Lecture 3 Cytoskelton

Question 1

Know basic structure of the subunit for each type of cytoskeletal protein and compare and contrast cytoskeletal proteins regarding:

– Polarity

– General filament structure / relative stability

Answer 1

Intermediate Filaments: Tetramer of two sets of coiled – Most Stable NO POLARITY

Microtubules: Polymers of tubulin is a heterodimer of alpha and beta tubulin: HAS POLARITY when lined in parallel fashion.NO POLARITY when extend out of membrane

Microfilaments: monomer of actin – Least Stable Has POLARITY

Question 2

Know basic structure of the subunit for each type of cytoskeletal protein and compare and
contrast cytoskeletal proteins regarding:
– Nucleotide tri-phosphate binding molecule (ATP/GTP)

Answer 2

Intermediate Filaments: Are used for cell and tissue integrity

Microtubules are used for Surface Area

Actin: Motor proteins

Question 3

Know basic structure of the subunit for each type of cytoskeletal protein and compare and
contrast cytoskeletal proteins regarding:
– Nucleotide tri-phosphate binding molecule (ATP/GTP)

Answer 3

• ACTIN:
  
  • When ATP is Attached it is in the T-Form this is the soluble form or free floating form
  • When ADP is attached, Hydrolyzed, D-form. This is when attached end to end
• Microtubules:
  
  • When GTP is bound it is always on Alpha tubulin
  • When GTP is bound to B-Tubulin in the T-from
    
    • but when GDP is bound then in D-Form

Question 4

Be able to interpret this graph and know what processes are most likelyoccurring during lag phase, growth phase (i.e., nucleation, elongation)

Question 5

Describe nucleation

Answer 5

Actin and microtubule polymer assembly initiation

END TO END. +-+-+-+-

As nucleation occurs then when reaches a specific stability then will enter into elongation phase

Question 6

Describe critical concentration (Cc)

Answer 6

Critical concentration is when monomers are at a steady state

they are going to stay the same length and not grow both ends are goin to grow and fall off respectively

Question 7

Contrast “T” and “D” forms of actin and microtubules subunits

-Which nucleotide is bound to actin monomers in T and D forms

Answer 7

Actin: T form: ATP

Actin D form: ADP

Microtubules Alpha unit: GTP is always bound in T form

Microtubules Beta Unit T form: GTP

Microtubules Beta Unit D form: GDP

Question 8

Contrast “T” and “D” forms of actin and microtubules subunits

-which subunits form “t” and “d” has a higher affinity for polymerization? what are the implications of the on Cc(t) and Cc(d)

Answer 8

Affinity is high for T-Form to add on the + end

Affinity is low for the D-form but will still ass on but just on the - end

Question 9

Be able to read/interpret this graph
– What is treadmilling? Identify treadmilling range on a graph like this

Question 10

Describe dynamic instability

-what happens in catastrophe

Answer 10

if the GTP cap is lost then the D form subunits will disassociated at the plus end

Question 11

Describe dynamic instability

-rescue

Answer 11

Polymerization as the conc of t-forms increase then T can be added to D at plus end and elongation occurs