organisation

• what is a tissue?

  A group of cells that act together to perform a specific function.
• what is epidermal tissue?


  human skin and the waxy covering of some plants
• epithelial tissue?

  lines the outer surface of organs and blood vessels
• muscular tissue?

  can contract to bring about force and motion
• mesophyll tissue?

  capable of photosynthesis
• what is a cell?


  the fundamental units of all organisms
• what is an organ?

  A group of tissues that work together to perform a specific function in the body.
• glandular tissue?


  produces digestive juices that break down the stomach's contents.
• what is an organ system?

  A group of organs that work together to perform a specific function in the body.
• what are the organs which make up the digestive system and what are their functions?

  glands (salivary glands in the mouth and the pancreas) which produce digestive juices containing enzymes which break down food

  stomach produces hydrochloric acid to kill bacteria and to provide the optimum pH for the protease enzyme to work

  liver produces bile which is stored in the gall bladder which helps with the digestion of lipids

  large intestine absorbs water from undigested food to produce faeces which passes out the boy through the rectum and anus
• what does the small intestine do in the digestive system?

  digests food and absorbs soluble food molecules.
• what is an organism?

  the highest level of organisation in a multicellular organism where organ systems work together
• what are enzymes?

  biological catalysts , proteins which increase the rate of reaction
• • enzymes are present in many reactions so that they can be controlled
  • they can break up large molecules and join small ones
  • they are protein molecules and the shape of the enzyme is vital to its function because each enzyme has its own uniquely shaped active site where the substrate binds so one enzyme is specific to one substrate's chemical reaction
• what is the lock and key hypothesis?

  1. substrate collides with the active site of the enzyme and becomes attached because active site has a complementary shape to the substrate
  2. enzyme catalyses the breakdown of the substrate
  3. products released from active site and enzyme molecule is unchanged so can be reused
• how does temperature affect enzyme action?


  low temperatures - the number of successful collisions between the enzyme and substrate is reduced because their molecular movement decreases

  The human body is maintained at 37°C as this is the optimum temperature which enzymes work at

  higher temperatures above the optimum temperature changes the shape of the active site as the bonds in the structure will break which will reduce its activity or stop it from working so the enzyme will be denatured
• how does pH affect enzyme action?

  • Enzymes have an optimum pH, for most enzymes is 7 but some that are produced in acidic conditions e.g the stomach have a low optimum pH
  • If the pH changes away from the optimum pH, the enzyme activity decreases.
  • If the pH is too low or too high, the enzyme is denatured as the forces which hold the forces that hold the amino acid chains that make up the protein will be affected which changes the shape of the active site and the enzyme will not function.
• what do digestive enzymes do?

  The digestive enzymes catalyse (speed up) the breaking down of large and insoluble molecules of food into smaller, soluble molecules that can be absorbed into the bloodstream.
• what are the main 3 digestive enzymes?

  amylase, protease and lipase
• Why is it necessary to break down large, insoluble food molecules into smaller, soluble molecules?

  large insoluble molecules cant be absorbed into the bloodstream. Small, soluble molecules can be absorbed into the bloodstream and are used to construct new carbohydrates, proteins and lipids in the body. some glucose produced by digestion is used for respiration
• what is bile?

  an alkaline substance which is produced in the liver and stored in the gal bladder
• why is bile important?

  optimal enzyme conditions - enzymes in the small intestine operate best in alkaline conditions , bile neutralises acid form the stomach to stop these enzymes becoming denatured

  bile breaks up fats into tiny droplets through emulsification, the tiny droplets have a higher surface area which increases the rate of lipases-catalysed reactions that break fats down
• what is amylase?

  a type of carbohydrase which can break down starch in our bodies
• where is amylase produced?

  Pancreas and salivary glands
• what is the function of amylase?

  to break down starch into simple sugars like glucose
• what are the action sites of amylase?

  Mouth and small intestine
• what do carbohydrase enzymes do?

  Break down carbohydrates into simple sugars.
• what is the function of the digestive enzyme protease?


  to break down proteins into amino acid
• where is protease produced?

  pancreas, stomach
• where are the sites of action of proteases?

  small intestine and the stomach
• what is lipase?

  a type of digestive enzyme which breaks down lipids into fatty acids and glycerol
• where is lipase produced?

  small intestine and pancreas
• what is the test for starch?

  add iodine solution : if starch is present it will turn blue/black
• how do you test for protein?

  add biuret agent and if protein is present it will turn blue - purple
• how do you test for sugar?

  add benedict's reagent and heat in a water bath for 2 minutes. if sugar is present it will turn blue to brick red
• Investigating the rate of enzyme activity

  1. pH

  2. Temperature

  3. Enzyme concentration

  4. Substrate concentration
• what effect does pHhave on enzyme activity?

  Every enzyme has an optimum pH. Extremes of pH will cause the enzyme to denature. pH can be kept constant by using a buffer.
• what affect does Temperaturehave on the rate of enzyme activity?

  Increasing the temperature will initially increase the rate of enzyme activity as the enzymes will have more kinetic energy. Above a certain temperature, enzymes denature as the high temperature breaks the bonds holding together the enzyme.
• what affect does Enzyme concentration have on enzyme activity?

  Increasing the enzyme concentration increases the number of active sites available, which causes the rate of reaction to increase.
• what affect does increasing Substrate concentration have on the rate of enzyme activity?

  Increasing the substrate concentration increases the rate of enzyme activity, as there are more substrate molecules to bind to the enzyme active site.