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.

Which ones would have cells?

Which ones would have cells?

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

How Cells Were Discovered… 1673 Anton von Leeuwenhoek: looked at pond scum through a microscope and discovered single-celled organisms called protists. Amoeba, an example of a protist

How Cells Were Discovered… 1838 Matthias Schleiden: studied plants and concluded that all plant parts were made of cells. Tomatoes: http://www.bigblogofgardening.com/how-to-prune-tomato-plants/ http://creativebits.org/inspiration/snow_leopard_desktop_pictures http://www.gertens.com/learn/Trees/why-plant-a-tree.htm

How Cells Were Discovered… 1839 Theodor Schwann: studied animals and concluded that all animal tissues are made of cells. Pueblan Milk snake Clown fish Grizzly bear

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

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 1 & 2: building block/legos 3. Just like all animals must come from another animal, or plants come from the seeds of another plant; we don’t just come from rocks or thin air.

How Big are Cells? Most cells are so tiny that you have to use a microscope to see them. 1 & 2: building block/legos 3. Just like all animals must come from another animal, or plants come from the seeds of another plant; we don’t just come from rocks or thin air.

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 surface area (the cell’s surface). 1 & 2: building block/legos 3. Just like all animals must come from another animal, or plants come from the seeds of another plant; we don’t just come from rocks or thin air.

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. 1 & 2: building block/legos 3. Just like all animals must come from another animal, or plants come from the seeds of another plant; we don’t just come from rocks or thin air.

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.

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 1 & 2: building block/legos 3. Just like all animals must come from another animal, or plants come from the seeds of another plant; we don’t just come from rocks or thin air.

Prokaryotes 1 & 2: building block/legos 3. Just like all animals must come from another animal, or plants come from the seeds of another plant; we don’t just come from rocks or thin air.

Eukaryotes 1 & 2: building block/legos 3. Just like all animals must come from another animal, or plants come from the seeds of another plant; we don’t just come from rocks or thin air.

Prokaryotic Cell (Prokaryote) Eukaryotic Cell (Eukaryotes) 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