enzymes

Question 1

Enzymes:

Answer 1

globular proteins with tertiary structure, acting as a biological catalyst. They speed up chemical reactions by lowering the activation energy (Ea). Tertiary structure (3D) provides a specific shape of active site. Needed in small quantities and can be reused.

Question 2

Activation Energy:

Answer 2

minimum energy required to start the reaction, make new bonds in product, break bonds in substrate
▪ Can be lowered by using heating or using enzymes

Question 3

what makes an enzyme specific?

Answer 3

• specific sequence of amino acids in primary structure
• determine the arrangement and the type of R groups
• which determines the type of bonds and interaction between R groups
• Thus in turn, it determine the overall folding and coiling of the polypeptide,
  giving a precise 3D shape ( tertiary structure ) which brings amino acids close together
  So enzymes have specific shape of active site

Question 4

Structure of Enzyme

Answer 4

▪ Globular protein, 3D shape, tertiary structure
▪ Has active and catalytic site
▪ Made up of many amino acid but only few become part of the active site and others become part of catalytic site

Question 5

Protein property

Answer 5

Globular protein

Tertiary structure - provide specific shape

Provides shape of active site where reaction occurs

Influence by temperature and pH at extreme of temperature and pH, they denature

Question 6

Catalytic property

Answer 6

Remains unchanged at the end of reaction/ can be reused

Increases the rate of reaction

Reduces activation energy

specific

Question 7

Site of action of enzymes

Answer 7

All enzymes are proteins that are produced via the process of protein synthesis inside cells , some enzymes remain inside cells, whilst others are secreted to work outside of cells. Enzymes can therefore be intracellular or extracellular, referring to whether they are active inside and outside the cell respectively
▪ Intracellular enzymes are produced and function inside the cell
▪ Extracellular enzymes are secreted by cells and catalyze reactions outside cells ( example: digestive enzymes in the gut). Some organisms secrete enzymes outside their bodies. Fungi, for example, often do this in order to digest the food on which they are growing.

Question 8

Types of enzymes based on metabolic reaction

Answer 8

▪ Catabolic - breaking of large molecules into small
Anabolic- building up of large molecules from small one

Question 9

2 main approaches to investigate if a reaction took place

Answer 9

▪ Disappearance of reactants
Appearance of products

Question 10

How do enzymes catalyze specific reactions? (4m)

Answer 10

Active site has specific shape ( in reference to the active site ) which is complementary to the substrate combine to form enzyme-substrate complex, substrate alters shape of the active site, induced fit. Reference to temporary bonds (Hydrogen, ionic and disulphide)

Question 11

Active site

Answer 11

the site on the surface of enzymes with a particular shape into which only one type of substrate can fit. It is represented by 3-12 amino acids, it consists of R groups which are free to make bonds with substrate

Question 12

Allosteric site

Answer 12

amino acid which is not a part of active site

Question 13

process of ESC

Answer 13

Process
1) Substrate enters the active site: enzyme changes shape such that its
active site enfolds the substrates( induced fit)
2) Substrates held in weak interactions, such as hydrogen bonds and ionic
bonds
3) Active site can lower activation energy and speed up the reaction
4) Substrate is converted to products
5) Products are released
Active site is now available for new substrate

Question 14

Answer 14

Question 15

Answer 15

Question 16

Answer 16

Question 17

How are enzymes soluble in cytoplasm?

Answer 17

Globular proteins, enzyme molecules are coiled into a 3D shape, hydrophilic R groups ( side chains) on the outside of the molecule to make them soluble

Question 18

Substrate

Answer 18

molecules that bind to the enzyme

Question 19

Lock and key hypothesis:

Answer 19

ypothesis for enzyme action, the substrate is a complementary shape to the active site of the enzyme and fits exactly into the site , the enzyme shows specificity to the substrate
▪ Each enzyme will act on only one type of substrate molecule . This is because the shape of the active site will only allow one shape of the molecule to fit. The enzyme is said to be specific for this substrate.

Question 20

The substrate is held together in place by

Answer 20

temporary bonds which form between the substrate and some of the R groups of the enzymes amino acids, the combined structure is called the ES complex.

