enzymes

Question 1

enzymes are

Answer 1

biological catalysts

Question 2

what is a catalyst

Answer 2

a substance that can speed up a chemical reaction, without itself being chemically changed at the end of the reaction

Question 3

what are enzymes made up of

Answer 3

protein molecules that are folded to take on 3 dimensional globular shapes

Question 4

the energy needed to start a chemical reaction is called

Answer 4

activation energy

Question 5

what are enzymes used in

Answer 5

all metabolic reactions that occur in cells

Question 6

all chemical reactions that occur in the cells are termed as

Answer 6

metabolic

Question 7

2 types of metabolic reactions

Answer 7

• anabolic
• catabolic

Question 8

anabolic reactions refer to

Answer 8

the process of synthesising macromolecules from monomers or simpler molecules

(e.g. sythesis of proteins from amino acids)

Question 9

catabolic reactions refer to

Answer 9

the process of breaking of macromolecules into monomers or simpler molecules

e.g. catalase breakdowns hydrogen peroxide to oxygen and water molecules

Question 10

example of catabolic reaction

Answer 10

• Hydrogen peroxide is sometimes produced during chemical reactions in the cells.
• This substance is toxic to the cells. Both plant and animal cells produce the enzyme catalase to break down hydrogen peroxide to water and oxygen
• hence removing the toxic effect. Catalase is especially abundant in blood and the liver of mammals.

Question 11

enzymes that are involved in digestion are called the

Answer 11

digestive enzymes

Question 12

examples of digestive enzymes

Answer 12

• amylase
• maltase
• protease
• liapse

Question 13

purpose of amylase

Answer 13

catalyses the digestion of starch to maltose

Question 14

purpose of maltase

Answer 14

catalyses the digestion of maltose to glucose

Question 15

purpose of protease

Answer 15

catalyses the digestion of protein to polypeptide then to amino acids

Question 16

purpose of lipase

Answer 16

catalyses the digestion of lipids to fatty acids and glycerol

Question 17

features of enzyemes

Answer 17

• specific in action
• speed up chemical reactions
• required in minute amounts and remain unchanged at the end of reactions

Question 18

why is an enzyme specific

Answer 18

• an enzyme has a specific three-dimensional (3-D) shape. It has a depression called the active site
• Only the substrate with a 3-D shape complementary to that of the active site can fit Into the enzyme.
• This results in the formation of an enzyme- substrate complex.

Question 19

what is the active site

Answer 19

groves or pockets on the surface of an enzyme molecule into which the substrate molecule(s) with the matching shape can fit — just like a lock and key.

Question 20

which one is the lock

Answer 20

enzyme

Question 21

which one is the key

Answer 21

substrate

Question 22

what happens while the substrate is attached to the active site

Answer 22

• a chemical reaction occurs
• The substrate is converted to the products.

Question 23

general equation of enzymes

Answer 23

e + s → es → e + p

(e = enzyme, s = substrate, p = product)

Question 24

how do enzymes speed up chemical reaction

Answer 24

speed up a chemical reaction by lowering the activation energy needed to start the reaction

Question 25

why are enzymes required at small amounts and remain unchanged

Answer 25

- Enzymes are very efficient molecules. - Since they remain unchanged in the reactions they catalyse, the same enzyme molecules can be used over and over again. - Thus, a small amount of an enzyme can catalyse the reaction for a large amount of substrate.

Question 26

what are enzymes affected by

Answer 26

- temperature - pH - substrate concentration - enzyme concentration

Question 27

how are enzymes affected by temperature

Answer 27

- An enzyme is less active at low temperatures. - As the temperature Increases, the rate of enzyme reaction increases. - Increasing the temperature above the optimum causes a rapid decrease In the rate of enzyme reaction.

Question 28

why is an enzyme less active at low energy

Answer 28

At low temperature, the kinetic energy of molecules is low. Enzyme and substrate molecules move slowly. The rate of the substrate molecules colliding with the enzyme is very low.

Question 29

why does the rate of enzyme reaction increase as the temperature increases

Answer 29

- increasing the temperature increases the kinetic energy of molecules. - The rate of effective collision (i.e. the rate of substrate molecules colliding and fitting into the active site of the enzyme) is increased. - This increases the rate of enzyme-substrate complex formation.

