1. The Cell 7 th Grade Science Mrs. Christopherson Mrs. Goede

2. History of Cells 1665: Robert Hooke used a compound microscope to look at cork. 1674: Anton von Leeuwenhoek observes microorganisms in pond water 1838: Matthias Schleiden concludes all plants are made up of cells. 1839: Theodor Schwann concludes all animals are made up of cells. 1855: Rudolph Virchow proposes that all cells come from existing cells, completing the cell theory.

3. Cell Theory 1. All organisms are composed of one or more cells –Organisms can be unicellular or multicellular 2. The cell is the basic unit of organization of organisms 3. All cells come from pre-existing cells –Cells reproduce to make exact copies of themselves

4. Two Types of Cells Prokaryotic Cells: –No nucleus –No organelles –Mostly unicellular organisms –Cell wall or membrane

5. Two Types of Cells Eukaryotic Cells: –Nucleus –Organelles surrounded by membranes –Mostly multicellular –organisms –Cell wall or membrane

6. Prokaryotes No Nucleus Single celled Little or no organization within cell wall and membrane Eukaryotes Have a nucleus Contain membrane-bound organelles that have specialized tasks Single-celled or multicellular Both Cell wall Cell membrane

7. Cell Specialization Multicellular organisms have cells that do many different jobs. –For example, there are blood cells, muscle cells, nerve cells, etc. These cells are said to be “specialized”. –Specialized cells perform only their specific functions and cannot live on their own.

8. Levels of Organization Within Organisms In multicellular organisms, cells are grouped together in tissues. –A tissue is a group of similar cells that do a specific job. –An example is our skin. Tissues that work together form organs. –An example of an organ is the heart. Organs and tissues working together from organ systems. Example: the digestive system The largest level of organization is the organism itself.

9. Levels of Organization Within Organisms

10. Cell Organelles Cell wall: a tough outer covering that protects the cell and provides support. –Only plant cells have cell walls. Can you guess why?

11. Cell Organelles Cell membrane: a protective covering that surrounds the cell. –Materials entering the cell must pass thru the cell membrane. Some materials can easily enter while others cannot cross at all. –Selectively permeable. –Both plant and animal cells have cell membranes

12. Cell Organelles Cytoplasm: gel-like material found inside the cell, contains the organelles. Nucleus: genetic material is stored here in the form of chromosomes, which are made of DNA. –The nucleus is usually the largest organelle found in the cell! Nuclear membrane: surrounds and protects the nucleus.

13. Cell Organelles Endoplasmic Reticulum: is responsible for transporting materials in the cell. –Smooth ER: does not contain ribosomes, makes lipids and membrane proteins –Rough ER: contains ribosomes, makes proteins Ribosomes: produce proteins and are attached to the endoplasmic reticulum.

14. Cell Organelles Mitochondria: transform the energy in food to energy the cell can use to drive chemical reactions. –The “powerhouse” of the cell Vacuoles: store substances in the cell. Lysosomes: involved in digestion of old cell organelles as well as breaking large molecules into smaller ones.

15. Cell Organelles Golgi Body: packages products from the ER and distribute them around or outside of the cell.

16. Cell Organelles

17. Cell Growth and Division Multicellular organisms grow because cell division increases the number of cells in them. Cells become specialized during the development of an organism. Cells that are damaged or worn out are replaced by cell division.

18. Cell Growth and Division: The Cell Cycle Interphase: The part of the cell cycle when the cell is not dividing. –This is the longest phase in the cell cycle. –Cells grow and go about their daily routines in this part of the cycle. –DNA (genetic material) replicates.

19. Cell Growth and Division: The Cell Cycle Mitosis: the part of the cell cycle where the nucleus divides. Occurs in non- reproductive cells and produces exact copies of the parent cell. –Prophase: The chromosomes condense –Metaphase: The chromosomes line up in the middle of the cell. –Anaphase: The chromosomes separate and are pulled to either end of the cell. –Telophase: The new nuclear membrane forms. –Cytokinesis: The cell splits in half.

20. Cell Growth and Division: The Cell Cycle