Cell bio chap 17.docx - Cell bio chap 17 Cytoskeleton 1 The cytoskeleton a Gives cell its shape b Allows cell to move c Allows organization of internal

Cell bio chap 17.docx - Cell bio chap 17 Cytoskeleton 1 The...

This preview shows page 1 - 4 out of 9 pages.

Cell bio chap 17 Cytoskeleton 1. The cytoskeleton a. Gives cell its shape b. Allows cell to move c. Allows organization of internal organelles d. Made out of microtubules and actin filaments and intermediate filaments 2. Intermediate filaments a. Ropelike fibers b. 10nm diameter c. One type forms a meshwork called the nuclear lamina just beneath the inner nuclear membrane d. Other types extend across the cytoplasm, giving cells mechanical strength e. In epithelial tissue, they span the cytoplasm from one cell-cell junction to another, thereby strengthening the entire epithelium 3. Microtubules a. Long hollow cylinders b. Made of tubulin c. Outer diameter of 25nm d. More rigid than actin filaments e. One end is usually attached to a single microtubule- organizing center (MTOC) called a centrosome f. Really important for organization g. Makes up mitotic spindle 4. Actin filaments a. Also called microfilaments b. 2 stranded helical polymers of actin c. 5-9nm diameter d. Highly concentrated in the cortex, just beneath the plasma membrane INTERMEDIATE FILAMENTS 1.Intermediate filaments form a strong network in the cytoplasm a.Withstand mechanical stress when cells are stretched b.Toughest and most durable cytoskeletal filamentsc.Surround nucleus and extend to peripheryd.Anchored to plasma membrane at cell-cell junctions (desmosomes) 2.Twisted strands of alpha-helix form a rope like structure
Image of page 1
3.Filament structure strengthens the cell 4. 4 classes of intermediate filaments a. Cytoplasmic i. Keratins 1. In epithelia 2. Most diverse ii. Vimentin and vimentin-related 1. In connective tissue, muscle cells, and glial cells iii. Neurofilaments 1. In nerve cells b. Nuclear i. Nuclear lamins 1. In all animal cells 2. Protect our DNA 5. Keratins a. Keratins- most diverse family of intermediate filaments i. In humans, 54 functional keratin genes b. Span interior epithelial cells from end-to-end filaments in adjacent cells connect indirectly thru desmosomes c. Make our skin cells tough and hold our skin cells together d. Blisters- when the skin cells aren’t held together enough, and fluid can get between the layers e. Epidermolysis bullosa simplex- keratins don’t function correctly- their skin comes apart at the slightest touch. i. Skin becomes severely blistered and falls off 6. Intermediate filaments also provide structure to the nuclear envelope- nuclear lamina a. Lamins- intermediate filament class found in nucleus i. Disassemble and reform at each cell division they phosphorylation and dephosphorylation b. Helps protect the DNA c. Defects in nuclear lamina can cause “progeria” i. A rare premature aging disorder – lamina doesn’t form and act like its supposed to so the DNA doesn’t stay protected ii. Patients die of old age at a very young age
Image of page 2
MICROTUBULES 1.
Image of page 3
Image of page 4

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture

  • Left Quote Icon

    Student Picture