Final answer:
The organelles directly responsible for the production of new molecules within a cell are ribosomes, which synthesize proteins, and mitochondria, which produce ATP through cellular respiration.
Step-by-step explanation:
Organelles directly responsible for the production of new molecules within a cell are ribosomes and mitochondria. Ribosomes are essential for protein synthesis in all cells and mitochondria are known as the 'energy factories' of the cell.
While ribosomes assemble amino acids into proteins, mitochondria produce adenosine triphosphate (ATP), the main energy-carrying molecule of the cell, through a process named cellular respiration. Cellular respiration involves breaking down glucose and other nutrients and, in the presence of oxygen, producing ATP and carbon dioxide as a byproduct.