4 - Enzymes

Question 1

amylase and trypsin catalyse extracellular reactions
t/f

Answer 1

true
extracellular- work outside of the cells that made them (like in digestion)
amylase- breaks down starch into maltose
trypsin- catalyses digestion of proteins into smaller peptides

Question 2

catalase catalyses intracellular reactions t/f

Answer 2

true
intracellular- enzymes that act within the cells
breaks down hydrogen peroxide into oxygen and water

Question 3

what does Zn 2+ act as a prosthetic for

Answer 3

carbonic anhydrase

Question 4

Which of the following, A to D, is true of a competitive enzyme inhibitor?
A binds to a site other than the active site
B can bind irreversibly to the active site
C changes the shape of the active site
D effects can be overcome by adding more substrate

Answer 4

D is true
A - that is non competative
B - there effect is reversible
C - it blocks the substrate from binding to the active site
D - yes

Question 5

definition of the term coenzyme

Answer 5

A non-protein organic molecule, not permanently attached to an enzyme, but needed to allow the
enzyme to function.

Question 6

13. A chemical produced by a metabolic pathway binds to the initial enzyme in the pathway. The chemical
    binds to the enzyme at a site away from the active site and inhibits the enzyme action.
    Which of the following statements about the mode of action of the chemical is / are correct?

Statement 1: It is an end product inhibitor.
Statement 2: It is a competitive inhibitor.
Statement 3: It binds to the allosteric site of the enzyme

Answer 6

1 and 3

Question 7

. Zinc ions are necessary for the enzyme carbonic anhydrase to work.
Which statement correctly describes the nature and function of zinc ions in their interaction with carbonic
anhydrase?
A. inorganic ions and coenzymes
B. vitamins and prosthetic groups
C. inorganic ions and prosthetic groups
D. vitamins and coenzyme

Answer 7

C
zinc is inorganic as it is obtained by the diet as minerals
prosthetic groups- they are cofactors that are require to by he enzyme to carry out certain functions (a permanent feature of the enzyme)

Question 8

17. Which of the following factors does not affect the shape of the active site of an enzyme?
    A a drop in temperature
    B non-competitive inhibitor
    C a change in pH
    D binding of substrate

Answer 8

A
B-binding of it to allosteric site change the tertiary shape
C- pH does affect shape
D - induced fit model

Question 9

19. Which inorganic ion can act as a cofactor for amylase?
    A OH−
    B PO43−
    C Cl−
    D HCO3-

Answer 9

C
amylase (catalyses the breakdown of starch) contains Cl- which is important for the formation of the correct active site

Question 10

The haem molecule bound to each polypeptide
chain of catalase
suitable term?

Answer 10

prosthetic group

Question 11

Binding of the hydrogen peroxide substrate to
catalase causes a change in the shape of the
active site of catalase.
suitable term?

Answer 11

Induced fit

Question 12

Cyanide ions decrease the action of catalase even
at high concentrations of hydrogen peroxide

Answer 12

non-competitive inhibition

Question 13

. Which of the statements about enzyme catalysed reactions is true?

A Binding of a substrate to the active site can weaken bonds in the substrate.
B Enzymes allow reactions to happen at a rate faster than the Vmax.
C Enzymes increase the rate of reactions by increasing the activation energy.
D Every 10 °C increase in temperature will approximately double the rate of all enzyme controlled
reactions

Answer 13

A
B- that’s just mad
C- Ea is decreasing bozo
D- nah cuz denaturation is a thing

Question 14

Enzymes are proteins which speed up the rate of biological reactions. They form an
1……………………………………………………………… by binding to their substrate at a site known as
the.2…………………………………………………………….. . This site has a specific shape created by
the 3…………………………………………………………….. structure of the protein molecule. This
means that each enzyme can bind to only one type of substrate molecule.
This is explained by the lock and key hypothesis. In an alternative hypothesis, the binding site
changes shape to fit more closely around the substrate molecule. This is called the
.4……………………………………………………………… hypothesis. This hypothesis can help to
explain how enzymes enable reactions to occur at lower temperatures by reducing the
.5……………………………………………………………… required for the reaction to occur

Answer 14

enzyme–substrate complex
active site
tertiary
induced fit
activation energy

Question 15

. There are two models for the mechanism of enzyme action. Outline how changes in
temperature can affect these mechanisms of lipase action

Answer 15

enzyme action
1 enzyme‐substrate complex formed
2 enzyme‐product complex formed
3 product(s) leave the active site
4 lock and key = shape of substrate and
enzyme’s active site are complementary and
so enzyme is specific
5 induced fit = enzyme active site changes
shape to accommodate substrate once
substrate binds

effect of temperature
reactants
6 increase in temperature increases kinetic
energy of molecules
7 results in more successful collisions
8 more enzyme‐substrate complexes form
9 decrease in temperature reduces kinetic
energy of molecules
10 results in fewer successful
collisions11 fewer enzyme‐substrate
complexes form
active site
12 enzymes have an optimum temperature
13 (small) increase in temperature affects
the bonds involved in tertiary structure
14 change in shape of active site
15 prevents substrate binding to active site
16 high temperature results in denaturing
17 effects of high temperature are
irreversible
18 effects of low temperature are reversible

Question 16

. Amylase activity is increased in the presence of chloride ions.
State the name given to any inorganic ion that increases the activity of an enzyme.

