A Level Biology Practice Exam

What characteristic is common to all antibodies?

1. They are made of carbohydrates

2. They are proteins

3. They have a lipid structure

4. They are nucleic acids

The correct answer is: They are proteins

All antibodies share the characteristic of being proteins. They are complex molecules composed of long chains of amino acids folded into unique three-dimensional structures that enable them to perform their specific functions in the immune response. Antibodies, also known as immunoglobulins, are produced by B cells in response to foreign antigens, such as bacteria and viruses. The protein nature of antibodies allows them to exhibit a high degree of specificity and affinity for their target antigens, which is crucial for effectively neutralizing pathogens and marking them for destruction by other immune cells. The structure of antibodies includes constant regions that determine their class and variable regions that provide specificity for binding to particular antigens. Other options are not applicable to antibodies. Carbohydrates, lipids, and nucleic acids each play different roles in biological systems but do not characterize antibodies.