Enzymes and digestion

• Carbohydrates are made of long sugar molecules
• Carbohydrates are broken down into small molecules by the body
• Carbohydrates provide energy
• Proteins are made up of chains of small molecules
• There are over 20 different amino acids that make up proteins
• Proteins are used by the body for growth and repair
• The 7 food groups

  • Carbohydrate
  • Lipids/Fats
  • Fibre
  • Minerals
  • Protein
  • Vitamins
  • Water
• Carbohydrate


  Used for source of energy, sugars, starch
• Lipids/Fats


  Stored as an energy reserve, used to make cell membranes
• Fibre


  Not digested, helps move food through the digestive system
• Minerals


  Keeps the body healthy, e.g. calcium for bones
• Protein


  Needed to make new cells in the body
• Water


  Keeps us hydrated, acts as a medium for chemical reactions
• Deficiency - inadequate supply of essential nutrients in the diet resulting in malnutrition or disease
• Carbohydrate


  A macromolecule made up of carbon, hydrogen and oxygen atoms, used by organisms as a source of energy
• Enzymes


  Biological catalysts that speed up the rate of a reaction without being used up
• Enzymes


  • Made of proteins
  • Work best at an optimal pH and temperature
  • Become denatured at high temperatures
• Substrate


  The molecule that an enzyme acts upon
• Active site


  The specific part of an enzyme where the substrate binds
• Enzymes are specific, meaning they will only work with one substrate
• Enzyme catalysis


  1. Substrate binding

  2. Transition state facilitation

  3. Catalysis

  4. Release
• Enzymes are not used up in the reactions they catalyse
• Enzymes increase the rate of reactions without altering the chemical equilibrium
• Factors affecting enzyme activity

  • Temperature (optimal temperature, denaturation at high temperatures)
  • pH (optimal pH)
• Mechanical digestion involves physical breakdown of food into smaller pieces, e.g. by chewing
• Chemical digestion involves enzymes breaking down large food molecules into smaller molecules
• Mechanical digestion


  Increases the surface area of food for enzymes to act upon, speeding up chemical digestion
• The Benedict's test is used to test for reducing sugars
• The iodine test is used to test for the presence of starch
• Bile produced by the liver helps digest fats
• There are many diseases linked with poor diet. Some of these are deficiency diseases. This medical disease is caused when there is not enough of a nutrient in the diet. Deficiency diseases can lead to symptoms and changes will need to be made to the diet to manage/treat the disease and stop it from reoccurring.
• Goitre


  A swelling of the thyroid gland that causes a lump in the front of the neck. The lump will move up and down when you swallow.
• Scurvy


  A disease resulting from a lack of vitamin C (ascorbic acid). Early symptoms of deficiency include weakness, feeling tired, and sore arms and legs. Without treatment, decreased red blood cells, gum disease, changes to hair, and bleeding from the skin may occur. Scurvy is easily treated by adding some vitamin C to your diet, such as fresh fruit and vegetables. A GP may also recommend taking vitamin C supplements until you feel better.
• Rickets


  A condition that affects bone development in children. It causes bone pain, poor growth and soft, weak bones that can lead to bone deformities. A lack of vitamin D or calcium is the most common cause of rickets. Vitamin D largely comes from exposing the skin to sunlight, but it's also found in some foods such as oily fish and eggs. Vitamin D is essential for the formation of strong and healthy bones in children.
• Iron deficiency anaemia


  Caused by a lack of iron, often because of blood loss or pregnancy. It is treated with iron tablets prescribed by a GP and by eating iron-rich foods. Foods that contain iron include red meat, eggs, lentils, pumpkin seeds and green vegetables. Some of the symptoms include tiredness and lack of energy, shortness of breath, and pale skin.
• Obesity


  Describes someone who's very overweight and has a high percentage of body fat. Obesity is generally caused by consuming more calories, particularly those from fatty and sugary foods, than you burn off through physical activity. The excess energy is stored by the body as fat. The best way to treat obesity is to eat a healthy, reduced calorie diet and exercise regularly.
• Coronary heart disease (CHD)


  A major cause of death both in the UK and worldwide. Coronary heart disease is the term that describes what happens when your heart's blood supply is blocked or interrupted by a build up of fatty substances in the coronary arteries. Over time, the walls of your arteries can become furred up with fatty deposits. Heart disease can be caused by lifestyle factors and other conditions such as smoking, high cholesterol, high blood pressure, diabetes. Treatment can include lifestyle changes such as regular exercise and stopping smoking, medication and surgery.
• Starch

  A carbohydrate which is made of long chains of identical small sugar molecules. Long chains of repeating molecules are known as polymers. The small molecules from carbohydrates are used by the body to release energy to allow muscle contraction. The test for starch is to add iodine solution, which will turn blue-black if starch is present.
• Sugars


  React with Benedict's reagent to turn it from blue to orange-red. But it is a slow reaction, so needs speeding up by placing in a water bath.
• Proteins


  Like carbohydrates, are made of long chains of small molecules. In proteins, these small molecules are not identical. Proteins are made up of chains of small molecules called amino acids. There are over 20 different kinds of amino acid. Proteins are used by the body for growth and repair.