Unit 10 - Cytoskeleton

Question 1

Why is Cytoskeleton important?

Answer 1

• determines cell shape, position of organelles
• allows movement of organelles/components within cells
• coordinates movement of chromosomes during mitosis
• allows movement of cells themselves, forms flagella, cilia

Question 2

Intermediate Filaments

Answer 2

• structural, provides mechanical strength
• not dynamic
• forms a network through cytoplasm of most animal cells extending out to cell periphery
• anchored on plasma membrane at desmosomes

Question 3

Structure of Intermediate Filaments

Answer 3

• long, twisted strands
• strands consist of fibrous proteins, globular N-terminal head and globular C-terminal tail
• consist of many different proteins
• ‘rope-like’

Question 4

Classes of Intermediate Filaments

Answer 4

1. Keratins (epithelia)
2. Vimentin (connective tissue)
3. Neurofilaments (nerve cells)
4. Nuclear Lamins (animal cells)

Question 5

the surface of our skin is…

Answer 5

a dead flattened cell layer packed with keratin

Question 6

Microtubules

Answer 6

• 25 nm, hollow, relatively stiff
• crucial organizing roles in eukaryotic cells
• forms stable structures on certain cells - cilia, flagella

Question 7

Microtubule Organizing Centre

Answer 7

• structures from which microtubules originate and radiate outwards
• Centrosome (2 centrioles)

Question 8

Tubulin

Answer 8

• hollow tubes which make up microtubules
• consist of alpha & beta, bound together tightly
• protofilaments have structural polarity –> alpha exposed at one end, beta at the other (entire tubule has polarity)
• dynamic, constantly growing and shrinking

Question 9

Motor Proteins

Answer 9

-class of biological motors, which are powered by the hydrolysis of ATP

Question 10

Myosin

Answer 10

• actin motor

- muscle contraction, vesicle and organelle transport, cell motility, cytokinesis

Question 11

Kinesin

Answer 11

• microtubule motor
• moves towards plus end (nerve axon)
• large protein superfamily

Question 12

Dyneins

Answer 12

• microtubule motors
• move towards minus end (cell body)
• includes motor proteins which drive movement of cilia & flagella

Question 13

Eukaryotic Cilia & Flagella

Answer 13

‘9 + 2’ array

Question 14

Microfilaments

Answer 14

• two long strands of actin subunits coil
• 7 nm
• positive & negtaive ends
• dynamic, growing & shrinking as actin is added and removed

Question 15

Most abundant protein in animal cells is…

Answer 15

Actin

Question 16

Cell Movement

Answer 16

• actin helps in cell movement without flagella/cillia
• cell pushes out protrusion(s) at the leading edge
• these protrusion(s) stick to the surface
• rest of cell drags itself forward