Carbohydrates, Lipids & Fats - Science Notes PDF

CARBOHYDRATES Monosaccharides, Disaccharides, and Polysaccharides Carbohydrates are compounds composed of mainly carbon, oxygen, and hydrogen. Hydrogen and oxygen in carbohydrates exist in a 2:1 ratio. They are used as a source and storage of energy (e.g., sugary foods and starches) and may also se...

CARBOHYDRATES Monosaccharides, Disaccharides, and Polysaccharides Carbohydrates are compounds composed of mainly carbon, oxygen, and hydrogen. Hydrogen and oxygen in carbohydrates exist in a 2:1 ratio. They are used as a source and storage of energy (e.g., sugary foods and starches) and may also serve a structural function (e.g., cellulose in the cell wall of plants). Carbohydrates are very important because they give us energy. They're like the fuel that keeps our bodies going, especially for our brains and muscles. Not only that, but they also help with digestion and keeping our blood sugar levels in check. So, whether we're studying hard or playing sports, carbohydrates are our go-to source for staying active and healthy! BIOLOGICAL FUNCTIONS Carbohydrates serve a number of functions in nature. In plants, they provide a rigid structure. Sweet and soluble in water. Carbohydrates lower water potential by increasing solute concentration, which causes water to move into areas with higher solute concentration through osmosis. Primary source of energy, providing an immediate energy source during short bursts of different activities. 1. Monosaccharides Monosaccharides are the monomers or the building blocks of carbohydrates. They are simple sugars that cannot be further broken down into simpler carbohydrate molecules. Combining these molecules forms more complex carbohydrates like disaccharides and polysaccharides. Glucose: A monosaccharide found in blood, serving as the main energy source of the body. Found in plants and animals, and used as an ingredient in syrup, candy, honey, sports drinks, and desserts. Fructose: A monosaccharide commonly found in plants, particularly in fruits, some vegetables, and honey. Referred to as "fruit sugars." Galactose: A monosaccharide naturally present in mammalian milk and in milk products like cheese, butter, and yogurt. 2. Disaccharides Disaccharides are sugars made of two monosaccharides joined by a dehydration reaction (synthesis). Two monosaccharides are connected by a glycosidic bond. The glycosidic bond is formed through a dehydration reaction, producing water as a byproduct. The glycosidic bond can be broken by hydrolysis, which requires water and results in two monosaccharides. 3. Polysaccharides Polysaccharides are complex carbohydrates made of numerous monosaccharide units. These molecules are formed through a series of dehydration reactions and are held together by glycosidic bonds. Starch: The primary energy storage in plants, stored in roots, fruits, and seeds. It can be broken down into simpler carbohydrates. Cellulose: Provides the structural framework of the plant cell wall, offering protection against rupture or damage. Cellulose chains form microfibrils, which assemble into larger microfibrils that encase plant cells, reinforcing the cell wall. Glycogen: The primary storage form of carbohydrates in mammals, stored in the liver and skeletal muscles. It serves as an important long-term energy source. For example, when fasting, the body breaks down glycogen to form glucose, producing energy. LIPIDS Key Points on Lipids: Lipids are organic compounds primarily made of carbon, hydrogen, and a small amount of oxygen. They are non-polar and do not dissolve in water. Types of Lipids: 1. Triglycerides: Primary energy reservoir, found in oils and fats. 2. Phospholipids: Essential for cell membrane structure. Triglycerides: Composed of glycerol and three fatty acids. Dehydration reactions form ester bonds between glycerol and fatty acids. Hydrolysis reactions break down triglycerides by adding water. Types of Fatty Acids: 1. Saturated Fats: ○ No double bonds (C=C) between carbons. ○ Straight-chain, solid at room temperature. ○ Found in animal products (meat, dairy) and some plant oils. ○ Can raise cholesterol levels, increasing heart disease risk. 2. Unsaturated Fats: ○ At least one C=C double bond. ○ Bent shape, liquid at room temperature. ○ Monounsaturated (1 C=C bond) and polyunsaturated (multiple C=C bonds). ○ Found in plant-based foods (nuts, seeds, vegetable oils). ○ Can help lower cholesterol and reduce heart disease risk.  3. Trans Fats: ○ Formed by hydrogenation, turning liquid oils into solid fats. ○ Found in processed foods (baked goods, fried foods). ○ Can increase bad cholesterol (LDL) and lower good cholesterol (HDL), raising heart disease risk. ○ Limit intake of trans fats. Phospholipids: Similar to triglycerides but with a phosphate group