Chapter 4 Proteins And Amino Acids

Question 1

Most of the aminoacids are?

Answer 1

Alpha- amino acids

Question 2

Most abundant organic molecules of living system?

Answer 2

Proteins

Question 3

Proteins constitute about ________% of dry weight of a cell?

Answer 3

50

Question 4

Proteios means?

Answer 4

Holding the first place

Question 5

Entire study of galaxy of proteins is given the term?

Answer 5

Proteiomics

Question 6

Function of proteins may be grouped as?

Answer 6

1.Static (structural)
2.Dynamic

Question 7

What are the structural proteins?

Answer 7

That perform brick and mortar functions.
Structure and strength

E.g:
Collagen
Elastin
- both in bone matrix and vascular tissues
a-keratin - in epidermal tissues

Question 8

What are dynamic proteins?

Answer 8

Act as enzymes, harmones, immunoglobins, storage proteins etc

• regarded as working horses of cell

Question 9

Content of nitrogen in protein?

Answer 9

16%

Question 10

Estimation of nitrogen in laboratory is mostly done by?

Answer 10

Kjeldahl’s Method

Question 11

Proteins are polymers of?

Answer 11

L-a-aminoacids

Question 12

Proteins are hydrolysed by?

Answer 12

Concentrated HCl

Question 13

How many amino acids occur in nature?

Answer 13

300

Question 14

How many amino acids are known as standard amino acids?

Answer 14

20

Question 15

1.Trick to remember aliphatic amino acids?

2. Trick to remember aromatic aminoacids?

Answer 15

Aliphatic amino acids;
(Glaciers in Alaska Valiantly Locate Isolated Prowlers)

Glycine (only one containing non-chiral carbon)
Alanaine
Valine
Leusine
Isoleusine
Proline (only one containing ring but not aromatic)

2. (The Aroma of Fine pine & Yellow Timber are Worth the Tryp)
   Aroma—aromatic:

•Phenylalanine (F)
•Tyrosine (Y) (also contains OH group)
•Tryptophan (W)
(2 aromatic rings, 1st—5 membered, 2nd—6 membered)

Question 16

1. Trick to remember amino acids containing hydroxyl group?
2. Trick for basic amino acids?

Answer 16

1. (Alcohol is a Serious Threat)
   Alcohol—alcoholic group (-OH)

•Serine
•Threonine

2. (Basically,
   His
   Lost Kid
   Always Returned)
   Basically—-basic amino acids

•Histidine (H)
•Lysine (K)
•Arginine (R)

Question 17

Trick for acidic amino acids & their amide?.

What are the sulfur containing amino acids?

Answer 17

(As he Digested the Glue his stomach became acidic)

Aspartic acid (D)
(Amide—-Asparagine (N))
Glutamic acid (E)
(Amide—-Glutamine (Q))

2. Methionine
   Cysteine
   Cystine

Question 18

Importance of amino acids regarding charges & polar/non-polar nature?

Answer 18

1. charged
   Acid & basic amino acids
2. Non-polar
   •All aliphatic
   •2 aromatic
   (phenylalanin & tryptophan)
   • methionine
3. Polar
   •All alcohols & amide
   •Aromatic —-Tyrosine (bcz has OH group)
   •Cysteine

Question 19

1.All amino acids show optical isomers except?

2. What type of amino acids are proteins composed of?
3. Name the branched chain amino acids?
4. Cystine is formed by?
5. What are the 2 amino acids incorporated during protein synthesis? With special groups??

Answer 19

1.Glycine (no chiral/asymmetrical carbon)

2. L-a-aminoacids
3. There are 3 aliphatic amino acids with branched chains:
   Valine
   Leucine
   Isoleucine
4. Condensation of 2 molecules of cysteine
5. 2 sulfur containing;
   Methionine (thioether group)
   Cysteine (sulfhydryl group)

Question 20

1. What are the dicarboxylic monoamino acids?
2. Groups in arginine & histidine? What kind of aminoacids are these?
3. What is an imino acid? Name it?
4. Name heterocyclic amino acids?

