2 Enzymes

Question 1

Proteins constitute about _% of the total dry weight of typical plant cells

Answer 1

30

Question 2

If we exclude inert materials, such as the cell wall and starch, which can account for up to _% of the dry weight of some cells, proteins and amino acids represent about _to _% of the dry weight of the living cell

Answer 2

90

60- 70

Question 3

• major function of proteins in metabolism is to serve as _,
• biological catalysts that greatly increase the rates of biochemical reactions

Answer 3

enzymes

Question 4

Enzymes have been called the “_”

Answer 4

agents of life

since they control
almost all life processes

Question 5

Enzymes AKA

Answer 5

biological catalysts

Question 6

first step in enzyme catalysis is the formation of a tightly bound, noncovalent complex
between the enzyme and the substrate(s)— _

Answer 6

the enzyme–substrate complex

Question 7

enzymes will convert about a _ molecules of substrate to product in 1 s

Answer 7

thousand

some will convert as many as a million

Question 8

enzymes do not change the position of the chemical equilibrium but rather _ the reaction rate

Answer 8

increase

large protein molecules that increases the rates of chemical reaction without
themselves undergoing change by 10^9
to 10^20 times

Question 9

Enzyme as catalyst are extremely specific, that is, each of them
speeding up only _ particular reaction or class of reactions

Answer 9

one

Question 10

protein-degrading enzyme of the stomach and its optimum pH

Answer 10

pepsin

a pH optimum around 2.0

Question 11

• – from hyperthermophilic (“extreme heat-loving”) archaebacterium Pyrococcus furiosus*;
• oxidizes H2 at a temperature optimum greater than 95^0C;
• the presence of this enzyme in Pyrococcus enables them to grow optimally at 100^0C

Answer 11

hydrogenase

Question 12

each enzyme has been named in a systematic fashion, on the basis of the reaction it catalyzes, by the (organization)

Answer 12

International Union of Biochemistry

Question 13

reactants of enzyme catalyzed reactions are called as _ and each
enzyme is quite specific in character

Answer 13

substrate

Question 14

enzymes are made of proteins with occasional non-protein part

many enzymes need only proteins in their structure for their activity while others require one or more non-protein components called _

Answer 14

cofactors

• nonprotein component of enzymes ;without it, enzymes will lack their catalytic activity
• some cofactors can either be organic or metallic in nature

Question 15

protein or polypeptide portion of the enzyme is called _

Answer 15

apoenzyme

some apoenzyme cannot catalyze a reaction without its cofactor nor can the cofactor function without an apoenzyme

Question 16

organic cofactors are called as _ which are transiently associated with the
apoenzyme and are themselves changed in the reaction

Answer 16

coenzymes

Question 17

example of these coenzymes are the electron carriers

Answer 17

• nicotinamide adenine dinucleotide (NAD+) reduced to NADH
• flavin adenine dinucleotide (FAD) reduced to FADH2

both are reduced in a dehydrogenation reaction

Question 18

metal ion cofactors such as _ are sometimes referred to as metal
activators

Answer 18

Fe, Mo, Cu, and Zn

Question 19

their non-protein co-factors that are more or less permanently associated with the enzyme protein are called _

Answer 19

prosthetic groups

Question 20

Enzyme catalysis

Answer 20

E + S -> E-S -> E + P

enzyme+substrate ->enzyme-substrate complex -> enzyme + product

Question 21

the compound on which the enzyme works and whose reaction is being speed up is
called the _

Answer 21

substrate

Question 22

the substrate usually binds to the enzyme surface while it undergoes the reaction on a
specific portion called the _

Answer 22

active site

Question 23

_ can also be found on active sites

Answer 23

coenzymes

Question 24

enzymes are able to catalyze or speed up particular reactions because they _ the
amount of activation energy required to initiate the reaction

Answer 24

lower

Question 25

catalysis occurs at the active site which is composed of the_ and the _

Answer 25

binding site catalytic group

Question 26

active site of an enzyme contains specific _ that form temporary bonds with the substrate

Answer 26

amino acid residues

Question 27

active site of the enzyme occupies _ % of the total volume of the enzyme

Answer 27

~10 – 20

Question 28

_ is the most important part of the enzyme that catalyzes the chemical reaction

Answer 28

active site

Question 29

the active site of the enzyme contains only _ amino acids

Answer 29

three to four

Question 30

* location of substrates binding with the enzyme; * one of the two components of the active site of the enzyme; * bind and orient substrate molecules

Answer 30

binding site

Question 31

the binding site attracts and positions the _ while the catalytic group (the reactive side chains of amino acids or cofactors) carry out the _ reactions involved

Answer 31

substrate bond-breaking and bond-forming

Question 32

- location in active site where the catalysis of the chemical reaction occurs in the enzyme

