okay is he late
Mary
by the way what are the list of courses offered by a newly admitted student for microbiology
Mary
Needham's experiments with beef gravy and infusions of plants material reinforced this idea.
Gum
what drugs are given to a person with Otis nerve problem(ear problem)
Gum Reply

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Source:  OpenStax, Microbiology. OpenStax CNX. Nov 01, 2016 Download for free at http://cnx.org/content/col12087/1.4
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