UConn MCB 2210 Exam 3 correctly
answered to pass
The cytoskeleton is - correct answer ✔✔a group of several different types of filamentous
protein polymers that are crucial for most cellular functions.
Each type of cytoskeletal polymer consists of - correct answer ✔✔thousands of individual
protein subunits that assemble into that polymer
The cytoskeleton can form stable structures but is also highly dynamic - correct answer ✔✔•
Cytoskeletal organization helps create polarity. The cell is not symmetric: Front/Back,
Top/Bottom, Center/Periphery
• Some cytoskeletal structures are long lived, others exist only transiently.
• The cytoskeleton can resist external forces and generate pushing or contractile forces.
• Cytoskeletal polymers can grow and shrink (or both) as subunits are assembled or
disassembled, respectively.
• The cytoskeleton can rapidly reorganize itself in response to its environment and different
signaling inputs.
• The structure and dynamics of the cytoskeleton is intimately linked to its many functions.
Why do we have a Cytoskeleton ? - correct answer ✔✔Cell morphogenesis (shape and shape
changes)
Cell organization (positioning and movement of organelles)
Cell division (growth and reproduction)
Cell adhesion (contacting substrates and other cells)
Cell motility (whole cell movement)
,Cell Size & Shape - correct answer ✔✔•Most eukaryotic cells are 10-30μm in diameter, but vary
greatly in shape.
• Small molecules move into and out of cells by diffusion through the membrane: O2 and
nutrients must diffuse into the cell and CO2 and waste products diffuse out of the cell.
• As a spherical cell gets larger, its cytoplasmic volume increases as a cubic function (V=4πr3/3)
while its membrane surface area increases as a square function (4πr2).
• The amount of transport is limited by the amount of surface area. Surface area cannot keep
up with volume. This is a limit to the size of metabolically active cells.
• Growth is often coupled with division to maintain cells at a manageable size.
Diffusion: - correct answer ✔✔• The spread of particles through random motion
• Water molecules are in constant motion: They bump into each other and other molecules in
solution causing random movement - Brownian motion (i.e., there is NO directionality).
• The larger the molecule, the slower the movement: As distance increases, the time for it to
move that distance increases as a square function (100x longer to get 10x as far).
• How does the cell move large biological materials (nucleic acids, proteins, organelles) from
one place to another through a very crowded cytoplasm? -> The cytoskeleton
• The cytoskeleton drives cell shape changes, and motor proteins help move cargo around.
Actin is one of the most abundant proteins in eukaryotic cells. - correct answer ✔✔It comprises
from 1-20% of the total protein in cells. Cytoskeletal subunit proteins span the cell and are
generally abundant
The sequence of actin has been highly conserved through evolution. - correct answer ✔✔Actins
contain ~375 amino acids and have a molecular weight of ~42 kDa. Actins from amoeba and
humans are >80% identical to each other in sequence.
Simple eukaryotes like yeast have one actin gene. Mammals have - correct answer ✔✔several
genes that produce multiple types of actin: α-actin in muscle, β- and γactin in non-muscle cells
, Actin filaments are - correct answer ✔✔helical polymers composed of globular actin monomers
that bind ATP
Actin exists in two forms in the cell: - correct answer ✔✔as a monomer called G-actin (globular-
actin) and as a filamentous polymer called F-actin (filamentous-actin).
An individual G-actin monomer molecule is separated into two lobes by a deep cleft that binds
ATP or ADP complexed with Mg+2 - correct answer ✔✔Since one end of the molecule displays
this cleft and the other does not, the monomer has an intrinsic asymmetry or polarity.
F-actin is a helical polymer of G-actin subunits held together by non-covalent (hydrophobic and
ionic) interactions. - correct answer ✔✔All of the subunits within an actin filament are oriented
in the same direction. The cleft end of one monomer is bound to the non-cleft end of the next.
Thus, F-actin is a polar polymer; the two ends of the filament are structurally different. At one
end of the filament, the ATP cleft of the terminal subunit is exposed, while at the other end of
the filament, the ATP cleft of the terminal subunit is in contact with the neighboring subunit,
and the noncleft region is exposed .
The barbed end of actin - correct answer ✔✔can add monomers more quickly during
polymerization than the pointed end. Thus, the barbed end is also called the "+ end"
the pointed end of actin - correct answer ✔✔"- end"
The polarity of actin filaments can be determined by decorating the filaments with the actin-
binding "head" domain of the myosin II molecule (called subfragment-1 or S1). - correct answer
✔✔When S1 is mixed with actin filaments, it attaches to the sides at an angle, creating an arrow
head like pattern. Based on this, one end of the filament is called the pointed end and the other
is called the barbed end.
