Science - Biomolecule PDF

Biomolecule Chapter Biomolecule 9 The following topics are discussed in this chapter: 5 What is Organic molecule 5 Biomolecules...

Biomolecule Chapter Biomolecule 9 The following topics are discussed in this chapter: 5 What is Organic molecule 5 Biomolecules 5 Major organic molecules 5 carbohydrates 5 Nucleic acid 5 protein 5 lipids 5 Interrelationships of organisms The coexistence of plants and animals forms our beautiful biosphere. You must want to know where they all came from. Are all animals created from the same material or are there any differences in origin between plants and animals? Again, humans can eat green vegetables, but cannot digest grass. But the main food of cows is grass. That means all plants and animals must have some structural differences that set them apart. Generally, many molecules are directly involved in the formation of living organisms, they are called biomolecules. In this chapter we will discuss organic molecules. 9.1 Biomolecule Living cells are made up of numerous molecules. These molecules include small molecules and large molecules which are collectively known as biomolecules. These biomolecules are generally composed of more than 25 elements, of which six elements are considered as common components of biomolecules. These are carbon (C), hydrogen Academic year 2024 (H), nitrogen (N), oxygen (0), phosphorus (P) and sulfur (S). The abbreviation of the English spelling of all these basic substances is CHNOPS. As you have already read in detail about cells, all cells are made of these organic molecules. Carbon is the most important atom among the six atoms of CHNOPS in terms of the structure of the living 135  Science Vapor Electric conductor Direction of transmission Spark H2O CH4 NH3 H2 Gas Cooling System Cool water Water Heat Figure 9.1. Miller-Urey's experiments on the synthesis of organic molecules from inorganic molecules. world. That is why it is said that carbon is the basis of life on earth Organisms are made up of four types of biochemical substances namely carbohydrates, proteins, nucleic acids and lipids. Without these two organic chemicals, proteins and nucleic acids, living things are not made. From this it can be assumed that organic molecules were formed from the beginning of creation and as a result of various chemical reactions they were combined to form the first cells. Scientists believe that lightning or frequent electrical storms, and strong solar radiation accelerated some chemical reaction that led to the formation of these organic molecules from inorganic molecules on primeval Earth. To prove this idea, in 1953, scientists Stanley Miller Academic year 2024 and Harold Urey created an artificial model of an early Earth in the laboratory (Figure 9.1). Where in a completely enclosed system, a mixture of water, methane, ammonia and hydrogen was constantly circulating on the ancient Earth. There were electrical discharges simulating the lightning of that time. After a week, they saw the synthesis 136  Biomolecule Lipid Nucleic acid Carbohydrate Protein Figure 9.2. Four types of organic molecules of organic molecules called amino acids, that is, they proved that it is possible to create organic molecules from inorganic molecules in the natural environment. The basic components of living organisms, carbohydrates, proteins, nucleic acids and lipids are made up of biochemical substances called biopolymers of cells. For example, carbohydrates are simple sugars, proteins are amino acids, nucleic acids are mononucleotides, and lipids are biological polymers of fatty acids. In this chapter we will discuss these four types of biomolecules (Figure 9.2). 9.2 Carbohydrates Carbohydrates are an important structural, storage and energy source of the body. Carbohydrates are complex natural organic compounds that mainly consist of carbon (C), hydrogen (O) and oxygen (O) elements. Carbohydrates Academic year 2024 contain carbon, hydrogen and oxygen atoms in the ratio of Figure 9.3: C₂H₂O of glucose, type molecule: CHO 1:2:1 137  Science Carbohydrates are produced from carbon dioxide and water in the presence of sunlight and with the help of chlorophyll in the process of photosynthesis in the green part. A large part of our daily diet consists of sugars or carbohydrates. Carbohydrates are one of the main 7 nutrients (water, carbohydrates, fiber, fat, protein, vitamins and minerals) related to