1. C ELLS & T HE C ELL T HEORY

2. Cells are the basic unit of life. Cells are classified as prokaryotes or eukaryotes C ELL O VERVIEW Cells ProkaryoteEukaryote

4. H ISTORY OF THE C ELL

5. T HE C ELL T HEORY All living things are composed of cells or cell fragments. All cells come from previously existing cells. Cells Cells are organized into two groups. Prokaryotic Eukaryotic

6. All cells are surrounded by a plasma membrane. The semifluid substance within the membrane is the cytosol, containing the organelles. All cells contain chromosomes which have genes in the form of DNA. All cells also have ribosomes, tiny organelles that make proteins using the instructions contained in genes. P ROKARYOTIC AND EUKARYOTIC CELLS DIFFER IN SIZE AND COMPLEXITY

7. A major difference between prokaryotic and eukaryotic cells is the location of chromosomes. In an eukaryotic cell, chromosomes are contained in a membrane-enclosed organelle, the nucleus. In a prokaryotic cell, the DNA is concentrated in the nucleoid without a membrane separating it from the rest of the cell.

8. Fig. 7.4 The prokaryotic cell is much simpler in structure, lacking a nucleus and the other membrane-enclosed organelles of the eukaryotic cell.

9. 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 P ROKARYOTES

10. E UKARYOTES Plant cell Examples: Single Celled – algae Multicellular - onion Animal cell Examples: Single Celled: Amoeba, Protozoan Multicellular: Human

11. 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 E UKARYOTE

12. E UKARYOTES 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

13. C ELL ( 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

14. C YTOPLASM 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

15. N UCLEUS 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

16. C HROMATIN & C HROMOSOMES 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.

17. R IBOSOMES Ribosomes construct 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

18. E NDOPLASMIC R ETICULUM 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

19. G OLGI B ODIES 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

20. L YSOSOMES 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.

21. C HLOROPLASTS 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

22. C ELL W ALL 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

23. M ITOCHONDRIA 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.

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

25. C YTOSKELETON 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)

26. C ENTRIOLES Pair of tubular structures Important in cell division of animal cells and protists

27. C ILIA & F LAGELLA 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

28. M ULTICELLULAR O RGANISMS 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

29. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 7.7

30. Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings Fig. 7.8