Chp. six

Question 1

____ tells if a reaction can thermodynamically happen, but it doesn’t say that it will happen. Rate of reaction is a function of specialized enzymes.

Answer 1

delta G

Question 2

Molecules that should react with one another often _____ because they lack sufficient energy.

Answer 2

do not

Question 3

___ is the minimum amount of energy that 2 molecules must have in order to react.

Answer 3

activation energy Ea

Question 4

For a reaction to occur you must have a ______ and

Answer 4

favorable delta G and enough energy to reach Ea

Question 5

The rate of enzymatic reaction is proportional to _____ that have an evergy content >=

Answer 5

fraction of molecules

Question 6

Under most biologically normal conditions, the Ea is ___ that few molecules have that much energy.

Answer 6

so high

Question 7

The rates of uncatalyzed reaction in cells are ____

Answer 7

very slow.

Question 8

non-reacting molecules are ____ unstable but ____ stable in a metastable state.

Answer 8

thermodynamically, kinetically

Question 9

life depends on the high Ea to ____ cellular reactions from happening at appreciable rates ____ in the presence of a suitable catalyst.

Answer 9

prevent, except

Question 10

Providing a reactive surface is the task of a_____`

Answer 10

catalyst

Question 11

Protein catalysts are called

Answer 11

enzymes

Question 12

RNA catalyst are called

Answer 12

ribozymes

Question 13

3 basic properties of catalysts

Answer 13

1. All catalysts increase the rate of a reaction by lowering the Ea requirement.
2. All catalysts act by forming transient intermediate complexes with the substrate molecules and thus position them in a manner that facilitates their interaction.
3. All catalysts change only the rate at which equilibrium is reached; no effect on the position of the equilibrium.

Question 14

Every enzyme contains, somewhere within its 3 prime structure, a characteristic cluster of ______ forming an _____.

Answer 14

amino acids, active site

Question 15

What is the location of domain on the enzyme’s structure where the actual catalytic action occurs

Answer 15

active site

Question 16

what is usually a groove or pocket with chemical or structuaral properties that accommodate the intended substrate with high specificity

Answer 16

active site

Question 17

Active site involves only about ____ of the surface area of the enzyme.

Answer 17

5%

Question 18

Amino acids most commonly found at an active site

Answer 18

cysteine, histidine, serine, aspartate, glutamate, lysine

Question 19

The amino acids that make up the active site of an enzyme are not usually contiguous along the ___ sequence of a polypeptide. Instead, they are brought into the right conformation by the specific ____ folding of the polypeptide chain and by additional conformational change when the substrate binds.

Answer 19

1 prime, 3-D

Question 20

The reaction seen in peroxisomes is _____ favorable… yet hydrogen peroxide exists in nature in a _____ state.

Answer 20

thermodynamically, metastable

Question 21

When ferric ions are added to the solution it increases the reaction rate about

Answer 21

30,000X

Question 22

fe+3 reacts with O2 to form iron oxides and drive the break down of

Answer 22

H2O2

Question 23

If ____ is present the reaction occurs about 1x10^9 X faster than if uncatalyzed

Answer 23

catalase

Question 24

if a catalase is present the reaction occurs about ____ faster than if uncatalyzed.

Answer 24

1x10^9 X

Question 25

ion groups that are integral parts of enzyme structure

Answer 25

prosthetic groups

Question 26

Prosthetic groups can be ___ organic molecules or ___ ions or combination of ____

Answer 26

small, metal

Question 27

Prosthetic groups function as ____ acceptors since none of the a.a. are good _____ acceptors.

Answer 27

electron, electron

Question 28

Prosthetic groups are usually associated with the ____ and are indispensable for ____.

Answer 28

active site, catalytic activity

Question 29

Not all enzymes have prosthetic groups; ones that do RedOx reaction ____

Answer 29

require one

Question 30

While all of the vitamins may have been discovered, new catalytic cofactors and prosthetic groups are ______.

Answer 30

still being found. They are too numerous to mention.

Question 31

The coenzyme ____ is a hydrogen carrier that replaces ____ in certain bacterial alcohol dehydrogenases.

Answer 31

PQQ, NAD

Question 32

____ is a cofactor for amino oxidases found in bacterial, plan, and human tissues. It is a prosthetic group that is formed by oxidation of a specific tyrosine in the active site.