Question 21

Induced fit hypothesis (more flexible)

Answer 21

a hypothesis for enzyme action, the substrate is a complementary shape to the active site of the enzyme, but not an exact fit - the enzymes or sometimes the substrate can change the shape slightly to ensure a perfect fit, but is still described showing specificity
Mostly same as lock and key hypothesis buy it adds the idea that sometimes the substrate molecules enters the enzyme in order to ensure a perfect fit. This makes the catalysis even more efficient

Question 22

Answer 22

How an enzyme catalyzes the breakdown of a substrate molecule into 2 product molecules

Question 23

Answer 23

Question 24

Answer 24

Question 25

Answer 25

Question 26

Answer 26

an enzyme has a cleft in its surface, called the active site. the substrate molecule has a complementary shape

Question 27

Answer 27

Question 28

Answer 28

Question 29

Answer 29

the interaction of the substrate with the active site breaks the substrate apart . an enzyme-product complex is briefly formed before the two product molecules leave the active site, leaving the enzyme molecule unchanged and ready to bind with another substrate molecule

Question 30

Answer 30

random movement of enzyme and substrate brings the substrate into the active site. an enzyme- substrate complex is temporarily formed. the R groups of the amino acids in the active site interact with the substrate

Question 31

the overall rate of reaction for both locke and key and induced fit is

Answer 31

very high

Question 32

Answer 32

In this example: the enzyme is catalyzing the joining together of 2 molecules

Question 33

factors affecting enzyme action

Answer 33

1)ph
2) enzyme concentration
3) substrate concentration
4) temperature

Question 34

how does ph affect enzyme con

Answer 34

it measures the concentration of H+ in a solution. Most Enzymes work in a narrow range of ph. At Optimum Ph Enzymes show its maximum activity above or below the optimum pH enzyme activity decreases. Change in Ph breaks ionic and hydrogen bond between the R groups, it changes the 3D shape of enzymes. Active site of enzyme is deformed. Substrate can no longer fit into the active site. Reaction of reaction slows down and stops

Question 35

enzyme graph ph

Answer 35

Question 36

Answer 36

Question 37

enzyme con graph

Answer 37

Question 38

Answer 38

As the enzyme con. Increases, there’s an increase in con. After x has
no effect on rate and it remains constant at y, rate becomes plateau

Question 39

describe region A

Answer 39

As the concentration increases , rate of reaction increases gradually at an enzyme con. Of x, the rate of the reaction was its maximum y

Question 40

explain region A

Answer 40

With more enzyme molecules there are more molecules , there are more active site available for the substrate to fit. Many enzyme substrate complex formed/ more product. Limiting factor- enzyme, con. substrate are free

Question 41

describe region B

Answer 41

As the enzyme is above the value of km constant at y

Question 42

explain region B

Answer 42

All the substrate have formed enzyme complex. Enzyme con. Is no longer the limiting factor but the substrate con. Is the limiting factor, active site are free

Question 43

Answer 43

As substrate con. Increases, rate of reaction increases,
After a point there’s an increase in substrate
concentration has no effect on rate and the curve
Reaches a plateau

Question 44

describe region A

Answer 44

As the con. Of the substrate increases, the rate of reaction, gradually increases, after point X, it has no effect on the rate of reaction at y which is at its max

Question 45

explain region A

Answer 45

With more sub molecules of them can fit into the free action sites, more enzyme substrate complex is formed, with more product being formed , rate increases, sub. Con is limiting factor

Question 46

describe region B

Answer 46

As the con. Of substrate increases above X, rate of reaction remains constant at y

Question 47

explain Region B

Answer 47

All the enzymes have formed enzyme substrate complex, substrate con. Is no longer the limiting factor but enzyme con. Is, there are no free active site substrate to bind

Question 48

Answer 48

increase in the temperature increases, the rate of reaction, it reaches
Its maximum optimum temperature, above the optimum temperature,
Above the optimum temperature, the rate of reaction decreases and
Become 0

Question 49

describe region A

Answer 49

As the temperature increases, rate of reaction a, it reaches its max optimum temperature

Question 50

explain region A

Answer 50

Increasing the temperature provides more heat energy, it allows enzyme and substrate to attain more KE. Which helps them to move fast and result in more effective collisions, more Enzyme substrate complex formed, more product formed, rate of reaction increases

Question 51

Describe region B

Answer 51

As the temperature increases above the optimum temperature, rate of reaction decreases and become 0

Question 52

explain region B

Answer 52

As the temperature increases above the optimum. More neat energy is given, KE increases, bond holding the tertiary structure of protein ( Hydrogen bonds and ionic bonds), it changes the 3D shape of enzymes and active site changes shape, substrate no longer fit into the active site. No enzyme substrate complex, no product and enzyme is said to be denatured

