Organisation

• Cells


  The basic building blocks of all living organisms
• Tissue


  A group of cells with a similar structure and function
• Organs


  Aggregations of tissues performing specific functions
• Organ systems


  Organs are organised into organ systems, which 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
• Enzymes


  Proteins which act as biological catalysts (they speed up a reaction without being broken down or changed)
• Equation for rate


  Rate = 1/time
• Metabolism


  The sum of all the reactions in a cell or the body
• What is the energy transferred by respiration in cells used for by the organism?

  The continual enzyme controlled process of metabolism that synthesises new molecules
• Give 2 examples of metabolic reactions

  1. Conversion of glucose to starch, glycogen and cellulose

  2. The formation of lipid molecules from a molecule of glycerol and three molecules of fatty acids
• The active site is...

  ...specific/complementary to the substrate
• What 2 factors affect the rate of reaction of enzymes?

  Temperature and pH
• If temperature increases up to 40 degrees C, the rate of reaction will....

  ...increase as the enzymes have greater kinetic energy, there are more frequent collisions between enzyme and substrate
• What is the optimum temperature for human enzymes?

  40 degrees C
• If temperature goes above 40 degrees C, the enzyme will...

  ...be denatured as the bonds in the active site break, it changes shape, and the substrate doesn't fit
• An extreme pH causes enzymes to...

  ...denature as a change in pH affects the forces between the different parts of the protein molecule
• Why do enzymes catalyse specific reactions in living organisms?

  Due to the shape of their active site
• What is the function of digestive enzymes?

  To convert food into small soluble molecules that can be absorbed into the bloodstream
• Structure of the digestive system

  Check your knowledge against this diagram

  
• Describe the digestion process in the mouth, including the type of digestion

  1. Physical digestion - chewing

  2. Chemical digestion - saliva contains amylase (which breaks down starch into glucose)
• Describe the digestion process in the oesophagus

  Moves food by peristalsis (waves of muscular contraction)
• Describe the digestion process in the stomach, including the type of digestion

  1. Physical digestion - churning

  2. Chemical digestion - enzyme pepsin ( a type of protease which breaks down protein into amino acids)

  3. Hydrochloric acid - kills pathogens in food
• Amylase: what does it do, where is it produced, where is it released to?

  1. Breaks down starch into glucose

  2. Produce in salivary glands and pancreas

  3. Released into mouth and small intestine
• Protease: what does it do, where is it produced, where is it released to?

  1. Breaks down proteins into amino acids

  2. Produced in the stomach, pancreas and small intestine

  3. Released to stomach and small intestine
• What do carbohydrases do?

  Break down carbohydrates into simple sugars
• Lipase: what does it do, where is it produced, where is it found?

  1. Breaks down lipids (fats) to glycerol and fatty acids

  2. Produced by the pancreas and small intestine

  3. Released into small intestine
• All the enzymes produced in the pancreas...

  ...are released into the small intestine
• Where is bile produced and stored? (2)

  1. Produced in the liver

  2. Stored in the gall bladder
• What does bile do? (3)

  1. Alkaline to neutralise hydrochloric acid from the stomach

  2. Emulsifies fat to form small droplets which increases the surface area

  3. Alkaline conditions and large surface area increase the rate of fat breakdown by lipase
• How is starch detected?

  Iodine solution - turns from yellow to black-blue in the presence of starch
• How is glucose detected?

  Benedict's solution - gradually turns from blue to cloudy orange or brick red when heated with a reducing sugar (may also turn yellow, green orange to indicate rough concentration of glucose)
• How are lipids detected?

  Add a few drops of distilled water and ethanol to a food sample, shake, goes cloudy if lipids present
• How are proteins detected?

  Biuret reagent - turns from blue to mauve/purple
• How do you investigate the effect of pH on the enzyme amylase? (5)

  1. starch, amylase and acid/alkali in test tubes in a water bath

  2. iodine reagent on spotting tile

  3. combine liquids in 1, stir, return to water bath

  4. drop onto iodine every 30 seconds until it does not turn blue black

  5. repeat with acid (e.g. hydrochloric)and alkali (e.g. sodium hydroxide)
• What are some problems with our experiment on the effect of pH on the enzyme amylase, and how can we improve? (2)

  1. only measuring every 30 seconds so only have an approximate reaction time - measure every 10 secs

  2. colour change is gradual - so ask several people to look at tile
• How are the lungs adapted for gas exchange? (3)

  1. Clusters of alveoli and folded alveolar walls provide large surface area

  2. Alveoli have a rich supply of blood capillaries, maintaining a steep concentration gradient

  3. Capillaries only 1 cell wide
• How does ventilation work?

  The contraction and relaxation of intercostal muscles changes the pressure inside the chest cavity so air is forced in and out the lungs as a result of differences in pressure
• Describe what happens as you breathe in (3)

  1. As ribs move up and out, diaphragm flattens, volume of chest increases

  2. Decreased pressure in chest

  3. Air is drawn into lungs as it is higher pressure
• Describe what happens as you breathe out (3)

  1. As ribs fall, diaphragm moves up, volume of chest decreases

  2. Increases pressure in chest

  3. Air is forced out of lungs
• What happens during gas exchange in the alveoli?

  1. Oxygen moves into blood by diffusion

  2. Carbon dioxide passes out of blood by diffusion