Proteins

Question 1

Urea cycle is also known as

Answer 1

Ornithine cycle ( first member of the reaction is ornithine )

Question 2

2 nitrogen atoms of the urea formed are derived from two different sources ,name the sources

Answer 2

One from ammonia
Other directly from alpha amino group of aspartic acid

Question 3

What is the step 1 in urea cycle

Answer 3

Formation of carbamoyl phosphate

Question 4

Step 2 in ornithine cycle

Answer 4

Formation of citrulline

Question 5

Which step in the ornithine cycle is the formation of urea

Answer 5

Step 5

Question 6

Step 3 in urea cycle

Answer 6

Formation of argininosuccinate

Question 7

Step 4 in ornithine cycle is

Answer 7

Formation of arginine

Question 8

Cytoplasmic enzyme involved in the synthesis of pyrimidine

Answer 8

Carbomyl phosphate synthestase II

Question 9

Rate limiting step in urea cycle

Answer 9

CPS-I

Question 10

Explain the first step in urea cycle

Answer 10

One molecule ammonia condenses with CO2
Presence of 2 molecules of ATP
To form carbonyl phosphate
Enzyme :CPS-(mitochondrial enzyme )
Irreversible and allosterically regulated

Question 11

In what aspects does CPS I differ from CPS II

Answer 11

Site Mitochondria , cytoplasm
Pathway urea ,pyrimidine
Positive effector NAG , nil
Source of N ammonia , glutamine
Inhibitor nil , CTP

Question 12

Where does the second reaction of ornithine cycle take place

Answer 12

Mitochondrial (just like 1st)

Question 13

Which are two mitochondrial steps in urea cycle

Answer 13

First 2

Question 14

How is citrulline formed in the urea cycle

Answer 14

Carbamoyl group transferred to NH2 group of ornithine
By ornithine transcarbamoylase (OTC)

Question 15

Which product in urea cycle leaves the mitochondria

Answer 15

Citrulline leaves to the cytoplasm

Question 16

Citrulline is present in

Answer 16

Milk
Not present in tissue proteins or blood

Question 17

What is an inhibitor of step 3 of urea cycle

Answer 17

Ppi ( inorganic pyrophosphate)

Question 18

How is argininosuccinate formed

Answer 18

One molecule of aspartic acid adds to citrulline forming C-N bond , second nitrogen of urea.
Catalyzed by : argininosuccinate synthetase
Needs hydrolysis of ATP to AMP level (2 high energy phosphate bonds are utilized )

Question 19

Inhibitor of cps II

Answer 19

CTP

Question 20

Argininosuccinate is cleaved by what in the fourth step of urea cycle

Answer 20

Argininosuccinate lyase (argininosuccinase )

Question 21

Argininosuccinate is cleaved to what

Answer 21

Arginine and fumarate , argininosuccinase is inhibited by fumarate

Question 22

How is the inhibition of argininosuccinase avoided

Answer 22

Cytoplasmic localization of the enzyme

Question 23

Which step in urea cycle involves aspartic acid

Answer 23

Step 3

Question 24

Other purposes of fumarate formed during the formation of arginine

Answer 24

Funneled into tca cycle to be converted to malate and then to oxaloacetate to be transaminated to aspartame

Question 25

How is the urea cycle linked to TCA cycle

Answer 25

By fumarate

Question 26

Citrulline +aspartate ——> Summary of 3rd and 4th step

Answer 26

Arginine +fumarate

Question 27

Donation of amino group by asparate takes place in which reaction other than urea cycle

Answer 27

Purine nucleotide synthesis

Question 28

The final reaction in ornithine cycle / urea cycle

Answer 28

Hydrolysis of arginine to urea and ornithine By arginase

Question 29

Why does the ornithine return mitochondria after the formation of urea

Answer 29

To react with another carbonyl phosphate and cycle is proceeds

Question 30

Which component is a catalyst that gets used and regenerated in urea cycle

Answer 30

Ornithime

Question 31

Energetics of the urea cycle

Answer 31

Consumes 4 high energy phosphate bonds 1NADH is produced (=2.5 ATP) Hence net energy expenditure = 1.5 high energy phosphates

