Lecture 7 Flashcards
How does the cytoskeleton get organized to move things
Things - means stuff inside the cell (organelles, chromosomes) and the cell itself
-motor proteins
- centrosomes
-cilia and flagella
Motor proteins
-walk along cytoskeleton filaments carrying vesicles and other organelles
-Bind the filament on one end, bind cargo on the other
-energy for walking comes from ATP
-no motors for intermediate filaments
-no known motors in prokaryotes
Motor families
Myosins: walk along microfilaments
Kinesins: walk along microtubules
Dyneins: walk along microtubules
Tail domain
Carries cargo
Motor domain
Walks on cytoskeleton
Centrosomes (animal cells)
-tether microtubules at their bases
- this creates cell polarity and contributes to shape
- found at:
- mitotic spindle poles to organize microtubules
- base of cilia and flagella
-consist of 2 centrioles surrounded by a dense matrix of proteins
Centrioles inside a ____?
Centrosome
Centrioles are composed of specialized microtubules
Flagella
Movements propel through watery medium
Ex. Sperm motility
The tail
Cilia
Shorter, move fluids over cell surface
-can propel the cell (like a paramecium)
-line air passages of lungs and sweep out bacteria, dust particles, and other contaminants
Cilia and flagella both have in common
Both surrounded by plasma membrane
Cilia and flagella movement by microtubules and motor proteins
Dyneins cross link microtubules and cause them to bend when active
Prokaryotic flagellum
-totally different machanism in bacteria
-uses rotating socket at the base to turn and create whipping motion
Extracellular Matrix (ECM) and cell walls
Functions
Support
Adhesion
Protection
Gateway for in/out and intercellular communication
Secreted from cells
Animals- extracellular matrix
-mostly proteins and glycoproteins (proteins with sugars attached)
- widely variable composition depending on cell type
Plants fungi bacteria- cell walls (technically ECMs but referred to as walls)
Plants- mostly cellulose (polysaccharide)
Fungi- mostly chitin (polysaccharide)
Bacteria- mostly peptidoglycans (polysaccharides with peptide (small proteins) attached)
Animal ECM roles
-adhesion (hold cells together or to a surface)
-support
-shape/ migration
-cell division
Lots of intermediate filament proteins such as collagen
Forms the mass of skin, bones, tendons
Animal cell junctions
-Hold cells together
-allow selective intercellular movement of stuff
- seal neighbouring cells to prevent passage
Animal cell junction types
-anchoring junctions
Hold together
- tight junctions
seal cells together
-gap junctions
Allow passage
Plant cell wall functions
Support and cell shape
Hold cells together
Protection
Intercellular communication
Plant cell walls composition
Cellulose
Other polysaccharides
Proteins
Primary cell wall structure
Pectin rich middle lamella joins adjacent cells
Perforations called plasmodesmata allow intercellular transport and communication
Bacterial cell wall and surface structure
-mostly peptidoglycans (polysaccharides with short peptides attached)
-cell wall typically coated with polysaccharides called a CAPSULE
- capsule can also form a gooey “slime layer” to aid in surface adhesion and biofilm formation
Eukaryotic cell examples
Animals plants fungi
Eukaryotic cell size
10-100 micrometers in diameter
