Cell Structure
Read this resource to learn about important organelles. Most organelles are membrane-bounded and only appear in eukaryotic cells, which are structurally more complex than prokaryotic cells from which they evolved. Pay close attention to Figure 4.1 to see the main differences between animal cells, plant cells (both of which are eukaryotic), and bacterial cells (which are prokaryotic).
Figure 4.1 (a) Nasal sinus cells (viewed with a light microscope), (b) onion cells (viewed with a light microscope), and (c) Vibrio tasmaniensis bacterial cells (seen through a scanning electron microscope) are from very different organisms, yet all share certain basic cell structure characteristics.
Close your eyes and picture a brick wall. What is the wall's basic building block? It is a single brick. Like bricks, cells are the building blocks that make up your body.
Your body has many cells, each specialized for a specific purpose. As we use various materials to build a home, the human body is constructed from many cell types. For example, epithelial cells protect the body's surface, covering the organs and body cavities. Bone cells help to support and protect the body. Immune system cells fight invading bacteria. Blood and blood cells also carry nutrients and oxygen throughout the body while removing carbon dioxide. Each cell type plays a vital role during the body's growth, development, and day-to-day maintenance. Despite their enormous variety, however, cells from all organisms - even ones as diverse as bacteria, onions, and humans - share certain fundamental characteristics.
Source: OpenStax, https://openstax.org/books/biology-2e/pages/4-introduction
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