4.1 - Enzyme Action

Question 1

What are the propertes of enzymes?

Answer 1

• Globular protein - 3D shape to interact with substrates specifically
• The active site is complementaty to the shape of a substrate
• Lowers E_a of a reaction
• Enzyme left unchanged after a reaction

Question 2

What are the roles of enzymes?

Answer 2

• Catalyses metabolic & anabolic reactions
• Enzymes can be intracellular (catalase) - converts H₂O₂ (toxic metabolic product) to water and oxygen
• Enzymes can be extracellular (amylase, trypsin)
  
  • Amylase -

Question 3

What are intracellular enzymes and their roles?

Answer 3

• Enzymes that act within cells
• Enzymes have a role in structure and function of cells and organisms.
• Enzymes needed or synthesis of polymers - e.g. polysaccharides from glucose

Question 4

How can enzyme controlled reactions be successful?

Answer 4

Enzymes and substrates must collide in the correct orientation Increase in temperature and pressure means more successful collisions and rate of reaction increases

Question 5

What is activation energy and how does it relate to enzymes?

Answer 5

Activation energy is the minimum amount of energy required to start a reaction - this may be too high under normal conditions Enzymes lower the activation energy by providing alternative reaction pathways helping molecules to collide more successfully.

Question 6

Define active site.

Answer 6

Area within enzyme’s tertiary structure with a shape specifically complementary to its substrate.

Question 7

Describe the lock and key hypothesis.

Answer 7

• Substrate binds to active site forming enzyme-substrate complex
• The substrate reacts and is converted to a product forming the enzyme-product complex
• The product is released from the enzyme which is left to catalyse another reaction

Question 8

How does the substrate stay bound to the enzyme during the lock and key hypothesis?

Answer 8

The substrate is held to the enzyme as R-groups of the active site interact with the substrate forming temporary bonds.

Question 9

Describe the induced-fit hypothesis.

Answer 9

• Active site is not perfectly complementary to the substrate
• Once the substrate interacts with the active site, it inteferes with the active site bonds to alter the shape
  
  • This gives a perfect complementary fit for the substrate
• Since the active site shape changes, it is easier to make and break bonds (reducing activation energy)

Question 10

Describe the process of starch digestion (use of extracellular digestion)

Answer 10

1. Polysaccharides are broken into the disaccharide maltose by amylase
   
   • Amylase is produced by the salivary glands and the pancreas
2. Maltose is then broken down to the monosaccharide glucose by maltase
   
   • Maltase produced in the small intestine

Question 11

Describe the process of protein digestion.

Answer 11

• Involves protease Trypsin - a type of protease
  
  • produced by pancreas in small intestine
• catalyses digestion of protein into smaller peptides
• Other proteases break peptides into amino acids
• These amino acids are absorbed by cell lining of digestive system
  
  • absorbed into blood stream.