ABC transporters are a part of a superfamily of transporters that have two nucleotide binding domains that bind __________, which is necessary for primary active transport.

• A. ADP.
• B. Phosphate.
• C. ATP.
• D. GTP.
• E. AMP.

Answer: (C)

Verified step by step guidance

1. Understand the role of ABC transporters: ABC (ATP-Binding Cassette) transporters are a large family of proteins that utilize the energy from ATP hydrolysis to transport various molecules across cellular membranes.
2. Identify the key components of ABC transporters: They consist of two main parts - transmembrane domains that form the pathway for the substrate and nucleotide-binding domains (NBDs) that bind and hydrolyze ATP.
3. Recognize the function of nucleotide-binding domains: These domains are responsible for binding and hydrolyzing ATP, which provides the energy required for the transport process.
4. Consider the options provided: The question asks which molecule is necessary for primary active transport in ABC transporters. The options are ADP, Phosphate, ATP, GTP, and AMP.
5. Recall the energy source for primary active transport: ATP is the molecule that provides energy for primary active transport by being hydrolyzed to ADP and inorganic phosphate, thus driving the transport process in ABC transporters.