II: 5 - Enzymes

Question 1

Define

catalyst

Answer 1

A substance that increases the rate of a chemical reaction and is not changed by the reaction.

Question 2

Define

enzymes

Answer 2

Proteins that function as biological catalysts

Enzymes lower the amount of energy needed for the reaction to take place.

Question 3

Explain enzyme action in terms of the ‘lock and key’ model

Answer 3

Only substrates that can fit into the active site of the enzyme can take part in the reaction. When the substrate(s) fit into the active site, the reaction takes place and the products are released.

Question 4

What is the difference between an anabolic and catabolic reaction?

Answer 4

Reactions in which large molecules are built up from smaller molecules are called anabolic reactions.

Reactions in which large molecules are broken down to form smaller molecules are called catabolic reactions.

Enzymes are used in both types of reaction.

Question 5

Describe and explain the effects of changing temperature on enzymes.

Answer 5

• Enzymes have an optimum temperature: the temperature at which they work best giving the fastest reaction ≈ 37°C in animals
• When temperature increases, molecules move faster so collide with an enzyme in less time
• Having more energy makes them more likely to bind to active site.
• If temperature is too high, enzyme molecules vibrate too vigorously and enzyme is denatured; it loses its shape and will no longer bind with a substrate.
• When the temperature is too low there is not enough kinetic energy for the reaction so it reacts too slowly.

Question 6

Describe and explain the effect of changes in pH on enzyme activity.

Answer 6

• Some enzymes work best in an acid and others in an alkaline
• Enzymes work best at their optimum pH
• If the pH is changed then the enzyme will denature and will no longer fit with the substrate- no reaction will take place
• Hydrogen bonds with enzyme, changing its shape
• Only extremes of pH will completely denature enzymes, else the changes are usually reversible

Question 7

Describe the role of enzymes in germinating seeds.

Answer 7

• The enzymes in a seed need to be activated by water before the seed can being to germinate
• The enzymes help in the digestion of stored food
• Digested food is used to release energy in respiration so growth can occur

Question 8

Describe the role of enzymes in biological washing powders.

Answer 8

Enzymes are added to washing powders to help remove stains for example:

• Lipase for lipids from fatty foods and greasy fingerprints
• Protease for proteins from blood stains

Question 9

Describe the uses of enzymes in food production

Answer 9

• Isomerase converts glucose to fructose which is sweeter, so less is needed to give a sweet taste
• Pectinase helps break down cell walls in fruit juice production so it increases yield, lowers viscosity and reduces cloudiness

Question 10

Outline the use of microorganisms and fermenters to manufacture the antibiotic penicillin

Answer 10

Penicillin: an antibiotic produced by a fungus called penicillium.

• Stainless steel fermentation vessel is filled with medium containing sugars and ammonium salts.
• Penicillium is added to produce penicillin. They use sugar for respiration and ammonium salts to make protein and nucleic acids
• The fermentation vessel consists of
  
  • Probes to monitor temperature and pH
  • Air to provide oxygen for aerobic respiration in fungus
  • Water-cooled jacket to remove heat to maintain temperature of 24C.
  • Stirrer to keep the microorganism suspended (allowing access to nutrients and oxygen) while maintaining an even temperature.
• Filtered to remove fungus and then can be crystallized to make capsules.