Enzymes

Question 1

enzymes

Answer 1

enzymes are molecules that act as catalysts to speed up the rate of biological reactions by reducing activation energy

Question 2

key info

Answer 2

• often end in ASE
• enzymes are proteins
• enzymes are not consumed during the reaction, they are reusable
• the compound on which an enzyme acts to the substrate (a molecule that an enzyme reacts with)
• when a substrate binds to an enzyme an enzyme-substrate complex is formed
• enzymes are substrate specific

Question 3

Biochemical pathways

Answer 3

chemical reactions in cells take place in a series of steps, called biochemical pathways. Each step is controlled and regulated by a specific enzyme

Question 4

Catabolic

Answer 4

when enzymes break a single structure into compartments (big to small)

Question 5

Anabolic

Answer 5

join two or more substrate molecules together (small to big)

Question 6

enzyme-substrate complex

Answer 6

the structure is formed when an enzyme and substrate are bound together

Question 7

Enzyme active site

Answer 7

• The substrate binds to an enzyme’s active site.
• The shape of the active site is complementary to its substrate
• Enzymes are substrate specific meaning an enzyme active site will fit with one type of substrate
• enzymes shape of the active site is determined by the molecule’s tertiary structure

Question 8

endothermic (endergonic)

Answer 8

• endothermic reactions absorb energy from the surroundings and convert it to stored chemical energy

Question 9

exothermic (exergonic)

Answer 9

• exothermic releases energy to the surroundings through the conversion of stored chemical energy

Question 10

effect of temp on enzymes

Answer 10

• enzymes catalyse reactions fastest at their optimum temperature
• at low temperatures, molecules move around slowly and the rate of collisions between enzymes and substrates reduces
• at increasing temps molecules move faster and the rate of collisions increases
• above optimum temp, enzymes denaturation occurs, and the shape of the enzyme changes, meaning substrates can no longer bind to the active site

Question 11

Effects on pH on enzymes

Answer 11

• Enzymes catalyst reactions fastest at their optimum pH
• Extremes of pH (very acidic or alkaline) away from enzyme optimum can result in enzyme denaturation

Question 12

Enzyme concentration

Answer 12

• Rate of reaction continues to increase in enzyme concentration
• This relationship assumes unlimited amount of substrate

Question 13

substrate concentration

Answer 13

• the rate of reaction increases and then plateaus with increasing substrate concentration. At the plateau, enzymes become saturated and are catalysing reactions at their fastest rate
• this relationship assumes a fixed amount of enzyme

Question 14

enzyme inhibitors

Answer 14

prevent the substrate from binding to the enzyme’s active site, deactivating the enzyme e.g drugs and toxins

Question 15

Reversible inhibitors

Answer 15

are used by cells to control enzyme activity

Question 16

Irreversible inhibitors

Answer 16

bind tightly and permanently to the enzymes destroying their catalytic activity

Question 17

competitive inhibitors

Answer 17

inhibitors block the substrate’s access to the active site. The shape of the inhibitor complements the active site allowing it to bind

Question 18

non-competitive inhibitors

Answer 18

inhibitors bind to another region of the enzyme (allosteric site), causing a change in the shape of the active site. May slow down or stop enzyme active

Question 19

co-enzymes

Answer 19

Co-enzymes are small organic non-protein molecules. They assist enzyme activity by binding to enzymes or by functioning as carriers of energy, electrons and protons. E.G) may vitamins work as coenzymes, cofactors have similar functions