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Biological Molecules: Carbohydrates 1. Carbohydrates (also called starch/saccharides) are molecular compounds made from just three elements: hydrogen, oxygen and carbon. 2. Glucose is a monosaccharide. Monosaccharides are the simplest carbohydrates and are often called single sugars. They are the building blocks from which all bigger carbohydrates are made 3. Give the chemical formula of glucose C6H12O6 4. Sucrose, maltose and fructose are disaccharides. What is a disaccharide? These form when two monosaccharides react. Examples of disaccharides are sucrose, lactose and maltose. 5. A polysaccharide is a long chain, large sugar molecule. Examples of polysaccharides are starch and glycogen and cellulose. 6. Carbohydrates are one of the most important biological molecules because: a source of fuel for the body e.g. glucose and a store of energy, e.g. starch in plants building blocks for polysaccharides (giant carbohydrates), e.g. cellulose in plants and glycogen in the human body components of other molecules e.g. DNA, RNA 7. If many simple sugars join together, we call this a polysaccharide. Most of these are insoluble, meaning they don’t dissolve in water. Humans get most of the carbohydrates in our diet from starch, which is found as a storage carbohydrate in many plants. Animal cells contain glycogen, which can be found in the liver and muscle, where it acts as a store of energy. Another carbohydrate which is a polysaccharide is found in plant cell walls: cellulose. Humans cannot digest this, as our gut does not make the enzyme required to break it down. Instead it forms part of our diet as fibre. 8. Describe how you would test for the presence of starch? Iodine (yellow) turns blue-black in the presence of starch. 9. Describe how you would test for the presence of glucose (a reducing sugar) and what result you would expect to see. Called the Benedict’s test – Benedict’s solution is blue and turns red/orange when heated if reducing sugars present. Biological Molecules: Proteins 1. What are proteins made from? Amino acids. 2. How many different types of the above are there? 20 3. Which 4 chemical elements does protein contain? a. nitrogen b. carbon c. oxygen d. hydrogen 3. Why are proteins such an important biological molecule? It is used for growth and repair, to make new cells. Humans must obtain nine essential amino acids through their food because our bodies are not capable of manufacturing them. A missing amino acid restricts the protein synthesis and may lead to a protein deficiency, which is a serious type of malnutrition. 4. Proteins come in many different shapes. The shape is important because most enzymes are proteins and therefore their function is specific to their structure. 5. Humans must obtain 9 essential amino acids through their food because our bodies are not capable of manufacturing them. 5. Describe how you would test for the presence of protein? Use Biuret solution (copper sulphate and sodium hydroxide), this is blue in colour. If this solution turns purple/violet/lilac this is a positive test for protein. Biological molecules: Lipids 1. Lipids contain the 3 elements: carbon+ hydrogen + oxygen. However the proportion of oxygen is much lower than in carbohydrates. 2. The picture below is a simple picture of a lipid (fat) molecule. Label X and Y. X = glycerol Y = fatty acids 3. Fats are made up of fatty acids and glycerol. Fats are large molecules that are composed of three fatty acid molecules bonded to a glycerol molecule. 3. Most animal fats are solid at room temperature, but will melt if you warm them up. Plant lipids are usually liquid at room temperature and are called triglycerides. 3. Fat molecules are insoluble, meaning that they don’t dissolve in water. They are, however, soluble in alcohol/ethanol 4. List 3 functions of fats in the human body: a. They make up cell membranes b. Long term energy source – they release as twice as much energy as carbohydrates/protein. c. Good thermal insulators, reducing heat loss. 5. Describe how you would test for the presence of lipids? They will dissolve in ethanol, if a solution of fat in ethanol is added to water it goes cloudy. 7. Fats are broken down into fatty acids and glycerol by the enzyme lipase. Biological molecules: Cellulose 1. Cellulose is made from sugars (carbon, hydrogen and oxygen). 2. Cellulose is a polysccharide, a long chain molecule or natural polymer which makes it incredibly strong. 3. It is the main component of plant cell walls. 4. Although potentially a major food source, humans lack the enzymes to break it down.