In vitro, actin polymerization (assembly) can be initiated by - correct answer ✔✔adding salts
(Mg+2 , K+) to a solution of pure G-actin.
answered to pass
The cytoskeleton is - correct answer ✔✔a group of several different types of filamentous
protein polymers that are crucial for most cellular functions.
Each type of cytoskeletal polymer consists of - correct answer ✔✔thousands of individual
protein subunits that assemble into that polymer
The cytoskeleton can form stable structures but is also highly dynamic - correct answer ✔✔•
Cytoskeletal organization helps create polarity. The cell is not symmetric: Front/Back,
Top/Bottom, Center/Periphery
• Some cytoskeletal structures are long lived, others exist only transiently.
• The cytoskeleton can resist external forces and generate pushing or contractile forces.
• Cytoskeletal polymers can grow and shrink (or both) as subunits are assembled or
disassembled, respectively.
• The cytoskeleton can rapidly reorganize itself in response to its environment and different
signaling inputs.
• The structure and dynamics of the cytoskeleton is intimately linked to its many functions.
Why do we have a Cytoskeleton ? - correct answer ✔✔Cell morphogenesis (shape and shape
changes)
Cell organization (positioning and movement of organelles)
Cell division (growth and reproduction)
Cell adhesion (contacting substrates and other cells)
Cell motility (whole cell movement)
,Cell Size & Shape - correct answer ✔✔•Most eukaryotic cells are 10-30μm in diameter, but vary
greatly in shape.
• Small molecules move into and out of cells by diffusion through the membrane: O2 and
nutrients must diffuse into the cell and CO2 and waste products diffuse out of the cell.
• As a spherical cell gets larger, its cytoplasmic volume increases as a cubic function (V=4πr3/3)
while its membrane surface area increases as a square function (4πr2).
• The amount of transport is limited by the amount of surface area. Surface area cannot keep
up with volume. This is a limit to the size of metabolically active cells.
• Growth is often coupled with division to maintain cells at a manageable size.
Diffusion: - correct answer ✔✔• The spread of particles through random motion
• Water molecules are in constant motion: They bump into each other and other molecules in
solution causing random movement - Brownian motion (i.e., there is NO directionality).
• The larger the molecule, the slower the movement: As distance increases, the time for it to
move that distance increases as a square function (100x longer to get 10x as far).
• How does the cell move large biological materials (nucleic acids, proteins, organelles) from
one place to another through a very crowded cytoplasm? -> The cytoskeleton
• The cytoskeleton drives cell shape changes, and motor proteins help move cargo around.
Actin is one of the most abundant proteins in eukaryotic cells. - correct answer ✔✔It comprises
from 1-20% of the total protein in cells. Cytoskeletal subunit proteins span the cell and are
generally abundant
The sequence of actin has been highly conserved through evolution. - correct answer ✔✔Actins
contain ~375 amino acids and have a molecular weight of ~42 kDa. Actins from amoeba and
humans are >80% identical to each other in sequence.
Simple eukaryotes like yeast have one actin gene. Mammals have - correct answer ✔✔several
genes that produce multiple types of actin: α-actin in muscle, β- and γactin in non-muscle cells
, Actin filaments are - correct answer ✔✔helical polymers composed of globular actin monomers
that bind ATP
Actin exists in two forms in the cell: - correct answer ✔✔as a monomer called G-actin (globular-
actin) and as a filamentous polymer called F-actin (filamentous-actin).
An individual G-actin monomer molecule is separated into two lobes by a deep cleft that binds
ATP or ADP complexed with Mg+2 - correct answer ✔✔Since one end of the molecule displays
this cleft and the other does not, the monomer has an intrinsic asymmetry or polarity.
F-actin is a helical polymer of G-actin subunits held together by non-covalent (hydrophobic and
ionic) interactions. - correct answer ✔✔All of the subunits within an actin filament are oriented
in the same direction. The cleft end of one monomer is bound to the non-cleft end of the next.
Thus, F-actin is a polar polymer; the two ends of the filament are structurally different. At one
end of the filament, the ATP cleft of the terminal subunit is exposed, while at the other end of
the filament, the ATP cleft of the terminal subunit is in contact with the neighboring subunit,
and the noncleft region is exposed .
The barbed end of actin - correct answer ✔✔can add monomers more quickly during
polymerization than the pointed end. Thus, the barbed end is also called the "+ end"
the pointed end of actin - correct answer ✔✔"- end"
The polarity of actin filaments can be determined by decorating the filaments with the actin-
binding "head" domain of the myosin II molecule (called subfragment-1 or S1). - correct answer
✔✔When S1 is mixed with actin filaments, it attaches to the sides at an angle, creating an arrow
head like pattern. Based on this, one end of the filament is called the pointed end and the other
is called the barbed end.
In vitro, actin polymerization (assembly) can be initiated by - correct answer ✔✔adding salts
(Mg+2 , K+) to a solution of pure G-actin.
