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

Cells http://www.youtube.com/watch?v=IcevP5tkWH0&feature=related

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

Cells All cells are classified as either Prokaryote Eukaryote

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

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)

Figure 4.4a Figure 4.4

E. coli

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

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

Figure 4.6b Figure 4.6b

Figure 4.7b Figure 4.7b

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

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

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

Prokaryote vs. Eukaryote

Prokaryote or Eukaryote??

Prokaryote or Eukaryote??

Prokaryote or Eukaryote??

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.

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!

Cell Membrane

Pg 64 Pg 64

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

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.

The Nucleus  Figure 4.6a

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

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

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

DNA Double Helix Bases: Cytosine C Thymine T Adenine A Guanine G C T A http://www.youtube.com/watch?v=qy8dk5iS1f0

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.

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.