CHAPTER 1: BIOMOLECULES PART 3- NUCLEIC ACID

CHAPTER 1: BIOMOLECULES PART 3- NUCLEIC ACID

Biomolecules - Proteins

Protein:

• Proteins are the biomolecules with the greatest diversity.
• About half of the dry weight is made up of protein.
• G.J.MULDER invented the word "protein" (1802-1880).
• PROTEIOS is derived from the Greek word PROTEIOS, which meaning "first in rank."
• All proteins, according to EMIL FISCHER (1902), are made up of chains of smaller units known as AMINO ACIDS.
• Proteins are therefore “Polymers of Amino Acids.”
• Amino acids, as monomeric units or building blocks, make up proteins.
• The amino (one or two), carboxyl (one or two), and "R" groups are all present in a typical amino acid (also called as side chain).

Amino Acids:

• A total of 20 amino acids are found in the human body.
• AMINO ACID POOL is formed when amino acids are found abundantly in the cytoplasm matrix.
• The R-molecular group's structure distinguishes one amino acid from the next.

NATURALLY OCCURING AMINO ACID

Properties of Amino Acids

• The side chain of each amino acid determines the majority of its characteristics, which can vary in size, shape, charge, reactivity, and ability to hydrogen bind.
• Non-polar or hydrophobic R group amino acids: Valine, leucine, and isoleucine are three amino acids.
• Amino acids with a polar but uncharged R group include the following: threonine, serine
• Lysine, arginine, and histidine are positively charged polar amino acids.
• Aspartic acid and glutamic acid are polar, negatively charged amino acids.

Protein Formation

• The amino acid molecule comprises a basic or amino group (-NH2) as well as an acidic or carboxylic group (-COOH).
• As an amino acid may act as both an acid and a base, AMPHOTERIC MOLECULES are substances that have both acidic and basic characteristics.
• This feature aids in the formation of complex proteins by allowing amino acids to bond together.
• When the amino group of one amino acid reacts with the carboxylic group of another amino acid, water molecules are lost.
• PEPTIDE LINKAGE OR PEPTIDE BOND is the condensation process of two amino acid molecules by the –NH–CO linkage.

Types of Proteins

Structural levels of Protein

• Ribosomes produce proteins that are a LINEAR SEQUENCE OF AMINO ACIDS.
• The removal of water between successive amino acids forms a peptide bond, which is POLYMERIZED.
• Have no biological function and exist as a randomly coiled chain with no particular form.
• Protein folds into THREE DIMENTIONAL FORM after a few seconds after synthesis complete.
• The folding is consistent across all molecules of the same type of protein, and it may now catalyse reactions.
• PROTEIN ORGANIZATION ON FOUR LEVELS

Primary Protein Structure:

• The amino acid sequence of a protein.
• The peptide bondings between amino acids determine this.
• Other covalent connections in proteins are also included. e.g.
• Disulphide INSULIN has a bridge between the sulphur atoms of the Cysteine amino acid.

Secondary Protein Structure:

Any polypeptide chain that has a regular repeating structure.

The amino acid folds into a repeating pattern due to hydrogen bonding in the peptide backbone.

Secondary protein structures are divided into three categories:

1. HELICAL STRUCTURE (Alpha-Keratin), 
2. PLEATED SHEET STRUCTURE (Fibroin of Silk), 
3. EXTENDED CONFIGURATION (Stretched Keratin)

Tertiary Protein Structure:

• The HELICAL AND NON HELICAL portions of a polypeptide chain are folded back on themselves to form a more compact shape.
• Specific Protein folding pattern in three dimensions due to side chain interactions.
• IONIC BONDS, HYDROPHOBIC BONDS, and DISULPHIDE BONDS are examples of weak secondary bonds.

Quaternary Protein Structure:

• The particular orientation of these chains, as well as the kind of connections that sustain this orientation, is referred to as quaternary protein structure in proteins made up of two or more polypeptide chains.
• HYDROPHOBIC FORCES, HYDROGEN BONDS, IONIC BONDS, and DISULPHIDE BONDS bind the proteins together.

Functions:

• Proteins are responsible for the most varied and perhaps biggest number of biological activities. The following are some of the most important functions:
• Enzyme-catalyzed biocatalysis: Enzymes catalyse almost all biological processes. These are substrate-specific and carry out reactions at extremely high speeds under physiologically moderate circumstances. To date, thousands of enzymes have been discovered.
• Membrane Structure: Membranes are made up of lipoproteins and contain some proteins as well. In nature, receptors on the membrane are also proteins.
• Small molecules are frequently transported by proteins in the physiological context; 
• for example, haemoglobin is important for transporting oxygen to tissues.
• Muscles are made up of proteins, and actin and myosin proteins contract them.
• Collagen, a protein, strengthens the skin and bones mechanically.
• Immune system antibodies are protein structures.
• Proteins make up many hormones and growth factors, such as insulin and thyroid stimulating hormone.