nutrition in our body. Carbohydrates provide our body with necessary energy and if present in excess, it gets stored in the body as fat. After the breakdown of sugar in the body, it is divided into various small sugar molecules and when it reaches the smallest part in stages, it is absorbed in various parts of the body. You all know that carbohydrates can be classified in several ways,. A type of carbohydrate that is sweet in taste, granular and soluble in water is known as sugar. Glucose (Figure 9.3) is an example of a sugar. The other is starch, which is not sweet, granular and insoluble in water. Rice, flour, potato etc. from our familiar plants contain large amounts of starch. Carbohydrates can be divided into several categories on the basis of molecular structure, molecular weight and chemical religion. Monosaccharides are the smallest and simplest units 2- Deoxyribose Ribose among them. It serves as Figure 9.4. Two types of pentose sugars the building block of other complex carbohydrates. Their common symbol is CnH2nOn. If the number of carbon atoms in their molecule is 5, it is called a pentose sugar. Figure 9.4 shows two pentose sugar molecules, one a deoxyribose sugar and the other a ribose sugar. Ribose and deoxyribose sugars are structurally similar but the only difference is that one carbon of deoxyribose sugar does not have oxygen. As you read about nucleic acids, you will see that this pentose sugar is one of the main components of nucleic acid, a very important biological molecule in life Academic year 2024 Physiological role of carbohydrates: 1. Carbohydrates are the main source of energy in the body. Carbohydrates are broken down into glucose when ingested as food, and most cells use this glucose for energy or 138  Biomolecule store it as glycogen in the liver and muscles for future use. 2. Glucose from carbohydrates serves as the sole energy supplier for the brain and central nervous system. 3. Carbohydrates provide energy to the body's muscles. Glycogen is one of the heart's main sources of energy. 4. Carbohydrates ensure that protein is not diverted from its intended vital physiological function and converted into energy. 5. Complex carbohydrates such as indigestible carbohydrates and cellulose, pectin help in the formation and elimination of stool. 6. Adequate fiber-rich complex carbohydrates in the diet regulate blood glucose levels. 9.3 Nucleic acid Nucleic acids are actually large organic molecules, which are essential for every living organism. The organic molecules present in the chromosomes and ribosomes of the nucleus are called nucleic acids. In addition to the nucleus and ribosomes, mitochondria and plastids contain nucleic acids. Nucleic acid A type of organic molecule composed of a pentose sugar, a nitrogenous base or base, and phosphoric acid, which controls all activities of an organism, including the process of heredity. There are two types of nucleic acids, DNA and RNA. 9.3.1 DNA DNA or de-oxyribonucleic acid is the most important permanent chemical molecule in the cell. It contains and controls all the biological functions and hereditary characteristics of the cell or the organism as a whole. All living cells except a few viruses contain DNA. Chromosomes are made up of DNA and some proteins. DNA is attached to Academic year 2024 these proteins to form long threads, known as chromosomes. DNA can also be found in mitochondria and plastids. The amount of DNA in the cells of certain species is fixed. DNA is a type of chemical organic compound whose molecules are made up of many small molecules called nucleotides. Figure 9.5 shows the structure of DNA. 139  Science Two strands of the helical structure is made of sugar Nucleotide and phosphate molecules Nitrogen base 5’ Phosphate 4’ 1’ Adenine attached to Thymine (Carbon Number) (A-T) and Guanine attached to 3’ 2’ Cytosine (G-C) Pentose Sugar The opposite A strands are attached One turn in- (3' to 5' and 5' to cludes 10 nucle- T 3') side by side otides (3.4 nm) C 3' 3'→5' G 1 nm Major groove 0.34 nm 5'→3' Minor groove NH2 O O NH2 N N N NH NH N 2 nm N N NH2 N O N O H N H H H Double stranded DNA dou- Adenine (A) Guanine (G) Thymine (T) Cytosine (C) ble helix looks like a spiral staircase Purine Pyrimidine Nitrogen Base Figure 9.5 The structure of DNA. You can see in the diagram that each nucleotide is made up of a pentose sugar, a phosphate group and a nitrogenous base or base. Nucleic acids contain two types of Academic year 2024 pentose sugars. One of these is ribose sugar and the other is deoxyribose sugar. The pentose sugar in DNA is the deoxyribose sugar. DNA has four nitrogenous bases which are adenine, guanine, cytosine and thymine. 