1.4-biological reactions and enzymes

Question 1

what is the lock and key theory?

Answer 1

-each enzyme reacts with a specific complimentary substrate in the enzymes active site to form enzyme-substrate complexes

Question 2

what are enzymes?

Answer 2

-biological catalysts that speed up reactions
-all enzymes are tertiary proteins where polypeptide chains are folded back on itself into a spherical globular shape

Question 3

what are anabolic enzymes?

Answer 3

enzymes that build larger products from smaller substrate molecules

Question 4

what are catabolic enzymes?

Answer 4

enzymes that break larger substrate molecules into small products

Question 5

what are lysozymes?

Answer 5

-enzymes found in tears and other secretion
-destroy pathogenic bacteria by breaking down their cell walls (catabolic reaction)

Question 6

how do lysozymes break downt bacterial cell walls?

Answer 6

-a bacterial cell wall is a polysacchardie consisting of chains of amino acids. lysozymes break down the glycosidic bonds between amino sugars

Question 7

what is the induced fit theory

Answer 7

-the substrate changes the shape of the active site to bind perfectly to the enzyme to form an enzyme-sunbstrate complexes
-this means that multiple substrates can fit to one enzyme

Question 8

what does it mean when enzymes have a high turnover number?

Answer 8

they can convert masny molecules of substrates into products per unit time

Question 9

what is activation energy?

Answer 9

the minimum amount of energy needed to break the existing chemical bonds inside molecules

Question 10

what do enzymes do to the activation energy?

Answer 10

-lower it so that less energy is needed for the reactions

Question 11

what factors affect enzyme activity?

Answer 11

-temperature
-pH
-substrate concentration
-enzyme concentration

Question 12

how does temperature affect enzyme activity?

Answer 12

-an increase in tempreature means that molecules greater kinetic energy this means that the likelihood of successful collissions to form enzyme-substrate complexes
-as a general rule the rate of a reaction doubles for each 10C (continues until the optimum is reached-usually 40C)

Question 13

what happens to enzyme activity as 25C?

Answer 13

-the kinetic energy is low
-enzymes and substrates collide less often so few successful collissions to form enzyme-substrate complexes
-products are produced slowly as enzyme activity is low

Question 14

what happens to enzyme activity at 37C?

Answer 14

-high kinetic energy
-more successful enzyme substrate complexes
-product production is quicker
-enzyme activity levels off as substrate concentration becomes a limiting factor

Question 15

what happens to enzyme activity at 60C?

Answer 15

-initially products are formed quickly due to high kinetic energy
-enzymes quickly denature as vibrations break hydrogen bonds within the active site of the enzyme causing the shape of active site to change. this means that less succesful enzyme-substrate complexes are formed
-unconverted substrates molecules remain

Question 16

how does pH affect enzyme activity?

Answer 16

-enzymes have a narrow optimum pH range
-small changes in the pH can cause reversible changes in enzme structures
-extreme changes in pH can denature an enzyme

Question 17

why would an enzyme active site and substrate molecule repel each other?

Answer 17

-for enzyme-substeae complexes to form the charges on amino side chains of the active site must attract charges on the substrae molecule
-the charges of the enzyme’s active site are affected by free Hydrogen (H+) and hydoxyl (OH-) ions
-if there are too many H+ions (too acidic) the active site and substrate may end up with the same charge causing them to repel one another

Question 18

what happens to enzyme activity if the enzyme concentration remains constant?

Answer 18

the rate of reation will increase as the substrate concentration increases
-the reaction will level off when all active sites are occupied and the number of available active sites becomes a limiting factor at higher substrate concentrations

Question 19

how does enzyme concentration affect enzyme activity?

Answer 19

as the enzyme concentration increases the rate of reaction also increases due to a greater number of available active sites

Question 20

what is catalase and what does it do?

Answer 20

-enzyme found in all living cells that breaks down the toxic waste products (hydrogen peroxide) into water and oxygen

Question 21

what is an enzyme inhibitor?

Answer 21

any substance which decreases the rate of an enzyme reaction
-they are either competitive or non-competitive inhibitors

Question 22

what are competitive inhibitors?

