Cells

1. Cells Functions and structure

2. Can weseecells? • Howmanycells do youhave in yourbody?

3. All living organisms on Earth are divided in pieces called cells. There are smaller pieces to cells that include proteins and organelles. There are also larger pieces called tissues and systems. • A cell is a small, membrane enclosed structure filled with an aqueous solution where organelles and other subcellular structures are found. • Cells are small compartments that hold all of the biological equipment necessary to keep an organism alive and successful on Earth.

4. Looking at cellfunctions • A main purpose of a cell is to organize. Cells hold a variety of pieces but in the big picture, a cell's purpose is much more important than acting as small organizational pieces, there are several main functions that the cell has to carry out: molecule transport, reproduction, and energy conversion.

5. Celltypes • Living cells are divided into two types - procaryotic and eucaryotic (sometimes spelled prokaryotic and eukaryotic). This division is based on internal complexity.

6. PROKARYOTES - MISSING A NUCLEUS • If you're looking to learn about cells with a nucleus, this is the wrong place. Prokaryotes do not have an organized nucleus. Their DNA is kind of floating around the cell. It's clumped up, but not inside of a nucleus.

7. Most prokaryotes are bacteria and bacteria can do amazing things. Although they are very simple organisms, they are found everywhere on the planet. Some scientists even think that they may be found on other planets (maybe even Mars). Some places you can find bacteria every day are in your intestines, a cup of natural yogurt, or a bakery. Prokaryotes are the simplest of simple organisms.

8. Prokariotic main characteristics are: (1) Prokaryotes have no organized nucleus. Like we said, the DNA is clumped in an area but there is no organized nucleus with a membrane. (2) Prokaryotes do not usually have any organelles. They will probably have ribosomes inside of their cells, but ribosomes are not technically considered organelles. No chloroplasts. No mitochondria. No nucleus. Not much at all. (3) Prokaryotes are very small. Because they don't have all of the normal cell machinery, they are limited in size. As always in biology, there are exceptions, but generally, prokaryotes are very small (compared to other cells). Mind you, compared to a virus they are big, but next to an amoeba, tiny.

9. Prokaryotic structure ExternalStructure InternalStructure

10. InternalStructure Bacteria have a very simple internal structure, and no membrane-bound organelles. Back

11. Nucleoid: DNA in the bacterial cell is generally confined to this central region. Though it isn't bounded by a membrane, it is visibly distinct (by transmission microscopy) from the rest of the cell interior. Back

12. Ribosomes: Ribosomes give the cytoplasm of bacteria a granular appearance in electron micrographs. Though smaller than the ribosomes in eukaryotic cells, these inclusions have a similar function in translating the genetic message in messenger RNA into the production of peptide sequences (proteins). Back

13. Surface Structure Beginning from the outermost structure and moving inward, bacteria have some or all of the following structures: Back

14. Capsule: This layer of polysaccharide (sometimes proteins) protects the bacterial cell and is often associated with pathogenic bacteria because it serves as a barrier against phagocytosis by white blood cells. Back

15. cellwall: Composed of peptidoglycan (polysaccharides + protein), the cell wall maintains the overall shape of a bacterial cell. The three primary shapes in bacteria are coccus (spherical), bacillus (rod- shaped) and spirillum (spiral). Mycoplasmaare bacteria that have no cell wall and therefore have no definite shape. Back

16. Plasma membrane: This is a lipid bilayer much like the cytoplasmic (plasma) membrane of other cells. There are numerous proteins moving within or upon this layer that are primarily responsible for transport of ions, nutrients and waste across the membrane. Back

17. Pili: These hollow, hairlike structures made of protein allow bacteria to attach to other cells. A specialized pilus, the sex pilus, allows the transfer of plasmid DNA from one bacterial cell to another. Pili (sing., pilus) are also called fimbriae (sing., fimbria). Back

18. Flagella: The purpose of flagella (sing., flagellum) is motility. Flagella are long appendages which rotate by means of a "motor" located just under the cytoplasmic membrane. Bacteria may have one, a few, or many flagella in different positions on the cell. Back

19. QUIZ

20. Which of these would not be found in a prokaryotic cell? A. ribosomes B. cell membrane C. nucleus D. DNA • Prokaryotic cells have the following structures: A. Ribosomes, cell membrane, nucleus, cell wall B. Capsule, cell wall, plasma membrane, nucleoid , ribosomes C. cell wall, plasma membrane, nucleoid, ribosomes and mitochondria D. Capsule, cell wall, plasma membrane, nucleus , ribosomes

21. http://www.cellsalive.com/cells/cell_model.htm • http://www.biology4kids.com/files/cell2_main.html • Thecellsong: http://www.youtube.com/watch?v=oNZsvG_ODG4&feature=related • How the body works (video): http://www.neok12.com/php/watch.php?v=zX606f017b425c70037a435d&t=Cell-Structures • Cell structure Video: http://www.mhln.com/ob/assets/00035501/htm/00035804/00035804.htm