BIOLOGICAL MOLECULES

 BIOLOGICAL MOLECULES

BIOCHEMISTRY:
The branch of biology which explains the biochemical basis of life is called biochemistry.

Importance Of Biochemistry:

• It provides information about all the processes carried out in the living organism.
• It helps us to understand abnormal mechanisms which lead to disease and development of medicines and equipment for the treatment of diseases.
• It also provides information on cell differentiation.
• It also explains about growth of cells.
• It has enabled us to understand the mechanism of memory.

CHEMICAL COMPOSITION OF CELL:
All living organisms are composed of cells and living cells contain a living material called protoplasm which chemically contains 70 to 90% of water. Besides water, organic molecules and biochemicals are the main constituent of protoplasm.

BIOCHEMICAL’S:
The compounds produced by living organisms are called biochemicals. Only six elements—carbon, hydrogen, nitrogen, oxygen, phosphorus, and sulfur—form 98% of the biochemical and body weight of organisms.

Types Of Biochemical’s:

• Proteins
• Carbohydrates
• Lipids
• Nucleic acids
• Conjugated molecules

WATER:
Water is the most abundant component of organisms. Its amount in living cells varies from 70% to 90%. Water provides the medium in which all biochemical reactions take place and has played a major role in the evolution of biological systems. Water is a polar molecule. The oxygen part of the molecule has a net negative charge, and the hydrogen part has a net positive charge. Thus the molecule as a whole shows polarity.

Biologically Important Properties Of Water:
Some biologically important properties of water are given below:

• Behave As Best Solvent:
  Water properties as a solvent depend on the fact that it is a polar molecule. Water effectively weakens the attraction between ions of opposite charge. Water is therefore a good solvent, ionic solids, and polar molecules readily dissolving in it. It also acts as a solvent to many non-polar substances. This is of great biological importance because all the chemical reactions that take place in cells do so in aqueous solutions.

• Slow To Absorb And Release Heat (High Specific Heat Capacity):
  Water has a very high heat capacity. This means that water is good at maintaining its temperature. This thermal stability makes it the most suitable medium for cells.

• High Heat Of Vaporization And Low Freezing Point:
  It is also an important thermal property of water. Water requires a higher amount of heat energy to change into vapors and also requires to lose a lot of heat to freeze. Thus in the presence of water, protoplasm is not at the risk of boiling or freezing except in drastic conditions.

• An Amphoteric Molecule:
  Water molecules are amphoteric because they act both as an acid and a base. Therefore, it is a perfect medium for the biochemical reactions occurring in cells. It acts as a buffer and helps to prevent changes in the pH of cells, which reduces the chance of any interference in the metabolism of the cell.

• Cohesive Force In Water Molecules:
  Due to cohesive forces, water molecules do not break apart, which helps it flow freely. The strong cohesion forces that exist between water molecules play an important part in the movement of water up the capillary-like vessels and tracheids in the stems of plants.

• Organic Molecules:
  The modern definition of organic molecules is modified as the molecules containing carbon as the basic element bonded covalently with a hydrogen atom.

Synthesis Of Large Molecules By Condensation:
Large molecules or macromolecules are huge and highly organized molecules that form the structure and carry out the activities of cells. Macromolecules are constructed from monomers by a process called condensation. This type of condensation is called dehydration synthesis because two monomers join together when water is removed and a bond is made.

Breaking Of Large Molecules By Hydrolysis:
A process during which polymers are broken down into their subunits (monomers) by the addition of H₂O is called hydrolysis. During this process, a water molecule breaks into H⁺ and OH⁻ ions. -OH group attaches to one monomer, and H attaches to the other.

Carbon: Organic chemistry is the chemistry of carbon of the living world. Carbon very widely in their properties and adaptations. Carbon is a tetravalent element. It forms four covalent bonds with other atoms.

Biological Molecules:

Proteins:

Introduction: Proteins play a vital role in the formation of structure in organisms. The dry weight of the cell contains about 50% of proteins. The name protein was suggested by Berzelius in 1838 and in 1883 G.J. Murdler recognized the importance of protein.

Definition: Proteins can be defined as the polymers of amino acids, where specific amino acids link together in a definite manner to perform a particular function of protein.

