The structures that make up a cell are called organelles. 5. The large, rounded brain near the center of the cell is the nucleus. 6. The jellyish substance inside the cell but outside the nucleus is the cytoplasm. 7. The cell's powerhouses which release energy from food are the mitochondria. 8. Ribosomes make most of the protein for the cell. 9. Vacuoles act like storage areas within the cell.