enzyme structure & function

Question 1

what do enzymes do?

Answer 1

they speed up metabolic reactions and lower the activation energy of the reaction

Question 2

what is activation energy?

Answer 2

the energy required to start any reaction.

Question 3

what must happen in order for a reaction to occur?

Answer 3

the reactants must absorb energy before the reaction occurs. activation energy is often supplied in the form of heat. the reactants must collide with sufficient kinetic energy and a specific orientation. the reactants must collide with enough energy to break existing bonds

Question 4

how do enzymes reduce activation energy?

Answer 4

less energy is needed if the reactants collide at the right angle.
an enzyme reduces the activation energy needed for a reaction to occur by providing the reactants with better orientation, thereby increasing the frequency of successful collisions and the rate of reaction

Question 5

what are the characteristics of enzymes?

Answer 5

• biological catalysts
• proteins
• specific
• have specific active site
• are not used up in the reaction

Question 6

what is the active site?

Answer 6

• part of the enzyme that interacts with the substrate. has a shape that complements the shape of the binding site of the substrate

Question 7

what is the lock and key model?

Answer 7

• has a static active site
• molecules fit into the active site where chemical change occurs

Question 8

what are the problems with the lock and key method?

Answer 8

• the molecular shape of the active site is not always complementary to that of the substrate

Question 9

what is the induced fit model?

Answer 9

• enzymes can change the shape of their active sites to fit the substrate. the substrate produces changes in the conformation of the enzyme. it allows better binding and catalytic effects

Question 10

what are the steps involved in enzyme catalysed reactions?

Answer 10

1. substrates enter active site; enzyme changes shape such that its active site enfolds the substrates
2. substrates held in active site by weak interactions, such as hydrogen bonds and ionic bonds.
3. the active site can lower activation energy and speed up a reaction by
   - acting as a template for substrate orientation
   - stressing the substrates and stabilising the transition state
   - providing a favourable microenvironment and/or
   - participating directly in the catalytic reaction
4. substrates are converted to products
5. products are released
6. the active site is available for two new substrate molecules