Tag: proteins and enzymes

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Multiple choice bio-chemistry proteins denaturation of protein proteins and amino acids proteins and enzymes

Which structural feature distinguishes proline from other natural $\alpha$-amino acids :

  1. It is optically inactive

  2. It contains aromatic group

  3. It is dicarboxylic acid

  4. It has a secondary amine

  5. It contains two amino groups
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Proline is the only proteinogenic amino acid whose side-group links to the -amino group and, thus, is also the only proteinogenic amino acid containing a secondary amine at this position.

Multiple choice bio-chemistry proteins denaturation of protein proteins and amino acids proteins and enzymes

The sequence in which amino acids are linked to one another in a protein molecule is called its:

  1. Primary structure

  2. Secondary structure

  3. Tertiary structure

  4. Quanternary structure
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Proteins may have one or more polypeptide chains. Each polypeptide in a protein has amino acids linked with each other in a specific sequence and it is this sequence of amino acids that is said to be the primary structure of that protein.

Multiple choice bio-chemistry proteins denaturation of protein proteins and amino acids proteins and enzymes

What type of a chemical reaction takes place when,
(i) lime stone is heated?
(ii) proteins are converted into amino acids?

  1. In both (i) and (ii), a combination reaction takes place

  2. In (i), a decomposition reaction takes place while in (ii), a combination reaction takes place

  3. In both (i) and (ii), a decomposition reaction takes place

  4. In (i), a combination reaction takes place while in (ii), a decomposition reaction takes place
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Lime stone is calcium carbonate which, upon heating, decomposes into calcium oxide and carbon dioxide.

$CaCO _3 \rightarrow CaO + CO _2$
 Similarly, proteins also undergo decomposition to form amino acids.
$ (-Amino \ acid-) _n \rightarrow n Amino \ acids$

Multiple choice bio-chemistry proteins denaturation of protein proteins and amino acids proteins and enzymes

When liquids are heated, they turn into gases. The yellow egg yolk present inside the egg is a liquid but when it is heated, it changes into an omelet, which is solid. Why?

  1. Sometimes, liquids turn into solids

  2. Omelet does not follow the above rule

  3. Strictly speaking, the rule does not apply to complex mixtures and egg yolk is a complex mixture

  4. None of the above
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The egg still contains more water than protein, but the water is now dispersed in the protein web so it can no longer flow together, turning the liquid egg into a semi-solid. This happens at around $145^{o}F$ for egg white and $150^{o}F$ for egg yolk. Continued heating causes more bonds to form, leaving less space for the water, that's why after heating the yolk converts in solid omelet.

Multiple choice bio-chemistry proteins denaturation of protein proteins and amino acids proteins and enzymes

The primary structure of proteins is associated with this:

  1. amino acid sequence
  2. $\beta$ -pleated sheet structure

  3. conformation

  4. relative position of subunits
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Primary structure refers specifically to the unique sequence of amino acids in a polypeptide chain. Other options describe higher-level folding or structural organization.

Multiple choice bio-chemistry proteins denaturation of protein proteins and amino acids proteins and enzymes

The bonds responsible for the tertiary structure of proteins are:

  1. hydrogen bonds

  2. Vander wall forces

  3. disulphide bonds

  4. All the above.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

The tertiary structure of proteins is stabilized by various interactions between the side chains of amino acids. These include hydrogen bonds, Van der Waals forces, ionic bonds, and covalent disulphide linkages. Since multiple types of interactions are responsible, all the listed options play a role.

Multiple choice bio-chemistry proteins denaturation of protein proteins and amino acids proteins and enzymes

Myoglobin can be analysed for its quaternary structure.

  1. True

  2. False
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Myoglobin is a simple protein consisting of a single polypeptide. Since the quaternary structure is composed of an assembly of subunits of polypeptides, myoglobin does not have a quaternary structure. Due to the lack of multiple subunits, it has the highest level of structure as tertiary. Hemoglobin, on the other hand,  is composed of multiple polypeptide subunits, each capable of binding and transporting one molecule of oxygen in the blood, thus giving it a quaternary structure.

Multiple choice bio-chemistry proteins denaturation of protein proteins and amino acids proteins and enzymes

 Peptide linkages ($\displaystyle CONH$) are present in the primary structures of proteins while the secondary structures of proteins involve ______. 

  1. Coordinate bonding

  2. Ionic bonding

  3. hydrogen bonding

  4. none
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

While primary structure is held together by covalent peptide bonds, secondary structures (like alpha-helices and beta-pleated sheets) are formed and stabilized by hydrogen bonding between the backbone atoms.

Multiple choice bio-chemistry proteins denaturation of protein proteins and amino acids proteins and enzymes

The building block of proteins are:

  1. $\alpha$-hydroxy acid
  2. $\alpha$-amino acid
  3. $\beta$- hydroxy acid
  4. $\beta$- amino acid
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The building block of proteins are $ \displaystyle \alpha-$amino acids.
On hydrolysis, proteins gives  $ \displaystyle \alpha-$amino acids.
 $ \displaystyle \alpha-$amino acids have structure  $ \displaystyle H _2N- \underset {  \displaystyle   { \underset {  \displaystyle  \text { R } }{ | } } }{CH }-COOH$
Proteins $ \displaystyle \xrightarrow {H _2O}n H _2N- \underset {  \displaystyle   { \underset {  \displaystyle  \text { R } }{ | } } }{CH }-COOH$
Proteins are polypeptides and contain peptide linkage ($ \displaystyle - \underset {  \displaystyle   { \underset {  \displaystyle  \text { O } }{ || } } }{C }-NH-$ linkage)