Looking for a Tutor Near You?

Post Learning Requirement »
x

Choose Country Code

x

Direction

x

Ask a Question

x

x
x
For better view click here
x
Hire a Tutor
DISCOVER

Biomolecules

Loading...

Published in: Bio Chemistry
1,720 Views

Notes contains brief explanation about basic concepts of biomolecules.

Saraswathi / Bangalore

2 years of teaching experience

Qualification: M.Sc (university of Mysore - 2006)

Teaches: Bio Technology, Biology, Botany, Bio Chemistry, Microbiology

Contact this Tutor
  1. BIOMOLECULES: All carbon compounds that are found in the living tissues are called BIOMOLECULES. Eg: Carbohydrates, fat, lipids, proteins, amino acids. Biomolecules are classified into two groups based on their molecular weight Microbiomolecules: Biomolecules which have their molecular weights lesser than 1000 Daltons are called as Microbiomolecules. Eg: amino acids, nucleotides, sugars, lipids Macrobiomolecules: Biomolecules which have their molecular weights greater than 1000 Daltons are called as Macrobiomolecules. Eg: Polysaccharides, Proteins, Nucleic acids. Primary and secondary metabolites: These are biomolecules present within the living cell. Primary metabolites: are those which have identifiable functions and play specific roles in normal physiological processes. Eg. Amino acids, nitrogenous bases, proteins and nucleic acid. Secondary metabolites :are product of certain metabolic pathways from primary metabolites. Few examples of secondary metabolites are: Pigments — anthocyanin, carotenoids Drugs — vinblastin, curcumin Alkaloids - morphine, codeine Essential oils — lemon grass oil Polymeric compounds - rubber gum, cellulose, resins Toxin-Abrin,ricin Amino acids: Amino acids are organic compounds containing an amino group and an acidic group attached to the same carbon atom i.e., the a-carbon.Hence, they are called a-amino acids. There are four substituent groups occupying the four valency positions. These are hydrogen, carboxyl group, amino group and a variable group designated as R group. Based on the nature of R group there are many amino acids.
  2. However, there are only 21 types of amino acids which occur in proteins. The amino, carboxyl and the R functional groups decide the chemical and physical properties of an amino acid. Amino acid with a hydrogen is called glycine, one with a methyl group is called alanine, one with hydroxyl methyl group is called serine, etc. Based on the number of amino and carboxyl group, the amino acids can be acidic, basic or neutral. A particular feature of amino acid is the ionizable nature of NH2 and COOH groups. Hence, structure of amino acids changes in solutions of different pH. COOH H-C-NH2 Glycine Lipids: COOH H-C-NH2 CH3 Alanine COOH H-C-NH2 CH2-OH Serine Lipids are usually insoluble in water. Lipids can be simple fatty acids and some lipids have phosphorous and phosphorylated organic compounds in them. Lipids; containing phosphorus; are called phospholipids. A fatty acid has a carboxyl group attached to an R group. The R group can be a methyl or ethyl or higher number of CH2 group (1 carbon to 19 carbons). Fatty acids could be saturated or unsaturated. Many lipids have both glycerol and fatty acids. In this case, the fatty acids are found esterified with glycerol. They can be monoglycerides, diglycerides and triglycerides. On the basis of melting points, they can be termed as fats and oils. Oils have lower melting points while fats have higher melting points. There are a number of carbon compounds; with heterocylic rings; found in living organisms. Some of them are nitrogenous bases, e.g. adenine, guanine, cytosine, uracil and thymine. When a nitrogenous base is attached to a sugar, it is called a nucleoside, e.g. adenosine, guanosine, thymidine, uridine and cytidine. If a phosphate group is also found esterified to the sugar then they are called nucleotides, e.g. adenylic acid, thymidylic acid, guanylic acid, uridylic acid and cytidylic acid. Proteins: Proteins are polypeptides, polymer of amino acids. They are linear chains of amino acids linked by peptide bonds. Each protein is a polymer of amino acids. As there are 21 types of amino acids (e.g., alanine, cysteine, proline, tryptophan, lysine, etc.), a protein is a heteropolymer and not a homopolymer. A homopolymer has only one type of monomer repeating 'n' number of times .Dietary proteins are the source of essential amino acids. Therefore, amino acids can be essential or non-essential. Non-essential amino acids are those which is synthesized by the body itself whereas essential amino acids are obtained through our diet/food.
