enzymes

Question 1

what are catalysts?!!!!

and biological catalysts?

Answer 1

a substance that can speed up a chemical reaction without itself being chemically changed at the end of the reaction
to catalyse = to speed up
- in living organisms, the biological catalysts are called enzymes

Question 2

what is activation energy and how are chemical reactions catalysed?

Answer 2

• for a chemical reaction to be started, activation energy is needed
• enzymes catalyse chemical reactions by lowering activation energy

Question 3

what about enzymes?

Answer 3

• catalysts found in living organisms
• biological in origin
• made of proteins -> have some properties that are different from inorganic catalysts

Question 4

definition of enzymes!!!

Answer 4

enzymes are proteins that function as biological catalysts. they catalyse or speed up the rate of chemical reactions in living organisms. they remain chemically unchanged at the end of the reaction.

Question 5

what do enzymes catalyse?

Answer 5

• reactions that build up complex substances
  e.g. protein synthesis
  photosynthesis
• reactions that break down complex substances
  e.g. respiration
  decomposition of hydrogen
  peroxide

Question 6

lock-and-key hypothesis

Answer 6

• used to describe how an enzyme will only act on a specific substance called the substrate
• an enzyme is like a lock that have special depressions
• these depressions have a specific shape that will enable the right key to fit into. the substrate is the key
  complementary does NOT mean the same

Question 7

enzymes speed up chemical reactions

Answer 7

• due to enzymes’ ability to lower activation energy of reactions

Question 8

enzymes are specific in action

Answer 8

• due to specific shape of active site for the substrates - each have a specific 3D shape
• only a substrate that has a shape complementary to the enzyme’s active site will be able to bind to the enzyme and cause a chemical reaction.

Question 9

enzymes are required in small quantities

Answer 9

• as they remain chemically unchanged
• once the products leave, the enzyme’s active site is free to bind to another substrate molecule
• they can hence be reused and are only required in minute quantities

Question 10

enzymes are affected by temperature

Answer 10

• typically, before the optimum temperature is reached, the rate of enzyme activity doubles for every 10 degrees rise in temperature.
  ! optimum temperature for enzyme activity varies among different enzymes

Question 11

enzymes are affected by pH

Answer 11

• the optimum pH in which an enzyme works best varies among different enzymes
• extreme acidity or alkalinity of a solution will cause enzymes to denature