2 - Organisation

• What is a tissue?

  A tissue is a group of cells with a similar structure and function.
• What is an organ?

  An organ is a group of tissues working together for a specific function.
• What are organ systems?

  Organ systems are groups of organs which work together to form organisms.
• What is the function of the digestive sytem?

  - break down large molecules of food into smaller, soluble ones so that they can be absorbed into the bloodstream
• What is the function of the mouth in the digestive sytem?


  - food is chewed

  - amylase enzymes released by the salivary glands begin to digest starch
• What is the function of the stomach in the digestive sytem?

  - protease enzymes begin the digestion of proteins

  
  

  - contains hydrochloric acid which provides the optimal pH conditions for the protease

  
  

  - churning turns the food into a fluid which increases the SA for enzymes to digest
• What is the function of the pancreas in the digestive sytem?

  - pancreas releases amylase and protease enzymes into the SI which continue the digestion of starch and protein, and begin the digestion of lipids
• What is the function of the liver and gall bladder in the digestive sytem?

  - releases bile into the SI

  - gall bladder stores bile
• What is the function of the SI in the digestive sytem?

  - walls of the SI release enzymes to continue the digestion of protein and lipids

  
  

  - here, small food molecules are absorbed into the bloodstream
• What is the function of the LI in the digestive sytem?

  - here, water is absorbed into the bloodstream
• What is the function of the rectum and anus in the digestive sytem?

  - rectum stores faeces

  - faeces is released from anus
• What happens to the products of digestion after?

  - products used by the body to build new carbohydrates, lipids, and proteins

  
  

  - some of the glucose produced is used in respiration
• What is the function of enzymes?

  What are enzymes?

  Enzymes catalyse (speed up) chemical reactions.

  Enzymes are protein molecules.
• How do enzymes work?

  Enzymes have an active site where only a specific substrate fits into. The enzyme then breaks down the subtrate into the products.

  
  

  Enzymes lower the activation energy.
• What is the enzyme and substrate theory called?

  The 'lock and key theory' shows that enzymes are specific and the substrate must fit perfectly into the active site.
• What are proteins broken down into?

  
  

  What happens after the products are absorbed into the bloodstream?

  Proteins (chains of amino acids) are broken down into amino acids by protease.

  
  

  When the amino acids are absorbed by the body cells, they are joined together in a different order to make human proteins.
• What are carbohydrates broken down into?

  What is the specific case for starch?

  Carbohydrates (chain of simple sugars) are broken down by carbohydrases into simple sugars.

  Starch is broken down by amylase.
• What is the structure of lipids?

  
  

  What are lipids broken down into?

  A lipid molecule consists of a glycerol molecule attached to 3 fatty acid molecules.

  
  

  Lipids are broken down by lipase enzymes into glycerol and fatty acids.
• What are the 2 functions of bile?

  - bile emulsifies lipids (increase SA => increase rate of lipid breakdown)

  
  

  - the alkaline bile also neutralises the HCL to provide the optimum conditions for lipase enzymes => increases rate of lipid digestion
• What happens if we increase the temperature for enzymes? Why?

  - activity of the enzyme increases and the reaction is faster because the enzyme and the substrate are moving faster, colliding more frequently
• What happens at the optimum temperature?

  enzymatic reactions occurring at maximum possible rate

  - maximum frequency of successful collisions
• What happens if we increase the temperature past the optimum? Why?

  - enzyme activity rapidly decreases to zero and active site is denatured

  - at high temperatures, enzyme vibrates and the shape of the active site changes so substrate no longer fits
• How can we test for starch?

  * Take the food sample and grind with distilled water using a mortal & pestle; transfer paste to a beaker, add more distilled water, stir to dissolve; filter

  
  

  1) Add 2cm3 of food solution to test tube.

  2) Add a few drops of iodine solution.

  3) If starch, iodine: orange => blue-black
• How can we test for reducing sugars?

  *

  
  

  1) Add 2cm3 of food solution to a test tube.

