Nucleic Acid / Protein structure & Functions

Structure & Functions Of Nucleic Acids & Proteins

1. Name : Chanaka Lakshan Student ID : BS/15/10/15 Facilitator: Ms. Gaayathri Subject : Molecular Biology & Genetics Stream : Biomedical Science

2. Structure & Functions Of Nucleic Acids & Proteins

3. Contents Structure Of Nucleic Acids Functions Of Nucleic Acids Structure Of Proteins Functions Of Proteins

4. Nucleic Acid Structure

5. Introduction It refers to the Nucleic Acids Like DNA & RNA. It is divided into 4 levels : Primary Secondary Tertiary Quaternary

6. Primary structure It is a linear sequence of nucleo tides that are linked together by Phosphodiester bonds . It makes Primary structure of DNA or RNA. Nucleotides consist of 3 components: Nitrogenous base; Adenine Guanine Cytosine Thymine   (   DNA only ) Uracil ( RNA only ) 5-carbon sugar which is called  Deoxyribose  (found in DNA) and  Ribose  (found in RNA). One or more phosphate groups . The nitrogen bases Adenine and Guanine are  Purine in structure . Cytosine , Thymine and Uracil are Pyrimidine in Structure.

7. Secondary structure It is the set of interactions between bases . In DNA double helix, the two strands of DNA are held together by H- Bonds . It is responsible for the shape that the nucleic acid assumes. Purines consist of a Double Ring Structure. Pyrimidines has a Single Ringed Structure. A Purine base always pairs with a pyrimidine base (Guanosine (G) pairs with Cytosine(C) and Adenine(A) pairs with Thymine (T) or  Uracil  (U)). DNA 's secondary structure is predominantly determined by Base Pairing of the two Polynucleotide Strands wrapped around each other to form a Double Helix. In RNA , Secondary Structure consists of a Single Polynucleotid e . The Antiparallel Strands form a Helical Shape . The 4 basic elements in the secondary structure of RNA are; Helices Loops Bulges Junctions . 

8. Tertiary structure It is the locations of the atoms in 3D space. Large-scale folding in a linear polymer occurs and the entire chain is folded into a specific 3D shape. There are 4 areas in which the structural forms of DNA can differ. Handedness - right or left Length of the helix turn Number of base pairs per turn Difference in size between the major and minor grooves The tertiary arrangement of DNA's  Double Helix in space includes; B- DNA A-DNA Z-DNA B-DNA is the most common form of DNA and it is a more narrow, elongated helix than A-DNA. Its wide major groove makes it more accessible to proteins. A-DNA is a form of the DNA duplex observed under dehydrating conditions. It is shorter and wider than B-DNA. RNA adopts this double helical form, and RNA-DNA duplexes are mostly A-form. Z-DNA  is a relatively rare left-handed double-helix. Its function is unclear. It has a more narrow, more elongated helix than A or B.

9. Quaternary structure It refers to a higher-level of organization of nucleic acids(interactions of the nucleic acids with other molecules). The most commonly seen form is Chromatin which leads to its interactions with the Histone Proteins. It is also refers to the interactions between separate RNA units in Ribosome.

10. Functions of Nucleic Acids DNA: Transmission of Hereditary Characters. Store house of genetic information control protein synthesis in cell. Direct synthesis of RNA.  RNA:  Direct synthesis of Specific Proteins. m-RNA takes genetic message from RNA. t-RNA transfers activated amino acid, to the site of protein synthesis. r-RNA are mostly present in the ribosomes, and responsible for stability of m-RNA.

11. Protein Structure

12. Introduction It is the 3D arrangement of atoms in a Protein Molecule . Proteins are polypeptides made from sequences of monomer amino acids. Proteins fold into one or more specific spatial conformations driven by a number of Non-Covalent interactions such as  H-Bonding, Ionic Interactions, Van Der Waal Forces, and Hydrophobic packing . Protein structures range in size from tens to several thousand amino acids. A protein may undergo reversible structural changes in performing its biological function. The alternative structures of the same protein are referred to as different conformations.

13. Primary Structure It refers to the linear sequence of amino acids in the polypeptide chain . It is held together by  Covalent Bonds like Peptide Bonds. The 2 ends of the Polypeptide Chain  are referred to as the Carboxyl Terminus (C-terminus) and the Amino Terminus(N-terminus ). It is determined by the Gene corresponding to the Protein.

14. Secondary Structure It refers to highly regular local sub-structures on the actual polypeptide backbone chain. There are 3 main types of Secondary Structures; Alpha Helix Triple Helix Beta Pleated Sheet The Alpha Helix is a right-handed coiled strand. The stability to the structure is given by H-bonding. The Triple Helix is 3 polypeptide chains woven together. H -bonding between –OH groups gives a strong structure. The Beta –Pleated Sheet is created by inter-strand H- Bonding. It is more stable due to the well-aligned hydrogen bonds.

15. Tertiary Structure It is the overall 3D shape of an entire protein molecule. The alpha-helixes and beta pleated-sheets are folded into a compact Globular Structure. There are; Disulphide Bonds  - A strong double bond (S=S) is formed between the Sulphur atoms within the Cysteine monomers. Ionic Bonds  - If 2 oppositely charged 'R' groups (+ve and -ve) are found close to each other, and ionic bond forms between them. Hydrogen Bonds  - Typical H-bonds. Hydrophobic and Hydrophilic Interactions  - Some amino acids may be hydrophobic while others are hydrophilic.

16. Quaternary Structure It is the Complete 3-D structure of a protein with multiple peptides or proteins. It is stabilized by a variety of bonding interactions including H-bonding, Salt bridges, and Disulfide bonds which holds the various chains into a particular geometry.

17. Functions Of Proteins Repair and Maintenance - Protein is termed the building block of the body. Energy - Protein is a major source of energy. Antibodies  - They are specialized proteins involved in defending the body from antigens (foreign invaders). Contractile Proteins  - They are responsible for movement. Examples include actin and myosin. Enzymes  -They are proteins that facilitate biochemical reactions. They are often referred to as catalysts because they speed up chemical reactions. Hormonal Proteins  - They are messenger proteins which help to coordinate certain bodily activities. Examples include insulin, oxytocin etc. Structural Proteins  - They are fibrous and stringy and provide support. Examples include keratin, collagen, and elastin. Storage Proteins  - It Store Amino Acids. Examples include casein, ferritin. Transport Proteins  - They are carrier proteins which move molecules from one place to another around the body. Examples include hemoglobin and Cytochromes.

18. Summary Nucleic Acid structure refers to the Nucleic Acids Like DNA & RNA. It is divided into 4 levels. Nucleic Acids Useful in Transmission of hereditary Characters, Direct synthesis of specific proteins etc. Protein Structure is the 3D arrangement of atoms in a Protein Molecule. It is divided into 4 Structures. It has H-Bonding, Ionic Interactions, Van Der Waal Forces etc. Proteins Helps for Repair and Maintenance, Energy etc.

19. References Websites healthyeating.sfgate.com biology.about.com nutristrategy.com sophia.org Journals Proteins: Structure, Function, and Bioinformatics( ISI Journal Citation Reports © Ranking: 2014: 37/73 (Biophysics); 148/290 (Biochemistry & Molecular Biology)) Nucleic Acids – Chemistry and Applications ( J. Org. Chem. , 2013.Copyright © 2013 American Chemical Society)

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