Chpater 3; Enzymes

Question 1

Explain what type of protiens are enzymes

Answer 1

Globular proteins,(so roughly spherical, and hydrophilic r groups on outside allows to be soluble)
-most with either tertiary or quaternary structure

Question 2

In which two ways can enzymes be classified and give examples

Answer 2

Intracellular enzymes and extracellular enzymes

Intracellular, are catalase (breaks down hydrogen peroxide into water and oxygen)
and dna polymerase

Extracellular are amalyse (breaks down starch into glucose and maltose)

Question 3

Explain the function of catalase, potential harm and where it is found

Answer 3

An intercellular enzyme that breaks down hydrogen peroxide into water and oxygen,
Bc hydrogen peroxide is a toxic metabolic product in tissues and so, if it builds up it causes damage so needs to be removed

-howver catalase can also be harmful to cells

Found in most living tissues n

Question 4

Explain the function of amalyse and where it is found

Answer 4

Extracellular enzyme that breaks down starch into maltose and glucose.
(Through hydrolysis)

-secreted by the pancreas and salivary glands to function in the small intestine and mouth

Question 5

Explain what gives enzymes their specificity

Answer 5

The active site.
Which is determined by the primary strutcure (specific sequence of amino acids, bonded by covalent peptide bonds)
-only some amino acids in the primary structure howver are catalytic, so not all of them are nvolved in forming te active site

Question 6

Explain the lock and key theory and the induced fit theory

Answer 6

Lock and key theory, that enzyme and substrate have complimentary but rigid and fixed shapes prior to bonding.
Induced fit theory, that the enzyme active site changes shape around the substrate as it enters to become complimentary to it

Question 7

Explain how the induced fit theory works

Answer 7

-Substrate is not entirely complimentary to active site, but active site is partially flexible
-as substrate enters the a active site, r groups on the active site interact with the substrate
-this puts strains on the bonds and so makes ot easier to form or break bonds, therfore lowering activation energy
-The enzyme and substrate now have a better fit and an enzyme substrate complex is formed

Question 8

What are important factors that influence a successful collision of substrate with an enzyme

Answer 8

-must be at right orientation
-must collide with enough energy

Question 9

Explain anabolic and catabolic reactions and give examples of each

Answer 9

Anabolic, using smaller molecules to make more complex molecules.
Eg protein synthesis and photosynthesis

Catabolic, breaking down complex moleucles into simpler molecules.
Eg hydrolysis and respiration

Question 10

Definition of activation energy

Answer 10

Energy required by a substrate to become just unstable enough for a reaction to occur and for products to form.

Question 11

What is the role of enzymes in terms of activation energy

Answer 11

They lower the activation energy by proving an alternative route,
Bc destabilize bonds in the substrate
So bonds can therfore be broken or made more easily and so
Reaction can occur more easily

Question 12

Explain how the formation of enzyme substrate molecules changes with temperature

Answer 12

As temperature increases
Enzymes have more kinetic energy
Therfore the frequency of successful collisions increases between substrate and enzyme active site
So more enzyme substrate molecules formed

Question 13

Explain the effect of very high temperatures on enzyme substrate formation

Answer 13

Very high temp causes hydorgen and ionic bonds in the tertiary structure to break
-so tertiary structure changes and so the active site shape changes
-active site permantly damaged and no longer complimentary to the substrate
-so substrate can no longer bind to active site and so less enzyme substrate complexes formed

Question 14

Explain how high ph can affect eznyme substrate formation

Answer 14

The h plus ions interact with the r groups of amino acids on the enzyme tertiary structure
So hydorgen and ionic bonds which hold tertiary structure together begin to break
Active site changes chape
Active site no longer complimentary to substrate
So less enzyme substrate complexes are formed

Question 15

Explain the graph for substrate concentration, given that the enzyme concentration remains constant.

Answer 15

As substrate concentration increases higher the rater of reaction
Bc the higher the likelihood of enzyme substrate complexes forming
Howver at a certain point, all enzymes active sites become saturated, (as enzymes become a limiting factor)
So therfore an increase in substrate concentration will not increase the rate of reaction because substrates will have nowhere to bind

Question 16

Explain the graph for enzyme concentration rate of reaction, given that the substrate concentration remains fixed

Answer 16

As enzyme concentration increases, rate of reaction increases,
This is because more active sites for substrate to be able to bind to
\so frequency of successful collisions between enzyme active site and substrate therefore increases
So more enzyme susbatrets complexes formed

Howver at a certain point substrate concentration becomes a limiting factor
So less enzyme substrate complexes formed and reaction levevels off

Question 17

Explain what the Michaelis menton constant is (Km), in terms of wo definitions

Answer 17

The substrate concentration at which an enzyme can function at half its maximum velocity
(So is equivalent to 1/2 max)

Or is a measure of affinity of an enzyme for its substrate

Question 18

Explain what a lower Km values means in terms of affinity

Answer 18

Low km means higher affinity,
Because this means that it requires less substrate to reach 1/2 max
So therfore more enzyme susbatre complexes are able to be formed in the same amount of time
So enzyme has a higher affinity (and so a better fit for its substrate)

Question 19

Explain what a higher km value means in terms of affinity

Answer 19

Higher km means lower affinity,
This is because it requires more substrate to reach half vmax
Therfore less enzyme substrate complexes formed in the same amount of time
S enzyme has a lower affinity (so a worse fit for its substrate).

