Life’s Structure and Classification Section 3: Cell Structure

"My work, which I've done for a long time, was not pursued in order to gain the praise I now enjoy, but chiefly from a craving after knowledge, which I notice resides in me more than in most other men. And therewithal, whenever I found out anything remarkable, I have thought it my duty to put down my discovery on paper, so that all ingenious people might be informed thereof." - Anton Van Leeuwenhoek Letter, June 12, 1716

A. Cells were first seen 400 years ago, when van Leeuwenhoek invented the first microscope.

Unfortunately, none of Anton Van Leeuwenhoek's microscopes exist today Unfortunately, none of Anton Van Leeuwenhoek's microscopes exist today. His instruments were made of gold and silver and were sold by his family after he died, none have been recovered.

B. Improvements to the microscope and more observations led to the cell theory

It states: All organisms are made up of one or more cells. 2. The cell is the basic unit of organization in organisms. All cells come from cells. Human epithelial cells

C. Cells are either prokaryotic or eukaryotic. Prokaryotic cells lack membrane-bound structures

1. cell wall – tough, rigid outer coverings that protect cells and give them their shape

2. cell membrane – regulates interactions between the cell and its environment.

3. cytoplasm – gelatinlike substance that constantly flows inside the cell membrane of all cells

4. ribosomes – structures that make proteins

5. organelles - structures within the cytoplasm of eukaryotic cells. Most organelles are surrounded by a membrane

6. nucleus – directs all cellular activities; contains long, threadlike, hereditary material made of DNA

7. Chloroplasts – green organelles in the cytoplasm of plant cells; use light energy to make a sugar called glucose ( C 6 H 12 O 6 )

8. mitochondrion – where energy is released when food is broken down into carbon dioxide and water

9. endoplasmic reticulum, also called ER – is a series of folded membranes in which materials can be processed and moved around inside the cell. Rough ER contains ribosomes

10. Golgi bodies - stacked, flattened membranes that sort and package materials and move them to the outside of the cell

11. vacuole - membrane-bound space that can store water, waste products, food, and other materials

12. lysosomes – help break down and recycle food molecules, cell wastes, and worn-out cell parts

C. In a many-celled organism, each cell depends on other cells in the organism

1. tissue – group of similar cells that work together to do one job organ – structures made up of two or more tissues that work together

3. Organ system – group of organs working together to perform a certain function 4. Organ systems work together to make up an organism