organisation

• Enzymes - biological catalysts that speed up the rate of reaction by lowering activation energy, they do not get used up in the reaction
• lipase :

  • Breaks down lipids (fats) into fatty acids and glycerol
  • Produced in pancreas and small intestine.
• protease :

  • Break down protein into amino acids
  • Produced in stomach, pancreas and small intestine
• amylase :

  • Breaks down starch into maltose (sugars)
  • Produced in the salivary glands and pancreas
• Iodine test for starch from orange brown to blue black

  
  

  add iodine to the food (starch) it will turn blue - black
• Benedict test for glucose (sugar) from blue to yellow / red

  
  

  heat benedict's reagent in a water bath for two minutes, if glucose present it will turn red
• biuret test for protein colour from blue to purple

  
  

  add biuret reagent to food (protein) is its present it will turn purple
• cells - basic building blocks of life
• tissue - a group of cells with a similar structure and function working together
• organs - group of different tissues working together forming specific functions
• organs are organised into organ systems, which work together to form organisms
• digestive system is an example of an organ system in which several organs work together to digest and absorb food
• as an organ develops cells differentiate to form different types of cells - they become specialised
• root hair cells - lots of mitochondria for active transport of minerals

  - long projection to increase the surface area to absorb water and minerals
• muscle tissue - contract to bring about movement
• glandular tissue - produce substances such as enzymes and hormones
• epithelial tissue - converts all parts of the body
• enzymes are large properties
• space within the protein (enzyme) molecule - active site
• enzymes work best at optimum temperature pH
• lock and key theory - the chemical that reacts is called the substrate (key) and it fits into the enzyme's active site (lock)
• high temperature and extreme pH makes enzymes change shape - denaturing
• enzyme cannot work once it has been denatured
• digestive enzymes are produced by specialised cells in glands and the lining of the gut :

  1. enzymes pass out of the cells into the digestive system
  2. they come in contact with food molecules
  3. they catalyse the breakdown of large insoluble food molecules into smaller soluble molecules
• relate knowledge of enzymes to metabolism : enzymes are proteins that help speed up metabolism or chemical reactions in the body
• bile is a liquid made in the liver and stored in the gall bladder
• bile is an alkali to neutralise hydrochloric acid from the stomach
• bile emulsifies fat to form small droplets , increasing the surface area for enzymes to act on
• required practical for enzymes:

  1. Put a test tube containing starch solution and a test tube containing amylase into a water bath 37 degrees
  2. After 5 minutes add the amylase solution to starch
  3. every 30 seconds take a drop from the mixture and test it for starch using iodine solution
  4. record how long it takes for the starch to be completely digested
  5. repeated the experiment at different pH values using different buffer solutions
• blood is a tissue
• blood is made of a liquid called plasma
• 3 different components in blood :

  • platelets
  • red blood cells
  • white blood cells
• digestive enzymes convert food into small soluble molecules that can be absorbed into the bloodstream
• products of digestion are used to build new carbohydrates , proteins and lipids. Glucose used in respiration
• plasma - transports various chemical substances around the body , such as products of digestion , hormones , urea
• red blood cells - contain haemoglobin which binds to oxygen to transport it from the lungs to the tissue and cells which need it for (aerobic) respiration
• red blood cells :

  • do not contain a nucleus (more room for haemoglobin)
  • very small, fit through tiny capillaries
  • shaped like discs giving them a large surface area that oxygen can quickly diffuse across
• white blood cells:

  • help protect the body against infections
  • can change shape
  • can squeeze out of the blood vessels into the tissues or surround and engulf microorganisms
• Platelets:

  • fragments of cells
  • collect at wounds and trigger blood clotting
• 3 types of blood vessels:

  • arteries
  • capillaries
  • veins