10th Chemistry Chapter 13 Long Questions PDF

# Long Questions ## Introduction Biochemistry is a very important field today. It deals with the naturally occurring macromolecules such as carbohydrates, proteins, lipids, nucleic acids, and vitamins. These macromolecules are synthesized by living organisms from simple molecules present in the envi...

# Long Questions ## Introduction Biochemistry is a very important field today. It deals with the naturally occurring macromolecules such as carbohydrates, proteins, lipids, nucleic acids, and vitamins. These macromolecules are synthesized by living organisms from simple molecules present in the environment. Macromolecules are essential for humans as they serve as reservoirs of energy. For example, carbohydrates that humans eat provide energy. Lipids are a major source of energy and are stored in the body to provide emergency energy supplies. They help humans to work during tough times. Proteins not only provide energy, they help humans stay strong by forming new bones and muscular tissues. Moreover, proteins protect humans against diseases. Nucleic acids are responsible for transmitting genetic information from generation to generation. ## 13.1 Carbohydrates ### Q.No.1 What is meant by carbohydrates? How it is synthesized? Give its classifications in detail. **Definition:** Carbohydrates are macromolecules defined as polyhydroxy aldehydes or ketones. They have general formula $C_n(H_2O)_n$. **Synthesis:** Carbohydrates are synthesized by plants through the photosynthesis process from carbon dioxide and water in the presence of sunlight and green pigment chlorophyll. The glucose is further polymerized to form starch and cellulose. **Classification:** Carbohydrates are classified as: - Monosaccharides - Oligosaccharides - Polysaccharides ### 13.1.1 Monosaccharide **Definition:** Monosaccharides are the simplest sugars which cannot be hydrolyzed. They consist of 3 to 9 carbon atoms. **Classification:** They are classified according to the number of carbon atoms in their molecules as trioses, tetroses, pentoses, hexoses, and so on. The important monosaccharides are hexoses like glucose and fructose, etc. Glucose is a pentahydroxy aldehyde while fructose is a pentahydroxy ketone having the open chain structures as follows and general formula $C_6H_{12}O_6$. **Glucose** ``` CHO | H-C-OH | OH-C-H | H-C-OH | H -C-OH | CH2OH ``` **Fructose** ``` CH2OH | C=0 | H-C-OH | HO-C-H | H-C-OH | CH2OH ``` **Properties:** - Monosaccharides are white crystalline solids. - They are soluble in water and have a sweet taste. - They cannot be hydrolyzed. - They are reducing in nature, therefore, these are called reducing sugars. ### 13.1.2 Oligosaccharides **Definition:** Oligosaccharides give 2 to 9 units of monosaccharide on hydrolysis. **Classification:** They are classified as disaccharides, trisaccharides, tetrasaccharides, etc., depending upon the number of units they produce on hydrolysis. The most important oligosaccharides are disaccharides like sucrose. On hydrolysis, sucrose produces one unit of glucose and one unit of fructose. $C_{12}H_{22}O_{11} + H_2O \xrightarrow[Heat]{Dilute HCl} C_6H_{12}O_6 + C_6H_{12}O_6 $ **Properties:** - These carbohydrates are white, crystalline solids easily soluble in water. - They are also sweet in taste. - They may be reducing or non-reducing. ### 13.1.3 Polysaccharides **Definition:** Polysaccharides are macromolecular carbohydrates consisting of hundreds to thousands of monosaccharide. **Properties:** - They are amorphous solids. - They are tasteless and insoluble in water. - They are non-reducing in nature. **Examples:** - Starch - Cellulose ### Q.No.2 Explain the sources and uses of Carbohydrates. **13.1.4 Sources and Uses of Carbohydrates:** Carbohydrates range from simple to complex ones. They have varied sources and uses. **Disaccharides are sucrose, lactose, and maltose.** **Sources of simple sugars:** - Glucose, fructose, and galactose are found in fruits, vegetables, honey, and cereals. - Sucrose is found in sugar beet, sugar cane, and fruits. - Lactose consisting of glucose and galactose is the main sugar in milk and dairy products. - Maltose, a disaccharide of two glucose molecules, is found in cereals. **Polysaccharides are starch and cellulose.** - Starch is found in cereal crops; wheat, barley, maize, rice, etc. - Cotton is pure cellulose. **Our body uses carbohydrates in the form of glucose.