Answer 20

1. Aspartic acid & glutamic acid
2. Arginine—-guanido
   Histidine—-imidazole
   —dibasic monocarboxylic aminoacids
3. Containing imino group (=NH) instead of amino (-NH2)
   Proline (pyrridole ring)—is an a-imino acid
4. Histidine
   Tryptophan
   Proline

Question 21

1. What are the polar amino acids with positive R group?
2. What are the polar amino acids with negative R group?
3. Polar amino acid but with no charge?

Answer 21

1. Basic amino acids:
   Histidine
   Lysine
   Arginine
2. Acidic amino acids:(dicarboxylic):
   Aspartic acid
   Glutamic acid
3. •Glycine
   Alcoholic
   •Serine
   •Threonine
   Sulfur containing
   •Cysteine
   Amide
   •Glutamine
   •Asparagine
   Aromatic
   •Tyrosine (-OH group)

Question 22

1. What are essential amino acids? Which of these are semi essential?

Answer 22

Which can’t be synthesized in the body
(Argentina.Valley. HILL M.P Threat.Tryp)
Arginine
Valine
Histidine
Isoleucine
Leucine
Lysine
Methionine
Phenylanaline
Threonine
Tryptophan

Semi essential
Can be synthesized by adults but not by growing children;
(Ah)
Arginine
Histidine

Question 23

1. What is the fate if amino acids?

Answer 23

1. Either as precursor of
   •Glucose—-(glycogenic aminoacids)
   (AA)
   Alanine
   Aspartate
   Glycine
   Methionine.

•Fat—-(ketogenic aminoacids)
(LL)
Leucine
Lysine

•Glycogenic & ketogenic aminoacids
4 amino acids:
(3 aromatic and 1 aliphatic)
Tryptophan
Tyrosine
Phenylalanine
Isoleucine

Question 24

1. What is the 21st amino acid? It is translated by which stop codon?
   Incorporated directly on protein by?
   It is found in?
   What is the difference in its structure compared to cysteine?
2. What is the 22nd amino acid? It is translated by which stop codon?

Answer 24

1. Selenocysteine
   –By UGA
   –By serine on tRNA
   – at the active sites of enzymes (selenoproteins) e.g
   Glutathione peroxidase
   5’-diodinase
   —-selenium in place of Sulfur atom of cysteine
2. Pyrrolysine
   By UAG

Question 25

1.What is chinese restaurant synrome? 2. Name amino acids that are Sweet Tasteless Bitter

Answer 25

Chinese restaurant syndrome is a term used to describe a collection of symptoms, such as headaches, flushing, and sweating, that some people may experience after consuming foods containing **monosodium glutamate (MSG)**. (**Ajinomoto**(brand name) --flavour enchancer) It was initially associated with Chinese cuisine, hence the name, but it can occur after consuming foods from various cuisines that contain MSG. 2. Sweet--- **Glycine, Alanine, Valine** Tasteless---**leucine** Bitter---**Arginine, Isoleucine**

Question 26

1. What are ampholytes? 2. Nature of amino acids in different pH? 3. What is isoelectric pH?

Answer 26

1.Ampholytes are substances that can **act as both acids and bases**. E.g **aminoacids** They have the ability to **donate (-COOH) (acidic) or accept protons (-NH2) (basic) depending on the pH** of the environment. It's like they can play both roles, kind of like being versatile! 2. **acidic pH**(low pH) Amino acid----+vely charged cation **alkaline pH**(high pH) Amino acid---- -vely charged anion **Neutral PH** As zwitter ion E.g *leucine* (pH=6.0) 3. The isoelectric pH, also known as the pI (isoelectric point), is the pH at which a molecule or substance has **no net electrical charge**. It exists as **zwitter ion or dipolar ion** It's like finding the perfect balance point where the molecule is neither positive nor negative.

Question 27

1. What happens on decarboxylation of amino acids? 2. Name biologically imp amines from corresponding amino acids? 3. Amides are formed by reactions of? 4. Which test is used for detection of amino acids & proteins?

