enzymes

Question 1

name 8 features of enzymes

Answer 1

• they act as biological catalysts (not used up in a reaction)
• all enzymes are globular proteins
• enzymes posses an active site and can form enzyme substrate complexes
• enzymes can catalyse forward or backward reactions (reversible)
• enzymes can remain unchanged by the reaction they catalyse
• only a very small number of enzyme molecules are needed
• enzymes can be inhibited
• enzymes may be denatured

Question 2

know the role of amino acids in enzymes

Answer 2

Enzymes are proteins comprised of amino acids linked together in one or more polypeptide chains. This sequence of amino acids in a polypeptide chain is called the primary structure. This, in turn, determines the three-dimensional structure of the enzyme, including the shape of the active site.

Question 3

what do many enzymes end in

Answer 3

ase
- E.g. catalyse, maltase

Question 4

what part fits into the active site of an enzyme

Answer 4

the substrate

Question 5

what are the two enzyme fit theories

Answer 5

• lock and key
• induced fit theory

Question 6

intracellular enzyme action

Answer 6

inside the cell

Question 7

what do enzymes do

Answer 7

they speed up the rate of reaction by being catalyst, by reducing the activation energy

Question 8

what does catalyse break hydrogen peroxide down to

Answer 8

oxygen and water

Question 9

what is extracellular enzyme action

Answer 9

the enzyme, is used outside of the cell it was made

Question 10

what is the structure of globular proteins

Answer 10

hydrophobic amino acids surrounded by hydrophilic amino acids
- remember this is why they are soluble in water

Question 11

what is the enzyme substrate complex

Answer 11

The enzyme substrate complex is a temporary molecule formed when an enzyme comes into perfect contact with its substrate

Question 12

what do we call the active sites bond to the substrate

Answer 12

specific/complementary fit

Question 13

why is the activation energy important

Answer 13

it must be reached in order for a reaction to take place, in order to form a product

Question 14

what does the tertiary structure do in order to form the active site?

Answer 14

it folds, in order to form a three dimensional shape

Question 15

what has to happen, in order to produce product

Answer 15

the a substrate must successfully react with the active site.

Question 16

what dictates the rate of an enzyme controlled reaction

Answer 16

the frequency of successful collisions between the substrate molecules and the active site

Question 17

why is temperature important, in enzyme controlled reactions

Answer 17

to high a temperature will lead to the enzyme denaturing due to there being to much kinetic energy causing vibrations, that would sperate the tertiary structure bonds, whilst too low of a temperature would mean that there would be a to little kinetic energy, resulting in a low rate of reaction

Question 18

what happens at the optimum temperature

Answer 18

we have the maximum frequency of successful collisions between the substrate and the active site

Question 19

can we reactivate denatured enzymes

Answer 19

NO

Question 20

how do we work out Q10 and what value is Q10 normally

Answer 20

it is normally a value of around 1, but only below the optimum temperature of the enzyme

Question 21

how can we contour act the impact of a competitive inhibitor

Answer 21

by increasing the substrate concentration

Question 22

how does one, lower the activation energy

Answer 22

by using enzymes ( as a biological catalyst)

Question 23

• what is the equation for initial rate
  and
• how is calculated

Answer 23

• change in y/ change in x
• by drawing a tangent at time= zero

Question 24

why does increasing enzyme concentration increase rate?

Answer 24

• more active sites available
• more frequent collisions
• more enzyme substrate complexes formed
• greater rate, due to more product being formed per second

Question 25

what is a control variable

Answer 25

A control variable is anything that is held constant or limited in a research study

Question 26

effect of increasing substrate concentration

Answer 26

- more successful collisions (between active site and substrate - more enzyme substrate complex's formed - greater rate, due to more product being made per second

Question 27

what is a buffer

Answer 27

chemicals, that are resistant to a change in pH

Question 28

what doe enzyme inhibitors do?

