Presentation on theme: "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,"— Presentation transcript:
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.
1665 Robert Hooke: Looked at a slice of cork through a microscope and discovered tiny boxes which he called “cells.”
1673 Anton von Leeuwenhoek: looked at pond scum through a microscope and discovered single- celled organisms called protists.
1838 Matthias Schleiden: studied plants and concluded that all plant parts were made of cells.
1839 Theodor Schwann: studied animals and concluded that all animal tissues are made of cells.
1858 Rudolf Virchow: discovered that cells could only come from other cells.
With all these discoveries, Schwann and Virchow came up with the cell theory: 1.All organisms are made of cells 2.The cell is the Basic unit of all living things 3.All cells Come from existing cells
Most cells are so tiny that you have to use a microscope to see them.
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 surface area (the cell’s surface).
– 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.
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.
Some cells are big because they don’t need to take in nutrients or get rid of wastes. Ie. Chicken egg is a cell
No nucleus 2 types: bacteria & archebacteria Smallest cells Organelles: DNA & ribosomes only Use flagellum (tail) to move Most prokaryotes are Unicellular (only 1 cell) 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) *DNA ribosomes, * cell membranes cytoplasm