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.

Math Focus p. 62 Read the sample information and then complete numbers 1-4.

The Cell All Cells have 4 components (part; element; ingredient) in common Cell Membrane Cytoplasm Organelles DNA

The Cell Cell Membrane – The cell membrane is the outermost part of the animal cell. It controls the flow of materials in and out of the cell and protects the cell from its environment. Organelles – The parts within the cell that perform specific functions.

The Cell Cell Membrane Organelles

The Cell Cytoplasm – The cytoplasm is a ‘jelly’ like substance the organelles float in inside the cell membrane. DNA – The genetic material that carries the information to build and maintain cells.

The Cell Cytoplasm DNA

The Cell Two Categories of Cells Prokaryotic Cells - A single celled organism that does not have a nucleus covering its DNA or membrane covered organelles. Example: Bacteria PRO rhymes with NO – no nucleus Eukaryotic Cells - an organism made up of cells (multi-cellular) that have a nucleus enclosed by a membrane. Example: Plants and Animals

Two Kinds of Cells: Prokaryotes: Bacteria and Archaea – textbook pages 64-65 Prokaryotes are single celled organisms that do not have a nucleus or “membrane-bound” organelles. Bacteria most common prokaryote smallest cells known live almost everywhere no membrane-covered organelles but they do have ribosomes have a cell wall with the cell membrane just inside of it DNA in this cell is a long, circular molecule shaped like a twisted rubber band

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.

Usually smaller than plant & animal cells BACTERIAL CELLS Usually smaller than plant & animal cells Have a cell wall, cell membrane, ribosomes, cytoplasm, & DNA. Does NOT contain a nucleus so it is a PROKARYOTE

Two Kinds of Cells: Prokaryotes: Bacteria and Archaea – textbook pages 64-65 Single-celled organism Their ribosomes are different from those of bacteria Three types of archaea: Heat-loving – extremophile – live in very hot water, like in hot springs Salt-loving – extremophile-live in areas that are extremely salty Methane-making – live deep in ocean near volcanic vents

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.

Eukaryotic Cells 10 times larger than most bacterial cells Have a nucleus – one type of membrane-bound organelle The nucleus holds the DNA These cells have other organelles that each have a specific job Most Eukaryotes are multicellular Plants, animals, including humans are eukaryotes Eukaryotes can be single celled like amoebas and yeast or multicellular like green algae and mushrooms

Eukaryotes Plant Cell Animal Cell

Compare Prokaryotes and Eukaryotes Make a Venn Diagram or a T chart to compare these two types of cells.

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

The Cell Questions: What are 4 things that all cells have in common? What is the difference between Prokaryotic and Eukaryotic cells? What is one purpose of the cell membrane? Describe cytoplasm – what could you compare it to?