In the context of vesicular budding, transport, and coat proteins, what is the primary mechanism that transports newly synthesized proteins between organelles such as the ER and Golgi within the cell?

• A. Ribosomes moving along microtubules while carrying completed proteins to their destinations
• B. Direct transfer of proteins through gap junctions between adjacent cells
• C. Free diffusion of proteins through the cytosol without membrane carriers
• D. Coated transport vesicles that bud from a donor membrane and fuse with a target membrane

Answer: (D)