Structure Composition Of Protein: Proteins are complex organic compounds having C, H, O, and N as elements but sometimes they contain P and S also.

Synthesis Of Protein Molecule: Amino acid as a building block of protein. Proteins are macromolecules or polymers of amino acid monomers. These amino acids are linked together by a specialized bond or linkage called peptide linkage.

During protein synthesis through condensation, each amino acid becomes joined to other amino acids forming a long continuous unbranched polymer called polypeptide. The sequence of amino acids in the peptide chain is specific for each protein.

Structure Of Protein: These are four basic structural levels of proteins.

• Primary Structure: Polypeptide chain containing a linear sequence of amino acids e.g., insulin.
• Secondary Structure: Polypeptide chains twisted or spirally coiled e.g., keratin.
• Tertiary Structure: The arrangement of secondary structure into the three-dimensional (fold or super fold) structure having peptide, hydrogen, ionic, and disulphide bonds e.g., lysozyme.
• Quaternary Structure: It is the arrangement formed by the union of two or more polypeptide chains e.g., hemoglobin.

Functions Of Protein:

• Proteins are a rich source of energy.
• Proteins, along with lipids, are used in the formation of plasma membranes and other membranes of the cell.
• Muscles are made up of two contractile proteins named Actin and Myosin.
• Contraction and relaxation of these muscle proteins are responsible for locomotion.
• The shape of the protein molecule is directly related to its function. In general, proteins fall into two groups.

Globular And Fibrous:

• Keratin is a fibrous protein. It is used in the formation of hair, nails, and is also found in the skin.
• Hemoglobin is the protein present in red blood cells and is responsible for the transport and supply of oxygen to body cells.
• All enzymes present in the body cells of animals and plants are proteins. They control all types of biochemical reactions occurring within cells.
• Proteins are stored food substances in plants. Stored food in seeds is used for the germination and development of seeds into young plants.

Carbohydrates: Carbohydrates are organic compounds present in all living organisms. The group contains carbon, oxygen, and hydrogen. Carbohydrates are called hydrated carbons because the hydrogen and oxygen are mostly found in the same ratio as in water, i.e., 2:1. Examples include sugar, starch, glycogen, and cellulose. Carbohydrates are divided into three classes.

Types of Carbohydrates:

1. Monosaccharides:

   • Simple sugars that cannot be hydrolyzed into smaller sugars.
   • General formula: $\text{C}_n\text{H}_{2n}\text{O}_n$.
   • Usually sweet, crystalline solids that dissolve in water.
   • Classified based on the number of carbon atoms (e.g., triose, tetrose, pentose, hexose).
   • Common examples: Glucose (found in fruits, sweet corn, honey), Fructose (found in sugarcane), Galactose (found in milk as part of lactose).

2. Oligosaccharides:

   • Composed of 2 to 10 monosaccharides.
   • Disaccharides (two monosaccharides) are the most common type, e.g., sucrose (table sugar), lactose (milk sugar), and maltose.
   • Oligosaccharides with 3 to 10 monosaccharides include substances like Dextrin.

3. Polysaccharides:

   • Made up of hundreds or thousands of monosaccharides linked by glycosidic bonds.
   • Common examples: Starch, Glycogen, Cellulose.
   • General formula: $(\text{C}_6\text{H}_{10}\text{O}_5)_n$.

Specific Polysaccharides:

• Starch: A storage carbohydrate in plants; consists of chains of glucose molecules in forms like amylose and amylopectin. Found in cereals, legumes, potatoes.
• Cellulose: Found in plant cell walls, made of long straight chains of glucose. It is hydrophilic and provides structural support.
• Glycogen: Known as "animal starch," it is a storage carbohydrate in animals, highly branched and stored in the liver, muscles, and other tissues.

Functions of Carbohydrates:

• Energy Source: Carbohydrates are a primary energy source for metabolism in the body.

These summaries cover the basic structure, types, and functions of carbohydrates. Let me know if you need further assistance or clarification on any specific topic.

Carbohydrates (Additional Functions):

• Storage Food Molecules: In plants, excess glucose is stored as starch, and in animals as glycogen.
• Structural Role: Carbohydrates serve as building blocks, with cellulose forming plant cell walls and chitin providing support in animal exoskeletons (like arthropods).
• Complex Molecules: They form complex conjugated molecules, including glycolipids and glycoproteins.

