Cytoskeleton Flashcards
What is a Cytoskeleton?
- Internal supporting structure for Eukaryotes
- Much less important in plant BUT its still present
What is the role of a Cytoskeleton?
-Helps maintain the shape and mechs for changing shapes and moving in Eukaryotes
How is the Cytoskeleton different in Plant cells?
- They use cell wall & osmotic pressure from central vacuole to maintain the shape
- They don’t move & change shape?
What is a Cytoskeleton made up of?
- Multiple types of protein fibers (any long thing, molecule, object)
- Can also be Fibril or Filament
- There’s 3 types of fibers
What are the 3 types of fibers that can form a Cytoskeleton?
- Microtubules
- Microfilament (actin fiber)
- Intermediate Filaments
What is the structure for Microtubules?
- Thickest fiber
- They’re hollow tubes made of Tubulin protein subunits
What is Tubulin?
- Protein subunits in Microtubules
- They are a Heterodimer= which is made up of 2 different polypeptides that associate noncovalently
- Then these Heterodimers associate noncovalently into tubule
- Alpha & Beta associate to form microtubular subunit
What is a Tubule?
- Product of Heterodimers associating noncovalently
- Have 2 opposite ends (plus & minus)= Polar fiber
- Can assemble & grow at the plus end and shrink at the minus end
What is the Function of a Microtubule?
- Structural support for cell (along w/ other skeletal components)
- Moves material within cells which makes Microtubules the highways of the cell
- Plays important role in cell movement bc these microtubules are major components of Cilia & Flagella
How is the Microtubule railroad track used?
- Vesicles follow this railroad track w/ the AID of motor proteins which “walks” the vesicles along
- It forms spindles that moves chromosomes when cells divide during mitosis & meiosis
What is the structure of a Microfilament?
- It’s the thinnest one out the the (3) fibers
- Long thin fibers of Actin protein subunits
- Its 2 helical strands of actin wrapped around eachother by noncovalent association
What is the function of a Microfilament?
- Structural support by forming Stress Fibers (bundles of microfilament)
- These stress fibers are at points of attachment to surfaces & other cells= Focal Adhesions
- Plays role in cell movement & shape changes
- Major participant in muscle contraction in specialized muscle cells
How does Microfilament help in Muscle Contraction?
-Myosin Filaments (thicker filaments) move closer to Actin Filaments (thinner filaments)
What are Intermmediate Filaments?
- They are an intermmediate thickness
- More of a class of several types of proteins= Kertain, Lamin (in lamina, Vimentin but they all assemble in a similar way
What is the structure of Intermmediate Filaments?
- They Line up end to end & then are twisted into a cable
- BUT they’re not hollow like the microtubule
What is the Function of Intermmediate Filaments
- Shape & Structural support but are MORE STATIC COMPONENT to the cytoskeleton
- Forms nuclear lamina (protein network immediately inside nuclear envelope)
- INTERMEDIATE FILAMENTS HAVE NO ROLE IN MOTION/ MOVEMENT
What do all 3 fibers have in common?
-They form a network associated w/ membrane & organelles
What are Microtubules associated with?
-Mitochondria & ER
What are Intermediate Filaments associated with?*
-IT ACTUALLY has little correlation to organelles bc Intermediate Filaments are PURELY STRUCTURAL
What is the Actin Filament associated with?
-Membrane
What do Tubule & Actin filaments have in common?
- They pervate the ENTIRE cytoplasm along w/ associated organelles
- They are constanly assembling & dissasembling
Why is change in the Cytoskeleton a good thing?
-It allows changes in shape & movement
How is change in the Cytoskeleton occur?
- When Actin filaments move against eachother in muscle & other cells
- Microtubules shorten, lengthen, & completely rearrange for cell division
- Some cells will move using Cilia & Flagella (same structure but may have different lengths & motion)
How do Microtubules change for cell division?
- They will shorten, lengthen, & completely rearrange themselves
- The old structures diassemble & spindles form for chromosome to separate during mitosis
What is the structure of Cilia & Flagella?
- 2 Pairs of inner Microtubules are surrounded by 9 Pairs of the outer Microtubules= 9+2 structure
- Protein Dynein is inside the structure= moves cilia & flagella
What is the distinct movement of Flagella?
- Its a rotary whip-like motion
- This motion is used in sperm & Kinetoplastid Trypanosome
What is the distinct movement of Cilia?
- Wave-like motion
- Used in cililate Paramecium
What do other cells use to generate motion & change shape?
- Microfilaments
- Amoeba moves via amoeboid movement= sends pseudopods out & drags the amoeba
What are the fibers from thickest to thinnest?
- Microfilaments
- Intermediate filaments
- Actin filaments