Question 53

Michaels Km constant

Answer 53

It is the substrate concentration at which an enzyme works at held its maximum rate( half vMax). It is the measure of affinity of the enzyme for its substrate, at this point held the at the active site of the enzyme is occupied by the substrate

Question 54

Lower the Km value

Answer 54

higher the affinity of the enzyme for its substrate , lower concentration of substrate is required to reach half Vmax

Question 55

Higher the Km value

Answer 55

lower the affinity of the enzyme

Question 56

vMax gives information about the

Answer 56

maximum rate of reaction and Km measures the affinity

Question 57

significance of enzymes

Answer 57

▪ An enzymes performance for its substrates concentration be compared quantitatively
▪ The performance of same enzyme in different organisms can be compared

Question 58

Inhibitor

Answer 58

substances that reduces the rate of the reaction

Question 59

Competitive inhibitor has a similar shape to the substrate

Answer 59

and Complementary to the active site

Question 60

competitive inhibitor

Answer 60

The inhibitor binds with the active site to form an enzyme Inhibitory complex, which stops the substrate from entering The active site, few enzyme-substrate complexes are formed, Initial rate of reaction is low. Increasing the concentration of substrate increases the rate of the reaction

Question 61

Answer 61

Question 62

Non- completive inhibitor

Answer 62

▪ Inhibitors binds with allosteric site, changes the shape
Of the active site, substrate is no longer able to bind with active site,
low vMax, high Km, permanent binding

Question 63

Answer 63

Question 64

End product inhibition

Answer 64

▪ Type of noncompetitive inhibition, when the concentration of products is high It acts as an inhibitor for any enzyme in the sequence, it binds to the allosteric site, when The concentration of product decreases, the enzyme is switched on

Question 65

Turns over number:

Answer 65

number of substrate molecules transformed into products per minute

Question 66

Immobilization of enzyme

Answer 66

Process of retaining/ trapping enzyme to an inert medium

Question 67

types of immobilization enzymes

Answer 67

1) absorption enzymes
2) covalent bonding
3) encapsulation

Question 68

absorption enzymes

Answer 68

surface phenomena where enzymes are attached to the surface of materials like Glass

Question 69

covalent bonding

Answer 69

binding enzyme to cellulose with help of covalent bonding

Question 70

Encapsulation:

Answer 70

encapsuled in a partially permeable membrane which allows substrate to enter and product to leave

Question 71

advantages of immobilization enzymes

Answer 71

1) Product not contaminated, can be collected easily
2) Enzymes can be retained/ reused
3) Longer shelf life
4) Enzymes more stable at higher temperature, extreme pH
Able to obtain more product per time

Question 72

disadvantages of immobilization enzymes

Answer 72

1) Expensive
2) Not efficient
Enzyme at the Centre of bead is less likely to bind with substrates

Question 73

When a substrate with complimentary shape fits into the active site

Answer 73

A temporary hydrogen/ionic/disulphide bond is formed between the R group of the enzymes amino acid and the substrate

Question 74

esc conc over time

Answer 74

starts off high and then falls to zero

Question 75

protease will remove/clean

Answer 75

deposits of enzymes

Question 76

when it comes to inhibitors

Answer 76

look at vmax! (high conc of inhibitor = even
lower ror

Question 77

optimum temp go for a

Answer 77

range

Question 78

ctivation energy required is greater =

Answer 78

ror is reduced or slower!

Question 79

inhibition is involbed in the regulation of

Answer 79

rate of enzyme-catalysed
reactions

Question 80

at the peak of ror,

Answer 80

ionic bonds begin to break

Question 81

product cpnc does not decrease,

Answer 81

it reaches a constant

Question 82

add substrate to compeitive inhibitor —>

Answer 82

ror increases

Question 83

disulphide bonds are the last to

Answer 83

break

Question 84

quarternary also controls the shape of

Answer 84

the active site

Question 85

all 4 protein structures can determine the specificity

Answer 85

of an enzyne and all 4 control the shape of the active site but only primary, secondary and tertiary must be involved in the
formation of an active site

Question 86

if an enzyme gets denatured at 50,

Answer 86

eaction stops before then only tertiary structure is always involved when comp and non comp inhibitor bind to enzymes

Question 87

denaturation does not involve

Answer 87

the primary structure

Question 88

comp inh dont have exactly the same shape as substrate, i

Answer 88

it is just
SIMILAR

Question 89

Enzyme w the lower vmax uses more of the substrate

Answer 89

cuz it has higher
affinity and lower km (draw out a graph)