Answer 32

catalytic site

Question 33

, the _ in the catalytic site of the enzyme are responsible for catalyzing the chemical reaction

Answer 33

amino acids

Question 34

catalytic site _ the activation energy of the chemical reaction

Answer 34

reduces

Question 35

catalytic site is one of the two main components of the _ of an enzyme

Answer 35

active site

Question 36

the main function of an enzyme is to _ under physiological conditions

Answer 36

catalyze a chemical reaction

Question 37

refers to a location on a macromolecule or cellular structure at which **chemical interaction with a specific active substance** takes place

Answer 37

Binding Site

Question 38

temporarily binds with the substrate

Answer 38

Binding Site

Question 39

binds and orients the substrate

Answer 39

Binding Site

Question 40

refers to a portion of an enzyme molecule at which the **actual reaction proceeds** and is considered to consist of one or more residues or atoms in a spatial arrangement

Answer 40

Catalytic Site

Question 41

in enzyme which catalyzes the reaction of the substrate

Answer 41

Catalytic Site

Question 42

reduces the chemical activation energy

Answer 42

Catalytic Site

Question 43

six major groups of enzymes based on type of reaction they catalyze

Answer 43

1. oxidoreductases 2. transferases 3. hydrolases 4. lyases 5. isomerases 6. ligases/ synthetases

Question 44

catalyze oxidation and reduction

Answer 44

Oxidoreductases

Question 45

– catalyze the transfer of a group of atoms from one molecule to another

Answer 45

Transferases

Question 46

catalyze hydrolysis reactions

Answer 46

Hydrolases

Question 47

catalyze the addition of a group to a double bond or removal of two groups from adjacent atoms to create a double bond.

Answer 47

Lyases

Question 48

catalyze isomerization reactions

Answer 48

Isomerases

Question 49

catalyze the joining of two molecules

Answer 49

Ligases/ Synthetases –

Question 50

When the type of reaction is omitted, it is _. like?

Answer 50

hydrolysis urease, lactase

Question 51

* explains the specificity of enzyme action by comparing the active site of an enzyme to a lock and the substrate to a key, * assumes that the **enzyme is a rigid, three-dimensional body**

Answer 51

Lock-and-Key Model

Question 52

* compares the active site to a glove and the substrate to a hand, that is, like a glove to a hand that **accommodates the shape of the substrate**

Answer 52

Induced-Fit Model

Question 53

reaction rates depend on the number of successful _ between substrate and enzyme molecules, which in turn depends upon their concentrations

Answer 53

collisions

Question 54

if we keep the **concentration of the substrate constant**, an **increase in enzyme concentration** would linearly _ the rate of enzyme activity

Answer 54

increase

Question 55

if we keep the concentration of the **enzyme constant** and **increase the concentration of the substrate**, there is a different scenario since rate _ continuously

Answer 55

does not increase

Question 56

a point where the rate stays the same even with increase substrate concentration called as the _

Answer 56

saturation point

Question 57

at saturation point, substrate molecules are bound to _ available active sites of an enzyme

Answer 57

all

Question 58

* increasing substrate concentration _ the frequency with which the enzyme and substrate collide * as a result, enzyme-substrate complexes form _ and the rate of reaction _

Answer 58

increases more quickly increases

Question 59

however, there is a limit as eventually there all the enzyme active sites are already occupied with substrate - the enzyme active sites become _

Answer 59

saturated ## Footnote * any further increase in substrate concentration has no further effect on the reaction rate * *Note that if there is excess substrate (the first part of the graph) the line can be approximated to a straight lin

Question 60

temperature affects enzyme activity because of _ of the three-dimensional structure of the enzyme

Answer 60

denaturation or the alteration ## Footnote * hence, the substrate may not be able to successfully fit the active sites * each enzyme has its own optimum temperature to work with

Question 61

pH influences the _ of substrates, _ state, and presence of charged and uncharged free amino or carboxyl groups in the enzyme

Answer 61

* ionization * denaturation

Question 62

* a **neutral** carboxyl group requires a _ pH optimum * while an **uncharged amino group** needs a _ pH optimum

Answer 62

low high

Question 63

_ any process that makes an active enzyme less active or inactive which is accomplished by compounds known as _

Answer 63

inhibition inhibitors

Question 64

Two types of Inhibitors

Answer 64

1. Competitive Inhibitors 2. Non-competitive Inhibitors

Question 65

bind to the active site of an enzyme surface, thereby, preventing the real substrate to bind

Answer 65

Competitive Inhibitors

Question 66

binds to some portion of the enzyme surface which may sufficiently alters the tertiary structure of the enzyme so that its catalytic effectiveness is slowed down

Answer 66

Non-competitive Inhibitors

Question 67

Both competitive and noncompetitive inhibitors are _ , but some compounds alter the structure of the enzyme permanently and thus, make it irreversibly inactive

Answer 67

reversible