CellBio3 - Extracellular Structures How is the Plasma...

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Unformatted text preview: Extracellular Structures How is the Plasma Membrane involved in Cell Adhesion and Recognition? Cells arrange themselves in groups by cell recognition and cell adhesion . They attach to each other using various extracellular proteins These processes can be studied in sponge cellsthe cells are easily separated and will come back together again. Roles of Extracellular Structures Figure 5.6 Cell Recognition and Adhesion (B) Page 91. Roles of Extracellular Structures The extracellular matrix supports tissue functions in animal cells Extracellular Matrix Strong fbrous network between cells that holds cells together to Form tissues and organs Made oF large glycoproteins ( e.g ., collagen) Cell Cytoskeleton is linked to the ECM Extracellular structures in plants-Plant Cell Walls Strong and thick (usually several m) Maintains cell shape rigidly (e.g, the wood oF a tree is made up oF cell walls) Fig 4.25 plant cell walls Cell junctions specialized structures that hold cells together: Tight junctions Desmosomes Gap junctions Animal Cell Junctions Two main functions: 1) helps cells to adhere to each other 2) facilitates communication between cells and facilitates or blocks transport of molecules between cells Tight junctions 1) Link cells together very tightly 2) Do not allow passage of materials in the space between the two cells 3) Do not allow movement of membrane proteins inside the membranes themselves Figure 5.7 Junctions Link Animal Cells Together (A) Tight junctions form a quilted seal, preventing movement of molecules in the space between the cells. Desmosomes 1) allows space between the cells 2) does not limit movement in the space between the two cells Figure 5.7 Junctions Link Animal Cells Together (B) Desmosomes are like spot welds Desmosomes Fig. 5.6 tight junctions A desmosome A Desmosome Visualized by Electron Microscopy Fig. 5.6 Gap junctions permits passage of large molecules between two cells made of special connecting protein channels that can open and close called connexons Figure 5.7 Junctions Link Animal Cells Together (C) Gap junctions allow communication Section 3 Chromatin, Chromosomes Cell Cycle in Prokaryotes and Eukaryotes Set 5 Cell Division in Prokaryotes and Eukaryotes Prokaryotic Chromosomes and Eukaryotic Chromosomes 4 signals required before cell division 1. Reproductive signal 2. Replication of DNA ++ 3. Segregation 4. Cytokinesis The Chromosome in Prokaryote Cells There is one chromosome (the DNA is contained in a single chromosome !) The Chromosome in Prokaryote Cells There is 1 chromosome The stretched out length of the chromosome is ~ 1500 m, but a bacterium is only 1 m in diameter Its DNA must be compacted!!! The Chromosome in Prokaryote Cells There is 1 chromosome The stretched out length of the DNA is ~ 1500 m, but a bacterium is only 1 m in diameter The DNA forms a closed circle and has many loops so it can Ft inside the cell...
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CellBio3 - Extracellular Structures How is the Plasma...

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