Chp 3 Chemical Basis of Life

• Inorganic molecules are substances that do not contain carbon and are generally found in the physical environment such as oxygen gas, CO2, H2O, and different materials.
• Water is the universal solvent, constituting 55 to 90% of the cell, and exists in nature in three phases: solid, liquid, and gas.
• Water acts as a medium for all metabolic activities like digestion, secretion, absorption, and other.
• Hydrophilic substances are those that readily dissolve in water.
• Cohesion is the tendency of water molecules to stick together, the principle behind the rising of water against the force of gravity up to various parts of the plant body.
• Surface tension is a measure of how difficult it is to stretch or break the surface of a liquid, attributed to the hydrogen bonds that connect the water molecules together.
• Organic molecules are chemical compounds that contain carbon, with the carbon atom possessing four valence electrons in its outer shell – a shell that holds eight – carbon can form up to four covalent bonds.
• Carbon is very good at forming large, chain-like molecules.
• Carbohydrates are organic molecules, made up of carbon, hydrogen, and oxygen with a ratio of 1:2:1, and include sugars and starches, which are important energy sources for most organisms.
• The major functions of carbohydrates are energy storage (food) and structural components (cell walls).
• Carbohydrates can be classified into three types: Monosaccharides, Disaccharides, and Polysaccharides.
• Monosaccharides are the simplest carbohydrates, with their carbon skeleton varying from 3-7 carbon atoms, and contain functional group hydroxyl (-OH) bonded to some carbon atoms.
• Examples of monosaccharides include Mannose, Fructose, Ribose, Deoxyribose, and others.
• Disaccharides are two monosaccharides joined by condensation (dehydration) reaction, with the dehydration synthesis of a molecule of disaccharide; synthesis of sucrose from glucose and fructose.
• Examples of disaccharides include Maltose and Sucrose.
• Polysaccharides are carbohydrates consisting of hundreds to a few thousands of monosaccharide units linked together by dehydration synthesis, represented by the empirical formula (C5H10O5)n, and serve as storage molecules that living things utilize to obtain energy – starch and glycogen; or as structural support as in the cell wall.
• Chitin and cellulose protect and support some living things.
• Many sugars are joined in long chains (macromolecules).
• Starch is a polysaccharide stored in the roots, tissues, and other parts of the plant body.
• Starch is composed purely of glucose units, which are arranged in a branched or unbranched fashion.
• Glycogen (animal starch) is stored in the liver and muscles of animals.
• Glycogen is also composed of several glucose units (up to 1000 glucose units) which are elaborately branched.
• Cellulose is a rigid material that encloses plant cells and the major component of the woody parts of plants.
• Cellulose is also composed of several glucose units.
• Cellulose cannot serve as a source of nutrients for humans, because it cannot be digested.
• Instead, cellulose serves as the bundles of “fibers” that clean our digestive tract.
• Chitin is the polysaccharide that forms the outer covering of arthropods – insects, spiders and shrimps, and cell walls of fungi like mushrooms.
• Polysaccharides containing glucose are a type of carbohydrates.
• Lipids are organic molecules that contain carbon, hydrogen, and oxygen with some forms containing small amounts of nitrogen and phosphorus.
• Lipids are insoluble in polar solvents like water but, they are soluble in non-polar solvents like benzene, ether, and chloroform.
• Lipids function as energy storage, building cell parts, providing a protective covering, forming an important component of hormones, and more.
• Complex lipids contain fatty acids such as triglycerides and phospholipids.
• Simple lipids do not contain fatty acids such as cholesterol, plant pigments, some vitamins, and hormones.
• Fatty acid is the basic building block of fatty acids, containing 14-22 carbon atoms in a chain.
• Fatty acid is a very non-polar molecule which is not soluble in water (hydrophobic, water-fearing).
• Fatty acids can be saturated (like stearic acid) or unsaturated (like oleic acid).
• Fats are large organic molecules formed by dehydration synthesis of a molecule of glycerol (C3H6O3), three-carbon alcohol, and three molecules of fatty acids.
• Fat molecules vary in length and characteristics, determined by the kind of fatty acid connected to the glycerol molecule.
• Fats may be saturated or unsaturated.
• Phospholipids compose the plasma membrane of the cell and are composed of Glycerol and fatty acids molecules.