Enzymes

• What does amylase do?

  -helps break down starch

  -into sugars

  -made in pancreas and small intestine
• What does protease do?

  -helps break down proteins

  -into amino acids

  -made in pancreas and small intestine
• What does lipase do?

  -helps break down lipids(fats)

  -into fatty acids and glycerol

  -made in pancreas and small intestine
• Explain why rate of reaction increases

  -enzyme and substrate have more kinetic energy

  -therefore, more collisions, forming enzyme substrate complexes
• Explain why rate of reaction decreases

  -enzyme denatures

  -active site changes shape

  -enzyme substrate complexes cant be formed
• Describe a test to identify fats

  -mix the food in ethanol and pour into water

  -white emulsion forms
• Explain why amylase cant break down protein

  -shape of active site of amylase has a specific shape which is complementary to starch.

  -protease breaks down protein

  -amylase breaks down starch
• What is the independent variable in the food test?

  PH
• What is the dependent variable?

  time taken for amylase to break down starch
• What is the control variable?

  -temperature

  -volume of starch

  -volume of amylase
• Colour of iodine when no starch

  yellow/orange
• Colour of iodine when starch present

  blue/black
• Amylase is produced by salivary glands and the pancreas. Explain why amylase is not produced in the stomach (2marks)

  -inside the stomach, there is hydrochloric acid so a low PH

  -the enzyme will become denatured

  -the active site changes shape

  -no enzyme substrate complex will form
• DESCRIBE THE GRAPH

  -

  as the temperature increases the rate of reaction increases up to the optimum temperature (B). Beyond the optimum temp rate of reaction decreases.

  
• EXPLAIN WHY THE RATE OF REACTION INCREASES FROM A TO B

  • the enzyme and substrate have more kinetic energy therefore more collisions forming enzyme substrate complexes

  
• EXPLAIN WHY RATE OF REACTION DECREASES FROM B TO C

  • the enzyme denatures and active site changes shape. Enzyme substrate complexes can’t be formed

  
• During the core practical iodine stops changing colour to blue/black. Suggest why

  all the starch has been broken down by amylase so no starch is present
• DESCRIBE

  • as substrate complex increases rate of reaction increases up to a certain point (optimum)
  • beyond optimum the rate of reaction slows down

  
• EXPLAIN THE SHAPE OF THE GRAPH BETWEEN POINT A AND B

  • there is enough enzymes per substrate so enzyme substrate complexes can form

  EXPLAIN THE SHAPE OF GRAPH BETWEEN POINT B AND C

  • all the active sites are occupied
  • rest of the substrates need to wait for a free active site
  • rate of reaction slows down

  
• Define the term enzyme

  a biological catalyst which speeds up the rate of reactions