A Level Biology Practice Exam

What type of bond links the two glucose molecules in maltose?

1. Covalent bond

2. 1, 4 glycosidic bond

3. Peptide bond

4. Hydrogen bond

The correct answer is: 1, 4 glycosidic bond

Maltose is a disaccharide composed of two glucose molecules linked together. The type of bond that connects these two glucose units is specifically known as a 1,4 glycosidic bond. This bond forms when a hydroxyl group (-OH) from one glucose molecule reacts with the hydroxyl group of the other glucose, leading to the release of a water molecule in a dehydration synthesis reaction. The "1,4" designation indicates the specific carbons involved in the linkage: the first carbon of one glucose molecule is connected to the fourth carbon of the other glucose molecule. This is essential for understanding how sugars can form more complex carbohydrates, as glycosidic bonds play a critical role in carbohydrate chemistry. In contrast, a covalent bond is a broader term that describes a bond formed by the sharing of electrons between atoms, and while glycosidic bonds are indeed a type of covalent bond, specifying it as a 1,4 glycosidic bond provides clarity about the specific relationship between the glucose units. Peptide bonds, on the other hand, are found in proteins and link amino acids together, while hydrogen bonds are a type of weak interaction that can occur between molecules but do not form the primary link between sugar