2.3 Carbohydrates and Lipids - 2.3 Carbohydrates Lipids Soniya Nahata IB Biology(SL Essential Idea Compounds of carbon hydrogen and oxygen are used to

2.3 Carbohydrates and Lipids - 2.3 Carbohydrates Lipids...

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Unformatted text preview: 26/09/15 2.3: Carbohydrates & Lipids Soniya Nahata IB Biology (SL) Essential Idea: Compounds of carbon, hydrogen and oxygen are used to supply and store energy. Understandings: U1. Monosaccharide monomers are linked together by condensation reactions to form disaccharides and polysaccharide polymers: • Monosaccharides: o Single sugar units o They can be linked together to make larger molecules. o They combine through a process called condensation: § This involves the loss of an –H from on molecule and an –OH molecule from another = H2O. § • The combination of subunits and yields water. Disaccharides: o Consist of two monosaccharides linked together. • Polysaccharides: o Consist of many monosaccharides linked together. • The linking of monosaccharides, disaccharides & polysaccharides is an anabolic process and energy has to be used to do it. ATP is supplied to the monosaccharides and this energy is then used when the condensation reaction occurs. • Condensation and hydrolysis reactions between monosaccharides and disaccharides: 16 26/09/15 2.3: Carbohydrates & Lipids Soniya Nahata IB Biology (SL) U2. Fatty acids can be saturated, monounsaturated or polyunsaturated: • Fatty acids: o There is a chain of carbon atoms, with hydrogen bonds linked to them by single covalent bonds: hydrocarbon chain. o Saturated fatty acid: § A fatty acid with single bonds between all of its carbon atoms, therefore it contains as much hydrogen as it possibly could. o Unsaturated fatty acid: § A fatty acid with one or more double bonds. Ø Monounsaturated: v One double bond Ø Polyunsaturated: v More than one double bond • Saturated: • Monounsaturated: • Polyunsaturated: 17 26/09/15 2.3: Carbohydrates & Lipids U3. Unsaturated fatty acids can be cis or trans isomers: • Soniya Nahata IB Biology (SL) Cis-­‐fatty acids o The hydrogen atoms are almost always on the same side as the two carbon atoms that have been double bonded. o There is a bend in the hydrocarbon chain at the double bond. o Triglycerides containing cis-­‐unsaturated fatty acids are less good at packing together; lowering their melting point; making them liquid at room temperature; oils. • Trans-­‐fatty acids: o The opposite of cis-­‐fatty acids where the hydrogen atoms are on the opposite side. o They do not bend in the hydrocarbon chain at the double bond; therefore they have a high boiling point and are solid at room temperature. o Produced artificially U4. Triglycerides are formed by condensation from three fatty acids and one glycerol: • Lipids: o Diverse group of carbon compounds that share the property of being insoluble in water. 18 26/09/15 • 2.3: Carbohydrates & Lipids Soniya Nahata IB Biology (SL) Triglycerides: o One of the principle groups of lipids o Made by combining three fatty acids with one glycerol. § Fatty acid connected to glycerol by a condensation reaction; three water molecules are produced. § Linkage formed between the fatty acid & glycerol is called a ester bond: Ø Formed when an acid reacts with an –OH group in an alcohol. Ø The reaction is between the –COOH group on a fatty acid and an –OH group on the glycerol. o Used as energy stores. o Energy released by aerobic cell respiration. o Do not conduct heat; insulators. • Formation of a Triglyceride: • Fats: o Liquid at body temperature (37ºC) o Solid at room temperature (20ºC) • Oils: o Liquid at body and room temperature. 19 26/09/15 Applications: 2.3: Carbohydrates & Lipids Soniya Nahata IB Biology (SL) A1. Structure and function of cellulose and starch in plants and glycogen in humans: A2. Scientific evidence for health risks of trans fats and saturated fatty acids: A3. Lipids are more suitable for long-­‐term energy storage in humans than carbohydrates: A4. Evaluation of evidence and methods used to obtain the evidence for health claims made about lipids: Skills: S1. Use of molecular visualisation software to compare cellulose, starch and glycogen: S2. Determination of body mass index by calculation or use of a nomogram: 20 ...
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