Question 90

What is meant by specificity of enzyme

Answer 90

Enzyme acts on only one substrate
Shape of active site complementary to substrate

Question 91

How does enzyme lower Ea: activation energy

Answer 91

Provides alternative energy pathway
Brings reactants close together to from ESC
Puts strain on reactant
So bonds break easily
Transfer of charges between groups
Changes orientation such that reaction is feasible

Question 92

How to describe and explain enzyme results (D = description, E = explain)

Answer 92

E - not all active site occupied
E - so substrate concentration is limiting
E - so fewer ESC formed
D - at high concentration less steep increase in rate of reaction
D - it levels out/plateaus at (XYZ) concentration
E - enzyme concentration is limiting
E - since all active sites are occupied/saturated
E - Vmax reached

Question 93

Advantages of enzymes with high optimum:

Answer 93

The production/process requires high temperature
High temperature so more collisions and more ESC
Higher ROR increases
More stable and can be used again and again
Less prone to denaturation
Works well over a range of temperatures and pH so works at higher rate

Question 94

Outline experiment that should be carried out to find out if inhibitor is competitive or non-competitive:

Answer 94

Carry out experiment with and without an inhibitor
At many different concentration of substrates
Keeping other variables constant (eg pH and temp)
Draw a graph of rate of reaction against substrate concentration
If inhibitor is competitive than Vmax is same as without inhibitor

Question 95

Describe mode of action of enzyme with induced fit

Answer 95

Active site changes shape OR moulds around substrate OR better fit
Active site becomes fully complementary to substrate
Formation of ESC
Lowers activation energy
By providing alternate energy pathway/puts strain on bonds
Breaking of bonds
Active site returns to initial stage AND can be reused

Question 96

After XYZ substance/device is used why does enzyme B have a lower Km and why does enzyme C have a higher Vmax

Answer 96

have a higher Vmax
B: increases affinity of enzyme for substrate
B: makes shape of active site more complementary
B: Makes position of active site more accessible
C: increase rate of ESC formed
C: increases rate of catalysis after binding
C: may lower activation energy required than normal

Question 97

Advantages of end-product inhibition when enzyme in intracellular:

Answer 97

Maintains balance
Efficient metabolism
Avoids osmotic problem that could be caused by build up of product

Question 98

Disadvantages of end-product inhibition when the enzyme is used extracellular and commercially

Answer 98

Loss of product
Slow rate of reaction
Product required continuously

Question 99

Why are immobilised enzymes more active over range of pH

Answer 99

Alginate covering is protective so the H+/OH- ions do not penetrate alginate beads so the shape of the active site is not disrupted.

Question 100

Explain what is meant by higher Km

Answer 100

Enzyme has lower affinity for substrate
Needs a higher concentration of substrate to reach Vmax
Less likely to be saturated by substrate

Question 101

Suggest one other advantage of using enzymes obtained from microorganisms, rather than enzymes extracted from barley seeds, in the production of sugar syrups.

Answer 101

easier to extract
idea that microorganisms can be cultured in large quantities and produce large amounts of enzyme
higher rate of reaction
active over a greater temperature range

Question 102

Advantages of immobilised enzymes compared to enzymes in free solutions:

Answer 102

(may be able to) obtain more product (per unit time) ;
can use higher temperatures (to obtain more product) / still active at higher temperatures ; A thermostable
does not denature (as easily as free) if temperatures increase / AW ;
enzyme can be easily recovered ;
downstream processing is easier ;
product, not / less, contaminated ; A less purification needed
longer shelf-life of enzyme ;
reduces product inhibition ;
enzyme is, more stable / less likely to denature or described ; A thermostable / can work at high temperatures A in context of change in pH I ‘can withstand changes in temperature’

Question 103

Explain how the addition of the competitive inhibitor results in the same value for Vmax but a higher value for Km.

Answer 103

Competitive inhibitor occupies the enzyme’s active site / competes with substrate
Reduces frequency of successful collisions / fewer ESC formed
Reduces reaction rate at low substrate concentration
idea that curve with inhibitor is to the right of the curve without inhibitor ;
At high substrate concentration, the effect of inhibitor is reduced
Therefore the Vmax is the same as it is determined by the concentration of enzyme
A explanation in terms of active sites, saturated / fully occupied
idea of intercept to curve gives a higher value for Km ;