140  Biomolecule DNA is a spiral structure of numerous nucleotides with two strands, one of which is a strand complementary to the other. Two DNA strands or strands of a DNA molecule twist around each other to form a spiral shape called a double helix structure. Scientists James Watson and Francis Crick proposed the DNA double helix model of the physical and chemical structure of DNA in 1953, which earned them the Nobel Prize in 1963. Functions of DNA: 5 Possesses and controls all the characteristics of the organism. 5 Acts as a structural component of chromosomes. 5 Acts as the molecular basis of heredity. 5 Life acts as a regulator of all physiological and biological functions. 5 When the structure of DNA is disturbed, it repairs itself. 5 It plays a key role in evolution by creating variation through mutation. 9.3.2 RNA RNA or ribonucleic acid exists in the cytoplasm of cells free or associated with ribosomes. The main difference between RNA and DNA is that it is not double- stranded like DNA, but a single chain of nucleotides (Figure 9.6). In the case of some viruses (eg Covid virus or SARS-Cov-2.) DNA is missing. That is, all viruses that are not made up of DNA have RNA as their nucleic acid. In these cases RNA acts as the genetic material. RNA is mainly of three types. Ribosomal RNA (Ribosomal RNA or rRNA), messenger RNA (Messenger RNA or mRNA), and transfer RNA (Transfer RNA or tRNA). We get an idea of the function of these RNAs when we read about the synthesis or structure of proteins Function of RNA : Academic year 2024 5 The main function of RNA is to synthesize proteins. 5 Carrying messages from DNA to ribosomes. 5 Carrying hereditary characteristics. 141  Science 9.4 Protein Protein is one of the most important biochemical substances and large complex organic molecules in living organisms. Gerrit Müller first used the term protein in 1838. Different types of proteins are made inside a cell, which play many important roles in the body. Biological reactions in cells are controlled by a variety of enzymes, antibodies, and hormones—all of which are proteins. It is also essential for the structure, function and regulation of body tissues and organs. Since more than one amino acid is arranged to form a protein, before knowing about protein, we need to know a little about amino acid. Amino Acid 20 different types of amino acids (Figure 9.7) combine in different arrangements to form the primary structure of a protein. Primarily proteins are long chains made of amino acids. The primary structure of each protein differs from each other due to differences in the arrangement of amino acids. You already know about the arrangement of nucleotides in DNA (ATGC). The arrangement of amino acids depends on the arrangement of these nucleotides. Usually three bases combine to form a signal for the addition of an amino acid. The carboxyl group of one amino acid joins with the alpha amino group of the next amino acid to form a peptide bond. Thus a polypeptide chain or protein is formed as a result of the joining of numerous amino acids. It should be noted here that out of 20 amino acids, 11 can be synthesized in the human body, the remaining 9 must be obtained from food. Protein synthesis Academic year 2024 Amino Acid Side Carboxyl Group Figure 9.8 shows the Chain process of protein synthesis. A T nucleotide Figure 9.7 : Structure of Amino Acid 142  Biomolecule is converted to a U when making RNA from DNA. Three nucleotides are linked by one amino acid in a polypeptide chain. Functions of Protein (1) Food containing protein provides energy to our body and helps in physical growth and maintenanc (2) Helps in numerous biochemical reactions inside and outside the cell. (3) Some protein hormones are chemical messengers, they help in communication between body tissues and organs. Amino Acid Ribosome tRNA Larger part Smaller part tRNA carrying amino acid to tRNA left and ribosome amino acid is Cytoplasm kept Nucleus mRNA mRNA translation Gene mRNA Ribosome adding tRNA left and translation amino acid to protein amino acid is kept chain DNA RNA Protein Chain mRNA trans- lation DNA RNA mRNA Protein Figure 9.8: Different steps of protein synthesis Academic year 2024 (4) Proteins play an important role in regulating and maintaining the balance of acid and alkali concentrations in the blood and other body fluids. (5) Proteins help our body produce antibodies to fight infections from foreign microorganisms. 