(a) Denaturation of protein

Definition : Denaturation is the process in which a protein loses its native three-dimensional structure — its secondary and tertiary structure — and hence its biological activity, when subjected to a change in physical or chemical conditions such as heating, or a change in pH.

Key points :

• The hydrogen bonds and other weak forces holding the folded shape are destroyed.
• The primary structure (the sequence of amino acids) remains intact, because peptide bonds are not broken.
• The globular protein uncoils into a random, fibrous form and becomes biologically inactive.

Examples : the coagulation of egg white on boiling; the curdling of milk.

(b) Invert sugar

Definition : The equimolar mixture of D-(+)-glucose and D-(−)-fructose obtained by the hydrolysis of sucrose is called invert sugar.

$$\underset{\text{sucrose}}{C_{12}H_{22}O_{11}} + H_2O \xrightarrow{H^+ \text{ or invertase}} \underset{\text{glucose}}{C_6H_{12}O_6} + \underset{\text{fructose}}{C_6H_{12}O_6}$$

Why it is called "invert" : The sign of optical rotation reverses during the hydrolysis.

Because fructose rotates light to the left much more strongly than glucose rotates it to the right, the mixture is overall laevorotatory. The rotation has been inverted from $+$ to $-$, which gives the mixture its name.