David Alan Walker FRS[1] (18 August 1928 – 12 February 2012) was a British scientist and professor of photosynthesis in the Department of Animal and Plant Sciences (APS) at the University of Sheffield.

Based on the meticulous attention to detail and technical prowess derived from his earlier training as an enzymologist, his work prompted totally new thinking about how this cycle was regulated and how it interfaced with the synthesis of ATP and NADPH in the light reactions of photosynthesis.

He then was able to study the process of photosynthesis in terms of the selective permeabilities of the outer membrane of a chloroplast in relation to the transfer of active components in the photosynthetic cycle.

Walker is specially distinguished for his contributions to knowledge of the enzymes concerned with carbon fixation by plants both in connection with photosynthesis and with his earlier studies on crassulacean metabolism.

"[19] Walker was also awarded a Doctor of Science degree from Newcastle University in recognition of his exceptional contributions of published work in his field.