Enzymes and the Digestive System

Question 1

what is an enzyme?

Answer 1

a biological catalyst that speeds up a reaction without being used up, lowers activation energy, bends the bonds within the substrate

Question 2

fun facts about enzymes:

Answer 2

• they’re globular proteins
• proteins of high weight to have substantial stability and strength
• sensitive to both temperature and PH hydrogen and ionic bonds specifically impacted
• catalyse both anabolic (building up) and catabolic (breaking down) reactions
• soluble in water - dependent on the R-group
• enzymes can be extracellular and intracellular

Question 3

groups of enzymes:

Answer 3

lyases: splitting of bonds other than hydrolysis or oxidation
hydrolases: hydrolysis of bonds - all digestive enzymes
ligases: joining of two molecules by formation of covalent bonds
isomerase: isomerisation of molecules

Question 4

what are activators?

Answer 4

inorganic groups permanently bound to enzymes and are a type of prosthetic group

Question 5

what are co-enzymes?

Answer 5

organic molecules that bind only temporarily to the enzyme transferring a chemical group necessary required for a reaction

Question 6

what is the active site?

Answer 6

3D specific tertiary structure complementary to the substrate

Question 7

what’s the substrate function?

Answer 7

the substrate binds to the active site -> creates enzyme/substrate complex bends bonds of substrate -> enzyme/product complex -> active site will release products they diffuse away - we know this as the lock and key theory

Question 8

what is the lock and key theory?

Answer 8

substrate is an exact complimentary shape to the active site

Question 9

what is the Induced Fit Model?

Answer 9

• this model takes into account the fact that protein active sites have some three-dimensional flexibility
• substrate binds to the enzyme at the active site similar complimentary shape to substrates but NOT exact
• binding of substrate induces the enzyme to change shape such that there is an exact fit in the active site once the substrate has bound
• reactions can only take place AFTER induced fit has occurred

Question 10

what are factors effecting the rate of reaction?

Answer 10

• temperature
• PH (log-[H+])
• concentration of substrate
• concentration of enzyme
• inhibitors
• activators

Question 11

describe the temperature graph?

Answer 11

bottom of curve: rate of reaction at its slowest, the internal kinetic energy of the molecules don’t reach the activation energy. Fewer successful collisions, fewer enzyme/substrate complexes, enzymes and substrate kinetic energy have little kinetic energy
mid of curve: increased temperature more kinetic energy, high number of successful collisions, high number of enzyme/substrate complexes, more product formed per second and a higher rate of reaction
optimum: fastest rate of reaction, most successful collisions per rate, highest rate of enzyme/substrate complexes and highest rate of product formation
after optimum: active site denatures - its 3d tertiary structure is no longer complimentary to the substrate, fewer successful collisions per second, lower rate of enzyme/substrate complexes forming, lower rate of product formation, decrease in rate of reaction -> structure of active site is no longer complimentary to the substrate temperature overcome tertiary structure bonds - hydrogen, ionic, disulphide are broken and this changes the 3d tertiary structure of the active site