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Understanding Cells: The Fundamental Unit of Life

Cells are the basic structural and functional units of all living organisms. Found in bacteria, plants, and animals, they require water and nutrients to survive. Notably, cells were discovered through the pioneering works of scientists like Robert Hooke and Anton van Leeuwenhoek. The cell theory, established by Schwann and Virchow, states that all organisms are made of cells, cells are the basic units of life, and all cells arise from existing cells. The size of cells is limited by their surface area-to-volume ratio, which affects their ability to acquire nutrients and expel wastes.

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Understanding Cells: The Fundamental Unit of Life

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  1. So, What IS a Cell? • A cell is the basic unit of structure and function in all living things. • It needs water and nutrients to survive. • It is found in all living things: bacteria, plants, and animals. • It is NOT found in non-living things.

  2. Which ones would have cells?

  3. Which ones would have cells?

  4. How Cells Were Discovered… 1665 Robert Hooke: Looked at a slice of cork through a microscope and discovered tiny boxes which he called “cells.”

  5. How Cells Were Discovered… 1673 Anton von Leeuwenhoek: looked at pond scum through a microscope and discovered single-celled organisms called protists.

  6. How Cells Were Discovered… 1838 Matthias Schleiden: studied plants and concluded that allplant parts were made of cells.

  7. How Cells Were Discovered… 1839 Theodor Schwann: studied animals and concluded that all animaltissues are made of cells.

  8. How Cells Were Discovered… 1858 Rudolf Virchow: discovered that cells could only come from other cells.

  9. ABC’s of the “Cell Theory” With all these discoveries, Schwann and Virchow came up with the cell theory: • All organisms are made of cells • The cell is the Basic unit of all living things • All cells Come from existing cells

  10. How Big are Cells? • Most cells are so tiny that you have to use a microscope to see them.

  11. Why are cells so tiny? • Because of the surface area-to-volume ratio: • Cells take in nutrients and get rid of wastes through their outside surface. • BUT the volume (space inside) grows faster than the surfacearea (the cell’s surface).

  12. Why are cells so tiny? • If the volume becomes too big, the cell cannot survive because…. • it can’t get enough nutrients in & • can’t get rid of wastes fast enough. Therefore, a cell only grows to a certain size.

  13. Balloon Analogy for Cell Size • If you blow into a balloon, the volume increases. • Eventually, the balloon’s surface • cannot stretch anymore. • When this happens, the balloon • cannot continue to exist and will pop. • Likewise, if a cell’s volume increases too much, the cell’s surface will not be able to get nutrients in or wastes out fast enough and it will die.

  14. A few cells are big • Some cells are big because they don’t need to take in nutrients or get rid of wastes. • Ie. Chicken egg is a cell

  15. Prokaryotes

  16. Eukaryotes

  17. Eukaryotic Cell (Eukaryotes) Prokaryotic Cell (Prokaryote) • Have a nucleus • Examples:plants, animals, and humans • Largest cells (10x larger than bacteria cells!) • DNA in nucleus • Many organelles • Most eukaryotes are multi-cellular (made of more than 1 cell) • No nucleus • 2 types: bacteria & • archebacteria • Smallestcells • Organelles: • DNA & ribosomes • only • Use flagellum (tail) • to move • Most prokaryotes are • Unicellular (only 1 cell) • *DNA • ribosomes, * cell membranes • cytoplasm

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