Fructose is the sweetest sugar and highly soluble in water and slightly soluble in alcohol. It is insoluble in ether fructose in laevorotatory hence, called laevulose.
202.
Glucose molecule reacts with $$X$$ number of molecules of phenylhydrazine to yield osazone. The value of $$X$$ is
Sucrose, being a non-reducing sugar, does not reduce Benedict’s solution. Remember that fructose has an $$\alpha $$ - hydroxy ketonic group, which is also reducing group ( different from ordinary ketonic group )
205.
The increasing order of $$pKa$$ of the following amino acids in aqueous solution is :
$$Gly{\text{ }}Asp{\text{ }}Lys{\text{ }}Arg$$
Structure of the given $$\alpha - $$ amino acids are :
Here, aspartic acid is an acidic and glycine is a neutral amino acid while lysine and arginine are basic amino acids. Also, arginine is more basic due to the stronger basic functional groups.
∴ The order of $$pKa$$ value is directly proportional to the basic strength of amino acids, i.e.
$$Arg{\text{ }} < Lys < Gly < Asp.$$
206.
Which of the following statements is not correct?
A
Only $$\alpha $$ - amino acids are obtained on hydrolysis of proteins.
B
The amino acids which are synthesised in the body are known as non-essential amino acids.
C
There are 20 essential amino acids.
D
$$L$$ - amino acids are represented by writing the $$ - N{H_2}$$ group on the left side.
Due to regular folding of backbone of the peptide chain, two most common secondary structures of proteins are $$\alpha $$ - helix and $$\beta $$ - pleated structures. In $$\alpha $$ - helix, all $$H$$ - bonds are formed by twisting the chain into a right handed helix. In $$\beta $$ - pleated, all peptide chains are stretched to maximum extension and then laid side by side and connected by hydrogen bonds.
208.
A compound which contains both ________ and ________ is called amino acid. The amino acids in polypeptide chain are joined by ________ bonds.