A sample of an unknown unicellular pathogen is isolated from a patient and analyzed under a high-resolution transmission electron microscope. Which of the following structural observations would definitively classify the pathogen as eukaryotic rather than prokaryotic?
A cell wall surrounding the outer surface of the plasma membrane.
Ribosomes distributed throughout the cytoplasm.
A membrane-bound organelle containing highly folded inner membranes (cristae).
A circular strand of DNA located within a distinct region of the cytoplasm.
40 exam-style questions on OCR GCSE Biology 1.1 Cell structures, covering 1.1.1 Viewing cells with light microscopes, 1.1.2 Sub-cellular structures and functions, and 1.1.3 Electron microscopy and resolution. Each one has a worked solution and a mark scheme showing where the marks go.