replacing one fatty acid. Have a hydrophilic (water-loving) head and hydrophobic (water-fearing) tails. Phospholipid bilayer: ○ Forms in water, with hydrophilic heads facing outward and hydrophobic tails inward. ○ Critical for cell membrane structure, serving as a barrier for molecule passage. PROTEINS Proteins are organic compounds made up of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. They are likely the most diverse biomolecules in terms of structure and function. Proteins are always present in cells, accounting for up to 50% of the dry mass of most cells. They perform most cellular tasks and are essential for the structure, function, and regulation of the body's tissues and organs. Proteins can be obtained from both animal and plant sources. Animal-based foods like meat, fish, and eggs are rich in protein, while plant-based foods such as seeds, nuts, beans, and tofu are great alternatives, especially for those who avoid animal-derived foods. Like other biomolecules, proteins are made up of monomers called amino acids. There are 20 naturally occurring amino acids that combine in different sequences to form specific proteins with distinct functions. AMINO ACIDS An amino acid is a molecule with a central carbon bonded to: An amino group (-NH2) A carboxyl group (-COOH) A hydrogen atom (H) A side chain (which can vary, making each amino acid unique). The side chain distinguishes one amino acid from another. TYPES AND FUNCTIONS OF PROTEINS 1. ENZYMES ○ Enzymes are proteins that act as biological catalysts, speeding up chemical reactions. ○ Example: Amylase breaks down starch into sugar during digestion, helping the body absorb sugar more efficiently. 2. MESSENGER PROTEINS ○ Messenger proteins (such as hormones) transmit signals between cells and organs to regulate body functions. ○ Example: Insulin, produced by the pancreas, helps control blood sugar levels. 3. STRUCTURAL PROTEINS ○ These proteins provide support, protection, structure, and movement. ○ Examples: Keratin in hair, nails, and skin; Collagen in tendons and cartilage, providing structural support for connective tissues. 4. TRANSPORT PROTEINS ○ Transport proteins carry essential substances throughout the body. ○ Example: Hemoglobin, an iron-containing protein in red blood cells, transports oxygen from the lungs to the rest of the body. Transport proteins are also found in the plasma membrane, helping move ions in and out of cells. 5. DEFENSE PROTEINS ○ Defense proteins, like antibodies, are part of the immune system, helping to identify and neutralize foreign invaders such as bacteria and viruses. Why Study the Nature of Science? Studying the nature of science is important for several reasons: Developing scientific and technological literacy in society. Building awareness and accurate understanding of science and technology. Increasing interest in learning about science and technology. Three Domains of Science Scientists have identified three key domains that contribute to scientific literacy and an appreciation of science: 1. Science as a Way of Knowing (Scientific Inquiry) 2. Science as a Way of Doing (Scientific Enterprise) 3. Science as a Way of Looking (Scientific World View) Science as a Way of Knowing (Scientific Inquiry) This domain focuses on the body of scientific knowledge, including facts, concepts, theories, and laws found in textbooks. Key concepts include: 1. Demands Evidence – Scientific claims must be supported by observable phenomena. 2. Explains and Predicts – Scientists create explanations and predictions based on observations. 3. Identify and Avoid Bias – Validity of scientific claims is based on evidence, and bias must be minimized in interpretations. Science as a Way of Doing (Scientific Enterprise) This domain emphasizes the activities and processes used to generate scientific knowledge, including experimentation, observation, and chance discoveries. Key concepts include: 1. Organized into Content Disciplines – Science is divided into various fields (e.g., biology, chemistry, physics), each conducted in different institutions. 2. Methods of Science – There is no single "scientific method." Different methods are used in varying sequences, with scientists often repeating steps to refine results and discover new insights. Science as a Way of Looking (Scientific World View) This domain examines the philosophical and social aspects of science, focusing on how scientists generate knowledge and view the world. Key concepts include: 1. Understandable World – Science assumes that the universe is comprehensible through systematic study. 2. Preliminary – Scientific knowledge is always subject to revision as new evidence emerges. 3. Durable Knowledge – While science can't "prove" things (due to the problem of induction), scientific conclusions are generally reliable and long-lasting. 