The correct answer is option 1: G-protein coupled receptors. The Nobel Prize in Chemistry for the year 2012 was awarded for the work done on G-protein coupled receptors.

G-protein coupled receptors are a type of protein that are embedded in the cell membranes of organisms. These receptors play a crucial role in cell signaling and communication. They are involved in various physiological processes, including vision, smell, taste, and regulation of hormone secretion.

The Nobel Prize in Chemistry is awarded annually to individuals who have made outstanding contributions to the field of chemistry. In 2012, the prize was specifically awarded to two scientists, Robert J. Lefkowitz and Brian K. Kobilka, for their studies on G-protein coupled receptors. Their work has greatly advanced our understanding of these receptors and their importance in various biological processes.

It is important to note that the other options mentioned (human stem cell cloning, anti-malarial vaccine, and neurotransmitters) are not the correct answers for the Nobel Prize in Chemistry in 2012.