Enzymes

Question 1

what are enzymes?

Answer 1

protein molecules that act as biological catalysts

Question 2

what do enzymes do?

Answer 2

• greatly increases the rate of a chemical reaction
• are not changed at the end of the reaction

Question 3

properties of enzymes?

Answer 3

• globular proteins with specifically shaped active sites
• effective in small amounts
• remains chemically unaltered after reactions
• lowers activation energy for reactions
• speeds up chemical reactions
• have a high degree of specificity

Question 4

what is the general structure of enzymes?

Answer 4

• relatively large molecules
• complex globular shape
• only the active site comes in direct contact with the substrate

Question 5

what is the definition of activation energy?

Answer 5

the energy required to make substance react

Question 6

how does the lock and key hypothesis work?

Answer 6

1. active site has a specific shape
2. substrate shape is complementary to the active site shape
3. substrate (key) fits exactly into the enzyme active site (lock) to form enzyme-substrate complexes
4. products no longer fit into the active site and leave

Question 7

how does the induced fit hypothesis work?

Answer 7

1. shape of substrate is complementary but does not fit exactly into the shape of active site
2. substrate binding with the active site induces a small conformation change of the enzyme
3. substrate fits more snugly into the active site to form enzyme-substrate complex
4. enzyme performs its catalytic function more effectively
5. products no longer fit and leave

Question 8

how does temperature affect enzymes?

Answer 8

• increase in kinetic energy
• increase in frequency of effective collisions between enzyme and substrate molecules
• more enzyme-substrate complexes formed
• rate of reaction increases with temperature until optimum temperature reached

Question 9

what happens when the temperature is increased beyond the optimum temperature of the enzyme?

Answer 9

the enzyme is denatured

Question 10

what happens when enzymes are denatured from high temperatures?

Answer 10

• excessive heat disrupts intramolecular bonds of the tertiary and secondary structure
• enzyme unfolds
• precise shape of active site is lost
• irreversible

Question 11

what happens when an enzyme is placed at freezing point?

Answer 11

enzymes are inactivated, but regains function when temperatures are raised

Question 12

what happens in optimum pH?

Answer 12

• intramolecular bonds which maintain protein structure are intact
• conformation of active site is the most ideal for binding
• highest frequency of effective collision between enzymes and substrates
• greatest number of enzyme-substrate complexes formed

Question 13

what happens when the enzyme is not at optimum pH?

Answer 13

• intramolecular bonds that maintain conformation of the enzyme is altered
• substrate binding is affected
• reversible but denatured when pH has extreme change

Question 14

what are the effects of increasing substrate/enzyme concentration?

Answer 14

• enzyme/substrate are fixed and limiting
• increase in frequency of enzyme and substrate collisions
• more enzyme-substrate complexes formed
• rate of reaction is increased

Question 15

what happens when the substrate concentration is limiting?

Answer 15

• active sites of enzymes are saturated
• substrate wait for enzyme-substrate complexes to release products
• rate of reaction is limited by the concentration enzymes

Question 16

what happens when the enzyme concentration is limiting?

Answer 16

increase in enzyme concentration does not result in further increase of rate reaction