Answer 16

cofactor

Question 17

Catalase is an intracellular enzyme with an iron-containing haem group.
i. State the term used to describe an ion that is essential for the enzyme to function.

Answer 17

cofactor / prosthetic group

Question 18

Name another conjugated protein apart from catalase hat contains a haem group

Answer 18

haemoglobin / myoglobin /
cytochrome

Question 19

what are enzymes?

Answer 19

• enzymes catalyse reactions and lower activation energy
• biological catalysts
• globular proteins that interact with a substrate

Question 20

anabolic reactions

Answer 20

building up reactions
-> synthesising large polymer based components

Question 21

example of anabolic reactions

Answer 21

cellulose and contractile filaments

Question 22

what is metabolism

Answer 22

sum of all the different reactions and reaction pathways within a cell of organism
- enzymes allow for metabolism

Question 23

what is Vmax

Answer 23

maximum initial velocity or rate of the enzyme-catalysed reactions

Question 24

what must happen for a reaction to occur

Answer 24

• molecules need to collide with the right orientation
• sufficient energy (Ea)
• correct enzyme and substrate colliding

Question 25

explain lock and key

Answer 25

• only a specific substrate will fit the active site of an enzyme
• when the substrate is bound it is called the enzyme-substrate complex
• the enzyme-product complex is when the substrate react and the products form
  -> the substrate is held in a way so that the atoms-groups are close to react. The r-groups of the active site interact with the substrate forming temporary bonds. this puts a strain on the bonds in the substrate
• the products leave and the enzyme remains unchanged

Question 26

what is the active site

Answer 26

an area within the tertiary structure of the enzyme that is complementary to the shape of a specific substrate molecule

Question 27

what is the induced fit hypothesis

Answer 27

• the active site changes shape as the substrate entres
• the initial interaction between the enzyme and the substrate is weak, but the weak interactions induce changes in the enzymes tertiary strucute that strengthen binding, putting a strain on the substrate

Question 29

competitive inhibition

Answer 29

• a molecule with a similar shape to the active site binds to the enzyme
• this blocks the substrate molecule from entering the active site and preventing the enzyme catalysing the reaction
• enzyme is inhibited
• the non-substrate molecule is a inhibitor and competes with the substrate

Question 30

what happens if u increase substrate in competitive inhibition
- how does competitive inhibitor effect Vmax

Answer 30

• so much more substrate than inhibitor so Vmax can be reached
• inhibitor doesn’t affect Vmax

Question 31

non competitive inhibition

Answer 31

• inhibitor binds to the allosteric site
• this causes the tertiary structure of the enzymes to change therefore so does the active site
• the substrate can no longer bind as the active site isn’t complimentary to it.
• cant catalyse the function

Question 32

examples pf competitive inhibition

Answer 32

Statins - are competitive inhibitors of an enzyme used in the synthesis of cholesterol. it helps to reduce

Aspirin - irreversibly inhibits the active site of COX enzymes , preventing the synthesis of prostaglandins and thromboxane (responsible for producing pain and fever)

Question 33

examples of irreversible non-competitive inhibitors

Answer 33

Organophosphates- used in insecticides and herbicides inhibit acetyl cholinesterase which is responsible for nerve impulse ACH

Proton

Question 34

general definition of cofactor and coenzyme, how are they different- and give examples

Answer 34

a non-protein helper component that helps carry out their function as biological catalysts

Cofactors- inorganic molecule obtained via the diet as minerals. Such as iron, calcium, and zinc ions.

-> amylase is a enzyme wit an inorganic cofactor- it contains a chloride ion necessary for correct shape of the active site

Coenzymes - the non-protein component is an organic molecule derived from vitamins.

-> vitamin B3 is used to synthesis NAD. NADP is also derived from vitamin B3

Question 35

what is a prosthetic group

Answer 35

tightly bound and a permanent cofactors of the enzyme

e.g FZE in haemoglobin and Zn2+ in carbonic anhydrase

Question 36

what is end-product inhibition

Answer 36

• when the product of ta reaction acts as an inhibitor to the enzyme that produces it

-it serves as a negative feedback control mechanism for the reaction (excess products are not made and resources are not wasted)

Question 37

steps of the respiration pathway as an example of end-product inhibition

Answer 37

• addition of two phosphate groups to the glucose molecule
• the addition of the second is catalysed by the enzyme phosphofructokinase (PFK)
• PFK is competitively inhibited by ATP
  -> when AATP is high, more ATP binds to allosteric site of PFK and prevents the addition of the second phosphate to the glucose, therefore preventing the breakdown of glucose. and vice versa

Question 38

what are inactive precursor enzymes
what is the point?
how do they work?

Answer 38

• enzymes that are produced in an inactive form
• to prevent damage within the cells producing them or the tissues where they are released
• precursor enzymes need to undergo a change in their tertiary structure to become active (particularly the active site).
  -> this can be done by adding a cofactor
  -> or a change in temp or pH
  -> or by the action of another enzyme

Question 39

what is an apoenzyme

Answer 39

a precursor enzyme that is yet to be activated by the addition of a cofactor

Question 40

what is a holoenzyme

Answer 40

when a cofactor is added to a precursor enzyme and it becomes activated it becomes a holoenzyme