Enzymes

Question 1

metabolism

Answer 1

the collection of all biochemical reactions in an organism

Question 2

enzyme

Answer 2

globular proteins with a specific tertiary structure which act as biological catalysts speeding up the rate of a reaction by lowering the activation energy

Question 3

activation energy

Answer 3

the amount of energy required for a reaction to proceed

Question 4

bonds present in tertiary structure

Answer 4

hydrogen
disulphide
ionic
hydrophobic/philic interactions

Question 5

anabolic reaction

Answer 5

metabolic reaction involving formation of bonds. Eg. photosynthesis

Question 6

catabolic reaction

Answer 6

metabolic reaction involving breaking of bonds. Eg. respiration

Question 7

active site

Answer 7

the functional part of an enzyme

Question 8

lock and key model

Answer 8

substrate fits to active site as they are complementary shapes to form an enzyme-substrate complex
products released will no longer fit the active site

Question 9

induced fit model

Answer 9

substrate and enzyme are NOT complementary shapes.
when a substrate bind the active site changes shape to fit the substrate.
placing strain on the substrate and distorting the bond, lowering activation energy.
when products are released the active site changes back to original shape

Question 10

properties of enzymes

Answer 10

specific
fast acting
soluble

Question 11

why are enzymes soluble

Answer 11

their hydrophilic R groups are on the outside of the molecule

Question 12

why are enzymes specific

Answer 12

due to the order and sequence (primary structure) of amino acids that make up their active site.

Question 13

what are the 5 factors affecting enzyme action

Answer 13

temperature
pH
substrate concentration
enzyme concentration
inhibitors

Question 14

what are the two types of inhibitors

Answer 14

competitive and non-competitive

Question 15

what does extreme pH do to an enzyme

Answer 15

denatures enzyme by altering the electrostatic charge the side chains of the amino acids.
if the active site has too many H+ ions (acidic) or OH- ions (alkali) then the enzyme will repel the substrate

Question 16

how do competitive inhibitors reduce rate of reaction

Answer 16

its shape is complementary to the active site and so it binds to it blocking the substrate meaning less enzyme-substrate complexes can form

Question 17

what point does the non-competitive inhibitor bind to

Answer 17

allosteric site

Question 18

an example of non-competitive inhibitor

Answer 18

cyanide

Question 19

an example of competitive inhibitor

Answer 19

Malonic acid

Question 20

immobilised enzymes

Answer 20

enzymes that are fixed, trapped or bound on an inert matrix

Question 21

how are enzymes immobilised

Answer 21

absorption onto insoluble matrix

covalent binding to solid

trapped within gel

encapsulated behind semi permeable membrane

Question 22

advantages of immobilised enzymes

Answer 22

easily recovered for re-use

product not contaminated
with enzyme

increased stability over a wider range of ph

increased stability over a range of temperatures

several enzymes with different temperature or ph optimums can be used in one process

enzymes can be easily added or removed

Question 23

allosteric site

Answer 23

a point on an enzyme that is not the active site

Question 24

competitive inhibitor

Answer 24

an inhibitor that is similar in shape to a substrate

Question 25

non-competitive inhibitor

Answer 25

an inhibitor that is dissimilar in shape to a substrate and binds at the allosteric site