Cell structure
All living things are made of cells. Animal cells have a cell membrane (controls what enters and leaves), cytoplasm (where reactions happen), a nucleus (contains DNA, controls the cell), mitochondria (aerobic respiration) and ribosomes (protein synthesis). Plant cells also have a cellulose cell wall (support), chloroplasts (photosynthesis) and a large permanent vacuole (cell sap, keeps cells firm). Bacterial cells have no nucleus: their DNA is a single loop, often with plasmids.
≈ 35 minSpecialised cells and magnification
Cells specialise to do particular jobs: root hair cells have a long extension for absorbing water; red blood cells have no nucleus and a biconcave shape to carry oxygen; sperm cells have a tail and many mitochondria. Similar cells form tissues, tissues form organs, organs form organ systems. Magnification , using the same units; .
≈ 40 min