The substrates needed for the synthesis of chlorophyll, cytochromes and steroids are provided by:

These are cylindrical or filamentous structures found in all aerobic eukaryotic cells except the mature and old mammalian RBCs. Each mitochondrion is a double membrane-bound structure enclosing a dense fluid called matrix. The inner membrane is folded inwards to form cristae which increase the surface area.  Mitochondria provide site for cellular respiration resulting in the formation of energy. Hence, they are termed as the power house or storage batteries or ATP mills. The respiratory pathways in the mitochondria (i.e. TCA cycle) provides substrates for the synthesis of important biomolecules such as chlorophyll, cytochromes and steroids.