1. Cell Features

3. A year later, German zoologist Theodore Schwann determined that cells animals are also made of cells

5. All living things are made of one or more cells

6. Cells are the basic units of structure and function in organisms

9. Cell Features Within the cytoplasm are many structures, often suspended in a system of microscopic fibers called the cytoskeleton

13. Prokaryotes are single-celled organisms that lack a nucleus and other internal compartments

14. Without separate compartments to isolate materials, prokaryotes cells cannot carry out many specialized functions

16. The cytoplasm of a prokaryotes contains everything inside the cell membrane

18. Prokaryotes Some prokaryotes cell walls are surrounded by a structure called a capsule. The capsule enables the prokaryotes to cling to almost anything; teeth, skin, food, etc. Many prokaryotes have flagella which are long, threadlike structures that protrude from the cell’s surface and enable movement Prokaryotic flagella rotate propelling the organism up to 20 cell lengths per second

19. Eukaryotic cells The first cells with compartments were primitive eukaryotic cells which evolved about 2.5 billion years ago A eukaryote is an organism whose cells have a nucleus The nucleus is an internal compartment that houses the cell’s DNA

20. Eukaryotic cells Other internal compartments, or organelles, enable eukaryotic cells to function in ways different from prokaryotes An organelle is a structure that carries out specific activities in the cell A complex system of internal membranes connects some organelles within the cytoplasm

21. Eukaryotic cells These membranes provide channels that guide the distribution of substances within the cell Many single celled eukaryotes use flagella for movement Short hairlike structures called cilia protrude from the surface of many eukaryotic cells Flagella or cilia propel some cells through their environment In other cells, cilia or flagella move substances across the cell’s surface

22. Eukaryotic cells A web of protein fibers makes up the cytoskeleton The cytoskeleton holds the cell together and keeps cell membranes from collapsing

23. Cytoskeleton The cytoskeleton provides the internal framework of an animal cell much like our skeletons provide our internal framework The cytoskeleton is composed of an intricate network of protein fibers anchored to the inside of the plasma membrane

25. Other fibers attach the nucleus and other organelles to fixed locations in the cell

29. Cytoskeleton Intermediate Fibers of the cytoskeleton provide a frame on which ribosomes and enzymes can be confined to particular regions of the cell The cell can organize complex metabolic activities efficiently by anchoring particular enzymes near one another

31. Cell membranes are not rigid like an eggshell but fluid like a soap bubble

32. The fluidity of a cell membrane is caused by lipids

34. The Cell Membrane As shown at right, a phospholipid has both a polar “head” and two nonpolar “tails” The head of a phospholid is polar and is attracted to water. In contrast, the two fatty acids, the “tails” are nonpolar and therefore they are repelled by water

35. The Cell Membrane In a cell membrane, the phospholipids are arranged in a double layer called a lipid bilayer The lipid bilayer allows lipids and substances that dissolve in lipids to pass through

36. Member Proteins Various proteins are located in the lipid bilayer of a cell membrane The motion and fluidity of phospholipids enables some membrane proteins to move around within the lipid bilayer

37. Member Proteins Cell membranes contain different types of proteins, among them marker proteins which attach to carbohydrates Receptor proteins bind specific substances Enzymes embedded in the cell membrane are involved in biochemical reactions within the cell Transport proteins aid the movement of substances into and out of the cell