B3 - Organisation and the digestive system

• Tissue


  A group of cells with similar structure and function working together
• Organ


  A collection of tissues, each containing several tissues all working together to perform a specific function
• Sperm


  • Specialised cell
  • Male reproductive system
• Kidney


  • Organ
  • Filters blood
• Stomach


  • Organ
  • Digestive system
• Stomach's role in digestion of food

  1. Contains muscular tissue to churn food and digestive juices

  2. Contains glandular tissue to produce digestive juices that break down food

  3. Contains epithelial tissue which covers the inside and outside of the organ
• The digestive system of humans and other mammals exchanges substances with the environment
• Food is made up of large insoluble molecules that need to be broken down or digested to form smaller, soluble molecules that can be absorbed and used by cells
• Main organs of the human digestive system

  • Mouth
  • Gullet
  • Stomach
  • Small intestine
  • Large intestine
  • Rectum
  • Anus
  • Liver
  • Gall bladder
  • Pancreas
• The small intestine


  Is where the soluble food molecules are absorbed into the blood
• The small intestine is adapted to have a very large surface area as it is covered in villi, has a good blood supply, and short diffusion distances to the blood vessels</b>
• The large intestine


  Is where water is absorbed from the undigested food into the blood
• The liver produces bile, which helps in the digestion of lipids
• Organ systems


  Groups of organs that perform specific functions in the body
• The digestive system is an organ system where several organs work together to digest and absorb food
• Carbohydrates


  Provide fuel that makes all other reactions of life possible, contain carbon, hydrogen, and oxygen, and are made up of units of sugars
• Simple sugars


  Carbohydrates that contain only one or two sugar units
• Complex carbohydrates


  Carbohydrates made up of long chains of simple sugar units bonded together, such as starch and cellulose
• Lipids


  Fats and oils, the most efficient energy store in the body, and important in cell membranes, hormones, and the nervous system, made up of three molecules of fatty acids joined to a molecule of glycerol
• Proteins


  Used for building up cells and tissues, as well as the basis of enzymes, made up of long chains of amino acids
• Proteins carry out many different functions in the body, acting as structural components, hormones, antibodies, and enzymes
• Carbohydrates, proteins, and lipids are the main compounds that make up the structure of a cell and are vital components in the balanced diet of any organism that cannot make its own food
• Testing for starch


  Use iodine test - yellow-red iodine solution turns blue-black if starch is present
• Testing for lipids


  Use ethanol test - ethanol added to a solution gives a cloudy white layer if a lipid is present
• Lipids can be either fats or oils


  Depending on the combination of fatty acids
• Simple sugars


  Are related to complex carbohydrates as they are the building blocks that make up the long chains in complex carbohydrates
• Benedict's solution


  Turns brick red on heating if a sugar such as glucose is present
• Biuret test


  Blue Biuret reagent turns purple if protein is present
• Ethanol test


  Ethanol added to a solution gives a cloudy white layer if a lipid is present
• Ethanol is highly flammable and harmful
• Carbohydrates


  • Made up of units of sugar
• Simple sugars


  Carbohydrates that contain only one or two sugar units - they turn blue Benedict's solution brick red on heating
• Complex carbohydrates


  Contain long chains of simple sugar units bonded together. Starch turns yellow-red iodine solution blue-black
• Lipids


  Consist of three molecules of fatty acids bonded to a molecule of glycerol. The ethanol test indicates the presence of lipids in solutions
• Protein molecules


  Made up of long chains of amino acids. Biuret reagent turns from blue to purple in the presence of proteins
• Catalysts increase the rate of chemical reactions without changing chemically themselves
• Enzymes


  Biological catalysts that catalyse specific reactions in living organisms due to the shape of their active site. This is the lock and key theory of enzyme action
• Enzymes


  • They are proteins. The amino acid chains are folded to form the active site, which matches the shape of a specific substrate molecule
• Metabolism


  The sum of all the reactions in a cell or the body
• Without enzymes, none of the reactions in your body would happen fast enough to keep you alive