KA 4: Proteins

• What do proteins have that allows them to serve different functions?

  A variety of shapes
• How does the shape of a protein relate to its function?

  It arises from the sequence of amino acids
• What are some functions of proteins in organisms?

  • Structural roles (e.g., keratin, collagen)
  • Enzymatic functions
  • Hormonal roles
  • Antibody functions
• What are chemicals that speed up chemical reactions called?

  Catalysts
• What type of catalysts are found in living cells?

  Enzymes
• What happens to catalysts during chemical reactions?

  They are not used up
• Why do living cells require enzymes?

  To speed up important reactions
• What is the substance an enzyme reacts with called?

  Substrate
• What are the substances formed by an enzyme called?

  Products
• What enzyme breaks down hydrogen peroxide?

  Catalase
• What are the products of the reaction catalyzed by catalase?

  Oxygen and water
• What are all enzymes composed of?

  Proteins
• What are the two main roles of enzymes in chemical reactions?

  • Degradation: breaking down larger molecules
  • Synthesis: building up larger molecules
• What does the enzyme amylase break down?

  Starch into maltose
• What does the enzyme pepsin break down?

  Proteins into peptides
• What does the enzyme lipase break down?

  Fats into fatty acids and glycerol
• What enzyme controls the synthesis of starch from glucose?

  Phosphorylase
• How does temperature affect enzyme activity?

  Activity increases up to 37°C
• What is the optimum temperature for most human enzymes?

  37°C
• What happens to an enzyme above its optimum temperature?

  Its shape changes and activity decreases
• What is the term for when an enzyme's shape changes?

  Denatured
• What is the active site of an enzyme?

  The position where substrate binds
• How does pH affect enzyme activity?

  Enzymes work best in a narrow pH range
• What pH do most enzymes like amylase function best at?

  pH = 7
• At what pH does pepsin work best?

  pH = 2
• At what pH does lipase work best?

  pH = 9
• What does it mean for an enzyme to be specific?

  Each enzyme acts on only one substrate