Y3Biology BiomoleculesFINAL

Biomolecules Notes Why is there a need for food? • Food provides energy for vital activities. • Food provides raw materials to make new cells / substances • Food helps organisms stay healthy. Carbon Compounds • Organic compounds: Compounds built from Carbon (C) and Hydrogen (H). • In living mass, carbon is the third most abundant element by mass, after oxygen. • Carbon has a unique collection of properties that make life possible o Can form stable bonds with many elements due to their 4 valence electrons. o Can form long chains, which are used for storage of energy. § C-C-C-C-C-C Macromolecules • Polysaccharides and proteins are the macromolecules that have been introduced in this topic. • Chemically described as polymers • Made by linking together similar building blocks called monomers o Proteins (polymers) are built from amino acids (monomers) o Polysaccharides (polymers) are built from monosaccharide sugars (monomers) Properties (Structures, Properties, Functions)

• The type of macromolecule depends upon the type of monomer from which it is built. • The order in which the monomers are combined decides the shape of the macromolecule. • The shape of the macromolecule decides its biological properties and determines its role in cells. - Monomers are linked together by condensation reactions, a reaction in which the elements of water are removed. - Hydrolysis reactions are the reverse reactions that require water and results in the release of individual monomers again. Carbohydrates (hydrated Carbon) • largest group of organic compounds • General Formula: Cx(H2O)y • Carbohydrates are needed: o as a substrate for respiration (to provide energy) o to form supporting structures (e.g. cell wall in plants) o to be converted into other organic compounds such as amino acids & fats o for the formation of nucleic acids in DNA o to synthesize lubricants (e.g. mucus) o to synthesize nectar in some flowers • contains three main elements: Carbon, Hydrogen, Oxygen Monosaccharides • Monosaccharides are carbohydrates with relatively small molecules. • Properties: o All monosaccharides are reducing sugars. o Monosaccharides taste sweet and are soluble in water. • Examples: o Glucose § especially important § all cells use glucose in respiration § our bodies transport glucose in blood o Fructose § also found in cells § sweetest common sugar o Galactose § forms part of glycolipids and glycoproteins Disaccharides • Disaccharides are carbohydrates made of two monosaccharides combined together. • A molecule of water is removed when two monosaccharides combine, so the reaction is called a condensation reaction. o Remove a molecule of water from glycosidic bond § The bond formed between the monosaccharides is called a glycosidic bond.

• Properties: o soluble in water • Examples: o Sucrose: made up of glucose and fructose § An important sugar § transported in the phloem tissue to stems, roots or carbohydrate storage sites in the plant § the “sugar” that humans prefer to use in food and drinks § mostly extracted and purified from sugar cane o Maltose (2 alpha-glucose): found in germinating barley o Lactose (beta-galactose and glucose): found in milk Polysaccharides • Polysaccharides are built from many monosaccharide molecules condensed together. • Properties: o insoluble in water • Polysaccharides, like cellulose and glycogen contain only one type of monomer. o Cellulose: beta-glucose o Glycogen: alpha-glucose • Starch is a mixture of 2 polysaccharides o amylose chain and amylopectin chain o has 2 types of glycosidic bond o forms helix structure o Starch is the major storage carbohydrate of most plants (stored in leucoplasts) § The molecule is compact and insoluble. Name of Polymer formed Structure Role in Organisms Occurrence Starch Made up of several thousand glucose molecules (amylopectin and amylose chain joined together) Form of storage in plants. When needed, starch can be digested to glucose to provide energy. Found in storage organs of plants (potato tubers and tapioca) Cellulose Made up of many glucose molecules but glycosidic bonds formed between glucose units are different from starch. Cellulose cell wall protect plant cells from bursting or damage. It cannot be digested in our intestines and serve as dietary fibre that prevents constipation. Present in cell walls of plants

Glycogen Is a highly branched molecule made up of many glucose molecules Form of storage in mammals. When needed can be digested to glucose to provide energy. Stored in the liver and muscles of mammals Lipids • Contain the elements carbon, hydrogen and oxygen but have no general formula • Insoluble in water • Lipids are soluble only in organic solvents such as alcohol, propanone and ether • Examples: o occur in animal fats (solid) and plant oils (liquid) o found in phospholipids of cell membranes o steroids from which many growth and sex hormones are produced o waxes found in plants and animals Triglycerides • Formed by condensation reaction that occurs between fatty acids and glycerol o 3 fatty acid molecules combine with 1 glycerol molecule to form a triglyceride • Fats and oils are the same structurally, except oils are liquids and fats are solid. • Triglycerides are large molecules, but are smaller than macromolecules like glycogen and starch. • Their hydrophobic properties make them clump together and appear to be macromolecules. • Ester bonds are formed in the production of triglycerides. o double bond O and simple bond O • Phospholipids have a similar chemical structure to triglyceride, except that one of the fatty acids is replaced by a phosphate group. The phosphate group is ionized and therefore water soluble. Structure Role in Cells Triglyceride High proportion of carbon and hydrogen to oxygen per unit mass, thus making it highly reduced. It is hydrophobic. Upon oxidation, these bonds release large amounts of energy and hence is a good energy store. • It releases water when oxidised during cellular respiration. This water is called metabolic water, which is extremely important to desert animals like camels. Does not affect water potential of cell when stored in large amounts. Phospholipid Hydrophobic fatty acid “tails” and a charged hydrophilic phosphate “head” Form a selectively permeable membrane where hydrophilic heads are exposed to the aqueous medium while

hydrophobic tails are excluded from aqueous medium in bilayer. Saturated and Unsaturated Triglycerides • Saturated: no C=C double bonds between the carbon atoms in their hydrocarbon tails • Unsaturated: one or more double bonds present in the hydrocarbon tails • When several double bonds occur the resulting fat is called polyunsaturated fat. • C=C double bonds will result in kinks (bends) in the hydrocarbon tails. Such kinks have biological significance in the structure of the cell surface membrane. The kinks ensure membrane fluidity by preventing hydrocarbon tails of phospholipids from aggregating too closely. Role of Fats and Oils in Living Things • Comparing mass for mass, fats and oils release more than twice as much energy as carbohydrates. o This means that in 1g of fat and 1g of carbohydrates, the fat is higher in calories and releases higher amounts of energy when burnt. • Fat forms a concentrated, insoluble energy store. • [check] Fats and oil do not affect water potential of cells when stored in large amounts. • Concentrated reserves of food for long unfavourable seasons. o Complete oxidation of fats and oils produce large amounts of metabolic water. § Helps animals to survive when there is no drinking water. § Development of embryos of birds and reptiles. o Buoyancy aid § Presence of adipose tissues function as a heat insulation layer. o Waterproofing for hair and feathers § Oil acts as water repellent for fur/hair/feathers. o Electrical insulation – in nerve cells (the myelin shafts) Proteins • contain the element nitrogen and sulfur • formed from many amino