Unit 2: Cells Chapter 3: Cells, The Basic Units of Life Lesson 3.1: The Diversity of Cells

The Diversity of Cells Most cells are so small they can not be seen by the naked eye. How did scientists find cell’s? CELL: the smallest unit that can perform all the processes necessary for life.

Cells and the Cell Theory Robert Hooke was the first person to describe cells (1665) He “discovered” cells by accident He was looking at a thing piece of cork under a microscope The cork looked like it was made of “little rooms” he called cells

THE CELL THEORY 1. All organisms are made of one or more cells 2. The cell is the basic unit of all living things. 3. All cells come from existing cells.

Cell Size – most cells are too small to be seen without a microscope (name one exception) Why Are Cells So Small??? Cells take in and get rid of wastes through their outer surface. As a cell gets larger, it needs more food and produces more waste. So, more materials pass through the outer surface.

Surface area-to-volume ratio: …is the ratio of the cell’s outer surface are to the cell’s volume. = surface area volume

Parts of a Cell: All cells have the following parts in common CELL MEMBRANE: a protective layer that covers the cell’s surface and acts as a barrier. It separates the cells contents from its environment, and controls what goes into and out of the cell CYTOPLASM: jell fluid in the cell All organelles “float” in the cytoplasm

ORGANELLES: structures that perform specific functions within the cell ORGANELLES: structures that perform specific functions within the cell. (see pg 74) 1. Nucleus 2. Ribosome 3. Endoplasmic Reticulum 4. Mitochondria 5. Chloroplast 6. Golgi Complex 7. Vacuole 8 Lysosome

Prokaryotic Cells: BACTERIA AND ARCHEA Prokaryotes are single-celled organisms that do not have a nucleus or membrane covered organelles

BACTERIA The most common PROKAYOTES The smallest cells known Do not have a nucleus Have DNA – it is a long, circular strand Have no membrane covered organelles Have a cell membrane just inside the cell wall See pg 64

ARCHEA – similar to bacteria But can live in places no other organisms can live – in extreme conditions Some times called extremophiles Heat-loving Salt-loving Methane-making See pg. 65

EUKARYOTIC CELLS – all other cells (ex. You & me & a tree) Largest cells – but most still microscopic About 10x larger than bacteria cells Have a nucleus DNA in nucleus Membrane covered organelles Some unicellular, most are multicellular

HW DUE TUES 11/22 Read Chapter 3 Lesson 2 “Eukaryotic Cell” Make a chart in your notebook listing the organelles and their function, and if it is found in plant cells, animal cells, or both. Include the 8 organelles in the chart on pg 74 and Cell Wall, Cytoplasm, Cell Membrane