Food

• Carbohydrates


  Organic compounds composed of carbon, hydrogen, and oxygen atoms, usually with the formula Cx(H2O)y
• Elements in carbohydrates


  • Carbon (C)
  • Hydrogen (H)
  • Oxygen (O)
• The elements present in carbohydrates are indicated by the name itself: carbon (C), hydrogen (H) and oxygen (O)
• Ratio of elements in carbohydrates


  Cx(HO)y, where x and y are the same number (i.e. xy). This means there is twice as much hydrogen as carbon or oxygen in a carbohydrate.
• Glucose


  A simple carbohydrate in which x and y are both equal to 6. The formula for glucose is CH2O.
• Types of carbohydrates


  • Monosaccharides
  • Disaccharides
  • Polysaccharides
• Monosaccharides


  • Carbohydrates composed of a single sugar unit
  • A single sugar unit is a ring of carbon atoms
  • Monosaccharides are the simplest and smallest type of carbohydrate
  • They are sweet to taste and are soluble in water
• Monosaccharides


  • Glucose
  • Fructose
• Glucose


  A very common molecule in biology, made by plants in photosynthesis and the main molecule from which living things get their energy. It is commonly found in sweets, chocolate, fruit and soft drinks.
• Fructose


  Has the same formula as glucose but its atoms are arranged differently. It is common in fruits and is much sweeter than glucose.
• Disaccharides


  • Carbohydrates composed of two sugar units joined together
  • They are sweet-tasting and soluble in water
• Disaccharides


  • Maltose
  • Sucrose
• Maltose


  Found in germinating seeds and is composed of two glucose molecules joined together.
• Sucrose


  Also known as table sugar, is composed of a glucose joined to a fructose.
• Polysaccharides


  • Carbohydrates composed of many sugar units
  • Insoluble or only slightly soluble in water
  • Not sweet-tasting
  • Very large molecules, often consisting of thousands of monosaccharides
• Polysaccharides


  • Starch
  • Cellulose
  • Glycogen
• All monosaccharides and some disaccharides (e.g. maltose, but not sucrose) are reducing sugars.
• Nutrition


  The way in which an organism obtains and uses food
• Nutrients


  Chemical substances, present in food, that are used by organisms
• Nutrients

  • Necessary to maintain metabolism and continuity of life for all living organisms
  • Necessary as a source of energy
  • Necessary to make chemicals needed for metabolic reactions
  • Necessary as the raw materials for the growth and repair of structures in the organism
• Elements present in food


  • Carbon (C)
  • Hydrogen (H)
  • Oxygen (O)
  • Nitrogen (N)
  • Phosphorus (P)
  • Sulfur (S)
  • Sodium (Na)
  • Magnesium (Mg)
  • Chlorine (Cl)
  • Potassium (K)
  • Calcium (Ca)
  • Iron (Fe)
  • Copper (Cu)
  • Zinc (Zn)
• Trace elements


  Elements that are only required in tiny amounts in the diet
• Biomolecules


  Chemicals that are made inside a living thing
• Major types of biomolecules found in food


  • Carbohydrates
  • Lipids (fats, oils)
  • Proteins
  • Vitamins
• Cellulose fibres in a plant cell wall
• Common sources of carbohydrate in our diet


  • Bread
  • Potatoes
  • Rice
  • Pasta
  • Sugars
  • Fruits
  • Sweets
  • Cakes
• Structural role of carbohydrates


  Cellulose is used to form plant cell walls
• Metabolic role of carbohydrates


  • Glucose is broken down in respiration to release energy
  • Glucose is made in photosynthesis
• Lipids contain the elements carbon, hydrogen and oxygen. Unlike carbohydrates, the elements in lipids have no simple ratio. However, lipids have very little oxygen.
• Fats


  Lipids that are solid at room temperature (20°C)
• Oils


  Lipids that are liquid at room temperature
• Structure of lipids


  The smallest lipids are made of one molecule of glycerol linked to three fatty acid molecules. This structure is called a triglyceride.
• Phospholipids are important in the structure of cell membranes
• Sources of lipids in our diet


  • Butter
  • Oils
  • Margarine
  • Cream
  • Fat on meat
  • Fried food
• Structural role of lipids


  Lipids are important food (or energy) stores in plants and animals. One gram of lipid contains twice as much energy as a gram of carbohydrate.
• In animals, the stored lipids have secondary functions, such as heat insulation (fat under the skin) and protection of organs (fat around the heart and kidneys).
• Metabolic role of lipids

  Lipids can be broken down in respiration to release energy
• Proteins


  Composed of amino acids. There are 20 common amino acids found in proteins.
• Peptide bond


  The bond between amino acids
• Peptide


  Made of a small number of amino acids (less than 20)