  3. Proteins carry out many functions in living organisms. Some Proteins and their Functions Protein Collagen Trypsin Insulin Antibody Receptor GLUT-4 Functions Intercellular ground substance Enzyme Hormone Fights infectious agents Sensory reception (smell, taste, hormone,etc.) Enables glucose transport into cells Collagen is the most abundant protein in animal world and Ribulose bisphosphate Carboxylase-Oxygenase (RUBISCO) is the most abundant protein in the whole of the biosphere Structure of proteins: Primary structure : Linear chain of aminoacids linked by peptide bonds The left end is represented by the first amino acid, while the right end is represented by the last amino acid. The first amino acid is also called N-terminal amino acid. The last amino acid is called C- terminal amino acid. Secondary structure: The folding of a linear polypeptide chain into specific coiled structure (u - helix) is called secondary structure and if it is with intermolecular hydrogen bonds the structure is known as ß - pleated sheet. u - helical structure is found in protein of fur, keratin of hair claws, and feathers. ß - pleated structure is found in silk fibres. Tertiary structure: The arrangement and interconnection of proteins into specific loops and bends is called tertiary structure of proteins. It is stabilized by hydrogen bond, ionic bond, hydrophobic bond and disulphide bonds. It is found in myoglobin (globular proteins Quaternary structure: Group of more than two tertiary structured proteins together form quaternary structure. The manner in which these individual folded polypeptides or subunits are arranged with respect to each other (e.g. linear string of spheres, spheres arranged one upon each other in the form of a cube or plate etc.) is the architecture of a protein otherwise called the quaternary structure of a protein. Eg: Haemoglobin consists of 2 subunits made of two alpha and two beta chain.
  4. Primary protein a. acids; Arnino Acid S helix Secondary protein structure occurs when •the sequence of a.rrønc• acids are linked by hydrogen Pleated sheet Tertiary protein structure -when certain attracbc•ns are pre—at between alpha and p—eted sheet— Alpha Quaternary strueture is -a protein of rner•e tilan one rune •ci:d cha.nm. STRUCTURAL ORGANISATION OF PROTEINS Nucleic acids: A nucleic acid is composed of nucleotide. There are three chemically distinct components in a nucleotide. One of them is a heterocyclic compound, the second is a monosaccharide and the third is phosphoric acid or phosphate. The heterocyclic compounds; present in nucleic acids are the nitrogenous bases, viz. adenine, guanine, uracil, cytosil and thymine. Adenine and Guanine are substituted purines, while uracil, cytosil and thymine are substituted pyrimidines. Based on the presence of purine or pyrimidine, the heterocyclic ring is called purine and pyrimidine. Polynucleotides contain either ribose sugar or 2' deoxyribose sugar. If ribose sugar is present then the nucleic acid is called ribonucleic acid (RNA). If deoxyribose sugar is present then the nucleic acid is called deoxyribose nucleic acid (DNA). Nucleic acids exhibit a wide variety of secondary structures. For example, one of the secondary structures exhibited by DNA is the famous Watson-Crick model. This model says that DNA exists as a double helix.
  5. The two strands of polynucleotides are antiparallel i.e., run in the opposite direction. The backbone is formed by the sugar-phosphate-sugar chain. A and G of one strand compulsorily base pairs with T and C, respectively, on the other strand. There are two hydrogen bonds between A and T. There are three hydrogen bonds between G and C. Each helix of DNA contains 10 base pairs with the length of 3.4 nm (34 Ao). Polysaccharides: The long chains of sugars are called polysachharides. If a polysaccharide is made up of similar monosaccharides, it is called homopolymer, e.g. cellulose. If a polysaccharide is made up of different monosachharides, it is called heteropolymer. The right end of a polysaccharide chain is called the reducing end and the left end is called the non-reducing end. NATURE OF BOND LINKING MONOMERS IN A POLYMER In a polypeptide or a protein, amino acids are linked by a peptide bond which is formed when the carboxyl (-COOH) group of one amino acid reacts with the amino (- NH2) group of the next amino acid with the elimination of a water moiety (the process is called dehydration). In a polysaccharide the individual monosaccharides are linked by a glycosidic bond. This bond is also formed by dehydration. This bond is formed between two carbon atoms of two adjacent monosaccharide. In a nucleic acid a phosphate moiety links the 3' -carbon of one sugar of one nucleotide to the 5' -carbon of the sugar of the succeeding nucleotide. The bond between the phosphate and hydroxyl group of sugar is an ester bond. As there is one such ester bond on either side, it is called phosphodiester bond. DYNAMIC STATE OF BODY CONSTITUENTS - CONCEPT OF METABOLISM Metabolism: All the biomolecules are constantly being changed into some other biomolecules and also made from some other biomolecules. The turnover of biomolecules takes place continuously. All these reactions are together called metabolism. Anabolism: When a complex biomolecule is synthesized from simple biomolecules through a biological process, the process is called anabolism. Energy is utilised during anabolism. Catabolism: When a complex biomolecule is disintegrated to produce simple biomolecules through a biological process, the process is called catabolism. Energy is released during catabolism. Metabolic Pathway: Metabolites are converted into each other in a series of linked reactions. Such a series of linked reactions is called metabolic pathway. Every chemical
