- All living things are made of one or more cells, which are the basic units of structure and function in organisms. Cells arise only from preexisting cells. - Cells come in two main types - prokaryotic cells which lack internal structures and a nucleus, and eukaryotic cells which have internal compartments including a nucleus. - The cell membrane encloses the cell, separating the cytoplasm from the external environment. It regulates what enters and leaves the cell through membrane proteins.

1. Cell Features

2. The Cell TheoryIn 1838, the German botanist MattiasSchleiden concluded that cells make up not only the stems of plants but every part of a plant.

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

4. In 1858, Rudolph Virchow, a German physician, determined that cells came from other cellsCell TheoryThe observations of Schleiden, Schwann, and Virchow form the cell theory which has three parts

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

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

7. All cells arise from existing cellsCell SizeSmall cells function more efficiently than large cells.Small cells can exchange substances more readily than larger cells because small objects have a higher surface area-to-volume ratio than larger objectsAs a result, substances do not need to travel as far to reach the center of a smaller cell

8. Common Cell FeaturesAll cells have a cell membrane, an outer boundary that encloses the cell and separates the cell interior, called the cytoplasm, from it’s surroundings.Cell FeaturesThe cell membrane also regulates what enters and leaves the cell including gases, nutrients, and wastes

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

10. Cell FeaturesMost cells have ribosomes as well

11. Ribosomes are the cellular structures on which proteins are madeCellular StructureAll cells also have DNAWhich provides Instructions for Making proteinsRegulates cellular activitiesEnables cells to reproduce

12. Features of CellsThe smallest and simplest cells are prokaryotes

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

15. For nearly two billion years, prokaryotes were the only organisms on EarthCharacteristics of ProkaryotesProkaryotes can exist in a broad range of environmental conditions

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

17. A prokaryotes enzymes and ribosomes are free to move around in the cytoplasm because there are no internal structures that divide the cell into compartmentsProkaryotesIn prokaryotes, the genetic material is a single circular molecule of DNAProkaryotic cells have a cell wall surrounding the cell membrane that provides structure and supportProkaryotes lack an Internal support skeleton so They rely on a strong cellwall to give the cell shape

18. ProkaryotesSome 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 movementProkaryotic flagella rotate propelling the organism up to 20 cell lengths per second

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

20. Eukaryotic cellsOther internal compartments, ororganelles, enable eukaryoticcells to function in waysdifferent from prokaryotesAn organelle is a structure that carries out specific activities in the cellA complex system of internal membranes connects some organelles within the cytoplasm

21. Eukaryotic cellsThese membranes provide channels that guide the distribution of substances within the cellMany single celled eukaryotes use flagella for movementShort hairlike structures called cilia protrude from the surface of many eukaryotic cellsFlagella or cilia propel some cells through their environmentIn other cells, cilia or flagella move substances across the cell’s surface

22. Eukaryotic cellsA web of protein fibers makes up the cytoskeletonThe cytoskeleton holds the cell together and keeps cell membranes from collapsing

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

24. CytoskeletonBy linking one region to another, they support the shape of the cell, much as steel beams anchor the sides of a building together

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

26. Because protein fibers are too small for a light microscope to reveal, biologists visualize the cytoskeleton by attaching flourescent dyes to antibodies. CytoskeletonThere are three types of cytoskeleton fibersLong slender microfilaments made of the protein actinHollow tubes called microtubules made of the protein tubulinThick ropes of protein called intermediate fibers

27. CytoskeletonThe actin fibers of the cytoskeleton form a network just beneath the cell surface that is anchored to membrane proteins embedded within the cell membrane

28. By contracting or expanding, actin plays a major role in determining the shape of animal cells by pulling the plasma membrane in some places and pushing it out in othersCytoskeletonMicrotubules within the cytoskeleton act as a highway system for the transportation of information from the nucleus to different parts of the cellRNA molecules are transported along microtubular “rails” that extend through the interior of the cell like train tracks

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

30. The Cell MembraneThe cytoplasm of a cell is contained by it’s membrane