Organisation and the digestive system

• five levels of organisation in living organisms:

  • cells- basic building blocks
  • tissues- groups of cells that have similar structures and functions
  • organs- groups of tissues working together to perform a specific function
  • organ system- groups of organs working together
  • organisms- organ systems work together, forming an organism
• pancreas makes enzymes: amylase, lipase, and protease
• liver makes bile
• mouth where food is chewed
• gall bladder stores bile – bile is alkaline to neutralise hydrochloric acid

  from the stomach, and emulsifies fat to form small droplets with a large surface area
• small intestine where digested food is absorbed into the blood
• large intestine where water and minerals are absorbed into the blood
• salivary glands make saliva containing the enzyme amylase
• oesophagus carries food to the stomach
• stomach; churns food, releases protease – able to digests proteins and releases hydrochloric acid – killing pathogens
• rectum stores faeces
• anus expels faeces
• Digestive enzymes convert food into small, soluble molecules that can then be absorbed into the bloodstream. For example, carbohydrases break down carbohydrates into simple sugars.
• amylase is produced in the salivary glands, pancreas & small intestine
• protease is produced in the stomach, pancreas & small intestine
• lipases is produced in the small intestine & pancrease
• amylase reaction catalysed: starch ➞ glucose
• proteased eaction catalysed: proteins ➞ amino acids
• lipases reaction catalysed: lipids ➞ fatty acids and glycerol
• Enzymes are large proteins that catalyse

  (speed up) reactions. Enzymes are not changed in the reactions they

  catalyse.
• lock & key theory

  1.The enzyme’s active

  site (where the

  reaction occurs) is a

  specific shape.

  2. The enzyme (the lock) will only catalyse a specific reaction

  because the substrate (the key) fits into its active site.

  3. At the active site, enzymes can break molecules down into

  smaller ones or bind small molecules together to form

  larger ones.

  4. When the products have been released, the enzyme’s active

  site can accept another substrate molecule.

  
• Different enzymes have different optimum

  pH values.
• the different optimum pH values allows enzymes to be adapted to work

  well in environments with different pH values. For example, parts of the digestive system greatly differ in pH
• the effect of temperature on enzymes

  A) optimum temperature – this is when the reaction works a

  B) as the temperature increases, the rate of reaction incr

  C) the enzyme is denatured and stops working

  
• denaturation 


  At extremes of pH or at very high temperatures,

  the shape of an enzyme’s active site can change.

  The substrate can no longer bind to the active

  site, so the enzyme cannot catalyse the reaction

  – the enzyme has been denatured.

  
• digestive system:

  label

  A) pancrease

  B) liver

  C) gall badder

  D) small intestine

  E) large intestine

  F) mouth

  G) salivary glands

  H) oesophagus

  I) stomach

  J) rectum

  K) anus

  
• what does denatured mean


  shape of an enzyme’s active site is changed by high

  temperatures or an extreme pH, so it can no longer bind

  with the substrate
• what is a tissue

  group of cells with similar structures & functions
• what is a organ


  group of tissues working together to perform specific function
• what are enzymes


  protein molecules that catalyse specific reactions in organisms
• what are two factors that affect the rate of activity of an enzyme

  temperature & pH
• an organ system is a group of organs working together to perform a

  specific function
• the function of protease is to break down fatty acids & glycerol
• what is function of saliva

  lubrication to help swallowing – contains amylase to break down starch
• affect of temperature on enzyme activity

  as temperature increases, rate of reaction increases

  until it reaches the optimum for enzyme activity –

  above this temperature enzyme activity decreases and

  eventually stops
• affect of pH on enzyme activity

  different enzymes have a different optimum pH at which

  their activity is greatest – a pH much lower or higher

  than this enzyme activity decreases and stops
• Why do different digestive enzymes have different

  optimum pHs?

  different parts of the digestive system have very

  different pHs – the stomach is strongly acidic, and the

  pH in the small intestine is close to neutral