Lecture 7. Metabolism of N-Containing Compounds

Question 1

The two forms of N readily available to the
plants for absorption are _____ and _____.

Answer 1

nitrate (NO3), NH3 (ammonia)

Question 2

_____ is the mostly absorbed form.

Answer 2

NO3

Question 3

_____ is only absorbed under flooded condition.

Answer 3

NH3

Question 4

The synthesis of other amino acids which are
important components of proteins arise via
________.

Answer 4

transamination reaction

Question 5

The C-skeleton donors include _____, _____, and _____.

Answer 5

pyruvic acid, oxaloacetic acid, α-ketoglutaric

Question 6

Nature of Enzymes

Answer 6

1. Enzymes are active in extremely small amount
2. Enzymes are ideal catalysts
3. Enzymes do not affect the equilibrium of reaction
4. Catalytic action of enzyme is specific
5. Enzymes catalyze a given reaction by reducing the activation energy needed for reaction to proceed

Question 7

Enzymes are named according to the ________ or the type of reaction they catalyze.

Answer 7

substrate they attack

Question 8

Enzymes are named by adding suffix ______ to the name of the substrate attacked

Answer 8

ase

Question 9

T or F

Enzyme may be grouped under a more general term describing a certain group of compound
attacked.

Answer 9

T

Question 10

T or F

Enzymes may be named according to the type of reaction they catalyze.

Answer 10

True

Question 11

Enzymes are specific, meaning their catalytic
property is confined to ________ or a group of
related reactions.

Answer 11

one group

Question 12

Enzyme specificity is confined to a certain ________.

Answer 12

chemical linkage

Question 13

Reasons for enzyme specificity:

Answer 13

a. Conformation of the complex protein molecule
b. Uniqueness of its active site
c. Structural configuration of the substrate
molecule

Question 14

Classification of Enzymes:

Answer 14

1. Hydrolytic enzyme
2. Oxidation-reduction enzyme
3. Phosphorylases
4. Transferases
5. Carboxylases
6. Isomerases
7. Epimerases

Question 15

condensation or synthetic enzymes because reaction is reversible – catalyze addition of the elements of water to a specific bond of the substrate.

Answer 15

Hydrolytic enzyme

Question 16

catalyze the removal or addition of hydrogen, oxygen or electrons from or to the substrate which is oxidized or reduced.

Answer 16

Oxidation-reduction enzyme

Question 16

removal or addition of CO2 e.g. glutamic decarboxylase – removes CO2 to yield δ-aminobutyric acid

Answer 16

Carboxylases

Question 17

Catalyze reversible phosphorolytic cleavage of a specific bond on a substrate.

Answer 17

Phosphorylases

Question 18

Transfer of a group from a donor molecule to an acceptor molecule

Answer 18

Transferases

Question 19

interconversion of aldose and ketose sugars

Answer 19

Isomerases

Question 20

conversion of sugar or sugar derivative to its epimer (molecules that differ only in the configuration of a single C atom)

Answer 20

Epimerases

Question 21

enzymes in addition to their protein structure have an attached non- protein group.

Answer 21

Conjugated proteins

Question 22

enzymes requiring loose association with certain organic substances for activity.

Answer 22

Cofactors or Coenzymes

Question 23

Factors Affecting Enzyme Activity

Answer 23

1. Substrate concentration
2. Enzyme concentration
3. Temperature
4. pH
5. Inhibitors

Question 24

Types of Inhibitors

Answer 24

a.Competitive b.Non-competitive

Question 25

-Composed of repeating units of amino acids linked together by a peptide bond. This peptide bond links the carboxyl group of one amino acid with one amino group of the other.

Answer 25

PROTEINS

Question 26

Protein Classification Based on solubility properties and known chemical and physical differences.

Answer 26

a.Simple proteins b. Conjugated proteins

Question 27

proteins that yield on hydrolysis of amino acids only; classification is based on solubility only.

Answer 27

Simple proteins

Question 28

aside from amino acids it has a non-amino component called prosthetic groups.

Answer 28

Conjugated proteins

Question 29

Simple proteins

Answer 29

1. Albumins 2. Globulins 3. Glutelins 4. prolamines 5. histones 6. Protamines

Question 30

Conjugated proteins

Answer 30

1. Nucleoproteins 2. Glycoproteins 3. Lipoproteins 4. Chromoprotein 5. Metalloprotein

Question 31

Protein Synthesis

Answer 31

* Transcription * Translation

Question 32

Transcription

Answer 32

process whereby genetic info in DNA is employed to order a complementary sequence of bases in a new RNA chain.

Question 33

Translation

Answer 33

process whereby genetic info in mRNA directs the order of insertion of the specific amino acids during protein synthesis.