** - Glucose is the only form of carbohydrates that is used directly by muscles for energy. - It is important to note that the brain needs glucose as an energy source, because it cannot use fat for this purpose. **Uses to body by carbohydrates:** - Besides, the energy providing materials, carbohydrates also provide the following usage our body. - They regulate the amount of sugar level in our body. Low sugar level in the body results in hypoglycemia. - They provide essential nutrients for bacteria in the intestinal tract that helps in digestion. - Dietary fiber helps to keep the bowel functioning properly. - Fiber helps in lowering of cholesterol level and regulates blood pressure. - Carbohydrates protect our muscles from cramping. **How carbohydrates are used as a source of energy?** Carbohydrates provide 17 kilo joules of energy per gram. Humans take carbohydrates as food. Long chains of starch (carbohydrates) are broken down into simple sugars (glucose) by digestive enzymes. The glucose is absorbed directly by the small intestine into the bloodstream. Bloodstream transports the glucose to its place of use, e.g., muscles. ## 13.2 Protein ### Q.No.3 Define protein and explain its properties. **Definition:** Proteins are highly complicated nitrogenous compounds made up of amino acids. **Composition:** Proteins consist of carbon, hydrogen, oxygen, nitrogen, and sulfur. They are polymers of amino acids. Amino acids are linked with each other through peptide linkage. Protein has more than 10,000 amino acids. All proteins yield amino acids upon hydrolysis. **Properties:** - Proteins are present in all living organisms. - They make up bulk of the non-bony structure of the animal bodies. - They are a major component of all cells and tissues of animals. - About 50% of the dry weight of the cell is made up of proteins. - They are found in muscles, skin, hair, nails, wool, feathers, etc. ### Q.No.4 What are amino acids? Explain the amino acids are the building blocks of protein. **Amino Acids:** Amino acids are organic compounds consisting of both amino and carboxyl groups. They have the general formula: (side chain) R-CH-COOH (carboxylic group) NH2 (amino group) **Side chain 'R' is different for different amino acids.** **Explanation:** There are 20 amino acids. Ten out of twenty amino acids can be synthesized by the human body. These amino acids are called non-essential amino acids. While other ten which cannot be synthesized by human bodies are called essential amino acids. Essential amino acids are required by human bodies and must be supplied through diet. **13.2.1 Amino acids are Building Blocks of Proteins:** Two amino acids link through peptide linkage. Peptide linkage (bond) is formed by the elimination of water molecule between the amino group of one amino acid and carboxyl acid group of another. When thousands of amino acids polymerize they form protein. $H_2N-CH-COOH + HNH – CH -COOH \xrightarrow[R]{H_2O} H_2N [-CH-C-NH.-]CH-СООН $ ### Q.No.5 Explain the sources and uses of proteins. **13.2.2 Sources and Uses of Proteins:** Proteins make up more than 50% of the dry weight of animals. Each protein has its source and carries out a specific function. Sources and uses of protein are as follows: - Sources of animals' proteins are meat, mutton, chicken, fish, eggs. These are used as food by human beings as they are essential for the formation of protoplasm. - Enzymes are proteins that are produced by the living cells. They catalyze the chemical reactions taking place in the bodies. They control the bleeding and treat blood cancer. - Hides are proteins. These are used to make leather by tanning. Leather is used to make shoes, jackets, sports items, etc. - Proteins are found in bones. When bones are heated they give gelatin. Gelatine is used to make bakery items. - Plants also synthesize proteins, such as pulses, beans, etc. These are used in food. ## 13.3 Lipids ### Q.No.6 What are lipids? Explain its properties. **Definition:** Lipids are macromolecules made up of fatty acids. Lipids include oils and fats. **Composition:** Oils and fats are esters of long chain carboxylic (fatty) acids with glycerol. The esters are made of three fatty acids, therefore, they are called triglycerides. **Genera formula of triglycerides is as under.