Cells are the basic unit of life. Cells are classified as prokaryotes or eukaryotes

1. Cell Overview • Cells are the basic unit of life. • Cells are classified as prokaryotes or eukaryotes Cells Prokaryote Eukaryote

2. Prokaryotes • Oldest cells – probably the first life on earth • Very simple cells composed of 2 main parts • Cell Membrane – the outer boundary of the cell • Cytoplasm – jelly-like interior of the cell • The name prokaryote comes from the Greek pros meaning “before” and karyon meaning “nut”, referring to the nucleus • Most prokaryotes are single celled organisms • Example: bacteria

3. Eukaryote • More advanced cells • Found in plants and animals • Eukaryotic cells are composed of 4 main parts: • Cell Membrane – the outer boundary of the cell • Cytoplasm – jelly-like interior of the cell • Nucleus – the control center of the cell which contains the cell’s genetic material (DNA) • Organelles – structures that carry out cell functions • Organisms can be single-celled or multicellular

4. Eukaryotes Animal cell Plant cell Examples: Single Celled: Amoeba, Protozoan Multicellular: Human Examples: Single Celled – algae Multicellular - onion

5. Eukaryotes • Organelles – membrane-bound compartments within a cell • Allow different internal environments within a single cell • Allow many different chemical reactions to take place without disturbing each other • Allow specialized functions • Almost all Eukaryotic cells have the same basic set of organelles • Some organelles are only found in plant cells, others are only found in animal cells

6. Cell (plasma) membrane • Defines the boundary of the cell • Regulates what comes in and goes out (selectively permeable) • Composed of proteins and special lipids called phospholipids • Outer side is hydrophilic • Inner side is hydrophobic • Molecules are fluid-like, not locked in place

7. Cytoplasm • The entire region of the cell between the nucleus and the plasma membrane • Consists of various organelles suspended in fluid • Cytoskeleton is a network of fibers throughout the cytoplasm that give the cells shape

8. Nucleus • Houses the cell’s DNA that directs all cellular activity • DNA is attached to proteins in long fibers called chromatin • Enclosed by a membrane (nuclear membrane) • Contains nucleolus • Nucleolus makes ribosomes

9. Chromatin & Chromosomes • Most of the time, the DNA exists as a mass of very long, thin fibers called chromatin • The instructions in the chromatin can be “read” so that the cell can produce proteins. • When the cell is getting ready to divide, the chromatin condenses into compact chromosomes. • Chromosomes are easier to move, but the instructions can’t be “read” to make proteins.

10. Ribosomes • Ribosomes onstruct proteins • Use instructions in the DNA to build proteins • Ribosomes are found on the Endoplasmic Reticulum • Make proteins for membranes and export outside the cell • Ribosomes are also found suspended in the cytoplasm • Make enzymes and proteins for use inside the cell

11. Endoplasmic Reticulum • A network of membranes in the cytoplasm. • Two types: rough ER and smooth ER • Synthesize proteins (rough ER) • Proteins can be secreted by the cell, or packaged and sent out of the cell to other cells • Synthesize lipids (smooth ER) • Example: hormones

12. Golgi Bodies • Takes products from the ER and modifies, stores, and routes to next destination • Enzymes in the golgi bodies refine and modify the ER products • Example: fold proteins into their final shape

13. Lysosomes • Contain digestive enzymes that can break down macromolecules such as proteins, nucleic acids, and polysaccarides • Digest food to nourish the cell • Help destroy harmful bacteria • Recycle damaged organelles to make molecules available for construction of new ones.

14. Chloroplasts • Photosynthetic organelles found in some plants and algae • Convert light energy from the sun to the chemical energy stored in sugars and other organic compounds

15. Mitochondria • Powerhouse of the cell • Site of cellular respiration • Releases energy from sugars and other organic molecules into an energy source the cell can use • The energy that a cell uses is called ATP. We will learn about it in the next chapter.

16. Vacuoles • Large membrane-bound sacs • Store undigested nutrients or chemicals • Many plants have a large central vacuole • Vacuoles in flower petals may contain pigments

17. Cell Wall • Protects the plant cell and maintains its shape • Located outside the plasma membrane • only plant cells and prokaryotes have cell walls • Animal cells do not • Made of cellulose

18. Cytoskeleton • A network of fibers extending throughout the cytoplasm • Microtubules – straight tubes of protein that give rigidity and shape to the cell. • Organelles can move along microtubules • Microfilaments – thin solid rods of protein that slide past each other to enable the cell to change shape • Looks like an oozing movement (ex. Amoeba or white blood cells)

19. Centrioles • Pair of tubular structures • Important in cell division of animal cells and protists

20. Cilia & Flagella • Flagella are long, thin, whip-like structures that enable some cells to move • Wave in an S-shaped motion that propels the cell • Cilia are short, hair-like structures that surround a cell • Have a back and forth motion that moves the cell • Can also be found on stationary cells in a multicellular organism • Example: the cells lining your windpipe have cilia that move mucus out of your lungs

21. Multicellular Organisms • Each organelle performs basically the same functions in all cell types • Organelles vary in amount and properties by cell type. • Allows cells to perform specialized functions • All cells carry on the basic activities of life • In a multicellular organism, each cell type also takes on specialized functions • A group of cells with the same specialization works together to perform a function • Tissues, organs, systems

22. R&C #1 p. 277 • Explain why it is important for all cells to have a cell membrane. Why might it be beneficial?

23. #2 a. Prokaryotes Vs. Eukaryotes Eukaryotes Prokaryotes

24. #2 b. Plant Cells vs. Animal Cells Animal Cells Plant Cells

25. R&C #4 p. 277 • What differences are likely to exist between single-celled organisms and the cell of a multicellular organism?

26. R&C #5 p. 277 • Build a concept map using the following words: atoms, carbohydrates, cells, elements, lipids, nucleic acids, organic molecules, and organism.