10.1 CARBOHYDRATES
Carbohydrate is an essential group of foods in human and animal diets. It is more realistic to define a carbohydrate as “polyhydroxy aldehydes and ketones or the substances that yield such compounds when they react with water on hydrolysis.” Carbohydrates are the main source of energy for tissues and organs of our body.
Key Concept
Carbohydrates are the body’s primary energy source. They’re found in foods like rice, potatoes, wheat, and barley. Remember: Carbs = Energy!
10.1.1 Classification based on structure
“Carbohydrates are classified as monosaccharides, disaccharides, oligosaccharide and polysaccharides”. This classification is based on the number of sugar unit present in carbohydrates.
| Type | Sugar Units | Examples |
|---|---|---|
| Monosaccharides | Single sugar unit | Glucose, fructose, galactose |
| Disaccharides | Two sugar units | Sucrose, lactose, maltose |
| Oligosaccharides | 3 to 10 sugar units | Kestose, melezitose |
| Polysaccharides | More than 10 sugar units | Cellulose, starch, glycogen |
Memorization Tip
Remember carbohydrate classification with the acronym “Mono-Di-Oli-Poly” – like “Monday, Die, Olive, Polly” – to recall the order from smallest to largest: Monosaccharides (1), Disaccharides (2), Oligosaccharides (3-10), Polysaccharides (10+).
Monosaccharides Classification
Monosaccharides are classified based on the number of carbon atoms:
| Class of Monosaccharide | Formula | Examples |
|---|---|---|
| Triose | C₃H₆O₃ | Glyceraldehyde |
| Tetrose | C₄H₈O₄ | Erythrose |
| Pentose | C₅H₁₀O₅ | Ribose |
| Hexose | C₆H₁₂O₆ | Glucose |
Memorization Tip
For monosaccharide classification: “Tri, Tetra, Penta, Hexa” correspond to 3, 4, 5, 6 carbons. Remember: “Tri-cycle has 3 wheels, Tetra-pak has 4 sides, Penta-gon has 5 sides, Hexa-gon has 6 sides.”
Glycosidic Linkage
“A glycosidic bond (O-C-O) is a type of covalent bond that join two monosaccharide units together to form a larger carbohydrate molecule”. It is formed through a condensation reaction with the elimination of water molecule.
Key Concept
Glycosidic bonds are like “carbohydrate glue” that holds sugar molecules together. They form through dehydration synthesis (removing water) and break through hydrolysis (adding water).
10.1.2 Importance of Carbohydrates
Carbohydrates are nutritionally significant bio molecules and are essential part of our balanced diet. Carbohydrates such as starch, sucrose, maltose etc convert into glucose in our digestive system which is then absorbed into the bloodstream and transported to the various cells.
Energy Equation
C₆H₁₂O₆ (glucose) + 6O₂ → 6CO₂ + 6H₂O + Energy
This cellular respiration equation shows how glucose is broken down to produce energy in cells.
Role of Common Carbohydrates in Health and Disease
Glucose: Vital component of our blood. Normal range: 70-110mg per 100dl. Exceeding this range can lead to Diabetes.
Fructose: Simple sugar found in fruits and honey. Sweetest carbohydrate. High intake associated with weight gain and obesity.
Lactose: Disaccharide found in milk (milk sugar). Broken down into glucose and galactose. Some adults lack lactase enzyme causing lactose intolerance.
Sucrose: Disaccharide made of glucose and fructose (table sugar). Excess can cause dental issues and other health problems.
Memorization Tip
Remember carbohydrate sources: Glucose (blood sugar), Fructose (fruit sugar), Lactose (milk sugar), Sucrose (table sugar). Connect each to their common source for easy recall.
10.2 PROTEINS
Proteins are naturally occurring macromolecules made up of long chain of amino acids that fold into precise three dimensional configurations. All living organisms including plants, animals and bacteria contain proteins and their presence is vital for the life.
Key Concept
Proteins are made of amino acids joined by peptide bonds. There are 22 different alpha amino acids that build proteins. The sequence of amino acids determines protein structure and function.