Answer 28

reduce the rate of enzyme controlled reactions because they have an effect on enzyme molecules

Question 29

what is a competitive inhibitor

Answer 29

mostly reversible and if binding irreversibly they are called inactivators

Question 30

what are 3 key things about competitive inhibitors

Answer 30

- have close structural resemblance to substrate of enzyme - compete with substrate for active site - increasing substrate conc, relative to inhibitor conc, then the initial rate increases

Question 31

give one example of a competitive inhibitor

Answer 31

statins, a drug used to treat coronary heart disease

Question 32

what is a non - competitive inhibitor

Answer 32

does not compete for the active site it has equal affinity (willingness to bind) for the enzyme and enzyme substrate complex

Question 33

what are the 5 key things about non - competitive inhibitors

Answer 33

- it has no structural similarity to the substrate - combines with enzyme at a point other than active site (allosteric active site) - active site becomes distorted (substrate no longer fits) - when inhibitor saturation is reached the rate of reaction is almost nil - increasing substrate conc will not affect the rate of reaction

Question 34

what is a key thing to remember with non - competitive inhibitors

Answer 34

- increasing the substrate concentration, does not increase the reaction rate.

Question 35

what is an anabolic enzyme

Answer 35

the building up/ synthesis

Question 36

what is a catabolic enzyme

Answer 36

the breaking down/degradation

Question 37

what is the general enzyme equation

Answer 37

Enzyme + Substrate ↔ Enzyme Substrate Complex ↔ Enzyme Product Complex ↔ Enzyme + products

Question 38

what is a prosthetic group

Answer 38

tightly bound to an enzyme permanently, often contains metal ions

Question 39

what are inorganic ions

Answer 39

not permanently bound to the enzyme, may bind temporarily to either the enzyme or the substrate

Question 40

what is a coenzyme

Answer 40

they bind to the active site, for short periods of time, before or at the same time as the substance they are **organic, non - protein molecules**

Question 41

what are respiratory enzyme responsible for

Answer 41

the breakdown of glucose and the formation of ATP

Question 42

phosphorylases act in cytoplasm

Answer 42

phosphorylates, add phosphate groups to glucose, to keep it in the cell + make it more reactive.

Question 43

decarboxylases and dehydrogenase act in the matrix of the mitochondria

Answer 43

aerobic respiration - decarboxylases remove carbon dioxide from a molecule and dehydrogenates remove H from a molecule

Question 44

what makes ATP

Answer 44

ADP + PI -> ATP

Question 45

suggest the advantages of having an internal digestive system compared with secreting enzymes outside the organism

Answer 45

- extracellular enzyme, secreted outside of an organism are lost to the environment - internal environment, can be regulated, to give optimum conditions.

Question 46

how do **enzymes** lower activation energy

Answer 46

- by orientating molecules, so that reacting bonds are near to each other - R groups, on the enzyme may donate or accept electrons, for oxidation/ reduction reaction. - water, may be excluded from the reaction, due to the hydrophobic R groups in the active site, this creates more favourable conditions for the reaction

Question 47

know how to measure the rate of enzyme controlled reactions

Answer 47

Question 48

what is the calculation to work out initial rate of reaction

Answer 48

rate = change in Y/ change in X

Question 49

why is enzyme concentration, usually relatively low, in cells

Answer 49

- enzyme can be reused - genes for enzymes can be switched on if required

Question 50

why must we keep pH and Temperature, constant when investing the rate of reaction, when changing the enzyme concentration

Answer 50

- only changing the enzyme concentration - control Ph using a buffer - controlled temp, by using a thermostatically controlled water bath.

Question 51

what happens, when we increase the substrate concentration

Answer 51

- more successful collisions between active site + substrate - more enzyme substrate complexes' - more product made per second - greater rate

Question 52

what is Vmax

Answer 52

the maximal reaction rate or velocity of an enzymatically catalyzed reaction when the enzyme is saturated with its substrate.

Question 53

reversible inhibitors

Answer 53

- most competitive inhibitors do not bind permanently to the active site - they bind for short periods and then leave - removal of inhibitor from a reaction mixture, leaves enzyme molecule unaffected

Question 54

irreversible inhibitors

Answer 54

- many non - competitive inhibitors bind permanently to enzyme molecules - inhibition cannot be reversed an any molecules bound by the inhibitor are inactivated. - **inhibition is not always a bad thing, as it can help to control metabolic reactions**

Question 55

what is one thing to note about inhibition

Answer 55

**inhibition is not always a bad thing, as it can help to control metabolic reactions**