Required Practical Activity

• The major nutrients required for a healthy diet are carbohydrates, proteins and lipids.
• The digestive system breaks down large molecules of food, which are then absorbed into the bloodstream.
• The digestive system consists of the mouth, pharynx, esophagus, stomach, small intestine, and large intestine.
• Enzymes are biological catalysts that speed up chemical reactions.
• Digestive enzymes are enzymes that break down food in the digestive system.
• The liver and digestion are closely related.
• The liver processes nutrients and produces bile, which aids in digestion.
• Amylase is an enzyme that can break down starch into simple sugars.
• The pH scale of acidity or alkalinity measures the acidity or alkalinity of a solution on a scale from 0 to 14.
• A pH (power of hydrogen) value below 7 is acidic, a pH value above 7 is alkaline.
• Buffer solutions produce a particular pH, and will maintain it if other substances are added.
• The amylase will break down the starch.
• A series of test tubes containing a mixture of starch and amylase is set up at different pHs.
• A sample is removed from the test tubes every 10 seconds to test for the presence of starch.
• BRO'S IN CONTROL is a related BBC programme.
• The rate of breakdown of starch can be calculated by calculating 1/t, obtaining a measure of the rate of reaction by dividing one by the time taken for the reaction to occur.
• Digestive enzymes are related to the topic of animal organisation.
• The rate of breakdown of starch can be calculated by dividing one by the time taken for the reaction to occur.
• As the reaction proceeded, the release of fatty acids would mean that the pH would decrease.
• Non-communicable diseases are related to the topic of animal organisation.
• The liver and digestion are related to the topic of animal organisation.
• Sample exam questions on animal organisation include questions on gaseous exchange systems, transport systems, and plant organisation.
• A similar experiment can be carried out to investigate the effect of temperature on amylase activity, setting up a series of test tubes at different temperatures using a water bath.
• Fatty acids react with glycerol to produce lipids (fats and oils), and glycerol reacts with fatty acids to form esters, found in nature as fats and oils.
• Theodosia's on a quest to save the world is a related BBC programme.
• The time taken for the disappearance of starch is not the rate of reaction, but gives an indication of the rate, with a shorter time taken indicating a greater rate of the reaction.
• The reciprocal of the rate is the shorter the time taken, the greater the rate of the reaction.
• Discovering dragons really do exist is a related BBC programme.
• Depending on the chemical reaction under investigation, the reaction can be monitored in a different way, for instance, if investigating the effect of temperature on the breakdown of lipids, the pH change can be monitored as lipids are broken down into fatty acids.
• Iodine solution is a solution of iodine in potassium iodide solution, also referred to as potassium triiodide solution, which will turn a blue/black colour when starch is present, so when all the starch is broken down, a blue-black colour is no longer produced.
• The iodine solution will remain orange-brown.
• A control is a part of the experiment in which all the variables except the dependent variable are kept the same.
• A control lets you observe the effect (if any) of changing the independent variable.
• An experiment is valid when it does what it sets out to do.
• When the starch solution is added, start timing immediately, remove a sample immediately, and test it with iodine solution.
• Sample the starch-amylase mixture continuously, for example every 10 seconds.
• For each pH investigated, record the time taken for the disappearance of starch, ie when the iodine solution in the spotting tile remains orange-brown.
• Wear safety goggles when handling amylase solution as it may cause allergic reactions.
• Iodine solution is an irritant and should be avoided contact with skin and eyes.