10.2.1 Classification of proteins based on function
| Type | Function | Examples |
|---|---|---|
| Catalytic proteins (Enzymes) | Biological catalysts that increase reaction rates | Lipase, Amylase, Protease |
| Storage proteins | Store nutrients or metal ions | Albumin, Globulin, Casein |
| Transport proteins | Move molecules across membranes and in bloodstream | Haemoglobin |
| Regulatory/Hormonal proteins | Regulate body functions and transmit signals | Insulin, Growth hormone |
Memorization Tip
Remember protein functions with the acronym “CSTR”: Catalytic, Storage, Transport, Regulatory. Think: “Can Steve Transport Rocks?” to recall the four main protein types by function.
10.2.2 Classification of proteins based on structure
| Classification | Description | Example |
|---|---|---|
| Primary | Linear sequence of amino acids in the protein chain | Any protein sequence |
| Secondary | Folding patterns due to interactions between nearby amino acids (alpha helix, beta sheets) | Alpha keratin, Silk fibroin |
| Tertiary | Three-dimensional arrangement of folded polypeptide chain | Myoglobin |
| Quaternary | Interaction of multiple protein subunits | Hemoglobin (4 subunits) |
Calorie Information
1 gram of carbohydrate ≈ 4 calories | 1 gram of protein ≈ 4 calories | 1 gram of fat (lipid) ≈ 9 calories
10.2.3 Properties of proteins
1. Water soluble due to di polar terminal of amino acids
2. Amphoteric nature (have both -COOH and -NH₂ groups)
3. Exhibit flexibility due to amino acid chain rotation
4. Some proteins have colors (e.g., haemoglobin is red)
5. Thermally stable but denatured by heat or pH changes
10.2.4 Importance of proteins
1. Provide energy (1g protein = 4 calories)
2. Transport oxygen (haemoglobin)
3. Regulate physiological functions (hormones)
4. Immune system function (antibodies)
Memorization Tip
Remember protein structure levels: “Primary is sequence, Secondary is local folding, Tertiary is 3D shape, Quaternary is multiple chains.” Use the mnemonic: “Please Study The Questions” for Primary, Secondary, Tertiary, Quaternary.
10.3 LIPIDS
“Lipids are naturally occurring heterogeneous organic compounds that are insoluble in water but soluble in Bloor’s reagent”. The term “lipid” originates from the Greek word “Lipos” meaning “fat like” due to their greasy or oily texture when touched.
Key Concept
Bloor’s reagent is a mixture of diethyl ether and ethyl alcohol in 2:1 ratio. Lipids are soluble in this reagent but insoluble in water, which is a key test for identifying lipids.
10.3.1 Classification of lipids
| Type | Description | Examples |
|---|---|---|
| Simple Lipids | Esters of fatty acids and alcohols; serve as energy source | Fats, oils, waxes |
| Compound Lipids | Esters of glycerol with two fatty acids and other compounds | Phospholipids, glycolipids, lipoproteins |
| Steroids | Derived lipids with four interconnected carbon rings | Cholesterol, cholic acid |
Fats and Oils
“These lipids are abundantly found in nature and chemically known as triglycerides or triesters”. They are formed by the condensation of three fatty acid and a glycerol molecule.
| Type of Fatty Acid | Description | Examples |
|---|---|---|
| Saturated Fatty Acid | Contains only single bonds between carbon atoms | Stearic Acid, Palmitic Acid |
| Unsaturated Fatty Acid | Contains at least one double bond between carbon atoms | Oleic Acid, Linoleic Acid |
Memorization Tip
Remember lipid classification: “Simple lipids store energy (fats/oils), Compound lipids have extra parts (phospho/glyco/lipo), Steroids have ring structures (cholesterol).” Use acronym “SCS” for Simple, Compound, Steroids.
10.3.2 Structure of lipids
The structure of lipids varies but basic structure consists of a hydrophilic head and a hydrophobic carbon tail.
10.3.3 Properties of lipids
Physical Properties
• Exist in different states: fats (solid), waxes (semisolid), oils (liquid) at room temperature
• Translucent or opaque in nature
• Insoluble in water, soluble in organic solvents
• Low density (float on water)
• Higher melting point for saturated lipids vs unsaturated
• Poor conductors of heat and electricity (insulators)
Chemical Properties
Addition reactions: Oils undergo hydrogenation to produce fats
Saponification: Fat/oil + Alkali → Soap + Glycerol
Rancidity: Oxidation and hydrolysis of fats leading to unpleasant taste/odor
Key Concept
Saponification is the process of making soap from fats/oils. Rancidity is what makes old fats smell bad. Remember: “Saturated fats are Solid at room temperature, Unsaturated fats are Liquid at room temperature.”
