Plant and animal cells under the microscope

All living things are made of cells. Under a microscope, onion skin cells look like neat rectangles, and cheek cells look like irregular blobs. Both kinds have a nucleus that controls the cell, jelly-like cytoplasm where chemical reactions happen, a thin cell membrane that controls what enters and leaves, and mitochondria that release energy by respiration. Plant cells also have a tough cell wall made of cellulose that gives them a fixed shape, a large central vacuole full of cell sap that keeps them firm, and, in the green parts, chloroplasts that make food by photosynthesis.