ENZYMES

Question 1

What is meant by enzyme specificity? (1)

Answer 1

enzymes are highly specific in their reaction, catalyse only one reactions or a very small group of highly similar reactions ‘recognises’ substrate molecules.

Question 2

what is a catalyst? (1)

Answer 2

a substance that increases the rate of a chemical reaction and is chemically unaffected by the reaction it catalyses.

Question 3

what is the optimum temperature in enzymes for humans? (1)

Answer 3

37 degrees

Question 4

what do enzymes do? (1)

Answer 4

lower the activation energy of a reaction.

Question 5

what is meant by the activation energy? (1)

Answer 5

the energy barrier that must be overcome before reactants reach their temporary transition state.

Question 6

what are the disadvantages of the lock and key model? (1)

Answer 6

studies show it is too simplistic (enzyme molecule does change shape)

Question 7

what happens when molecules react? (1)

Answer 7

they become unstable intermediates but only momentarily whilst they come to their transition state.

Question 8

what factors effect the rate of the reaction of enzymes? (4)

Answer 8

-temperature
-pH
-substrate concentration
-enzyme concentration

Question 9

what is needed for a reaction to occur? (2)

Answer 9

-there must be successful collisions between two molecules
-must collide at the right angle and the right velocity

Question 10

what is the lock and key model? (1)

Answer 10

the enzyme and substrate molecules have a fixed shape and the substrate fits into the active site of the enzyme (like a lock and key)

Question 11

what is an example of a catabolic reaction? (2)

Answer 11

-digestion of complex foods
-break down of sugars in respiration

Question 12

what are the properties of enzymes? (3)

Answer 12

-do not change the nature of the reaction they catalyse
-are effective in small concentrations
-remain chemically unchanged at the end of a reaction

Question 13

what are anabolic reactions? (1)

Answer 13

in anabolic reactions, larger molecules are built up from smaller molecules.

Question 14

what are the conditions for chemical reactions in the human body? (4)

Answer 14

-normal temperature
-neutral aqueous conditions
-low concentrations of reactants

Question 15

what is an example of a anabolic reaction? (2)

Answer 15

-synthesis of proteins from amino acids
-synthesis of polysaccharides from simple sugars

Question 16

what is a metabolite? (1)

Answer 16

used to describe any molecule involved in the reactions occurring in cells and organisms (involved in the metabolism)

Question 17

what are catabolic reactions? (1)

Answer 17

in catabolic reactions, larger molecules are broken down.

Question 18

how can industry induce a chemical reaction? (5)

Answer 18

-application of high temperatures
-applications of high pressures
-extreme pHs
-high concentrations of reacting molecules
-catalysts

Question 19

what are the two types of metabolic reactions? (2)

Answer 19

-anabolic reactions
-catabolic reactions

Question 20

what are enzymes known as? (1)

Answer 20

biological catalysts

Question 21

what is a limiting factor? (1)

Answer 21

any factor that limits the rate which a reaction or process can occur.

Question 22

what are non-competitive inhibitors? (1)

Answer 22

bind to the enzyme at a site other than the active site and by doing so cause the shape of the enzymes active sit to change.

Question 23

what have studies of enzyme inhabitation helped understanding of? (3)

Answer 23

-chemistry of the active site
-natural regulation of metabolism
-ways in which certain commercial pesticides and drugs work.

Question 24

is the effect of pH reversible? (1)

Answer 24

usually reversible.

Question 25

what are the two phases to an enzyme concentration curve? (2)

Answer 25

-lower enzyme concentration - rate increases in direct proportion to the increase in concentration.
-higher enzyme concentration - rate becomes constant, showing increase in enzyme concentration.

Question 26

what is an enzyme inhibitor? (1)

Answer 26

a substance that slows the rate of an enzyme controlled reaction by preventing binding of a substrate to the active site of an enzyme.

Question 27

what is the optimum pH? (1)

Answer 27

the value or narrow range of values over which an enzyme-catalysed reaction is fastest.

Question 28

is the effect of temperature reversible? (1)

Answer 28

no, its permeant change

Question 29

what is a substrate? (1)

Answer 29

a molecule that binds to the active site of an enzyme to form an enzyme-substrate complex, it is then converted to a product.

Question 30

what is an enzyme? (1)

Answer 30

an organic catalyst that speeds up a metabolic reaction in cells and organisms

Question 31

what are competitive inhibitors? (1)

Answer 31

bind directly to the enzyme active site, blocking access to the substrate.

Question 32

what are the types of enzyme inhibitors? (2)

Answer 32

-competitive
-non-competitive

Question 33

how does temperature effect a biological reaction? (3)

Answer 33

-the random thermal movement of particles cause the rate to increase
-the rate of denaturation of protein molecules which happens because high temperatures cause such violent movements of particles within a protein molecule that the bonds holding the protein molecule together break so its active site looses shape.

Question 34

what is meant by random thermal movement? (1)

Answer 34

the movement shown by all particles at temperatures above absolute 0. as the temperature increases so does the rate of random thermal movement.

Question 35

how do enzymes work? (2)

Answer 35

binds to a specific substance known as its substrate molecule at a specifically formed pocket in the enzyme called its active site. as they bind they form an unstable enzyme complex which immediately breaks down to form products.

Question 36

what are the two phases to a substrate concentration curve? (2)

Answer 36

-lower concentration - the rate increases in direct proportion to increases in substrate
-higher concentration - the rate of reaction becomes constant, no further increase.

Question 37

what is the induced fit hypothesis? (1)

Answer 37

a model used to explain enzyme reaction.
when an enzyme and substrate combine, the enzyme active site changes shape to become truly complementary to the part of the substrate to which it attaches.

Question 38

what is optimum temperature? (1)

Answer 38

the temperature at which the rate of an enzyme controlled reaction is fastest (there is a balance between an increase in successful collisions between E and S and loss of active enzyme molecules as a result of denaturation)

Question 39

how does pH effect a biological reaction? (1)

Answer 39

the structure of a protein (shape of active site) is maintained by various bonds within the 3D structure of a protein. a change in pH alters bonding patterns therefore the active site is progressively changed.

Question 40

what is active site? (1)

Answer 40

enzyme molecules usually much bigger than their substrate molecules. the active site is small part of the enzyme molecule that binds to its specific substrate and causes the catalysis.