Practice free Biomolecules (Chemistry) NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
In the quaternary structure of adult human haemoglobin, how many subunits are involved and what are their types?
The context states: 'Adult human haemoglobin consists of 4 subunits. Two of these are identical to each other. Hence, two subunits of $\alpha$ type and two subunits of $\beta$ type together constitute the human haemoglobin (Hb).'
A 'native protein' is described as having a unique three-dimensional structure and biological activity. Which level(s) of protein structure are essential for a protein to exhibit its biological activity in its native form?
The context implies that all higher-order structures (secondary, tertiary, and quaternary) are built upon the primary structure. The tertiary structure is stated to be 'absolutely necessary for the many biological activities,' and the quaternary structure is also involved in the function of multi-subunit proteins like hemoglobin. Therefore, for a protein to function in its 'native form,' all its structural levels are essential.
The type of chemical interaction absent in stabilizing the secondary structure of proteins, but present in tertiary and quaternary structures, is:
The text states secondary structure arises due to 'hydrogen bonding between C=O and –NH– groups.' For tertiary and quaternary structures, it mentions 'hydrogen bonds, disulphide linkages, van der Waals and electrostatic forces of attraction,' indicating disulfide linkages are found at these higher levels, but not explicitly mentioned for secondary structure stabilization.
Which of the following statements correctly defines a carbohydrate according to chemical properties?
The NCERT text states: 'Chemically, the carbohydrates may be defined as optically active polyhydroxy aldehydes or ketones or the compounds which produce such units on hydrolysis.' This definition aligns with option o1.
Acetic acid (CH$_3$COOH) has the molecular formula C$_2$(H$_2$O)$_2$. Why is it NOT classified as a carbohydrate, despite fitting the general formula C$_x$(H$_2$O)$_y$?
The NCERT text mentions acetic acid (CH$_3$COOH) fits the formula C$_2$(H$_2$O)$_2$ but is 'not a carbohydrate.' The chemical definition of carbohydrates states they are 'optically active polyhydroxy aldehydes or ketones or the compounds which produce such units on hydrolysis.' Acetic acid is a carboxylic acid, not a polyhydroxy aldehyde or ketone, and it does not yield such units on hydrolysis.
Which of the following is an example of a monosaccharide?
The NCERT text classifies carbohydrates into monosaccharides, oligosaccharides, and polysaccharides. Under monosaccharides, it lists 'Some common examples are glucose, fructose, ribose, etc.' Sucrose and lactose are listed as disaccharides (a type of oligosaccharide), and starch is a polysaccharide.
What is the primary characteristic that differentiates oligosaccharides from monosaccharides?
The NCERT text states: 'A carbohydrate that cannot be hydrolysed further to give simpler unit of polyhydroxy aldehyde or ketone is called a monosaccharide.' For oligosaccharides, it says: 'Carbohydrates that yield two to ten monosaccharide units, on hydrolysis, are called oligosaccharides.'
Which of the following polysaccharides is also known as 'animal starch' due to its structural similarity to amylopectin and its highly branched nature?
The NCERT text clearly states: 'The carbohydrates are stored in animal body as glycogen. It is also known as animal starch because its structure is similar to amylopectin and is rather more highly branched.'
All monosaccharides, whether aldose or ketose, share which of the following properties?
The NCERT text states: 'All those carbohydrates which reduce Fehling’s solution and Tollens’ reagent are referred to as reducing sugars. All monosaccharides whether aldose or ketose are reducing sugars.' Option o4 is also true for monosaccharides (by definition), but o3 describes a specific chemical property shared by all monosaccharides as 'reducing sugars'.
What is the role of cellulose in plant cells?
The NCERT text mentions: 'Cellulose occurs exclusively in plants and it is the most abundant organic substance in plant kingdom. It is a predominant constituent of cell wall of plant cells.'
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