** ``` O || H2C-O-C-R | O || HC-O-C-R | O || H2C-O-C-R ``` **Properties of oil** - Oils exist in a liquid form at room temperature. - They are triglycerides unsaturated fatty acids. **Properties of fats** - While fats exist in a solid form at room temperature. - They are triglycerides of saturated fatty acids. ### 13.3.1 Fatty Acids Fatty acids are building blocks of lipids. They are long chain saturated and unsaturated carboxylic acids. **Example** - $C_{15}H_{31}COOH$ Palmitic acid - $C_{17}H_{35}COOH$ Stearic acid These acids form esters (oils or fats) with glycerol in the presence of mineral acids. ### Q.No.7 Explain the sources and uses of Lipids. **13.3.2 Sources and Uses of Lipids:** Fats and oils are high energy foods. They are a source of vitamins A, D, and they are used to build brain cells, nerve cells, and cell membranes. They are insoluble in water but soluble in organic solvents. The fats stored in the body insulate it as these are poor conductors of heat and electricity. Fats and oils are synthesized naturally by animals, plants, and marine organisms. **Uses** - Animal fats are found in adipose tissue cells. Animals secrete milk from which butter and ghee is obtained. Butter and ghee are used for cooking and frying of food, for preparing bakery products, and sweets. - Animal fats are used in soap industry. - Plants synthesize oils and store them in seeds, such as, sunflower oil, coconut oil, groundnut, and These oils are used as vegetable oils or ghee for cooking and other purposes. - Marine animals like salmon and whales are also a source of oils. These oils are used as medicines, e.g., cod liver oil. **Hydrogenation of vegetables** - Vegetable oils are trimester of glycerol and fatty acids of unsaturated long chains. These oils are hydrogenated in the presence of a nickel catalyst at 250 to 300 °C to form vegetable ghee. $Ni$ vegetable oil + $H_2$ $\xrightarrow{250° C}$ vegetable ghee (unsaturated trimester) (saturated trister) **Interesting Information** - Margarine is produced by adding hydrogen to vegetable oil at 200 °C in the presence of a catalyst. Greater the amount of hydrogen is added, the more solid the margarine becomes. - Rancid butter has a foul smell because of botanic acid. However, the esters of botanic acid have a fruity smell. For example, methyl butanoate smells like apples and ethyl butanoate smells like pineapple. ## 13.4 Nucleic Acids ### Q.No.8 What are Nucleic acids? Explain its types in detail. **Nucleic acids** are essential components of every living cell. They are generally long chain molecules made up of nucleotides. **Composition:** Each nucleotide consists of the components are: - Nitrogenous base - Pentose sugar - Phosphate group **Types:** There are two types of nucleic acids: - Ribonucleic acid (RNA) - Deoxyribonucleic Acid (DNA) ### 13.4.1 Deoxyribonucleic Acid (DNA) DNA consists of deoxyribose sugar. Its structure was discovered by J. Watson and F. Crick in 1953. **Composition:** - It is a long double-stranded molecule consisting of two chains. - Each chain is made up of sugar, phosphate, and a base. - The sugar and phosphate groups make the backbone of the chains, and two chains are linked through bases. - The chains are wrapped around each other in a double helix form. **Importance of DNA:** - DNA is the permanent storage place for genetic information in the nucleus of a cell. - It carries and stores all genetic information of the cell. - It passes the information as instructions from generation to generation how to synthesize particular proteins from amino acids. - These instructions are genetic code of life. - They determine whether an organism is a man or a tree or a donkey and whether a cell is a nerve cell or a muscle cell. **Specific sequence:** The sequence of nitrogenous bases in DNA determines the protein development in new cells. The function of the double helix formation of DNA is ensuring that no disorder takes place. DNA carries genes that control the synthesis of RNA. **Genetic disease:** Errors introduced into the genes synthesize faulty RNA. It synthesizes faulty proteins that do not function the way they are supposed to. This disorder causes genetic diseases. ### 13.4.2 Ribonucleic acid (RNA) It consists of ribose sugar. It is a single-stranded molecule. It is responsible for putting the genetic information to work in the cell to build proteins. Its role is like a messenger. **Transcription and protein synthesis:** RNA is synthesized by DNA to transmit the genetic information. RNA receives, reads, decodes and uses the given information to synthesize new proteins. Thus RNA is responsible for directing the synthesis of new proteins. ## 13.5 Vitamins ### Q.No.9 What are Vitamins? Explain its types and importance in detail. In 1912 Hopkins noticed that in addition to carbohydrates, proteins, and fats there are other substances needed for normal growth. Although these substances were needed in a small quantity, yet these substances were called Accessory Growth Factors. Later Funk proposed the name 'Vitamin' for these substances. He discovered Vitamin B1 (Thiamin). ### 13.5.1 Types of Vitamins Vitamins are divided into two types: **(i) Fat Soluble Vitamins:** The vitamins which dissolve in fats are called fat soluble vitamins. **Types:** - Vitamin A - Vitamin D - Vitamin E - Vitamin K **Excess of vitamins cause disease:** If these vitamins are taken in a large quantity, they accumulate in the body and cause diseases. **Example:** Accumulation of vitamin D in the body causes bone-pain and bone-like deposits in the kidney. However, their deficiency also causes diseases. **Sources, uses, and diseases because of deficiency are provided in the Table.