Question 20

Difference between competitive inhibitors and non competitive inhibitors

Answer 20

Competitive inhibitors,
-have a similar shape to the substrate
-and bind to enzymes active site
-so compéte with substrate for the active site
-the effect of these on the rate of reaction can be reversed

Non competitive inhibitors
-do not have a similar shape to the substrate
-and bind to the allosteric site (not the active site)
-this disrupts hydrogen a bonds and hydrophobic interactions in tertiary structure and also changes active site and so enzyme no longer complimentary to the active site
-the effect of these on an enzyme can be either irreversible or reversible (end product inhibition)

Question 21

Explain what happens to the rate of reaction when inhibitor concentration is more than substrate concentration

Answer 21

Rate of reaction decreases
Because as inhibitor concentration becomes more than substrate concentration,
Due to the inhibitor being same shape as substrate,inhibitor begins to outcompete substrate
-so binds to active site temporarily
-which reduces the chances of substrate colliding and binding to the active site
So therfore less enzyme substrate complexes are formed

Question 22

Explain how the role of competitive inhibitors on the rate of reaction can be reversed

Answer 22

If substrate concentration increases and becomes more than inhibitor concentration.
Bc substrates outcompetes the inhibitor for the enzyjme active site
So more chance of substrate colliding with enzyme active site
So frequency of enzyme substrate complexes forming increases

Question 23

Explain how irreversible non competitive inhibitors affect the rate of reaction

Answer 23

-they bind to the allosteric site of the enzyme
-this disrupts the active sites shape by disrupting hydorgen and hydrophobic interactions within the tertiary structure
-3d shape of enzyme is therfore affected
-and substrate can no longer bind to the active site
So the enzyme function is therfore inhibited

Question 24

For both competitive and non competive (irreversible) inhibitors,
State how vmax and km changes

Answer 24

For competitive
-vmax stays the same
-but km would be higher, so lower affinity

For non competitive,
-vmax is lower w the use of an inhibitor
-but km so affinity would remain the same

Question 25

Explain how vmax is affected in terms of using competitive inhibitors

Answer 25

-vmax remains the same
This is because this occurs at high substrate concentrations
-where the competitive inhibitor will no longer have an effect on the reaction because this substrate will be outcompeting the inhibitor for the enzymes active site

Question 26

Explain how km is affected when using a competitive inhibitor

Answer 26

Km is more, so a lower affinity
This is because both inhibitor and substrate are competing for the enzymes active site
Therefore a higher substrate concentration is required to reach the same 1/2 vmax(which is same as km)

Question 27

Explain how km is affected when using an irreversible non competitive inhibitor

Answer 27

-km remains the same, so the enzyme has the same affinity,
-although due to the competive inhibitor changing the enzymes active site
There are less enzymes with functioning active sites
-however for the enzymes active sites which have not yet beeen altered they function as normal so have the same affinity for the substrate
so require same amount substrate concentration to reach 1/2 vmax

Question 28

Explain how vmax is affected when using a irreversible non competive inhibitor

Answer 28

Vmax is decreased
-bc inhibitor disrupts the active site of the enzyme
So less enzymes available w functioning active sites
-so therfore a lower vmax, bc this is dependant upon the concentration of enzymes available

Question 29

Explain the role of end product inhibition, and give an example of this occurring

Answer 29

Role is to act as a control for metabolic reactions inorder to maintain homeostasis (so ensure that no single enzyme continually generates too uch or too less of a particular product )

Eg is lactose, which has end product inhibition to ensue that too much of alpaca glucose is not produced bc this build up of monosaccharide could have osmotic effects

Question 30

Explain how end product inhibition occurs

Answer 30

An enzyme and substrate form an enzyme susbatrte complex
This then acts as a substrate for another enzyme and process relates
Eventually when the concentration of final product produced is high,
The end product can act as a non competive inhibitor
-can bind to allosteric site of original enzyme and change active site
So prevent formation of further e.s complexes
-end product can then later detach from enzyme
Enzyme will return to its original shape
And continue to catalyze reaction again

Question 31

State 4 properties of the materials that immobilized enzymes are surrounded by

Answer 31

Inert
Not toxic
Stationary
insoluble

Question 32

Explain how to encapsulate enzymes inside alginate

Answer 32

Add enzymes to sodium alginate
Add drop wise to calcium chloride to form the beads
Pack beads into a column, with mesh at bottom
Run substrate over immobilized enzymes and then collect product

Question 33

Explain the process of converting milk into lactose free milk using immobilized enzymes

Answer 33

Immobilized the enzyme lactase using alginate, to form alginate beads
-pass lactose (milk) through colum of alginate beads containing the enzyme lactase
-lactase will hydrolyze the lactose into glucose and galactose

Question 34

Explain three advantages of using immobilized enzymes

Answer 34

-enzymes can be reused bc they’re separate from the product, and this is cost effective and efficient
-products are uncontaimanted bc enzymes are separate from the product, so no further processing required
-end product inhibition is prevented bc enzymes are separate from th products

Question 35

Explain why immobilized enzymes have a greater tolerance to ph change

Answer 35

Because due to the alginate protecting the enzyme
It is less exposed to the solution
So h plus ions and oh ions less able to penetrate through into the beads
So shape of active site of enzymes are less disrupted

Question 36

Which bonds in the tertiary structure are involved in dénaturation of enzymes
And which bonds in tertiary strutcure are diruspted when an irreversible non competive inhibitor is present

Answer 36

Hydorgen bonds and ionic bonds.
Hydgen bonds and weak hydrophobic interactions

Question 37

Explain why immobilized enzymes have a grater tolerance to temperature

Answer 37

Because the immobilization stabilizes the 3d structure
So hydrogen bonds are less likely to vibrate at higher temperatures
So therfore fewer bonds within the enzyme breaks
So active site is less Leila to change
So less dénaturation