  6. reaction in the metabolic pathways is a catalysed reaction. The metabolic pathways are either linear or circular. The Living State: All living organisms exist in a steady state; characterized by concentrations of each of the biomolecules. The steady state is a non-equilibrium state. It can be said that the living process is a constant effort to prevent falling into equilibrium. Without metabolism, there cannot be a living state. ENZYMES An enzyme is a catalyst which is utilised in metabolic reactions. Almost all enzymes are proteins. The catalytic cycle of an enzyme action can be described in the following steps: 1. 2. 3. 4. The substrate binds to the active site of the enzyme, fitting into the active site. The binding of the substrate induces the enzyme to alter its shape, fitting more tightly around the substrate. The active site of the enzyme breaks the chemical bonds of the substrate and the new enzyme- product complex is formed. The enzyme releases the products of the reaction and the free enzyme is ready to bind to another molecule of the substrate. Factors Affecting Enzyme Activity Temperature and pH: Enzymes usually function in a narrow range of temperature and pH. Each enzyme shows its highest activity at optimum temperature and optimum pH. Beyond that range, the activity declines. Low temperature preserves the enzyme temporarily in inactive state, while high temperature destroys the enzyme. Concentration of Substrate: The velocity of enzymatic action at first rises with an increase in substrate concentration. But the velocity of reaction does not rise once it reaches a maximum velocity (V max). This happens because there are fewer molecules of enzyme and no free enzyme molecule is left to bind with the additional substrate molecules. Effect of Inhibitor: When the inhibitor closely resembles the substrate and inhibits the activity of an enzyme, it is known as competitive inhibitor. Because of its close structural similarity with the substrate, the inhibitor competes with the substrate for the binding site on the enzyme. Such competitive inhibitors are often used in the control of bacterial pathogens. Classification and Nomenclature of Enzymes Enzymes are divided into 6 classes each with 4-13 subclasses and named accordingly by a four-digit number. Oxidoreductases/dehydrogenases: Enzymes which catalyse oxidoreduction between two substrates S and S'
  7. Transferases: Enzymes catalysing a transfer of a group, G (other than hydrogen) between a pair of substrate S and S' Hydrolases: Enzymes catalysing hydrolysis of ester, ether, peptide, glycosidic, C-C, C- halide or P-N bonds. Lyases: Enzymes that catalyse removal of groups from substrates by mechanisms other than hydrolysis leaving double bonds. Isomerases: Includes all enzymes catalysing inter-conversion of optical, geometric or positional isomers. Ligases: Enzymes catalysing the linking together of 2 compounds, e.g., enzymes which catalyse joining of C-O, C-S, C-N, P-O etc. bonds. Co-factors In many cases, non-protein constituents are bound to the enzyme which makes the enzyme catalytically inactive. Such non-protein constituents are called cofactors. In such cases, the protein portion of the enzyme is called the apoenzyme. There are three kinds of cofactors, viz. prosthetic groups, co-enzymes and metal ions. Prosthetic Groups: Prosthetic groups are organic compounds. They are distinguished from other cofactors in that they are tightly bound to the apoenzyme. For example, in peroxidase and catalase, which catalyze the breakdown of hydrogen peroxide to water and oxygen, haem is the prosthetic group and it is a part of the active site of the enzyme. Co-enzymes: Co-enzymes are also organic compounds but their association with the apoenzyme is only transient. A co-enzyme's association, with apoenzyme; usually occurs during the course of catalysis. Moreover, co-enzymes serve as co-factors in a number of different enzyme catalyzed reactions. The essential chemical components of many coenzymes are vitamins, e.g., coenzyme nicotinamide adenine dinucleotide (NAD) and NADP contain the vitamin niacin. Metal Ions: A number of enzymes require metal ions for their activity. Such metal ions form coordination bonds with side chains at the active site and at the same time form one or more cordination bonds with the substrate, e.g., zinc is a cofactor for the proteolytic enzyme carboxypeptidase. Catalytic activity is lost when the co-factor is removed from the enzyme which proves that they play a crucial role in the catalytic activity of the enzyme.

Need a Tutor or Coaching Class?

Post an enquiry and get instant responses from qualified and experienced tutors.

Post Requirement

Related Study Notes

Upload Study Notes

If you have your own Study Notes which you think can benefit others, please upload on LearnPick. For each approved Study Note you will get 100 Credit Points and 100 Activity Score which will increase your profile visibility.

Upload Now
Home > Study Notes > Biomolecules