Biomolecules - Free MCQ Practice Test with solutions, NEET Chemistry

Glycogen is a branched chain polymer of αD glucose units in which chain is formed by C₁−C₄ glycosidic linkage whereas branchin occurs by the formation of C₁−C₆ glycosidic linkage. Structure of glycogen can be shown below similar to the sturcture amplopectin.

If blood glucose levels become too low, glucagon (pancreatic hormone) is released, which causes the liver to convert the stored glycogen back into glucose, and release it into the bloodstream.

• Sucrose (cane sugar) is a disaccharide: This means it is composed of two monosaccharides bonded together.


• Hydrolysis of sucrose: When sucrose is hydrolyzed, it breaks down into its two monosaccharide components.


• Components of sucrose: Sucrose is made up of one molecule of glucose and one molecule of fructose.


• Result of hydrolysis: Therefore, when sucrose is hydrolyzed, it gives one molecule of glucose and one molecule of fructose.

In α-helix, hydrogen bonds are present between –NH group of one amino acid residue to the >C= O group of another aminoacid residue.

The correct answer is option A
Nucleotides are joined together by phosphodiester linkage between 5′ and 3′ carbon atoms of pentose sugar.
 

Nucleotides are organic molecules that serve as the monomer units for forming the nucleic acid polymers deoxyribonucleic acid and ribonucleic acid, both of which are essential biomolecules within all life-forms on Earth.

The correct answer is Option C.
Glucose is an aldohexose having structural formula.

Glucose on heating with HI produces n hexane.
C₆H₁₂O_{6 --HI}→C₆H₁₄
Glucose does not give 2,4. DNP test due to its existence as cyclic structure shown below :

It is present in pyranose form, as shown below 

Pyranose means pyran (membered ring containing oxygen) like structure.

The primary structure of a protein refers to the sequence of amino acids in the polypeptide chain. The primary structure is held together by peptide bonds that are made during the process ofprotein biosynthesis.

Thymine is one of the four nucleobases in the nucleic acid of DNA that are represented by the letters G–C–A–T. The others are adenine, guanine, and cytosine. Thymine is also known as 5-methyluracil, a pyrimidine nucleobase. In RNA, thymine is replaced by the nucleobase uracil.

The correct answer is option  D
Vitamin B₁₂
The body has a limited capacity to store most of the B-group vitamins except B₁₂ and folate, which are stored in the liver.

Quinoline is an alkaloid, it is not present in DNA. DNA  has four nitrogen bases in adenine, guanine, cytosine and  thymine

Structures (I and II) differ only in the position of OH at C₂ and hence are anomers. 

Due to absence of free OH group at C₂ cyclic structure of glucose pentacetate cannot revert to open chain aldehydic form and hence cannot form an oxime. 

The correct answer is Option A.
 
I, II and III structures have D configuration with -OH group on the lowest asymmetric carbon is on the right side which is comparable to (+) glyceraldehyde.

The correct answer is option C
'a' carbon of glucose and 'b' carbon of fructose
Carbon adjacent to the oxygen atom in the cyclic structure of glucose or fructose is known as anomeric carbon. As shown in the structure above ‘a’ and ‘b’ are present adjacent to an oxygen atom. Both carbons differ in configurations of the hydroxyl group.

The correct answer is Option C.

(i)   The first structure is lactose, the linkage is (A) C₁−C₄ glycosidic linkage.
(ii)  The 2_nd structure has C₁−C₆ linkages.
(iii) The 3_rd structure has C₁−C₄ linkages.

The correct answer is D. Both b and c.
One of the common disaccharides is sucrose which on hydrolysis gives an equimolar mixture of D−(+)− glucose and D−(−) fructose. These two monosaccharides are held together by a glycosidic linkage between Cl of α- glucose and C2 of β- fructose. Since the reducing groups of glucose and fructose are involved in glycosidic bond formation, sucrose is a non-reducing sugar.

The correct answer is option B.
Amylopectin is insoluble in water and constitutes about 80−85% of starch. It is a branched-chain polymer of −D− glucose units in which chain is formed by C1−C4 glycosidic linkage whereas branching occurs by C1−C6 glycosidic linkage. Glycogen: The carbohydrates are stored in the animal body as glycogen. It is also known as animal starch because its structure is similar to amylopectin and is rather more highly branched.

The correct answer is option D. 
It also exists in two cyclic forms which are obtained by the addition of −OH at C5 to the group. The ring, thus formed is a five-membered ring and is named as furanose with an analogy to the compound furan. Furan is a five-membered cyclic compound with one oxygen and four carbon atoms.

The correct answer are options B.
In fibrous proteins, polypeptide chains are held together by hydrogen and disulphide bonds, in parallel manner. Due to which fibre-like structure is obtained. Such proteins are generally known as fibrous proteins. These proteins are generally insoluble in water e.g., keratin, myosin.

Purine bases in DNA and RNA are adenine (A) and guanine (G). Among the given options:

• Only guanine is a purine base.

Therefore, the correct answer is A.

Options A is correct.
In lysine,the amino group is attached to alpha carbon which makes it alpha amino acid and it has more amino groups as compared to -COOH groups, thus basic.