10.3.4 Importance of lipids
1. Store chemical energy (more than twice energy compared to carbs/proteins)
2. Fundamental building blocks of cell membranes (phospholipid bilayer)
3. Maintain body temperature and serve as insulation
4. Help absorption of fat-soluble vitamins (A, D, E, K)
10.4 MINERALS OF BIOLOGICAL SIGNIFICANCE
“Minerals are inorganic substances that are required to maintain physical health and prevent us from certain diseases”. Although more than twenty five minerals are present in our body but sixteen minerals are recognized as essential for the body health.
Key Concept
Minerals are inorganic and absorbed directly without digestion. Macro minerals are needed in larger quantities, micro minerals in smaller quantities.
10.4.1 Sources of important minerals
| Mineral | Sources |
|---|---|
| Calcium | Milk, Cheese, Yogurt, Leafy greens |
| Iron | Red meat, Poultry, Sea Food, Beans, Lentils |
| Zinc | Beef, Chicken, Sea Food, Beans |
| Phosphorous | Meat, fish, dairy products, nuts, seeds, whole grains |
10.4.2 Biological Significance
Iron: Crucial for oxygen transport, immune function, temperature regulation, red blood cell production.
Calcium: Builds strong bones and teeth, helps muscles contract/relax, aids blood clotting and immune system. Deficiency causes bone weakness.
Phosphorous: Important for healthy bones/teeth, part of DNA/RNA, protein synthesis, genetic information transfer, maintains heartbeat.
Zinc: Important for growth, wound healing, nervous system, immune function, insulin activity, sense of smell/taste. Deficiency causes weight/appetite/taste loss.
Memorization Tip
Remember minerals with their key functions: Iron = Oxygen transport (think “Iron in blood”), Calcium = Bones (think “Calcium in milk for bones”), Phosphorus = DNA/energy (think “Phosphorus in ATP”), Zinc = Immunity (think “Zinc for immune system”).
EXERCISES
Multiple Choice Questions
1. Starch and Sucrose are examples of:
2. Amino acid units bonded in protein molecule through:
3. Proteins are composed of:
4. A condensation polymer of amino acid is:
5. Saponification is the formation of soap by the reaction of fat and oil with:
6. Which of the following mineral is considered to be essential for immune system:
7. Rancidity is a chemical process involving:
8. Lipid which is a major component of cell membrane is:
9. Total numbers of alpha amino acids are:
10. Sugar molecules are classified as:
Short Questions
1. Mention the three main functions of lipids.
1. Store chemical energy (more than twice energy compared to carbs/proteins)
2. Fundamental building blocks of cell membranes (phospholipid bilayer)
3. Maintain body temperature and serve as insulation
2. Comparing with other nutrients, why lipids are better source of energy?
Lipids store more than twice the energy per gram compared to carbohydrates and proteins. While carbs and proteins provide approximately 4 calories per gram, lipids provide approximately 9 calories per gram, making them a more concentrated energy source.
3. Carbohydrates are necessary component of our diet. Give two dietary importance of carbohydrates.
1. Main source of energy for tissues and organs of our body
2. Components of DNA and RNA that transmit and store genetic information
4. What is meant by saponification? Give the reaction.
Saponification is the hydrolysis of fats/oils with an alkali to produce soap and glycerol.
Reaction: Triglyceride (fat/oil) + 3NaOH → 3R-COONa (soap) + CH₂OH-CHOH-CH₂OH (glycerol)
5. What is rancidity which chemical reaction involves in this process?
Rancidity is the process where animal fats develop an unpleasant taste and odor when exposed to moist air. It involves oxidation and hydrolysis reactions occurring simultaneously.
6. Write three essential functions of protein in the body.
1. Provide energy for the body (1g protein provides 4 calories)
2. Transport oxygen from lungs to tissues (haemoglobin)
3. Regulate physiological functions (hormones) and immune system (antibodies)
7. Write down the sources from which we intake fructose and lactose.
Fructose: Found in many fruits and honey
Lactose: Found in milk (5-8% in human milk, 4-6% in cow milk, 3-4% in goat milk) – also known as milk sugar