Cell Organisation

• what are tissues?

  group of cells with similar function and structure working together
• what are organs?

  collection of tissues working together to perform a specific function
• what are organ systems?

  group of organs that all work together to perform a specific function
• what is the purpose of the digestive system?


  so our food can be broken down into smaller soluble molecules so that they can be absorbed and used by your cells
• what is the order of the digestive system?

  mouth, oesophagus, liver, stomach, small intestine, large intestine, and anus
• what is the role of the liver?

  produces bile that neutralises stomach acid and emulsifies fats
• what is the role of stomach? (3)

  1) pummels the food with its muscular walls

  2) it produces the protease enzyme; pepsin

  3) it produces hydrochloric acid which kills bacteria and gives the right ph (pH2) for pepsin
• what is the role of the gallbladder?

  stores bile before releasing it into the small intestine
• what is the role of the pancreas?

  produces amylase, protease and lipase releasing these into the small intestine
• what is the role of the small intestine?

  1) produces protease, lipase and amylase to complete digestion

  2) where food is absorbed out of the digestive system into the blood
• what do carbohydrates do?

  they break down into glucose used in cellular respiration to provide energy for metabolic reactions in cells. simple carbs release energy slowly and complex carbs do the opposite.
• what do lipids do?

  storing energy, as lipids may be broken down to yield large amounts of energy
• what do proteins do? (3)

  1) act as hormone e.g., insulin

  2) act as structural components of tissues e.g., muscles and tendons

  3) act as antibodies
• how do you test for starch?

  add a drop of dilute iodine solution to the subject. If starch is present it will turn a 'blue-black' colour.
• how do you test for proteins?

  Buiret test and if protein is present the subject will turn purple
• how do you test for sugars?

  add Benedict's reagent to a sample in a water bath at 75C and if reducing sugars are present the solution will turn brick red
• how do you test for lipids?

  add ethanol to the solution and if lipids are present the solution will turn cloudy
• what is a safety risk with ethanol?

  ethanol is highly flammable and harmful
• what is a safety risk with Buiret solution?

  it is corrosive so chemical and splash-proof eye protection should be warned
• what is metabolism?

  sum of all chemical reactions in the body (or cell). enzyme control metabolism and different enzymes catalyse specific types of metabolic reactions
• explain the lock and key theory

  the lock is the enzyme and the key is the substrate. only the correctly sized key (substrate) fits into the key hole (active site) of the lock (enzyme). the reaction then takes place rapidly releasing products
• what do enzymes do (3)

  1) build large molecules from lots of smaller ones e.g., protein from amino acids

  2) changing one molecule into another e.g., glucose to fructose

  3) breaking down large molecules into smaller ones
• explain the required practical for testing for iodine solution (4)


  1) put 2cm³ of iodine solution into every well of a spotting tile

  2) mix 2cm³ go amylase + 2cm³ of buffer solution (to control the enzyme) and 2cm³ of pH2 into a test tube

  3) immediately start a stopwatch and in 30sec intervals starting from 0sec squeeze some of the solution into each spotting tile until the iodine solution stays orange instead of blue-black to observe how fast the reaction is

  4) repeat the experiment with different pH levels to see how pH affects enzyme reactions

  
  

  specify that temperature and volume of solutions need to stay the same