Answer 32

Topaquinone

Question 33

Topaquinone functions together with a nearby ___ ion which binds the ___ substrate. The same copper center and ___are apparently involved in ____ synthesis of the prosthetic group.

Answer 33

copper, O2, O2

Question 34

Formation of topaquinone is only one case of many, in which _____ groups are self-assembled using components of the ___ that carries the group.

Answer 34

prosthetic, protein

Question 35

A recently discovered example of formation is ______, from glycine and serine units of protein. The prosthetic group is involved in a previously hard-to-explain isomerization of histidine and phenylalanine.

Answer 35

4-methylidene-imidazole-5-one

Question 36

Enzyme must bind the substrate then ____ the reaction.

Answer 36

catalyze

Question 37

A consequence of the structure of the active site is that the enzymes display a high degree of substrate specificity.

Answer 37

Enzyme specificity

Question 38

Enzyme specificity can discriminate between very _____ molecules.

Answer 38

similar

Question 39

Enzyme specificity has a difference between an ____ catalyst vs. an ____ one

Answer 39

inorganic, organic

Question 40

Are all enzymes specific as others?

Answer 40

no

Question 41

Some enzymes accept a ____ of ____ related substrates.

Answer 41

number, closely

Question 42

Which enzymes tend to accept entire groups of substrates as long as they posses some common structural feature.

Answer 42

enzymes involved in synthesis or degradation of polymers.

Question 43

How many major classes are based on function, with subgroups used to define their function more precisely.

Answer 43

6

Question 44

maintains a narrow range of cellular temps

Answer 44

homeotherms

Question 45

Within this narrow range, the rate of an enzyme-catalyzed reaction increases with temp Why?

Answer 45

increases the kinetic energy of the molecules and their reactivity.

Question 46

Outside of this temp range the enzyme begins to fall apart or _____.

Answer 46

denature

Question 47

The temp range over which an denatures varies _____ from enzyme to enzyme and especially from organism to organism.

Answer 47

greatly

Question 48

organisms that live in an environment with a higher than average temperature for biotic life such as bacteria that thrive in environments that average 70 degrees C.

Answer 48

thermophiles

Question 49

They have essentially the same genes as other bacteria, however, the alleles for their proteins encode heat tolerate varieties of enzyme.

Answer 49

thermophiles

Question 50

Thermophiles enzymes operate at _____ teps and are critical to bio-technology.

Answer 50

high

Question 51

______ is an ex. DNA polymerase (replicates DNA) from Thermus aquaticus is the driving force of PCR and DNA sequencing.

Answer 51

thermophiles

Question 52

Most enzymes are active within a range of only _____pH units.

Answer 52

3-4

Question 53

The pH dependence is usually due to the need for one or more charged _______ at the active site.

Answer 53

amino acids.

Question 54

_____ dependence usually reflects the environment in which an enzyme is normally active

Answer 54

pH

Question 55

The active site of ______ involves the caroxyl groups from each of 2 glutamates (positions 72, 270)

Answer 55

carboxypeptidase A

Question 56

reaction type: oxidation-reduction reactions

Answer 56

class: oxidoreductases

Question 57

Reaction type: Transfer of functional groups from one molecule to another.

Answer 57

transferases

Question 58

Reaction type: Hydrolytic cleavage of one molecule into two molecules

Answer 58

classes: hydolase

Question 59

Reaction type: Removal of a group from, or addition of a group to , a molecule with rearrangement of electrons.

Answer 59

Classes: lyases

Question 60

Reaction type: Movement of a functional group within a molecule

Answer 60

classes: isomerases

Question 61

Reaction type: Joining of two molecules to form a single molecule

Answer 61

classes: Ligases

Question 62

List the six enzyme classes.

Answer 62

oxidoreductases, transferases, hydrolases, lyases, isomerases, ligases

Question 63

Enzyme name: alcohol dehydrogenase

Answer 63

oxidoreductases

Question 64

Enzyme name: Glycerokinase

Answer 64

transferases

Question 65

Enzyme name: Carboxypeptidase A

Answer 65

hydrolases

Question 66

Enzyme name: Pyruvate decarboxylase

Answer 66

lyases

Question 67

Enzyme name: Maleate isomerase

Answer 67

Isomerases

Question 68

Enzyme name: Pyruvate carboxylase

Answer 68

Ligases