Lipids:

• Definition: Lipids are organic compounds insoluble in water but soluble in organic solvents. They have less oxygen compared to carbohydrates and are primarily composed of fatty acids and glycerol.

Types of Lipids:

1. Acylglycerol (Fats and Oils):

   • Made of glycerol and fatty acids.
   • Provide energy and are divided into:
     • Saturated Fats: Found in animals, solid at room temperature (e.g., stearin).
     • Unsaturated Oils: Found in plants, liquid at room temperature (e.g., linoleic acid in cottonseed oil).

2. Waxes:

   • Simple lipids formed from fatty acids and long-chain alcohols.
   • Water-repellent and used for protection in plants and animals.

3. Phospholipids:

   • Key components of biological membranes, consisting of a hydrophobic and a hydrophilic end.
   • Vital for cell membrane permeability and transport functions.

4. Terpenoids:

   • Based on isoprenoid units, include classes like terpenes, steroids, and carotenoids.
     • Terpenes: Volatile, used in essential oils (e.g., menthol, camphor).
     • Steroids: Includes compounds like cholesterol.
     • Carotenoids: Pigments found in plants, aiding in photosynthesis (e.g., carotene).

Nucleic Acids:

• Discovery: Isolated by Friedrich Miescher from the nuclei of pus cells, named "nuclein," later renamed nucleic acid due to its acidic nature.
• Types:
• DNA (Deoxyribonucleic Acid): Confined to the nucleus.
• RNA (Ribonucleic Acid): Mostly found in the cytoplasm.

Nucleic Acids as Informational Macromolecules:

• DNA and RNA: Both are types of nucleic acids involved in storing and transferring genetic information. DNA encodes genetic instructions, while RNA assists in protein synthesis.

DNA as Hereditary Material:

• Early experiments, including Griffith’s transformation experiment and later confirmation by Hershey and Chase, established DNA as the genetic material.
• Genetic Code: DNA consists of specific sequences of nitrogenous bases, encoding vast amounts of information.

RNA as a Carrier of Information:

• Location: DNA remains in the nucleus, while RNA serves as an intermediary, carrying genetic instructions to the cytoplasm.
• Protein Synthesis: Genetic information flows from DNA to mRNA (messenger RNA) in two main steps:
  1. Transcription: DNA information is transcribed to mRNA, which then moves to the cytoplasm.
  2. Translation: tRNA (transfer RNA) and rRNA (ribosomal RNA) help translate the mRNA code into a specific sequence of amino acids, forming proteins.

The page also includes diagrams illustrating the transcription process in detail.

Conjugated Molecules:

Conjugated molecules are formed when biomolecules of two different types combine, functioning as a unit.

Types of Conjugated Molecules:

1. Glycolipids or Cerebrosides:

   • Formed when carbohydrates combine with lipids, producing glycolipids.
   • Important for brain function and are constituents of the nervous system. Examples include galactolipids and sulfolipids in chloroplasts.

2. Glycoproteins or Mucoproteins:

   • Produced when proteins conjugate with carbohydrates.
   • The protein forms the core structure, and the carbohydrate part extends as a branched chain.
   • Found in mucus, synovial fluid (as lubricants), connective tissue matrix, and cell membranes. Egg albumin and certain hormones like gonadotropins are also glycoproteins.

3. Nucleoproteins:

   • Nucleic acids conjugated with proteins.
   • Found in the nucleus, weakly acidic, and soluble in water.

4. Lipoproteins:

   • Formed by conjugating lipids with proteins.
   • Assist in lipid transport in the blood plasma.
   • Found in cell membranes, mitochondria, endoplasmic reticulum, and other cellular structures.

These conjugated molecules play various roles in biological systems, from structural functions to biochemical transport. Let me know if you need any more details on these or any other topics covered.

Nucleotide Structure:

• Components:
  • Pentose Sugar: Ribose in RNA, deoxyribose in DNA.
  • Phosphoric Acid: Attached to the fifth carbon of the sugar.
  • Nitrogenous Base: The organic base of the nucleotide.

These points offer a concise overview of carbohydrates, lipids, and nucleic acids in biological systems. Let me know if you'd like more details on any specific part.