Answer 27

1. **Amines** are formed 2. Histidine----**histamine** Tyrosine----**tyramine** Glutamate----**y-Amino Butyric Acid (GABA)** 3. Carboxyl group of dicarboxylic Aminoacids + NH3 4. **Ninhydrin test** Amino acids + Ninhydrin-----**purple/blue/pink complex** But **Proline & hydroxyproline**----**yellow** colour

Question 28

1. Collagen contains amino acid derivatives? 2. Which amino acid derivative is involved in blood clotting? 3. Amino acid derivatives found in histones?

Answer 28

1. **4-Hydroxyproline 5-Hydroxylysine** 2. **Y-Carboxyglutamic acid** found in plasma proteins 3. Methylated Phosphorylated Acetylated amino acids

Question 29

1. D-amino acids are found in antibiotics? 2. D-amino acids are found in brain tissue? 3.D-amino acids are found in bacterial cell wall?

Answer 29

1. **•Actinomycin - D •Valinomycin - D •Gramicidin - S** 2. **•D- Serine •D- Aspartate** 3. **•D-Glutamic Acid •D-Alanine**

Question 30

1.Name 3 amino acids used as drugs? 2. Which amino acid drug is used for treatment of cystic fibrosis? 3. Which drug is used for the treatment of wilson's disease? 4. Which amino acid drug is used as an anticonvulsant?

Answer 30

1. •D-pencillamine •N-Acetylcysteine •Gabapentin 2. **N-Acetylcysteine** As it acts as *antioxidant* ( by thinning the mucus in the airways, making it easier to cough up.) 3. **D-penicillamine (D-dimethylglycine)** *Chelation of copper* D-penicillamine treats Wilson disease by binding to copper and forming a complex that can be excreted in urine. This helps reduce copper levels in the body. 4. **Gabapentin (y-aminobutyrate)** Linked to *cyclohexane* (by binding to certain receptors in the brain that help reduce abnormal electrical activity and prevent seizures.)

Question 31

1. What is lathyrism? 2. What amino acids are responsible for it? 3. Which amino acids in it cause ammonia toxicity? 4. Which amino acids is responsible for parkinson's dimentia?

Answer 31

1.Lathyrism is a condition caused by the consumption of a legume called **Lathyrus sativus (kesari dal)**, which contains a **neurotoxin**. It can lead to **paralysis of the lower limbs**. 2. **L-Homoarginine** & **B-N- OxalylDiAminoPropionic acid (ODAP)** of lathyrus 3. **a,y-diaminobutyric acid** (Analogue of ornithine) ----bcz it disrupts urea cycle 4. **L-B-Methylaminoalanine** Of *Cycad seeds*

Question 32

1. Peptide bonds is charged or uncharged? Peptides may be also regarded as? 2. In polypeptide chains 2 adjacent a-carbons are placed? 3. Which structure of protein is primarily responsible for its function? 4. Which enzyme causes complete hydrolysis of proteins?

Answer 32

1. Peptide bond---- uncharged But peptides ---- charged (due to terminal carboxyl & amino group) Thus peptides-----**polyelectrolytes** 2. **0.36nm** apart 3. Primary structure 4. **Prolase** (a mixture of non-specific proteolytic enzyme)

Question 33

1. How amino acids can be separated after protein hydrolysis?

Answer 33

1. By **chromatography** (Amino acids can be separated by chromatography based on their **different properties, such as size, charge, and affinity** for the stationary phase. It's like giving each amino acid its own unique pathway to travel, allowing them to be separated and identified. )

Question 34

1. The non-covalent bonds between proteins are broken by? 2. Disulfide linkages are cleaved by? 3. Number of polypeptide chains can be identified by treatment of protein with? 4. Enzymatic cleavage is done by? 5. Chemical cleavage by?

