Prokaryotic Cells

2. Prokaryotic Cells Chapter 4

3. Prokaryotes • The first types of cells to develop evolutionarily were prokaryotes • The term prokaryote means “naked DNA” • Prokaryotes therefore, do not have a nuclear membrane surrounding their DNA

4. Prokaryotes • In fact, they have no membrane bound structures and are instead very simple in construction • Prokaryotes began, and continue to be, unicellular organisms • All bacteria are prokaryotes

6. Prokaryotes consist of the following structures: • Plasma Membrane – controls what enters and exits the cell • Sometimes has infoldings (called mesosomes) that increase the surface area of the membrane

7. Cell Wall – provides protection • Made of a protein/carbohydrate structure • Bacteria are identified based upon which of the two types of cell walls they have as based upon the Gram Stain Technique • Gram positive bacteria stain purple • Gram negative bacteria stain pink

8. Flagella – Tail-like structure that helps with locomotion • Pilli – Threadlike projections that help with attachment and sexual reproduction (through transfer of DNA) • Cytoplasm – clear, gelatinous fluid that takes up most of the space inside the cell and contains all necessary enzymes for metabolic processes

9. Ribosomes – Used for protein synthesis, which is a part of gene expression • Composed of two parts called the “heavy” and “light” pieces • Heavy and light pieces are 50s and 30s in size (s represents the svedburg unit) • Total measurement of prokaryotic ribosomes is 70s (doesn’t add up because s is not a measurement of size but sedimentation during centrifugation)

10. Nucleoid – Region where DNA can be found • In prokaryotes, DNA forms a closed loop • Many prokaryotes also have a smaller loop called a plasmid that contains a few genes and can be easily transferred to other cells

11. Prokaryotes

12. Conjugation • Form of reproduction in some prokaryotes • 2 prokaryotes attach to each other via the pilus and exchange genetic material. • Then go on to binary fission. NOTE: Conjugation does not create new prokaryotes!! It recombines the DNA before they go on to divide separately.

13. E. Coli infection http://www.biology.ualberta.ca/facilities/multimedia/uploads/microbiology/ecoli.html

14. Prokaryotes • Binary fission • Method of reproduction in prokaryotes • Asexual form of reproduction in which a cell divides into two same size cells that are genetically identical

15. Eukaryotic Cells Chapter 4

16. Eukaryotic Cells evolved after prokaryotes • The endosymbiotic theory states that eukaryotes came about when one prokaryote enveloped another

17. Eukaryotic Cells are much more complex than prokaryotes • Made up of smaller components with specialized functions called organelles

22. Eukaryotes • Cell Organelles • Nucleus – contains DNA • Ribosomes – create new proteins • Composed of a 40s and 60s unit which makes the ribosome overall to be 80s • Rough Endoplasmic Reticulum (Rough ER) – site protein synthesis • Called “rough” because it is studded with ribosomes

23. Smooth ER – site of lipid (fat) synthesis and storage • Lysosome – contains enzymes that break down cellular waste • Golgi Apparatus (aka Golgi Body) – packages and ships proteins (to other parts of the cell as well as outside of the cell)

24. Mitochondria – “powerhouse of the cells”; creates energy for the cell in the form of ATP • Cytoplasm – clear gelatinous fluid inside of the cell • Centriole – helps with cell division in animal cells

25. Chloroplast – found only in plant cells, this organelle is the site of photosynthesis • Cell Wall – found only in plant cells, this organelle gives support and structure to the cell • Plasma membrane – controls what enters and exits the cell

26. Microtubules and Microfilaments – linear protein structures that provide support for animal cells; sometimes aid in movement of cell organelles • Nucleolus – found within the nucleus, this organelle is in charge of creating new ribosomes • Vacuole – stores food, water, and/or waste; animal cells have multiple small ones while plant cells have one large vacuole for water storage only

27. Plant and animal cells are very similar but have a few distinct differences:

28. Animal Cell Mix-Match http://www.biology.ualberta.ca/facilities/multimedia/uploads/cell_biology/animalcell_DD.html Plant Cell Mix-Match http://www.biology.ualberta.ca/facilities/multimedia/uploads/cell_biology/plantcell_DD.html

29. 2.3.5

30. Roles of extracellular components: • Plant cell wall mantains cell shape, prevents excessive water uptake, and holds the whole plant up against the force of gravity • Animal cells secrete glycoproteins that integrate themselves in the plasma membrane • The glycoproteins help with support, adhesion and movement

32. Comparing Prokaryotes and Eukaryotes http://www.biology.ualberta.ca/facilities/multimedia/uploads/cell_biology/provseuk.html