Lecture 21 Flashcards
What is a tonoplast?
vacuolar membrane containing active transport systems allowing ions and molecule transport
Microtubules (MT)
- largest cytoskeletal element
- polymer of 2 diff proteins: a-tubulin, B-tubulin
What are associated proteins (MAPS)?
several diff proteins binding to MTs
- modulate assembly, function
- mediate interactions w/ other cellular structures
Plant Vacuole Functions
- intracellular digestion comparable to lysosomes
- mechanical support, turgor pressure
- gives rigidity to plant-supports soft tissues
- stretches cell wall during growth - storage
- solutes and macromolecules
- chemical storage (toxic compounds as well)
Microtubules structure
- a/B heterodimers form long protofilaments
- 13 protofilaments from longitudinal array creating structural polarity
- heterodimers are aligned in the same direction creating structural polarity
What are microfilaments?
a hollow tube formed from tubulin dimers
Cytoskeleton functions
1) structural support
2) spatial organization w/in cell
3) intracellular transport
4) contractility and mobility
What is a cytoskeleton made out of?
dynamic network of interconnected filaments and tubes- extended throughout cytosol of eukaryotes
What are microtubules?
double helix of actin monomers
MTs ends
fast-growing: plus end
slow-growing: minus-end
Cytoskeleton components
- microfilaments
- microtubules
- intermediate filaments
Microtubules assembly and disassembly
microtubules undergo dynamic assembly and disassembly
- shrinkage occurs very rapidly at + end - termed catastrophe
- formation of MTs is regulated/ controlled
What are intermediate filaments?
strong fiber composed of intermediate filament protein subunits
What do APs help do?**
form endocytic vesicles from plasma membrane to endosomes/lysosomes
What are the types of microtubules?
- Axonemal MT: organized stable part of structures involved in cell movement
- Cytoplasmic MT: loosely organized very dynamic in cytosol
What are the 2 classes of MAPS?
- Non-motor MAPs
- control MT organization in cytosol
- defective Tau protein - Motor MAPs
- kinesin (+) and dynein (-)
- ATP for generated force
- move material along MT track
- generated sliding force between MTs
Plant vacuoles
- fluid-filled membrane-bound
- take up 90% of cells volume
- involved in regulation of toxic ions, regulation of cell turgor, storage of amino acids, sugars and CO2 in malate form
What is the 2nd function of lysosomes?**
- Degradation of internalized material
- recycling of plasma membrane components like receptors and extracellular material
- destroy pathogens like bacteria and viruses- only in phagocytic cells
What is the AP complex?**
- Cathrin Adaptor Proteins
- coated vesicles move from TGN to other vesicles
- e.g. lysosomes, endosomes
What is dynamic instability?
rapid turnover of most MTs in vivo, half-life in minutes w/in cells
What is the first function of lysosomes?*****
- Autophagy: normal disassembly of unnecessary/ dysfunctional cellular components-organelle turnover
- membrane derived from ER engulfs target organelle: autophagosome formation
- lysosome fuses w/ ER-derived autophagic vesicle: autolysosome formation
- the content of autolysosome is enzymatically digested and released (exocytosis)
Autophagosome formation → Lysosome recruitment → Autolysosome → Digestion
and release