  2) Add 10 drops of Benedict's solution.

  3) Place tube into beaker and half-fill with hot water from kettle, leave for 5min.

  4) If sugar, Benedict's solution: blue => green/yellow/brick-red
• How can we test for proteins?

  *

  
  

  1) Add 2cm3 of food solution to a test tube.

  2) Add 2cm3 of Biuret solution.

  3) If protein, Biuret solution: blue => purple/pink
• How can we test for lipids?

  * but without filtering

  
  

  1) Add 2cm3 of food solution to a test tube.

  2) Add 3 drops of Sudan III.

  3) Shake test tube gently to mix.

  4) If lipids: red-stained oil layer will separate out and float on surface
• Why should no naked flames be present when testing for lipids?

  Sudan III contains ethanol which is flammable.
• Describe a method to investigate the effect of pH on amylase.

  1) Place 1 drop of iodine solution into each well of a spotting tile.

  
  

  2) In the first test tube, add 2cm3 of starch solution.

  
  

  3) In the second test tube, add 2cm3 of amylase solution.

  
  

  4) In the third test tube, add 2cm3 of pH5 buffer solution.

  
  

  5) Place all 3 test tubes in a water bath (30°C) for 10min to allow the solutions to reach the correct temperature.

  
  

  6) Combine the 3 solutions into 1 test tube and mix with a stirring rod. Return test tube to the waterbath and start a stopwatch.

  
  

  7) After every 30s, use the stirring rod to transfer 1 drop of solution into a spotting tile well.

  
  

  8) Iodine should turn blue-black if starch is present.

  
  

  9) Stop transferring when the iodine remains orange. (reaction complete). record this time.

  
  

  10) Repeat whole experiment with different pH buffers.
• What are some problems with thi method and how could we solve this issue.

  - samples taken every 30s (only have an approximate time for when the reaction is complete) => take samples every 10s

  
  

  - not obvious when iodine does not turn blue-black => ask several people to look at the spotting tile to decide the time => mean
• How is the small intestine adapted for absorption of food molecules?

  - length of 5m => very large SA

  
  

  - interior covered with millions of VILLI => increase SA

  - microvilli on the surface of villi

  - very good blood supply from capillaries => rapidly removes the products of digestion (maintains high concentration gradient)

  - thin membrane (short diffusion pathway)
• What is the problem of having a single circulatory system?

  Blood loses a lot of pressure so blood reaches organs relatively slowly => cannot deliver a great deal of oxygen
• What is advantageous about a double circulatory system?

  Blood passes through the heart twice which repressures it so it reaches organs quickly.
• What is, and what is the function of the heart?

  The heart is an organ, consisting mainly of muscle tissue, that pumps blood around the body.
• What is the order of the 4 chambers in the heart? (left to right on a diagram)

  Right Atrium > Left Atrium > Right Ventricle > Left Ventricle
• How are the atria separated from the ventricles?

  By atrioventricular valves
• What is the flow of blood through the heart?

  The vena cava brings in deoxygenated blood from the body.

  
  

  The blood passes from the heart to the LUNGS in the pulmonary Artery, where the blood becomes oxygenated.

  
  

  Oxygenated blood passes from the LUNGS to the heart in the pulmonary veIN.

  
  

  Oxygenated blood is pumped from the heart to the body in the aortA
• What is the role of valves?


  Valves prevent the backflow of blood.
• Why does the left side of the septum have a thicker muscular wall than the right side?

  The left ventricle has to pump pump to the entire body so it requires a greater force from the thicker muscular wall.
• What is the function of coronary arteries?

  The coronary arteries branch out of the aorta to supply the heart muscle with oxygen so it can be used in repiration to provide the energy for contraction.
• How is the natural resting heart rate controlled?

  
  

  What happens if this stops working correctly?

  By a group of cells located in the right atrium that act as a pacemaker.

  
  

  If the pacemaker becomes faulty, docotrs can implant an artifical pacemaker to correct irregularities in the heart rate.