** | No. | Vitamin | Sources | Uses | Diseases | |------|---------|---------|-------|----------| | i | Vitamin A | Dairy products, eggs, oils and fats, fish. It can also be obtained from the beta-carotene found in green vegetables, carrots, and liver. | Maintains the health of the epithelium and acts on the retina's dark adaptation mechanism. | Night blindness, eye inflammation. | | ii | Vitamin D | Fish liver, dairy products, oils, and fats. Vitamin D is formed in the skin when it is exposed to sunlight. | Has a role in the absorption of calcium which is essential for the maintenance of healthy bones. | Rickets | **(ii) Water Soluble Vitamins:** The vitamins that dissolve in water are called water soluble vitamins. **Definition:** These vitamins are B complex (this includes 10 vitamins) and vitamin C (ascorbic acid). **Advantages:** Water-soluble vitamins are rapidly excreted from the body. Hence these vitamins are not toxic even if taken in a large quantity. However, their deficiency causes disease. ### 13.5.2 Importance of Vitamins - Each vitamin plays an important role in the healthy development of the human body. - Natural vitamins are organic food substances found only in plants and animals. The human body is unable to synthesize vitamins. Because of this, they must be supplied either directly in the diet or by way of dietary supplements. They are absolutely necessary for normal growth. - Vitamins cannot be assimilated without ingesting food. This is why, it is suggested that vitamins must be taken with a meal. They help to regulate the body's metabolism. **Interesting Information:** - Cancer is caused by damage to DNA or interfering with the mechanism of its replication or passing information. So, by understanding the mechanism of action of DNA, cancer can be cured. ## Q.No.10 Write down the commercial use of enzymes. **Commercial uses of enzymes:** Enzymes are used on a commercial scale for different purposes. Common types of enzymes and their role in industry is described as: **Enzymes as a yeast:** - Enzymes present in the yeast are commercially used for the fermentation of molasses and starch to produce alcohol (Ethanol). These enzymes are diastase, invertase, and zymase. **Microbial enzymes:** - Microbial enzymes are used in detergents (powder or liquid). Upases decompose fats into more water-soluble compounds. Amylase removes starch-based stains. Cellulase degrades cellulose to glucose, a water-soluble compound. Bacterial proteases break down protein stains on clothes. Thus, enzymes containing detergents clean effectively and remove all stains and dirt. **Enzymes used as purification of fruit juices:** - Enzymes are used for the purification of fruit juices. They are added to fruit that has been crushed like grapes. This increases the yield of the juice extracted by removing suspended particles. It also improves the color derived from the fruit skins. **Amylase enzymes:** - Amylase enzymes are used in bread making because they can yield more starch of the flour. Even they are efficient enough to convert starch to sweet glucose syrup. This can be used as a sweetener in the food as well as bread making. **Lactase enzyme:** - Lactase enzyme is used to increase sweetness in ice cream. As lactose in milk is broken down to galactose and glucose, which are sweeter than lactose. **Enzymes in dairy industry:** - In the dairy industry, some enzymes are used for the production of cheeses, yogurt, and other dairy products while others are used to improve texture or flavors of the products. ## Skills **Solubility of starch and sugar:** - Solubility of starch and sugar in water can be checked in the laboratory as well as at home. Starch is insoluble in water while sugar is soluble in water forming a clear solution in water. **Denaturing of Protein:** - Denaturing of protein means precipitation or coagulation of protein. It can be carried out by heating or changing pH. A simple common method for denaturing of protein is boiling of an egg. White viscous fluid (albumen) present in an egg is protein. When egg is boiled for a few minutes, albumen coagulates i.e., solidifies. **Concept Diagram:** An image of a concept diagram showing the types and uses of carbohydrates, proteins, lipids, and nucleic acids.