Cell Structure and Function Exam 4 Questions
and Verified Answers
Cytoskeleton Correct Answer: Acts as cytoplasmic skeleton, giving structure and form to cells
primary way that cells generate force
used to drive cell division, trafficking of organelles, cell contraction in muscle cells, cell movement and
migration, beating of cilia, etc.
Three types of cytoskeletal filaments Correct Answer: Actin filaments, associated with cell cortex
(plasma membrane)
Microtubules, in cytoplasm, often emanating out of a centrosome (MTOC)
Intermediate filaments, in cytoplasm and nucleus
Actin filaments Correct Answer: Associated with cell cortex (plasma membrane)
shorter, smaller, and more flexible than microtubles
can drive contraction movements (muscle and cell division)
Microtubules, in cytoplasm Correct Answer: Often emanates out of centrosome (MTOC)
Long, hollow cylinders
Rigid structures
Can serve as highways for organelle and chromosome movement
Intermediate filaments, in cytoplasm and nucleus Correct Answer: Act as fairly flexible ropes that are
resistant to stretching
Function to help cells deal with mechanical stresss and not be torn apart
Cytoskeletal filaments can also form stable structures and direct polarity Correct Answer: Stereocilia (ear
hairs) will [hopefully] last a lifetime
, Epithelial cells
-stable F-actin microvilli
-microtubules direct apical basal polarity
ytoskeletal filaments are formed from assembly of smaller subunits Correct Answer: Often assemble to
have helical structure
assemble through non-covalent interactions (unlike individual proteins &
nucleic acids), so more weakly held together
Subunits assemble into protofilaments that then interact laterally to form filaments
-stabilizes interior of filament while allowing dynamic change at ends
Nucleation is a critical step in filament polymer formation Correct Answer: Very short polymers are
unstable due to absence of stabilizing interactions
Nucleation is often the rate limiting step in filament formation
Microtubule formation and organization Correct Answer: Microtubules are made of heterodimers of
alpha-tubulin and beta-tubulin proteins
Bind and can hydrolyze GTP
Heterodimers assembly head to tail in protofilaments, generates MT polarity
Microtubules are made of 13 protofilaments wrapped into a hollow tube
Gives microtubules rigidity
F-actin formation and organization Correct Answer: Actin filaments are made of monomers of actin
proteins
Bind and can hydrolyze ATP
Bends into helical structure
and Verified Answers
Cytoskeleton Correct Answer: Acts as cytoplasmic skeleton, giving structure and form to cells
primary way that cells generate force
used to drive cell division, trafficking of organelles, cell contraction in muscle cells, cell movement and
migration, beating of cilia, etc.
Three types of cytoskeletal filaments Correct Answer: Actin filaments, associated with cell cortex
(plasma membrane)
Microtubules, in cytoplasm, often emanating out of a centrosome (MTOC)
Intermediate filaments, in cytoplasm and nucleus
Actin filaments Correct Answer: Associated with cell cortex (plasma membrane)
shorter, smaller, and more flexible than microtubles
can drive contraction movements (muscle and cell division)
Microtubules, in cytoplasm Correct Answer: Often emanates out of centrosome (MTOC)
Long, hollow cylinders
Rigid structures
Can serve as highways for organelle and chromosome movement
Intermediate filaments, in cytoplasm and nucleus Correct Answer: Act as fairly flexible ropes that are
resistant to stretching
Function to help cells deal with mechanical stresss and not be torn apart
Cytoskeletal filaments can also form stable structures and direct polarity Correct Answer: Stereocilia (ear
hairs) will [hopefully] last a lifetime
, Epithelial cells
-stable F-actin microvilli
-microtubules direct apical basal polarity
ytoskeletal filaments are formed from assembly of smaller subunits Correct Answer: Often assemble to
have helical structure
assemble through non-covalent interactions (unlike individual proteins &
nucleic acids), so more weakly held together
Subunits assemble into protofilaments that then interact laterally to form filaments
-stabilizes interior of filament while allowing dynamic change at ends
Nucleation is a critical step in filament polymer formation Correct Answer: Very short polymers are
unstable due to absence of stabilizing interactions
Nucleation is often the rate limiting step in filament formation
Microtubule formation and organization Correct Answer: Microtubules are made of heterodimers of
alpha-tubulin and beta-tubulin proteins
Bind and can hydrolyze GTP
Heterodimers assembly head to tail in protofilaments, generates MT polarity
Microtubules are made of 13 protofilaments wrapped into a hollow tube
Gives microtubules rigidity
F-actin formation and organization Correct Answer: Actin filaments are made of monomers of actin
proteins
Bind and can hydrolyze ATP
Bends into helical structure
