Cytoskeleton

Question 1

What is a Cytoskeleton?

Answer 1

• Internal supporting structure for Eukaryotes

- Much less important in plant BUT its still present

Question 2

What is the role of a Cytoskeleton?

Answer 2

-Helps maintain the shape and mechs for changing shapes and moving in Eukaryotes

Question 3

How is the Cytoskeleton different in Plant cells?

Answer 3

• They use cell wall & osmotic pressure from central vacuole to maintain the shape
• They don’t move & change shape?

Question 4

What is a Cytoskeleton made up of?

Answer 4

• Multiple types of protein fibers (any long thing, molecule, object)
• Can also be Fibril or Filament
• There’s 3 types of fibers

Question 5

What are the 3 types of fibers that can form a Cytoskeleton?

Answer 5

• Microtubules
• Microfilament (actin fiber)
• Intermediate Filaments

Question 6

What is the structure for Microtubules?

Answer 6

• Thickest fiber

- They’re hollow tubes made of Tubulin protein subunits

Question 7

What is Tubulin?

Answer 7

• 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

Question 8

What is a Tubule?

Answer 8

• 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

Question 9

What is the Function of a Microtubule?

Answer 9

• 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

Question 10

How is the Microtubule railroad track used?

Answer 10

• 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

Question 11

What is the structure of a Microfilament?

Answer 11

• 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

Question 12

What is the function of a Microfilament?

Answer 12

• 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

Question 13

How does Microfilament help in Muscle Contraction?

Answer 13

-Myosin Filaments (thicker filaments) move closer to Actin Filaments (thinner filaments)

Question 14

What are Intermmediate Filaments?

Answer 14

• 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

Question 15

What is the structure of Intermmediate Filaments?

Answer 15

• They Line up end to end & then are twisted into a cable
• BUT they’re not hollow like the microtubule

Question 16

What is the Function of Intermmediate Filaments

Answer 16

• 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

Question 17

What do all 3 fibers have in common?

Answer 17

-They form a network associated w/ membrane & organelles

Question 18

What are Microtubules associated with?

Answer 18

-Mitochondria & ER

Question 19

What are Intermediate Filaments associated with?*

Answer 19

-IT ACTUALLY has little correlation to organelles bc Intermediate Filaments are PURELY STRUCTURAL

Question 20

What is the Actin Filament associated with?

Answer 20

-Membrane

Question 21

What do Tubule & Actin filaments have in common?

Answer 21

• They pervate the ENTIRE cytoplasm along w/ associated organelles
• They are constanly assembling & dissasembling

Question 22

Why is change in the Cytoskeleton a good thing?

Answer 22

-It allows changes in shape & movement

Question 23

How is change in the Cytoskeleton occur?

Answer 23

• 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)

Question 24

How do Microtubules change for cell division?

Answer 24

• They will shorten, lengthen, & completely rearrange themselves
• The old structures diassemble & spindles form for chromosome to separate during mitosis

Question 25

What is the structure of Cilia & Flagella?

Answer 25

- 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

Question 26

What is the distinct movement of Flagella?

Answer 26

- Its a rotary whip-like motion | - This motion is used in sperm & Kinetoplastid Trypanosome

Question 27

What is the distinct movement of Cilia?

Answer 27

- Wave-like motion | - Used in cililate Paramecium

Question 28

What do other cells use to generate motion & change shape?

Answer 28

- Microfilaments | - Amoeba moves via amoeboid movement= sends pseudopods out & drags the amoeba

Question 29

What are the fibers from thickest to thinnest?

Answer 29

- Microfilaments - Intermediate filaments - Actin filaments