2.4)Enzymes

Question 1

what are enzymes?

Answer 1

biological catalysts that speed up the rate of metabolic reactions without being used up

Question 2

what type of proteins are enzymes?

Answer 2

globular

Question 3

how do enzymes work?

Answer 3

interact with substrate mol. to form enzyme substrate complex (ES)

Question 4

what is the turnover number?

Answer 4

number of reactions that an enzyme can catalyse in one second

Question 5

what is a difference between chemical catalysts and enzymes?

Answer 5

-they can work at lower temp, neutral pH + lower press
-more specific than chemical catalysts

Question 6

what effects do gene mutations have on enzymes?

Answer 6

-alter the AA sequence of a protein
-alter the enzymes tertiary structure
-prevent enzyme from functioning

Question 7

what can a deficiency in enzymes cause?

Answer 7

metabolic disorder

Question 8

what is an active sight?

Answer 8

indentation or cleft on the surface of the enzyme consisting of about 6~10 AA

Question 9

what structure does the active sight have?

Answer 9

tertiary

Question 10

why is the tertiary structure of the active sight crucial?

Answer 10

-shape is complementary to the shape of the substrate binding to it

Question 11

why are enzymes specific?

Answer 11

the active sight is complementary to the substrate

Question 12

how to enzymes affect the activation energy ?

Answer 12

lowers the activation energy to get the reaction started

Question 13

what is the activation energy?

Answer 13

minimum energy to start a reaction

Question 14

what are intracellular enzymes?

Answer 14

-act within cells
-structure and function of cells

Question 15

what are the 3 pathways that intracellular enzymes take?

Answer 15

-metabolic
-anabolic
-catabolic

Question 16

what is the metabolic pathway?

Answer 16

each step catalysed by a different enzyme

Question 17

what is the anabolic pathway?

Answer 17

large mol. synthesised from small mol.

Question 18

what is the catabolic pathway?

Answer 18

large mol. broken down into smaller mol.

Question 19

what is one product of metabolic pathways?

Answer 19

hydrogen peroxide

Question 20

which enzyme breaks down hydrogen peroxide?

Answer 20

catalase

Question 21

how does catalase protect the cell from damage from reactive oxygen?

Answer 21

breaks it down into water + oxygen

Question 22

what are extracellular enzymes?

Answer 22

work outside the cell

Question 23

what is one type of the extracellular enzymes?

Answer 23

-digestive enzymes secreted from the cells lining the alimentary canal in the lumen of the gut
-digest large mol. (fat,protein + starch)
-absorbed into the bloodstream

Question 24

what are 2 types of digestive enzymes?

Answer 24

-amylase
-trypsin

Question 25

how do enzymes that work outside of the body work?

Answer 25

-release enzymes into their immediate surroundings
-breakdown large mol. into smaller mol.
-absorbed by cell

Question 26

what is a cofactor?

Answer 26

small non protein mol. that attaches to an enzyme

Question 27

what are cofactors for?

Answer 27

ensure that an enzyme catalysed reaction takes place at an appropriate rate

Question 28

what is a prosthetic group?

Answer 28

cofactor that is permanently bound with covalent bonds to an enzyme

Question 29

what is the prosthetic group in carbonic anhydrase?

Answer 29

zinc ion

Question 30

where is carbonic anhydrase found?

Answer 30

erythrocytes

Question 31

what reaction does carbonic anhydrase catalyse?

Answer 31

interconvention of CO2 + H2O to carbonic acid

Question 32

why is the catalytic reaction of carbonic anhydrase imporatant?

Answer 32

allows CO2 to be carried in the blood from respiring tissue to the lungs

Question 33

what hormone is zinc an important cofactor for?

Answer 33

polypeptide hormone into insulin

Question 34

can cofactors also be ions?

Answer 34

yes

Question 35

what type of bond is there between cofactors and substrate?

Answer 35

temporarily bound

Question 36

what effect do cofactors have on substrate on substrate mol.?

Answer 36

-ease the formation of the ES
-increase the rate of the enzyme catalysed reaction

Question 37

chloride ion is a cofactor for which enzyme?

Answer 37

amylase

Question 38

what are coenzymes?

Answer 38

small organic non proteins that bind temporarily to the AS

Question 39

what happens to coenzymes during chemical reaction?

Answer 39

chemically changed and need to be recycled to their original state

Question 40

what is the difference between a prosthetic group and a coenzyme?

Answer 40

prosthetic group bind permanently to enzyme, a coenzyme binds temporarily

Question 41

what effects can increased temperatures have on enzymes?

Answer 41

denature them

Question 42

what happens to the Ea when the substrate binds to the active sight?

Answer 42

-lowers the Ea

Question 43

what happens when there is a low Ea?

Answer 43

-⬆️ number of collisions
-speed up metabolic reactions

Question 44

what are the 2 hypothesis’ of the formation of an ES-complex?

Answer 44

1) lock & key
2) induced fit

Question 45

explain the lock & key hypothesis

Answer 45

-substrate fits into the AS like a key into a lock
-substrate held in way that the right atom groups are close enough to react
-R-groups react= form H bonds= ES-complex
-substrate mol. broken into smaller product mol. –> leave AS

Question 46

what type of energy do the enzyme + substrate have?

Answer 46

kinetic energy

Question 47

as the enzyme + substrate have KE, what does this cause?

Answer 47

-constantly moving
-2 mol. collide= ES-complex
-substrate mol. broken or built up to form= enzyme product complex
-product leaves AS = enzyme binds to another substrate mol.
-form another ES-complex

Question 48

who introduced the induced fit hypothesis?

Answer 48

Daniel Koshland

Question 49

what did the induced fit hypothesis suggest?

Answer 49

-substrate enters the AS
-induces a slight change in shape
-AS moulds itself around the substrate =good fit
-R-groups change shape slightly

Question 50

in an induced fit why is the conformation more precise?

Answer 50

R-groups change shape

Question 51

where is the ES-complex formed?

Answer 51

where the H bonds, ionic bonds, hydrophobic interactions + van der waals forces bind the substrate to the AS

Question 52

what happens when the product is released from the induced fit?

Answer 52

-has a slightly diff shape to the substrate
-detaches from the AS
-enzyme is free to bind to another substrate mol.

Question 53

what happens when a mixture of enzyme + substrate is heated?

Answer 53

-both mol. gain KE
-⬆️ number of collisions
-⬆️ rate of ES-complexes
-until the optimum temp

Question 54

what does increasing the temp cause to the bonds?

Answer 54

-mol. vibrate faster
-weaker bonds break
-H bonds + ionic bonds hold the tertiary structure together
-vibrations ⬆️= AS begins to change shape
-⬆️ temp even more= AS has irreversibly changed shape= no longer complementary
-denatured

Question 55

what does it mean when the enzyme has denatured?

Answer 55

-AS has completely changed shape
-no longer complementary

Question 56

which bonds break when the enzyme becomes denatured?

Answer 56

-tertiary bonds BREAK
-peptide bonds DO NOT break= primary structure is not altered

Question 57

what does the optimum temp mean?

Answer 57

temp at which the ROR is the highest

Question 58

why are some enzymes stable at really high temps?

Answer 58

-more disulphide bonds
-dont break with heat
-keep the shape of the tertiary structure

Question 59

how to calculate rate of reaction?

Answer 59

1/ time taken to reach end point

Question 60

what is the temperature coefficient Q10/

Answer 60

measure of how much the R.O.R increases with a 10C rise in temp

Question 61

what is the equation for Q10?

Answer 61

R.O.R at (T + 10C) / R.O.R at TC