Answer 34

1. **Urea** or **guanidine hydrochloride** (Converts proteins ---- polypeptides) 2. **Performic acid** 3. **Dansyl chloride** 4. **Trypsin** (Carbonyl side of peptide linkage containing **lysine & arginine**) 5. **Cyanogen bromide (CNBr)** (Carbonyl side of peptide linkage containing **methionine**)

Question 35

1. Determination of amino acids by? 2. Sequenator uses which principle?

Answer 35

1. **Sangers reagent** (1-fluoro 2,4-dinitrobenzene) **Edman's reagent** (Phenyl isothyiocyanate) Then amino acid by chromatography 2. An **automated machine** for amino acid sequence ---**Edman's principle** (PTH amino acid is liberated)

Question 36

1. The a-helix is stabilized by? 2. Each turn of a-helix has how many: Amino acids? Travels of distance of? Spacing of each amino acid? 3. Which a-helix is more stable?

Answer 36

1. Extensive Hydrogen bonding between **H-atom** of peptide N & **O-atom** of peptide C 2. Amino acids-----**3.6** Travels of distance of---**0.54nm** Spacing of each amino acid---**0.15nm** 3. Right handed a-helix is more stable than left

Question 37

1. In globular proteins, the core structure is formed by? 2. What are supersecondary structure of proteins? Stabilized by? Also called?

Answer 37

1. B-sheets 2. Intermediates between **secondary & tertiary** structures -combination of a-helices & B-structures ---stabilized by; •H-bonding •Salt bridges •Hydrophobic interactions ---also called --- **mortif**

Question 38

1. Bonds in tertiary structures of proteins? 2. What is domain? 3. A polypeptide with 200 amino acid contains how many domains? 4. What are oligomeric proteins? Examples? 5. Bonds in quaternary structure?

Answer 38

1. •Hydrogen bonds •**Disulfide bonds** •Ionic interactions •Hydrophobic interactions •**Van der waals forces** 2. Term used to represent the **basic unit of tertiary protein structure** 3. 2 or more domains 4. Having quaternary structure (2 or more polypeptides) E.g **Hemoglobin Aspartate transcarbamoylase Lactate dehydrogenase** 5. •Hydrogen bond •Hydrophobic interaction •Ionic interaction

Question 39

1. Chemically glutathione is? 2. How is it essential for protein function? 3. What is it's significance in eryhthrocyte? 4. Involved in amino acids transports in the intestine & kidney tubules by? 5. Peroxidases & free radicals are scavenged by?

Answer 39

1. **y-glutamyl-cysteinyl-glycine** Is a **tripeptide** composed of **3 amino acids** 2. Prevents oxidation of sulfhydryl groups of proteins to disulfide groups --- also with *glutathione reductase*--- formation of correct disulfide bonds 3. **Gutathione (reduced)**: •Maintains **RBC membrane structure** •Protects **Hb from oxidation** by H2O2 4. **y-glutamyl cycle/Meister cycle** 5. **Glutathione peroxidase** (A *selenium* containing enzyme)

Question 40

1. Name different peptides with different numbers of aminoacids (peptides)

Answer 40

**Dipeptide (2 amino acids)** •Aspartame **Tripeptides (3 amino acids)** •Thyrotrophin releasing hormone •Glutathione **Pentapeptide** •Methionine enkephalin **Octapeptide** •Angiotensin II **Nonapeptides** •Oxytocin •Vasopressin (ADH) •Bradykinin **Decapeptides** •Angiotensin I •Kallidin

Question 41

1. What are pseudopeptides? 2. Which peptide is found in brain? Its function? 3. What is the function of bradykinin and kallidin? 4. Aspartame is _____ times sweeter than? Used as? Produced by combination of?

Answer 41

1. Duplicate peptides produced by pharmaceutical industries to the efficiency of drugs E.g **B-peptides Y-peptides Oligoglycines Peptide nucleic acid (PNA) DNA cleaving pseudopeptides** 2. **Methionine enkephalin** (pentapeptide) ---opiate like function ---**inhibits sense of pain** 3. Vasodilators - produced from plasma proteins by **snake venom enzymes** 4. **200** times than **sucrose** ---artificial sweetener ---**aspartic acid & phenylalanine**

Question 42

What are covalent & non covalent bonds in protein structures?

Answer 42

1. **2 covalent** Peptide Disulfide **4 non covalent** Hydrogen bonds Hydrophobic bonds Electrostatic bonds Van der waals forces