biology topic 2- organisation

• what are cells?


  - the basic building blocks of all living organisms
• what is a tissue?

  -a group of cells with a similar structure and function
• what are organs?


  -aggregations of tissues performing specific functions
• what are organs organised into?

  - organ systems
• what do organs work together to form?

  - organisms
• what is the digestive system an example of?

  an organ system in which several organs work together to digest and absorb food
• describe the nature of enzyme molecules and relate their activity to temperature and pH changes

  -raising temperature speeds up a reaction, and lowering temperature slows down a reaction.

  -extreme high temperatures can cause an enzyme to denature and stop working

  - pH: Each enzyme has an optimum pH range. Changing the pH outside of this range will slow enzyme activity
• what do enzymes do?

  catalyse specific reactions in living organisms due to the shape of their active site
• use the 'lock and key theory' to explain enzyme action


  -substrate fits into the 'active site' of the enzyme

  -the substrate and 'active site' are complementary in shape

  -substrate acts as the key, enzyme the lock (they fit together like a lock and key)

  -enzyme catalyses the reaction to give a product
• recall the sites of production and the action of amylase, proteases and lipases

  - the pancreas
• what do digestive enzymes do?

  -convert food into small soluble molecules that can be absorbed into the bloodstream
• what does carbohydrase break down?

  Carbohydrates into simple sugars (glucose)
• what is amalyse?


  a carbohydrase that breaks starch into maltose.
• what do protease break down?

  proteins into amino acids
• what do lipases break down?

  lipids (fats) into glycerol and fatty acids
• what are the products of digestion used to build?

  -new carbohydrates, lipids and proteins

  -some glucose is used in respiration.
• where is bile made and stored?

  made in the liver and stored in the gall bladder
• why is bile alkaline?

  -to neutralise hydrochloric acid from the stomach

  -emulsifies fat to form small droplets which increases the surface area

  -The alkaline conditions and large surface area increase the rate of fat breakdown by lipase.
• required practical 4:use qualitative reagents to test for a range of carbohydrates, lipids and proteins

  1) take the food sample and grind this with distilled water using a mortar and pestle. we want to make a paste.

  2) transfer the paste to a beaker and add more distilled water. stir so the chemicals in the food dissolve in the water

  3) filter the solution to remove suspended food particles

  
  

  test for starch:

  1) place 2cm³ of food solution into a test tube

  2) add a few drops of iodine solution which is an orange colour

  3) if starch is present then the iodine solution will turn blue- black

  
  

  test for sugars:

  1) place 2cm³ of food solution into a test tube

  2) add 10 drops of benedict's solution which is a blue colour

  3) place the test tube containing our solution into a beaker and half fill the beaker with hot water from a kettle

  4) we now leave this for around 5 mins

  5) if sugars are present the benedict's solution will change colour

  6) green- small amount of sugar is present

  7) yellow- more sugar is present

  8) brick- red- a lot of sugar is present

  
  

  proteins:

  1) place 2cm³ of food solution into a test tube

  2) add 2cm³ of biuret solution which is blue

  3) if protein is present it will change from blue to purple/ lilac colour

  
  

  lipids:

  1) place 2cm³ of food solution into a test tube

  2) add a few drops of distilled water and a few drops of ethanol

  3) gently shake the solution

  4) if lipids is present it will turn a white cloudy
• required practical 5: investigate the effect of pH on the rate of reaction of amylase enzyme


  1) place one drop of iodine solution into each well of a spotting tile

  2) take 3 test tubes

  3) in the first test tube we add 2cm³ starch solution

  4) in the second test tube we add 2cm³ amylase solution

  5) in the third test tube we add 2cm³ pH 5 buffer solution

  6) place all 3 test tubes in a water bath at 30℃. leave them for 10 mins to allow solutions to reach the correct temperature

  7) now combine the 3 solutions into 1 test tube and mix with a stirring rod. return to the water bath and start a stopwatch

  8) after 30s, use the stirring rod to transfer 1 drop of solution to a well in the spotting tile which contains iodine

  9) the iodine should turn blue- black showing starch is present

  10) we now take the sample every 30s and continue until the iodine remains orange

  11) when the iodine remains orange this tells us that starch is no longer present the reaction has been completed

  12) repeat the whole experiment several times using different pH buffers e.g 6, 7 and 8
• what are some problems with this experiment?

  - we are only taking samples every 30s

  - this means we only have an approximate time for the reaction to complete

  -we could address this by taking samples every 10s

  
  

  - we are looking for the time when the iodine does not go blue- black. this is not always obvious

  - the colour change tends to be gradual. some wells might have a small amount of blue- black mixed with orange, so it can be difficult to see when the reaction has finished

  - we can address this by asking several people to look at the spotting tile and decide when the reaction has completed
• how are the lungs are adapted for gaseous exchange?

  - Large surface area - many alveoli are present in the lungs with a shape that further increases surface area.

  - Thin walls - alveolar walls are one cell thick providing gases with a short diffusion distance.

  - Moist walls - gases dissolve in the moisture helping them to pass across the gas exchange surface.

  - Permeable walls - allow gases to pass through.

  - Good blood supply - ensuring oxygen rich blood is taken away from the lungs and carbon dioxide rich blood is taken to the lungs.

  - A large diffusion gradient - breathing ensures that the oxygen concentration in the alveoli is higher than in the capillaries so oxygen moves from the alveoli to the blood. Carbon dioxide diffuses in the opposite direction.
• what is the heart?

  organ that pumps blood around the body in a double circulatory system
• where does the right ventricle pump blood to?

  to the lungs where gas exchange takes place
• where does the left ventricle pump blood to?

  around the rest of the body
• what is the natural resting heart rate controlled by?

  -by a group of cells located in the right atrium that act as a pacemaker
• what are artificial pacemakers?

  -electrical devices used to correct irregularities in the heart rate
• what are the three different types of blood vessel

  - veins

  - arteries

  - capillaries
• explain how the structure of these vessels relates to their functions

  veins:

  - always carries blood to the heart

  - always carries deoxygenated blood, except for the pulmonary vein

  -carry blood under low or negative pressure

  -have thin walls - have less muscular tissue than arteries

  - have less connective tissue than arteries

  -have a wide lumen

  
  

  arteries:

  -always carry blood away from the heart

  -carry oxygenated blood, except for the pulmonary artery

  - carry blood under high pressure

  - have thick muscular and elastic walls to pump and accommodate blood

  -a type of supporting tissue called connective tissue provides strength

  -the channel in the blood vessel that carries blood - the lumen - is narrow