A drug molecule is too large to pass through cell membranes. The drug travels in the blood to all cells in the body, but it only changes the activity of heart muscle cells.
Which statement explains both of these observations?
The membrane lets all molecules through, and only heart cells have receptors for the drug.
The membrane is a selective barrier, and only heart cells contain enzymes for the drug.
The membrane lets all molecules through, and only heart cells have ribosomes for the drug.
The membrane is a selective barrier, and only heart cells have receptors for the drug.
130 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.