Chapter More Pg Objective: I can describe various structures that lie outside of the cell membrane and relate them to how viruses infect cells.

 Boundary of the cell = Plasma membrane  Extracellular = outside the plasma mem.  Cells secrete substances:  Some leave the cell/organism entirely  Some stay near to help the cell ▪Provide external support ▪Connect cells, etc.

 Found in prokaryotes, plants, and fungi  Stronger than plasma membrane  Protects, maintains shape, etc. (stops excess)  Thicker than plasma membrane  Made of mix of fibers ▪Matrix of proteins and polysaccharides: ▪Cellulose  specific polysaccharide for plants  Exact chemistry varies between species

 Primary Cell Wall  First made by young cell  Thin and flexible (outside)  Middle Lamella  Sticky layer to glue cells  Made of pectin (plyscch.)  Secondary Cell Wall (some)  Several layers (much stronger) – closer to cell ▪Example: wood

 Found in Animal Cells (lack cell wall)  Made of glycoproteins/proteoglycans  Carbs + Proteins in 1 molecule  Also protein collagen in ECM  Connects to cell by…  Fibronectin: protein that attaches ECM to…  Integrin: protein embedded in plasma membrane  Purpose: communicate/influence cell

 Ways in which neighboring cells adhere, interact, and communicate with each other  Necessary, because… cells can organize in multicellular organisms (cells come together to make…) tissue, organs, organ systems

Singular = plasmodesma (desmos = to bind)  Channels that perforate cell wall (porous)  Lined with plasma membrane ▪P.M. of 1 cell continuous with other ▪Cytosol, water, and (macro)molecules freely move

 Tight Junctions  Proteins tightly bind cells together  Prevents seepage of extracellular fluid  Desmosomes  Strong “rivets” fastening cells together  Made of intermediate fibers (keratin)  Stronger, but less sealing  Gap Junctions  most like plasmodesmata  Channels that connect neighboring cells  Via membrane bound proteins Which of these is most like plasmodesmata?

 Structure  Viruses can come in many shapes, but they all essentially have: ▪Protein Coat ▪Nucleic Acid inside  Notice the lack of…  Cell membrane  Cytoplasm  Ribosomes T4 Bacteriophage

 Very, very small (~20 nm)  some can be smaller than a ribosome

 Viruses cannot reproduce on own  Inject DNA (or RNA) into host cell ▪Host cell cannot tell difference and follows viral DNA instructions ▪What are the instructions?  To make more viruses  Once host cell makes TONS of viruses, cell lyses (splits open) releasing more viruses to infect more cells

Viruses Bacterium

 Do not reproduce on their own  Do not have a metabolism  Do not “grow”  Are they alive?!  Are they an organism? HIV: Human Immunodeficiency Virus

 Rhinovirus / Influenza  Common cold / Flu  HIV: Human Immunodeficiency Virus  AIDS is NOT a virus…  HPV: Human Papilloma Virus  Warts ▪Link to cervical cancer!  Hepatitis B virus  Liver Cancer

 Why is this lecture about extracellular components and viruses? (write down YOUR answer in notes!)  Latest research to fight virus involves changing extracellular components to prevent infection  Check out Cell Craft! (on Moodle or just google it!)