Answer 22

inhibitors with a similar structure to the substrate molecule
-it can fit in the active site instead of the substrate
-prevents enzyme-substrate complexes from forming

Question 23

what can be one to prevent competitve inhibitors colliding with enzyme active sites instead of substrates?

Answer 23

-increasing substrate concentrations to increase the likelihood of successfull enzyme-substrate complexes

Question 24

what are non-competitive inhibitors?

Answer 24

-they do not bind to the active site but rather any other part of the enzyme
-they cause a change in the shape of the enzyme meaning that the substrate cannot fit into the active site anymore
-increasing substrate concentrations does not increase the rate of the reaction since the substrate does not fit into the active site (irreversible)

Question 25

what are immobolised enzymes?

Answer 25

-enzymes that are fixed/bound/trapped on an inert matrix such as alginate beads

Question 26

why is it preferred to immobolise enzymes on a membrane rather than alginate beads?

Answer 26

-enzymes can make direct contact with the substrate to allow quicker reactions -using alginate beads means that substrates and products must diffuse through the jelly matrix causing reactions to take longer

Question 27

what are the advanatges of using immobilised enzymes?

Answer 27

1) the enzymes do not contaminate the product 2)immobilised enzymes can be recovered and reused 3)only a small amount of enzymes are needed 4)enzymes have a greater stability and denautre at higher temperatures 5)enzymes can catalyse reactions over a wider range of pH 6)more than one enzyme can be used (added/removed) 7)greater control over the process 8)enzymes can be used in a continuous process

Question 28

how does lactase break down lactose in alignate beads

Answer 28

-as milk flows through the column the lactose (substrate)diffuses into the alginate matrix to form enzyme-substrate complexes -glucose+galactose (products) diffuse out of the beads and leave the column with the rest of the milk

Question 29

what would happen to enzyme activity if the flow rate of milk down a column was reduced?

Answer 29

allows more contact berrween enzymes and substrates so more complexes are formed

Question 30

what would happen to enzyme activity if smaller alginate beads are used?

Answer 30

-smaller beads can increase the surface area to allow diffusion to take place quciker

Question 31

immobilised enzymes graph question (volume of juice extracted against temp) -free enzymes

Answer 31

-between 20-40C the free enzymes have the greatest activity. bother enzymes and substrates are free to move and thereore there is a greater likelihood for successful collissions -as temp uncreases the kinetic energy increases allowing more collissions and enzyme-substrate complexes -between 40-60 the volume of furit juice decreases shaprly as the increased vibrations due to energy too great (H bonds in active sites are broken-enzymes denature)

Question 32

immobilised enzymes graph question (volume of juice extracted against temp) -immobilised in alginate beads

Answer 32

-enzyme activity continues to increase beyond the natural optimum -alginate gel fills and supports the enzyme active site, maintaining its shape and allowing enzyme-substrate complexes to form

Question 33

immobilised enzymes graph question (volume of juice extracted against temp) -bound to a membrane

Answer 33

membrane bound enzymes are in direct contat with the substrate and therefire the product is formed faster than enzymes immobilised in alginate beads

Question 34

immobilised enzymes graph question (volume of juice extracted against temp) -free enzymes/alginate beads/membrane bound (which will be picked?)

Answer 34

-the membrane bound method will be picked -at 60C the greatest yield of fruit juice is produced -to further increase the yield the membrane could be folded many times to increase the number of active sites available. this will also lower the flow rate to allow longeer contact between enzymes and substrates

Question 35

what do biosensors do?

Answer 35

-detect biologically important molecules very rapidly even in low concentrations -used to measure blood glucose concentrations for those will diabetes -they use immobilised enzymes on a gel membrane

Question 36

how does a biosensor display what it detects?

Answer 36

-detects chemical changes as a substarte is converted to products -transducer converts this chemcial change into an electrial signal -amplified and viewed on a display

Question 37

describe the process of how a biosensor detects urea molecules

Answer 37

small urea diffuse across the partially permeable membrane and forms an enzyme substrate complex with immobilised urease -the product formed is ammonium ions (chemical change) -the transducer converts this into an electrical signal -this signal is amplified and the reading is shown on the display urea->membrane(enzyme)->product->transducer-> amplifier->display