Cell Molecules Part 3 - Proteins
Cell Molecules Part 3 - Proteins:
Structure of protein:
- Proteins are made up of amino acids which are joined together by peptide bonds.
- Amino acids are amphoteric in nature as it contains an amino group (-NH2) and a carboxyl group (-COOH).
- Example – Hemoglobin, Chlorophyll
- Structure of protein is determined by the number of amino acids and their kind and order in which they arranged in the polypeptide chain.
- Proteins are globular or fibrous in shape.
- Globular proteins play a functional role and fibrous protein plays a structural role.
Biological importance of protein:
- Protein is the main constituent of enzymes which are responsible for biochemical reactions in cells.
- Proteins helps in formation of many hormones which regulates many metabolic activities of cell
- Antibodies made up of proteins and provides resistance against invading pathogenic bacteria
- It helps in respiration process by transport of oxygen.
Nucleic acids:
Structure of nucleic acids:
- Nucleic acids are polynucleotide made up of by joining two or more nucleotide unit together.
- Example- DNA and RNA
- Each nucleotide is made up of three sub units – sugar, nitrogenous base and phosphoric acid.
- Sugar is pentose type where DNA contains Deoxyribose sugar and RNA contains rebose sugar.
- Nitrogenous base are cyclic compound and are of two types
1. Purine – Adenine and Guanine
2. Pyrimidine – Cytosine, Thymine and Uracil
- DNA does not contains uracil and RNA does not contain thymine
- Phosphoric acid is associated with phosphate.
Formation of nucleic acid:
- A nitrogenous base attached with sugar by covalent bond and forms nucleoside
- Nucleoside is then attached with phosphoric acid by ester bond and forms nucleotide.
- Nucleotide joins together by phspho-di-ester bond and forms a chain of nucleotide called as polynucleotide.
- RNA contains one polynucleotide chain whereas DNA contains two polynucleotide chains.
Biological importance of nucleic acid:
- It acts as a currency of energy in cell in form of ATP.
- It is associated with co-enzymes and vitamins
- They are responsible for inheritance inc all organism.
Self study:
Example-1: Which of the following is not present in DNA?
a) Adenine
b) Guanine
c) Cytosine
d) Uracil
Answer: DNA does not contain Uracil.
Example-2: Nucleic acids are responsible for …………..in all organisms
a) Inheritance
b) Respiration
c) Reproduction
d) None
Answer: Nucleic acids are responsible for inheritance in all organisms
Example-3: Which of the following is the building block of proteins?
a) Carboxylic acid
b) Alcohol
c) Nucleic acid
d) Water
Answer: Nucleic acids are the building blocks of proteins.