Cytoskeleton Flashcards
Why do anti-cancer drugs target the cytoskeleton?
Because it hampers their cell division
What are microtubules comprised of?
Rigid, hollow cylinders of tubulin
What are microfilaments comprised of?
Flexible, contractile filaments of actin
Which cytoskeleton component is involved in organelle motility, chromosome separation, and cilia/flagella?
Microtubules
What cytoskeleton component is involved in muscle contraction and cell migration?
actin
What do microtubules require to form?
GTP
Which end of a microtubule binds GTP and promotes polymeriztion.
+ end
Which end of a microtubule associates with the centrosome?
- end
It can embed within the centrosome
What drives transport along microtubules?
motor proteins
Which motor protein moves organelles toward the plus end of a microtublue? Away?
Kinesisns – towards plus end
Dyneins – towards minus end
What energy source does actin require to form?
ATP bound to G-actin
Which cytoskeleton filament has continual turnover but no net change in length?
Actin
What are stress fibers?
Actin bundles along basal cell surface that stabilize integrin adhesions.
Provide scaffold for intracellular signal transduction.
What are adhesion belts?
Circumferential acitn near apical cell surface that stabilize cadherin-mediated adherens junctions
What is an erythrocyte?
Red Blood Cell
What is the cytoskeleton protein that lines the intracellular side of the plasma membrane and gives the cell shape, elasticity and flexibility?
Spectrin
Spectrin is most prominent in what type of cell?
Erythrocytes
Sickle cell is a modification of spectrin skeleton
What are epithelial cell intermediate filaments called?
cytokeratins
What are the two types of cytokeratins?
Type 1 (acidic polypeptides) Type 2 (neutral to basic polypeptides)
What is Vimentin?
Type 3 intermediate filament found in mesenchymal, endothelial and leudocytes. Useful maker of dedifferentiation of invasive cancer carcinomas.
What is carcinoma?
Cancer that develops from epithelial cells
Desmin
Type three intermediate filament in skeletal muscle Z disk and smooth muscle
Where are type 4 intermediate filaments (neurofilaments) found?
Axons and dendrites
Where does ATP generation happen in mitochondria?
Along the membranes of the cristae (electron transport chain).
What do mitochondrial porins do?
They are integral outer membrane proteins that form channels allowing molecules to pass from the cytoplasm to the intermembrane space.
How do condensed mitochondria form?
An uncoupling of oxidation from phosphorylation.
Why are condensed mitochondria found in brown fat?
Because they produce a lot of heat rather than ATP
Mitochondria contain their own _______ but most _______ are encoded in the cell nucleus and transported into the organelle.
DNA, ribosomes, protein synthetic machinery
proteins
What part of the body is a mitochondrial defect most likely to affecct?
Muscules and the nervous system because they use the most energy.
What is the primary site for noncytosolic protein synthesis?
Rough ER
What is the interior of ER called?
Lumen or cisterna
What color does rER stain in H and E?
basophilic
Where are phospholipids for new membranes produced?
cytosolic half of ER
Cells that make _____ have a lot of smooth ER?
Steroid hormones
What organelle is involved in drug detoxification?
Smooth ER
Drugs that affect the ______ can cause a proliferation of smooth ER.
Liver
Where is cholesterol produced in the cell?
ER
What is a negative Golgi?
When the golgi doesn’t take up the stain very well and appears as a translucent area in the cell.
What organelle modifies the sugars on proteins before they are secreted?
Golgi appartus
“Assembles proteoglycans”
What sugar does the golgi add to proteins that are targeted for lysosomes?
Mannose-6-phosphate
Where are peroxisomes primarily found?
Liver
What are the primary functions of the enzymes contained in peroxisomes?
Beta oxidation of long chain fatty acids
Detoxification of substances like ethanol
Also involved in bile acid synthesis in liver
HMG-CoA reductase, a peroxisome enzyme, is involved in cholesterol synthesis. What drugs target and competitively inhibit this enzyme to lower cholesterol production?
Statins
Name this syndrome.
No peroxisomes so long chain fatty acids accumulate in tissue.
Lethal within 1st decade of life
Peroxisomal enzymes are not transported to the organelle so the peroxisome remains empty.
Zellweger syndrome
The motor protein clathrin is found on the coating of vesicles and mediates transport of vesicles from where?
From the trans-golgi network and from the plasma membrane
Coatprotein (COP) coated vesicles transport between where?
The rER and Golgi and the various Golgi stacks.
What are the primary and secondary functions of lysosomes?
Primary – storage
Secondary – engaged in degradative process
Tubulovesicular structures formed by endocytosis from plasma membrane. Usually fuse with lysosomes.
Endosomes
Cell drinking via small vesicles
Pinocytosis
In what organ are there a lot of pinocytotic vesicles?
Kidney, esspecially the proximal tuble
What is the cholesterol binding protein that coats caveolae in clathrin independent endocytosis?
Caveolin
Small vesicles secreted by cells
exosomes
What lysosomal storage disease involves a deficiency in hexosaminidase and results in an accumulation of glycolipids in the nervous system?
Tay-Sachs Disease
What is Gauchers syndrome?
A lysosomal storage disease that involves defective glucocerebrosidase- Glucocerebrosides accumulate in CNS and spleen.
What are the 4 most common lysosomal storage diseases?
Tay-Sachs, Hurler’s syndrome, Gauchers syndrome, neiman-pick disease
What are some symptoms of Lysosomal storage diseases?
Unusual facial features Cloudy eyes Bluish skin rash Abdomen protrusions Short stature, skeletal deformities Muscle weakness/lack of control