4. Limitations of Science – Some matters cannot be examined scientifically, and there are areas beyond the reach of scientific inquiry. In summary, understanding the nature of science helps clarify the process of scientific discovery, fosters critical thinking, and emphasizes the evolving, yet reliable nature of scientific knowledge. Accuracy vs. Precision: Accuracy refers to how close a measured value is to the true value. Precision refers to how consistent repeated measurements are, regardless of whether they are close to the true value. Example: High accuracy means measurements are close to the true value (e.g., 10.0 cm). High precision means measurements are consistent, even if they’re not close to the true value (e.g., 9.8 cm, 9.8 cm, 9.8 cm). Ideally, both accuracy and precision are high for reliable results. Data Tables and Graphs Data Tables: Data tables organize information in rows and columns, making it easy to compare and analyze data. Types of Graphs: 1. Pie Graph: Shows parts of a whole, with each slice representing a proportion of the total (e.g., percentage of different fruit types). 2. Bar Graph: Uses rectangular bars to compare quantities across categories (e.g., number of students in different subjects). 3. Line Graph: Displays data points over time or continuous data, showing trends by connecting points with a line (e.g., temperature changes throughout the day). Key Features of Graphs: Title: Provides context for the graph. Axis Labels: Indicate what each axis represents. Legend: Explains different data series. Scale: Ensures consistent spacing for accurate representation. In summary, data tables and graphs help organize and visualize data, making it easier to understand and interpret trends, comparisons, and proportions. Physical Quantities and Units Everything around us can be measured either qualitatively or quantitatively. Measurement is an exact science that involves numbers to describe matter and phenomena. Systems of Measurements: 1. International System of Units (SI): The SI system is the modern metric system based on powers of 10 and is widely used globally. Common units in SI include degree Celsius (temperature), meter or kilometer (distance), and kilogram or gram (mass). 2. Imperial System: Used in countries like the UK, Liberia, and Myanmar, the Imperial system includes units such as inch, yard, mile (length), ounce (mass), and pound (weight). Conversion does not follow the consistent pattern of SI. Units and Physical Quantities: Unit: A label for a measure of a quantity. Quantities expressed as ratios do not have units. Fundamental Quantities: Also called base quantities, these are standardized quantities like length, mass, and time. Derived Quantities: These are combinations of two or more base quantities, such as speed (distance/time) or force (mass × acceleration). Scientific Skills and Attitudes Scientific skills and attitudes shape how scientists approach problems and interpret data. While honesty is essential in all fields, attitudes like tolerance for uncertainty are more specific to science. 1. Intellectual Honesty – Acknowledges others' work and reports all evidence, even if it contradicts expectations. 2. Curiosity – Actively seeks answers through research and experimentation. 3. Patience and Perseverance – Continues experimenting until desired results are achieved. 4. Logical and Systematic Thinking – Uses clear reasoning and structured methods. 5. Open-Mindedness – Considers multiple solutions and evaluates others' ideas. 6. Objectivity – Weighs all evidence impartially. 7. Critical Thinking – Identifies inconsistencies, challenges claims, and questions assumptions. These attitudes guide scientists to think critically, remain open to new ideas, and uphold ethical standards in their research. Atwater System Overview The Atwater System is used to calculate the energy content of food based on its macronutrient composition, expressed in Calories (C). It assigns the following energy values per gram of macronutrient: Protein: 4 kcal/g Carbohydrates: 4 kcal/g Fat: 9 kcal/g Alcohol: 7 kcal/g Additionally: 1 Calorie (C) = 1000 calories (cal) 1000 calories (cal) = 1 kcal Sample Computation Given the Nutrition Facts of a cereal (8 servings per container, serving size 55g): Declared energy: 230 C Carbohydrates: 37g Fat: 8g Protein: 3g The goal is to calculate the energy (E) based on the Atwater system and compare it to the declared energy. Computation Steps: 1. Energy from Carbohydrates (E₁): 2. Energy from Fat (E₂): 3. Energy from Protein (E₃): 4. Total Computed Energy (E): 5. Difference between Declared and Computed Energy: Summary: Computed energy from the cereal = 232 C Declared energy = 230 C The difference between declared and computed energy is -2 C, indicating a slight discrepancy.