[bio] enzymes

Question 1

what are enzymes & function?

Answer 1

biological catalysts that speed up the rate of chemical reactions without themselves being chemically changed at the end of chemical reactions

Question 2

can enzymes be reused?

Answer 2

yes

Question 3

what type of concentrations are enzymes effective in?

Answer 3

small concentrations

Question 4

what are catabolic reactions?

Answer 4

chemical reactions which break up complex molecules into simpler molecules

Question 5

example of catabolic reactions

Answer 5

hydrolysis - digestion in the alimentary canal

Question 6

what are anabolic reactions?

Answer 6

chemical reactions which build up simpler molecules into complex molecules

Question 7

examples of anabolic reactions

Answer 7

condensation reaction - synthesis of proteins from amino acids

Question 8

strucutre of enzymes

Answer 8

most enzymes are proteins with unique 3-dimensional strucutre

Question 9

characteristics of enzymes

Answer 9

specific in action

Question 10

what is an active site?

Answer 10

the site where substrates bind

Question 11

what is a substrate?

Answer 11

substrate is the molecule which an enzyme acts on

Question 12

how do enzymes speed up the rate of chemical reactions?

Answer 12

lowering the activation energy

Question 13

what is activation energy?

Answer 13

the energy that must be supplied to the reactant molecules for them to react

Question 14

how does lowering the activation energy allow faster chemical reactions?

Answer 14

• increases the speed of the reactant molecules/substrates
• collide more frequently and more forcefully in the correct orientation for chemical reactions to occur
• hence, higher rate of effective collision

Question 15

how does heating affect the enzymes?

Answer 15

when the temperature goes beyond the optimum temperature, the enzymes will be denatured and loses its 3d shape. This process is irrreversible

Question 16

explain the lock-and-key hypothesis

Answer 16

• the substrate is the “key”, and the enzyme is a “lock”
• the substrate, whose shape is complementary to the shape of the active site of the enzyme
• the substrate will fit exactly into the active site of the enzyme
• the substrate enters the active site, and binds with the active site
• enzyme-substrate complex is formed
• after the chemical reaction occurs, the products no longer fit the active site, and will get released
• the enzyme will be ready for the next reaction

Question 17

explain the induced fit model

Answer 17

• the substrate, whose shape is complementary to the shape of the active site of the enzyme
• shape of the active site will change slightly to fit the substrate more snuggly
• the substrate enters the active site, and binds with the active site
• enzyme-substrate complex is formed
• after the chemical reaction occurs, the products no longer fit the active site, and will get released
• the enzyme will be ready for the next reaction

Question 18

factors affecting the rate of reaction

Answer 18

1. temperature
2. pH
3. enzyme concentration
4. substrate concentration

Question 19

what is optimum temperature

Answer 19

the temperature at which the rate of enzyme activity is at its maximum

Question 20

general range of optimum temperature

Answer 20

37 to 45 degree Celsius

Question 21

what happens to enzyme at low temperature?

Answer 21

rate of enzyme activity is low at low temperatures of near or below 0deg.C, enzymes are less active at low temperatures, but structure is intact
it is a reversible condition where enzymes increases in activity when temperature increases.

Question 22

what happens from low temperature to optimum temperature?

Answer 22

as temperature increases, kinetic energy of substrate and enzyme molecules increases. enzymes start to be more active. substrate and enzyme molecules collide more often, and this increases the chances of effective collisions and formation of enzyme-substrate complexes and thus the rate of reaction increases

Question 23

what do you mean by effective collision?

Answer 23

it means that the substrate has entered the active site

Question 24

what happens at the optimum temperature?

Answer 24

the rate of reaction is the highest

Question 25

what is the optimum temperature of the human body?

Answer 25

usually higher than 40degC

Question 26

what happens to the enzyme beyond the optimum temperature?

Answer 26

as temperature increases beyond the optimum temperature, rate of reaction starts to decrease
the enzyme is denatured and loses its 3d shape and its active site is unable to bind to the substrate as their shapes are no longer complementary.
therefore, enzyme-substrate complex cannot be formed and the rate of reaction decreases to zero

Question 27

what happens after an enzyme is denatured? can it be reversed?

Answer 27

no, once an enzyme is denatured, it is irreversible, and it cannot regain its function even when the temperature is lowered

Question 28

what is optimum pH of an enzyme?

Answer 28

the pH at which enzyme activity is at its maximum

Question 29

what happens when an enzyme is at extreme pH?

Answer 29

at extreme pH, the enzyme is denatured, loses its 3d shape and the active site is unable to bind to the substrate. therefore, enzyme-substrate complex cannot be formed

Question 30

what is a limiting factor?

Answer 30

a limiting factor is any factor that is in the shortest supply

Question 31

effect of varying enzyme concentration (at low, high and maximum)

Answer 31

• at lower enzyme concentration, adding more enzyme increases the rate of chemical reactions [enzyme concentration is limiting]
• when the enzyme concentration increases, more effective collision occurs, resulting in the formation of more enzyme-substrate complexes
• at the plateau, the rate of reaction becomes constant and enzyme concentration is no longer a limiting factor. instead, substrate concentration is limiting.
• there are not enough substrates to occupy all the active sites of the enzymes

Question 32

effect of varying substrate concentration (at low, high and maximum)

Answer 32

• at low substrate concentrations, few substrate molecules are present. hence, there are many available enzyme active sites for effective collision to occur
• the rate of reaction increases with an increases in substrate concentration until a point when further increase in substrate concentration will no longer increase the rate of reaction
• the rate of reaction becomes constant and reaches a plateau
• at higher substrate concentrations, increasing the concentration of substrate cannot increase rate of reactions. enzyme concentration is the limiting factor.
• this is because all active sites of the enzyme molecules are saturated with substrate molecules, and the concentration of product formed per unit time remains the same

Question 33

how to measure the rate of reactions?

Answer 33

1. measuring the rate of concentration/volume/mass of products formed
2. measuring the rate of concentration/volume/mass of reactants used up