A molecule of lactose is formed by a glycosidic bond between

Options

A. Galactose and fructose
B. Galactose and galactose
C. Galactose and glucose
D. Fructose and galactose

Answer

To solve the question regarding the formation of a lactose molecule, we can follow these steps:

### Step 1: Understand the Composition of Lactose
Lactose is a disaccharide, which means it is composed of two monosaccharides.

**Hint:** Recall that disaccharides are formed from two monosaccharides through a specific type of bond.

### Step 2: Identify the Monosaccharides in Lactose
Lactose is specifically formed from two monosaccharides: galactose and glucose.

**Hint:** Think about common disaccharides and their components, especially those found in milk.

### Step 3: Recognize the Type of Bond
The bond that connects the two monosaccharides in lactose is called a glycosidic bond. This bond is formed through a dehydration reaction, where a water molecule is released.

**Hint:** Remember that glycosidic bonds are formed between the hydroxyl groups of the monosaccharides.

### Step 4: Specify the Glycosidic Bond Location
In lactose, the glycosidic bond is specifically between the C1 carbon of glucose and the C4 carbon of galactose, forming a β(1→4) glycosidic bond.

**Hint:** Consider how the carbon atoms in the sugar molecules are numbered and how they connect.

### Step 5: Conclusion
Based on the above steps, we conclude that a molecule of lactose is formed by a glycosidic bond between galactose and glucose.

**Final Answer:** C) Galactose and glucose.