1. Cellular Classification & Organelles: A Look at the Endomembrane System
Biology 111
Holyoke Walsh

2. Cells

3. COMPARING CELLS
The size & shape of a cell relates to its function.

4. Cells
All cells are classified as either
Prokaryote
Eukaryote

5. Prokaryote Cells
no membrane bound nucleus, chromosomes grouped together in an area called the "nucleoid"
no membrane bound organelles
smaller than eukaryotes

6. have cell wall and cell membrane, some have a capsule on the outside
ribosomes make protein
consist of bacteria and archaebacteria
Appendages include:  fimbriae/pili, flagella
*pili are usually longer and fewer than fimbriae, both function for attachment and recognition of host cells (pili has a function for sexual reproduction)

7. Figure 4.4a
Figure 4.4

8. E. coli

9. Eukaryotes
has a membrane bound nucleus
has membrane bound organelles in cytoplasm
Organelles perform specific functions
much larger than prokaryotes
Organisms within the animal, plant, fungi and protista kingdoms are all eukaryotes

10. We will be spending a lot of time on organelles and their functions.

11. Figure 4.6b
Figure 4.6b

12. Figure 4.7b
Figure 4.7b

13. Prokaryote vs Eukaryote Cells
Endosymbiosis theory: 
All organelles seem to share many properties with bacteria. Lynn Margulis proposed endosymbiont hypothesis: that organelles derived from ancient colonization of large bacteria (became the eukaryotic cell) by smaller bacteria (became the mitochondria, chloroplast, etc.) Symbiosis = "living together".
*Mitochondria & Chloroplasts have their own DNA
Animation at Microbiological Concepts

14. Commonalities…of all cells!!
Plasma Membrane
Cytoplasm
Chromosomes (DNA)
Ribosomes

15. Key Differences? The location of their DNA; membrane bound organelles
Prokaryote = nucleoid region
Eukaryote = nucleus

16. Prokaryote vs. Eukaryote

17. Prokaryote or Eukaryote??

18. Prokaryote or Eukaryote??

19. Prokaryote or Eukaryote??

20. Eukaryotes
In addition to the plasma membrane at its outer surface, a eukaryotic cell has extensive & elaborately arranged internal membranes, which divide the cell into compartments.
These provide different local environments that facilitate specific metabolic functions, so incompatible processes can go on simultaneously in a single cell
The plasma and organelle membranes participate directly in the cell’s metabolism b/c many enzymes are built right into the membranes themselves.

21. Cell Membranes..in general
Phospholipid bilayer
Embedded proteins
Each type of membrane has a unique composition of lipids and proteins suited to that membrane’s specific function
Ex: enzymes embedded in the mitochondrial membrane function in cellular respiration…which creates the ATP energy our cells need to function!

22. Cell Membrane

23. Pg 64
Pg 64

24. Eukaryotes…genetic info…
Two cellular components involved with the genetic control of the cell are the NUCLEUS & the RIBOSOMES
Nucleus – houses most of the cell’s DNA
Ribosomes – use information from the DN
A to make proteins

25. NUCLEUS
An intricate protein structure called a pore complex lines each pore and plays an important role in the cell by regulating he entrey and exit of most proteins and RNSs as well as large macromolecules.
Except at the pores the nuclear side of the envelope is lined by the nuclear lamina, a netlike array of protein filaments that maintains the shape of the nucleus by mechanically supporting the nuclear envelope.
As a cell prepares to divide, the thin chromatin fibers coil up (condense), becoming thick enough to be distinguished as the familiar separae structures we know as chromosomes (46 in somatic cells)…(23 in sex cells)
Nucleolus – appears as densely stained granules and fibers adjoining part of the chromatin. Here a type of RNA called Ribosomal RNA (rRNA) is made from instructions in the DNA….(starting the process of protein synthesis) Also, protein imported from the cytoplasm are assembled with rRNA into large and small ribosomal subunits. These subunits then exit the nucleus through the nuclear pore to the cytoplasm, where a large and small subunit call assemble into a ribosome.

26. The Nucleus 
Figure 4.6a

27. The Nucleus
Nuclear envelope contains nuclear pores for some things to enter and exit (nucleoplasm within)
Chromatin is DNA and proteins, when the cell begins to divide, chromatin condenses and forms chromosomes
DNA remains in the nucleus, it sends instructions to the cytoplasm via messenger RNA
RNA directs the synthesis of proteins on ribosomes in the cytoplasm
Nucleolus assembles ribosomes within the nucleus, ribosomes contain the "tools" to construct proteins

28. Chromosomes – made of DNA/Protein!
DNA: Polymer of millions of nucleotides
Nucleotide = Deoxyribose Sugar (pentose)
+Phosphate + Nitrogen Base

29. One Strand of DNA
The backbone of the molecule is alternating phosphates and deoxyribose sugar
The teeth are nitrogenous bases.
phosphate
deoxyribose
{Point to the 3-D mode, if you have one, to show the parts as you discuss them.}
bases 29 29

30. DNA Double Helix Bases: Cytosine C Thymine T Adenine A Guanine G C T A

31. Ribosomes Made of some RNA (genetic info) and Protein
each is composed of two subunits, one large and one small
Non-membranous organelles
Vary in size (smaller in prokaryotes)
Main function is to carry out protein synthesis.

32. Ribosomes cont…
Cells that have high rates of protein synthesis have particularly high rates of ribosomes
Located in the cytoplasm/ER (structurally identical)
Free ribosomes – function within the cytosol (ie. enzymes that catalyze reactions)
Attached ribosomes – generally destined for insertion into organelles membranes or for export (cells that secrete enzymes)
Why does the human pancreas have millions of ribosomes?
Human pancreas has millions of ribosomes b/c they are making proteins all the time…ie. insulin.