Question 30

in chemical reactions, for every 10'C,

Answer 30

the rate of reaction approximately doubles until optimum temperature

Question 31

optimal temperature for human enzymes

Answer 31

40-50°C

Question 32

why is there a rapid decrease in the rate of enzyme reaction when temperature increases after optimal temperature

Answer 32

the active site of the enzyme molecule begins to lose its original shape and is no longer complementary to the shape of substrate molecules

Question 33

what is denaturation

Answer 33

change in the 3D structure of an enzyme or any other soluble protein, caused by heat/chemicals (acids/alkalis)

Question 34

the pH of a solution is dependent on the

Answer 34

relative number of hydrogen ions(H⁺) compared to hydroxide ions (OH⁻) in the same solution

Question 35

why does water have a neutral pH

Answer 35

has an equal number of hydrogen ions and hydroxide ions

Question 36

changes in the pH of the reaction medium can have

Answer 36

an effect on the rate of an enzyme-catalysed reation

Question 37

each enzyme has

Answer 37

a narrow range of pH in which it functions effectively

Question 38

the rate of the reaction will reach its max at the

Answer 38

optimum pH of the enzyme

Question 39

what happens to the enzyme when there is a change in pH from the optimum values

Answer 39

causes the denaturation of the enzyme

Question 40

small changes in pH of the medium

Answer 40

alter the shape of globular proteins

Question 41

in what cases are the effects of pH reversible

Answer 41

the change in the surrounding pH is not too extreme | (very normal)

Question 42

if there is a constant amount of enzyme, | (substrate concentration)

Answer 42

- as the concentration of substrate increases, the rate of reaction will increase as well - because with more substrate molecules, there are more collisions between substrate and enzyme molecules

Question 43

at higher substrate concentrations | (substrate concentration)

Answer 43

- there comes to a point when there is more substrate than enzyme - as all the enzymes active sites are engaged in catalysis, the rate of reaction has reached its maximum

Question 44

adding more substrate | (after maximum rate at which enzymes can work as been reached)

Answer 44

does not increase the rate of reaction further | (thus the rate of reaction becomes constant)

Question 45

at a low concentration of the substrate, | (substrate concentration)

Answer 45

the enzyme occurs in excess

Question 46

since there are comparitively many more active sites available | (substrate concentration)

Answer 46

all substrate molecules can bind to the active site of enzymes immediately

Question 47

as substrate concentration increases | (substrate concentration)

Answer 47

the frequency of effective collision between the active site of enzymes and substrate increases

Question 48

more _ are formed, resulting in | (substrate concentration)

Answer 48

- enzyme-substrate complexes - more products formed per unit time - hence rate of enzyme reaction increases

Question 49

at high concentration of the substrate | (substrate concentration)

Answer 49

rate of enzyme reaction plateaus (remains at max)

Question 50

what are all active sites doing when the rate of enzyme plateaus | (substrate concentration)

Answer 50

- occupied and engaged - saturated - more substrate molecules present than enzyme molecules

Question 51

enzyme concentration when increasing substrate concentration is | (substrate concentration)

Answer 51

limiting factor

Question 52

what is limiting factor

Answer 52

directly affects the rate of a chemical reaction

Question 53

at low enzyme concentration | (enzyme concentration)

Answer 53

- the rate of reaction increases as enzyme concentration increases - more active sites are available to bind with the substrate molecules - The frequency of effective collisions between the active site of enzymes and substrates increases.

Question 54

more enzyme-substrate comples is formed, resulting in | (enzyme concentration)

Answer 54

more products formed per unit time

Question 55

As enzyme concentration increases to higher concentrations, | (enzyme concentration)

Answer 55

- rate of reaction plateaus or reaches a maximum and remains constant - This is because the number of substrate molecules is fixed and there is now an excess of enzyme molecules present. - All of the substrate molecules are bound to an enzyme’s active site and are engaged in the reaction.

Question 56

what is the limiting factor when increasing enzyme concentration | (enzyme concentration)

Answer 56

substrate concentration