CMB1004/L04 Cytoskeleton Flashcards
Name the 4 cytoskeletal filaments.
Intermediate filaments
Microtubules
Actin
Spectrin
Give 3 functions of the cytoskeleton.
Organisation
Cell shape and movement
Positioning of organelles
Directs intracellular transport
Where are intermediate filaments found? (2)
Cytoplasm
Nucleus
What is the function of intermediate filaments? (2)
Provide mechanical strength
Prevent overstretching
What is the function of microtubules? (3)
Move chromosomes in cell division
Intracellular transport
Drive cilia and flagella
What is the function of actin filaments? (2)
Maintain cell shape
Surface movement
What is the diameter of intermediate filaments?
10nm
Describe the structure of intermediate filaments.
A-helical coil
What is the assembly and disassembly of intermediate filaments regulated by?
Phosphorylation
How many tetramers associate to form an intermediate filament?
8 (16 dimers)
What groups are on the end of intermediate filaments?
-COOH and -NH2
What kind of intermediate filaments are in the nucleus?
Lamins
What is the function of nuclear lamins? (2)
Structural support
Anchorage site for chromosomes and nuclear pores
Name the 3 cytoplasmic intermediate filaments.
Keratins
Vimentin and related
Neurofilaments
Name the 3 nuclear lamins.
LMNA, LMNB, LMNC
What causes breakdown of nuclear lamins during mitosis?
Phosphorylation
What is the primary purpose of neurofilaments?
Structural support
How are intermediate filaments indirectly connected to neighbour epithelial cells?
Desmosomes
Why can the orientation of intermediate filaments not be determined?
Dimers align with ends facing opposite ends
What is the diameter of microtubules?
25nm
What are the globular monomers of microtubules?
Tubulin
Where do microtubules emerge from in cytoplasm?
Organising centres
What are cytoplasmic microtubules called?
Centrosomes
What are mitotic spindle microtubules called?
Spindle poles
What are cilia/flagella microtubules called?
Basal bodies
How many protofilaments are in a microtubule?
13
What energy source is used to form microtubules?
GTP
Which end of a microtubule is 1) positive and 2) negative?
1) Beta - positive
2) Alpha - negative
What does the polarity of microtubules determine?
Which way organelles move
What are the 2 microtubule motor proteins?
Kinesins and dyenins
What does the globular head of kinesins and dyenins bind?
ATP + microtubules
Which direction does kinesin move in?
Towards plus end
Which direction does dyenin move in?
Towards minus end
Which motor protein drives cilia and flagella?
Dyenins
What microtubule structure do motile cilia have?
9+2
What protein do microvilli contain?
Actin
What is the function of microvilli?
Increase surface area for absorption
What is the diameter of actin filaments?
6-8nm
What is the function of actin filaments? (2)
Cell motility + contraction
Adhesion + mechanosensing
Which monomers are added to each end in formation of actin filaments?
G-actin
How is actin filament assembly and organisation regulated?
Actin-binding proteins
What is the actin filament motor protein?
Myosin
What part of myosin binds to actin filaments?
Myosin head
What is the difference between myosin I and II?
Myosin I has 1 head
Myosin II has 2 heads
What do myosin tails bind to?
Plasma membranes, vesicles, other myosin molecules
What drives muscle contraction?
Sliding thick myosin filament
What links membranes to motor proteins and all major filament systems?
Spectrin