143  Science 9.5 lipids Lipid refers to fatty substances composed of carbon, hydrogen and oxygen. Lipids are important biochemical substances in plant and animal bodies. It plays important roles in cell structure, energy storage, thermoregulation and intercellular communication. In 1940 German scientist Bloor first used the term lipid. Lipids are generally found in animal and plant oils and fats. It is abundant in various parts of plant body especially fruits and seeds. Lipids are almost insoluble in water but soluble in solvents such as ether, alcohol, benzene, chloroform, acetone, petroleum etc. Lipid is colorless, tasteless and odorless, has no specific melting point, its melting point increases with increasing molecular weight. The relative importance of lipids is less than water, lipids float on water because they are lighter than water. At normal Protein spike to infect temperatures, some host lipids are liquid and some lipids are solid. Lipid membrane Lipids that are in solid form are called fats and lipids that are in liquid form are called Genetic material oils. Since lipids are hydrophobic, they act Figure 9.9. Corona virus as cell membranes. Due to the lipid membrane of the corona virus (Figure 9.9), which is responsible for the worldwide corona epidemic, it was possible to inactivate the virus by penetrating the membrane very easily with soap, disinfectant or some alcohol. That's why during the covid epidemic, a lot of importance was given to hand washing with soap or sanitizing Academic year 2024 hands for health protection. 144  Biomolecule Functions of Lipids: (1) Lipids combine with proteins to form lipoproteins, which are involved in energy production processes. (2) A type of lipid called phospholipids acts as a component in various membrane structures. (3) A type of lipid plays a special role in the photosynthesis process of plants. (4) Lipids such as fats and oils are stored in the plant body as food. of various oilseeds. Lipids are ingested during germination. (5) Waxy lipids form a layer on the outer coat of leaves to prevent excessive transpiration and it also protects the plant from various insect attacks. 9.6 Interrelationships of Biomolecules You already know that the major biomolecules of living organisms are carbohydrates, nucleic acids, proteins, and lipids. Each of these biomolecules is related to each other in structure and in carrying out biological functions. Below is a brief discussion on this topic Carbohydrates and Nucleic Acids: We have learned in the discussion that all living organisms. DNA controls physiological and biological functions, one example of which is cell division. This nucleic acid called DNA contains the genetic information of an organism. If you look at the structure of DNA, you will see that it is made up of a peltose sugar called deoxyribose, which is a carbohydrate. Carbohydrates and lipids: Carbohydrates are sometimes converted to glucose used as immediate energy, or stored as glycogen in the liver or muscles. Excess glucose is stored as long-term energy in a lipid called triglycerides. Academic year 2024 Carbohydrates and Proteins: Carbohydrates can be directly attached to proteins in a process called glycosylation to convert into protein structures. Proteins and Nucleic Acids: Proteins make up the structural components of our bodies, 145  Science and they regulate essential reactions. The messages stored in DNA are expressed by making proteins. A type of protein called histone helps bind nucleic acids. Proteins and lipids: A lipid called a phospholipid is essential for building the membrane of most cell membranes and often forms a lipid bilayer. By attaching proteins to this lipid bilayer, it creates channels, receptors or transporters that open the way for the movement of various types of organic molecules through the membrane.. You must realize that organic molecules are intimately related to each other in order to keep the living world functioning. If there is a disturbance in this relationship, various types of complications are created in the activities of the living world Academic year 2024 146