1. Nucleotides and
Nucleic acids

2. Nucleic acids 1. Nucleoside: Base + sugar ( ribose or deoxyribose)
The base part of the nucleosides:
Purine derivatives (double-ringed): adenine and guanine
Pyrimidine derivatives : Cytosine, thymine and uracil

3. Nucleic acids
base part
1. Nucleoside:
Pyrimidine

4. Nucleic acids 1. Nucleoside: nomenclature
The most common is the representation of the base pairs as letters—
an adenine A
guanine as G
cytosine as C
thymine as T
and in RNA, uracil as U
Additionally, the positions of the carbons in the ribose sugar that forms the backbone of the nucleic acid chain are numbered. This gives rise to directionality in nucleic acids
(see later)

5. Nucleic acids 1. Nucleoside: base part
Base , because in the ring the Nitrogenes have free electron pairs and they Can accept protons
The sugar part
Ribose or deoxyribose
On the C1 is the anomeric –OH group – the linkage between the base and the sugar is glycosidic bond

6. Nucleic acids 1. Nucleoside: Glycosidic bond adenosine ribose adenine
-H2O
adenosine
ribose
adenine

7. Nucleic acids
1. Nucleoside:

8. Nucleic acids 2. Nucleotide:
Base + sugar + one or more phosphate groups
Nucleoside (mono-di-tri)- phosphates
(nucleosides:Adenosine, guanosine, 5-methyl uridine, uridine,cytidine)
Nucleosides can be phosphorylated by specific kinases in
the cell, producing nucleotides, which are the molecular
building blocks of DNA ( a base linked to sugar and one
or more phospate) and RNA

9. Nucleic acids
2. Nucleotide:
AMP (adenosine monophosphate)
ADP
ATP

10. Nucleic acids 2. Nucleotide:
Inorganic ester bond!! ( phosphoester bond)
Acid anhydrate!! Anhydrate bond!!
Adenosine triphophate

11. Nucleic acids
5’ end 5’
Phosphodiester
Bond 3’
3’ end

12. Nucleic acids
Directionality, in molecular biology, refers to the end-to-end chemical orientation of a single strand of nucleic acid.
The chemical convention of naming carbon atoms in the nucleotide sugar-ring numerically gives rise to a 3′ end and a 5′ end.
The importance of having this type of naming convention is easily demonstrated by the fact that nucleic acids can only be synthesized in vivo in a 5′ to 3′ direction via a phosphodiester bond
Traditionally DNA and RNA sequences are written going from 5′ to 3′.

13. Nucleic acids 3′ end The 3′ (pronounced "three prime") end of a strand
and is known as the tail end.
The 3′-hydroxyl is necessary in the synthesis of new nucleic acid molecules as it is ligated (joined) to the 5′-phosphate of a separate nucleotide, allowing the formation of strands of linked nucleotides

14. Nucleic acids
5′ end
The 5′ (pronounced "five prime") end is named as the strand terminates at the chemical group attached to the fifth carbon in the sugar-ring
If a phosphate group is attached to the 5′ end, ligation of two nucleotides can occur, via a phosphodiester bond from the 5′-phosphate to the 3′-hydroxyl group of another nucleotide. If it is removed no ligation can occur.

15. Nucleic acids
DNA

16. Nucleic acids
DNA
Chemically, DNA is a long polymer of nucleotide units
DNA polymers can be enormous molecules containing millions of nucleotides.
It is the sequence of the four bases along the backbone that encodes information.
- This information is read using the genetic code, which specifies the sequence of the amino acids within proteins

17. Nucleic acids
DNA
The main role of DNA is the long-term storage of information
DNA contains the instructions needed to construct other components of cells, such as proteins and RNA molecules.
The DNA segments that carry this genetic information are called genes, but other DNA sequences have structural purposes

18. Nucleic acids DNA Physical and chemical properties
Nucleotide sequence – primary structure
Secondary structure: double helix
complementers are coupled
Tertiary structure: supercoil structure
-The DNA double helix is stabilized by hydrogen bonds between the bases attached to the two strands.

19. Nucleic acids
DNA

20. Nucleic acids
DNA
DNA can be twisted like a rope in a process called DNA supercoiling
With DNA in its "relaxed" state, a strand usually circles the axis of the double helix once every 10.4 base pairs, but if the DNA is twisted the strands become more tightly or more loosely wound
If the DNA is twisted in the direction of the helix, this is positive supercoiling, and the bases are held more tightly together.
If they are twisted in the opposite direction, this is negative supercoiling, and the bases come apart more easily.
In nature, most DNA has negative supercoiling