QCM : Enzyme Specificity and Carbohydrate Hydrolysis — 10 questions

Explication

The correct answer is the University of Veterinary Sciences Brno, which is explicitly cited in the content as the source for the definitions related to substrate specificity and molecular recognition.

Explication

The source of an enzyme directly causes its specific activity because saliva contains α-amylase that hydrolyzes starch, and yeast contains invertase that hydrolyzes sucrose. This origin determines the enzyme's substrate recognition and catalytic activity, making source the cause of specific enzyme activity.

Explication

Enzyme activity testing is primarily used as a qualitative method to determine whether an enzyme can hydrolyze its substrate into detectable products, such as reducing sugars or starch degradation, often using colorimetric indicators like Fehling's reagent or Lugol's solution.

Explication

Fehling's reagent is used to detect reducing sugars by forming a red precipitate of copper(I) oxide (Cu2O) when reducing sugars are present, making it a key indicator in enzyme activity tests involving carbohydrate hydrolysis.

Explication

Enzyme specificity refers to the enzyme's ability to recognize and catalyze a specific substrate transformation, primarily determined by the structure of its active site and molecular recognition mechanisms.

Explication

Emil Fischer is credited with proposing the lock-and-key model, which explains enzyme specificity based on the structural complementarity between enzyme active sites and substrates.

Explication

Reaction indicators such as Fehling's reagent are applied after incubation of enzyme and substrate mixtures. They are added to detect the presence of reducing sugars, which are formed when enzymes like α-amylase or invertase hydrolyze their substrates. The formation of a red precipitate of Cu2O indicates the presence of reducing sugars, thus confirming enzyme activity.

Explication

Invertase and α-amylase differ in their substrate recognition mechanisms because they hydrolyze different types of glycosidic bonds in different substrates: invertase hydrolyzes β-D-fructofuranosides in sucrose, while α-amylase hydrolyzes α(1→4) glycosidic bonds in starch and glycogen. Their substrate specificities are determined by the structure of their active sites, which recognize different bond types and substrate conformations. Therefore, they recognize and hydrolyze different bonds and substrates, making option 1 incorrect. Option 2 correctly states that both recognize specific glycosidic bonds but differ in the bond type and substrate structure, which aligns with the course content. Options 3 and 4 are incorrect because invertase recognizes disaccharides (sucrose), not monosaccharides alone, and both enzymes recognize substrates via structural complementarity, not non-specific interactions.

Explication

Reducing sugars are the products formed when enzymes like α-amylase and invertase hydrolyze carbohydrates. Their presence is detected using tests such as Fehling's reagent, making them useful indicators of enzyme activity. They do not act as enzymes themselves, nor do they inhibit enzyme function; instead, they reflect the extent of carbohydrate hydrolysis.

Explication

The correct answer is 'During the initial chewing and saliva secretion' because α-amylase in saliva begins to hydrolyze starch into smaller sugars immediately during mastication, marking the start of carbohydrate digestion.