Question 32

Why is it called the urea bicycle

Answer 32

Urea cycle and TCA cycle are interlinked

Question 33

What in the urea cycle produces 1NADH

Answer 33

Fumarate in 4th step converted to malate , malate when oxidized to oxaloacetate

Question 34

When is the activity of urea cycle elevated

Answer 34

During starvation , to meet the increased rate of protein catabolism

Question 35

What are the types of regulation of urea cycle

Answer 35

Coarse and fine regulation

Question 36

The one group not carried by tetra hydro folic acid (THFA)

Answer 36

Methyl group

Question 37

Which nitrogen atoms of THFA carry the one-carbon groups

Answer 37

N5 , N10 atoms of THFA

Question 38

The one carbon groups are contributed to the 1C pool by

Answer 38

Amino acids

Question 39

What is transamination

Answer 39

Exchange of alpha amino group between one alpha amino acid and another alpha keto acid The reaction is readily reversible .

Question 40

Common example of transamination

Answer 40

Interchanged between alanine and glutamic acid . (Almost all cases , amino group is accepted by alpha ketoglutaric acid so glutamic acid is formed )

Question 41

Enzymes catalyzing the transamination reaction as a group are called And the prosthetic group in it

Answer 41

Amino transferases Pyridoxal phosphate

Question 42

Ammoniagenesis helps in excretion of

Answer 42

Hydrogen ions

Question 43

What is chemical name of glutathione

Answer 43

Gamma-glutamyl-cysteinyl- glycine

Question 44

Miester cycle is also known as

Answer 44

Gamma glutamyl cycle

Question 45

Glycine can be synthesised by

Answer 45

1. By glycine synthase enzyme 2.from serine( serine hydroxy methyl transferase ) 3. From glyoxylic acid (glycine transaminase) 4. From threonine (threonine aldolase) 5. From choline

Question 46

Different degradation processes of glycine

Answer 46

Glycine cleavage Serine formation Transamination reaction Oxidative deamination

Question 47

End product of transamination of glycine by glycine transaminase

Answer 47

Glyoxylate + glutamate

Question 48

in collagen , every third amino acid is

Answer 48

Glycine

Question 49

Primary structure of protein.

Answer 49

Denotes number and sequence of amino acids in the protein Higher levels of organisation are decided by the primary structures

Question 50

Secondary structure of proteins

Answer 50

Preserved by non covalent forces or bonds like hydrogen bonds , electrostatic bonds , hydrophobic interactions and van der waals forces Different secondary structure - alpha helix , beta sheet , bends , loops , disordered regions

Question 51

What causes phenylketonuria

Answer 51

Inability to convert phenylalanine to tyrosine. due to absence/ deficiency of phenyl alanine hydroxylase

Question 52

Normal blood phenylalanine & abnormal PKU blood level

Answer 52

1 to 2 mg /dl PKU > 20mg/ dl

Question 53

Manifestations of PKU

Answer 53

Mental retardation low iq Seizure irritation Failure to walk hypopigmentation Eczematous dermatitis Mousy odor (lactic odour )

Question 54

Define transamination

Answer 54

Process of transfer of amino group from an amino acid to a keto acid converting the original keto acid to a new amino acid and the origin amino acid o a new keto acid Without the liberations of ammonia

Question 55

Examples of transamination

Answer 55

Aspartate + alpha ketoglutarate <——> oxaloacetate + glutamate (AST) Alanine + alpha ketoglutarate <—>Pyruvate + glutamate ALT (alanine transaminase )

Question 56

Alpha helix

Answer 56

*Most common secondary structure found in proteins * Seen in hemoglobin , myoglobin , alpha keratin , collagen * right handed coiled structure *stabilised by extenisve hydrogen bonding *hydrogen bonds are parallel to the alpha helix *bonds are individually weak , collectively maintain helical structure *Each turn of helix contains 3.6 amino acid residues and each amino acid is separated by a distance of 1.5 A°

Question 57

Denaturation of proteins

Answer 57

* process of disorganisation of native protein structure *loss of 2° 3° 4° structures without breaking primary structure *causes unfolding of 3 dimensional proteins PRIMARY STRUCTURE MAINTAINED BY STRING COVALENT PEPTIDE BONDS. higher structures - weak non-covalent bonds

Question 58

Alkaptonurea Metabolic defect :

Answer 58

lack of homogentisate oxidase enzyme