Lecture 03 Cytoskeleton and Cell Membrane HISTOLOGY CELL BIO Flashcards
What is the purpose of the cytoskeleton? Try to put it into your own words.
- Helps to form the shape of each cell (Form the scaffolding which defines cell shape and resiliency.)
- Maintains the integrity of the bilayer cell membrane (Distribute forces between adjacent cells and between cells and the basal lamina.)
- Cell Division (Are involved in cell division and various kinds of cell movements. )
Name the three types of structures that form the cytoskeleton. Name them in order from thinnest to thickest.
- Microfilaments (7 nm)
- Intermediate filaments (8-10nm)
- Microtubules (25 nm)
T/F Microfilaments are made up predominately of actin.
TRUE…
Describe how the six actin genes are expressed in mammals (in general.)
Four are expressed in muscles cells
Two are expressed in non muscle cells
List 4 characteristics of Actin filaments:
- 7nm thick
- they bind to specific TRANSMEMBRANE proteins either directly or indirectly.
- actin can exist as monomers (G-actin) and long chains (F-actin_
- Major varieties of actin include: alpha-muscle, beta-nonmuscle, gama-nonmuscle
Characteristics of microfilament assembly:
- Actin monomers have a binding site for ATP, which binds tightly to the G-actin.
- The ATP is hydrolyzed to form ADP following polymerization.
- Actin microfilaments consist of double helical chains of G-actin subunits.
- Actin filaments have a polarity resulting in a + and - ends.
Which end of the Actin filaments grows the slowest?
Minus end.
Explain what effect concentrations of G-actin has on the assembly and disassembly of actin filaments.
If [low], then G-actin will disassemble the filaments.
If [intermediate,] there is a dynamic equilibrium between the + and - end TREADMILLING, this results in a 0 net growth
if [high,] G-actin will add at both ends and will crow the actin filament.
What contributes to the function of actin filaments in different regions of a cell?
The actin-binding proteins… and not the actin itself.
Can you list the Actin-binding proteins?
- Cytochalasins
- Phalloidin
- Spectrin
- Dystrophin
- Villain and Fimbrin
- Calmodulin and Myosin I
- Alpha-Actin
- Filamin
how do cytochalasins contribute to microfilament formation?
They bind to barbed ends, they block elongation, and they can inhibit movements such as mitosis.
How does the actin-binding protein, PHALLOIDIN, behave?
Binds action filaments and prevents dissociation.
Can be labeled with florescent dyes to allow actin visualization
Name the Actin-binding protein that can be found in Red Blood Cells and binds the cortical cytoskeleton to the plasma membrane.
Spectrin
Name two Actin binding proteins that bind the cortical cytoskeleton to the plasma membrane.
Spectrin and Dystrophin
T/F Villin and Fimbrin are a bad lip syncing band from 1991 who sold over 2 million records.
FALSE!. Villain and Fimbrin create cross-links in microvilli.
Calmodulin and Myosin-I do what?
They cross link actin to plasma membrane in MICROVILLI
More actin binding proteins……. Can you describe what alpha-actinin does?
Alpha-actinin cross links stress fibers and connect actin to protein plasma membrane complex complexes
(Huh!)
Okay, moving on…. What does Filamin do?
It cross links actin at WIDE ANGLES to form screen-like gels.
The structure of biologic membranes can BEST be described as:
A. A phospholipid bilayer covered on each face by a continuous sheet of proteins.
B. A fluid-mosaic of proteins interspersed in a phospholipid bilayer.
C. A phospholipid bilayer with the hydrocarbon tails of the phospholipids oriented towards the cytoplasm. (LOL)
D. An internal layer of protein covered on either side by a layer of phospholipid.
B. A fluid-mosaic of proteins interspersed in a phospholipid bilayer.
Which of the following categories of membrane proteins is represented by proteins that have a hydrophobic domain and two hydrophilic domains? A. Peripheral membrane proteins. B. Transmembrane proteins C. Importins D. Spectrin Proteins
Transmembrane proteins
Which of the following is located within the membrane phospholipid bilayer and moderates membrane fluidity by restricting movement of phospholipid fatty acid side chains at high temperatures? A. Phosphatidycholine B. Phosphatidylethanolamine C. Cholesterol D. Phosphyatdylserine E. Sphingomyelin
C. Cholesterol
Which type of membrane transport molecule carries 2 molecules simultaneously or sequentially in opposite directions?? A. Unitransporter B. Symporter C. Antiporter D. Co-transporter
A. Antiporter
