enzymes

Question 1

what is metabolism?

Answer 1

the combination of anabolic and catabolic reactions that are catalysed by enzymes

Question 2

what is a metabolic pathway?

Answer 2

a series of enzyme controlled reactions.
product of one is the reactant in the next

Question 3

what are anabolic reactions?

Answer 3

build up molecules
e.g. protein synthesis

Question 4

what are catabolic reactions?

Answer 4

break down molecules
e.g. digestion

Question 5

definition of enzyme

Answer 5

a biological catalyst, globular protein, that alters the rate of a chemical reaction without being used up.
remains unchanged

Question 6

why are enzymes called a biological catalyst?

Answer 6

they are made up of living cells
they lower activation energy

Question 7

properties of enzymes

Answer 7

they:
speed up reactions
aren’t catalysed
aren’t used up
have a high turn-over number
are soluble

Question 8

structure of enzymes

Answer 8

protein tertiary structure
active site with specific 3D shape

Question 9

where are the sites of enzyme action

Answer 9

extracellular
intracellular (in solution or membrane bound)

Question 10

extracellular enzyme action

Answer 10

outside cells
enzymes secreted by exocytosis
e.g. amylase produced in salivary glands

Question 11

intracellular enzyme action in solution

Answer 11

inside cells
e.g. enzymes in glycolysis, cytoplasm respiration

Question 12

intracellular enzyme action membrane bound

Answer 12

attached to membranes
e.g. mitochondria cristae, chloroplast grana

Question 13

role of the active site

Answer 13

enzymes act on its substrate, making temporary bonds at the active site
form enzyme substrate complexes

Question 14

what is an enzyme substrate complex

Answer 14

temporary molecule formed when the substrate binds to the enzyme

Question 15

what is the lock and key model

Answer 15

substrate and active site have a complementary shape
only substrates that exactly fit the enzyme can be catalysed
enzymes are specific to 1 substrate

Question 16

enzyme specificity

Answer 16

enzymes are specific to 1 substrate

Question 17

what is the induced fit model

Answer 17

substrate binds to enzymes active site
shape of active site changes slightly
esc formed
product released

Question 18

lysozyme and the induced fit model

Answer 18

• antibacterial enzyme in mucus, saliva, tears
• folds around sugars in cell wall of bacteria
  disrupts structure
  breaks bonds
  bacterial cell wall absorbs water = bursts

Question 19

what is activation energy

Answer 19

the minimum energy put into a chemical system for a reaction to occur
molecules need enough KE to collide and react

Question 20

what is catalysis?

Answer 20

the lowering of activation energy

Question 21

what is the collision theory?

Answer 21

for a reaction to occur, particles involved must collide with enough energy so bonds are broken
higher temp = higher KE = more successful collisions = more ESCs formed

Question 22

how do different factors change enzyme action?

Answer 22

environmental conditions alter the 3D structure of enzymes
bonds in tertiary structure break = changes shape of active site = reduces ability to form ESCs = lowers reaction rate

Question 23

what is denaturation?

Answer 23

the permanent change of an enzymes structure
due to high temps or extreme pHs

Question 24

affect of low temperature on enzymes

Answer 24

particles have low KE
few successful collisions
less ESCs formed per unit time
fewer product formed

Question 25

affect of extremally high temperature on enzymes

Answer 25

KE increases vibrations in enzyme molecules weaken bonds holding the 3D tertiary structure of active site together active site loses shape substrate no longer complementary no more ESCs enzyme denatured

Question 26

affect of extreme pH on enzymes

Answer 26

small changes from optimum = reversible changes in enzymes = reduces efficiency large change from optimum = disrupts ionic / hydrogen bonds in enzyme = permanent changes to shape of active site = prevents ESC formation = enzyme denatures

Question 27

affect of enzyme concentration on enzymes

Answer 27

excess substrate, increase in enzyme conc = increased reaction rate (plenty of active sites) not in excess = substrate limiting = no effect of adding more enzymes

Question 28

affect of substrate concentration on enzymes

Answer 28

increased substrate conc = increase collisions = higher reaction rate eventually further substrate increase = no effect, enzymes all have full active sites (enzyme conc limiting)

Question 29

what are pH buffers?

Answer 29

counteract changes in pH neutralise acid or alkaline

Question 30

what is a cofactor

Answer 30

a non-protein substrate that binds to an enzyme allowing a reaction to occur

Question 31

what is an inhibitor?

Answer 31

a molecule/ion that binds to an enzyme, reducing the rate of reaction by interfering with the shape of the active site reversible or irreversible

Question 32

what is a competitive inhibitor?

Answer 32

complementary in shape to active site of enzyme prevents ESC formation by blocking the active site don't bind permanently - increases substrate conc reduces the effect

Question 33

what is an non-competitive inhibitor?

Answer 33

bind to enzyme away from active site, at allosteric site. alter shape of active site no ESCs form always produces a lower rate of reaction

Question 34

what are calibration curves?

Answer 34

used to predict the concentration of unknown solutions based on comparing concentrations of known solutions

Question 35

what are immobilised enzymes?

Answer 35

enzymes fixed, bound or trapped in an inert matrix e.g. cellulose microfibrils, sodium alginate beads

Question 36

advantages of immobilised enzymes

Answer 36

- increased stability = dentatutre at higher temps, used over wider range of pH - products uncontaminated with enzyme - enzymes easily added and removed = control over reaction - enzymes easily recovered for reuse

Question 37

uses of immobilised enzymes

Answer 37

- lactose free milk - high fructose corn syrup - biosensors

Question 38

how are immobilised enzymes used in making lactose free milk?

Answer 38

milk passed down column containing immobilised enzymes lactose binds to active site on lactase

Question 39

what are biosensors?

Answer 39

convert chemical into electrical energy used in blood glucose detection

Question 40

why is it more efficient to use enzyme immobilised onto a membrane than in beads?

Answer 40

it takes longer for substrate to diffuse into the beads to reach the centre where the active site is

Question 41

why does reducing flow rate increase the volume of product in immobilised enzymes?

Answer 41

- increases contact time between enzyme and substrate - more time for enzyme to function - more successful collisions - more ESCs form