CellBio51 - Cell junctions = specialized structures that hold cells together • Tight junctions • Desmosomes • Gap junctions Animal Cell

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Unformatted text preview: 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 outside the membranes themselves Tight Junctions Tight Junctions in red 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 / 6.7 • 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 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 μm, but a bacterium is only 1 μm 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 μm, but a bacterium is only 1 μm in diameter • The DNA forms a closed circle and has many loops so it can Ft inside the cell The Prokaryotic Chromosome is a Circle A spread out E. coli chromosome as seen by electron microscopy Cell Division in Prokaryotes • The duplicated chromosome is attached to the cell membrane to ensure proper distribution to the daughter cells • When the DNA replicates, the attachment points separate as the cell divides • The cells divide by fssion (splitting into 2 cells) Prokaryotic Cell Division Fig. 9.2 / 11.2 Prokayotic Cell Division DNA attached to the cell membrane Replication has occurred; note two copies, two attachment points Fission begins Fission is complete Fission as Seen by Electron Microscopy Fig. 9.2 Fission is almost complete (pg 183/ 212 ) Bacteria Growth movie http://www.youtube.com/watch?v=gEwzDydciWc Chromatin and Chromosomes in Eukaryotic Cells Cell division and The Cell Cycle in Eukaryotes The Eukaryotic Cell Cycle - Divided into 4 Main Stages Interphase consists of G1, S, and G2 The Eukaryotic Cell Cycle is Divided into 4 Main Stages...
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This note was uploaded on 10/16/2010 for the course MCDB MCDB 1A taught by Professor Senghuilow during the Spring '09 term at UCSB.

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CellBio51 - Cell junctions = specialized structures that hold cells together • Tight junctions • Desmosomes • Gap junctions Animal Cell

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