BIO 320 FINAL EXAM NEWEST 2025 ACTUAL EXAM WITH
CORRECT QUESTIONS AND ACTUAL ANSWERS[VERIFIED
ANSWERS] GRADED A+.
3 types of cytoskeletal proteins - ANSWERS-1.
Microfilaments (actin)
- Located more towards the periphery of the cell
- Play roles in cell movement and motility, contraction,
cytokinesis, changes in cell shape, etc.
- Coordinate movements in and and out of the cell
2. Intermediate filaments
- More for structural support
- Provides a way to move vesicles from one organelle to
another within the cell
3. Microtubules
- Make up spindle fibers, preserve cell's structural integrity
- Also important in vesicle and organelle transport
Size of cytoskeletal proteins - ANSWERS-In terms of size,
from smallest to largest : microfilaments -> intermediate
filaments -> microtubules
How are cytoskeletal proteins regulated? - ANSWERS-Cell
signaling
- Signal received (hormones, growth factors, etc.)-->
change in signal transduction pathway --> cytoskeleton -->
organization and movement of organelles or cell shape,
movement, contraction
,Microvilli - ANSWERS-Fingerlike extensions of plasma
membrane of apical epithelial cells present in intestines
- Functions to increase surface area for absorption
Overview of the cytoskeletons of an epithelial cell -
ANSWERS-Cytoskeletons help connect the inside of the cell
to the outside of the cell
- Hemidesmosomes function to anchor epithelial cells to
the extra cellular matrix
Actin - ANSWERS-A globular multi-functional protein that
acts as a monomer that forms microfilaments, and is also
involved in movement in other types of cell
- Made up of two types of actin :
1. G-actin (globular)
2. F-actin (filamentous)
- ATP is required to hold together the two different types of
actin monomers (energy-requiring process)
G-actin - ANSWERS-Globular actin
- Act as monomers/building blocks
- Forms helical bundles
- Prevalent in the cytosol
F-Actin - ANSWERS-A fibrous, filamentous actin protein
made of a long chain of G actin molecules twisted into a
helix
- Has 2 ends with differing polarity :
1. (-) end is a stable, static structure; gets capped
,2. (+) end is unstable, dynamic structure that is subject for
change; actin filament grows faster at this end
Actin cytoskeleton - ANSWERS-The actin cytoskeleton is
organized into bundles and networks of filaments, really
important for the movement of cells (filapodia)
- Bundles : stress fibers, actin proteins come together to
form thicker filaments
- Or it can form actin networks : cross-linking pattern, held
together by cross-linking proteins called fascin or filamin
- Eukaryotic cells contain abundant amounts of highly
conserved actin (for movement)
- Microfilaments involved in movement possess cell
surface receptors that can sense stimuli and move the cell
towards it
Fascin - ANSWERS-Cross-linking protein that interacts with
actin proteins and bring them together
- Binds the actin filaments together to form BUNDLES
Filamin - ANSWERS-An actin-binding protein that cross-
links actin filaments into NETWORKS
Actin networks in erthrocytes - ANSWERS-Erthrocytes (red
blood cells); cortical actin cytoskeleton networks are
connected to the plasma membrane by scaffolding
proteins
- This is how erthrocytes get their shape and maintain the
structure and dynamic function of the membrane
, 3 steps in actin polymerization - ANSWERS-1. Nucleation :
G-actin (the globular building block) undergoes nucleation;
binds to ATP and gets activated
2. Elongation : forms F-actin with two different polar ends
3. Steady state : polarity differences; F-actin has a (-) end
and a (+) end
- (-) end is a stable and static structure (anchored), gets
capped (to preserve the end)
- (+) end is unstable and dynamic, can be subject to
change; assembled or disassembled, added to or
subtracted from very quickly
Important actin-binding proteins - ANSWERS-- Severin
- Gelsolin
- CapZ
- Tropomodulin
Gelsolin - ANSWERS-Controls actin networks by severing
filaments; does so by removing the actin cross-linker
protein, also caps (+) end
Actin networks in muscle cells - ANSWERS-The cytoplasmic
protein, dystrophin, links actin filament networks that make
up muscle fiber to the extracellular matrix of the plasma
membrane
- This cell surface process is highly organized and
coordinated
- In a mutation of dystrophin, actin filaments lose the ability
to connect to the plasma membrane; muscle cells can no
longer maintain their shape
CORRECT QUESTIONS AND ACTUAL ANSWERS[VERIFIED
ANSWERS] GRADED A+.
3 types of cytoskeletal proteins - ANSWERS-1.
Microfilaments (actin)
- Located more towards the periphery of the cell
- Play roles in cell movement and motility, contraction,
cytokinesis, changes in cell shape, etc.
- Coordinate movements in and and out of the cell
2. Intermediate filaments
- More for structural support
- Provides a way to move vesicles from one organelle to
another within the cell
3. Microtubules
- Make up spindle fibers, preserve cell's structural integrity
- Also important in vesicle and organelle transport
Size of cytoskeletal proteins - ANSWERS-In terms of size,
from smallest to largest : microfilaments -> intermediate
filaments -> microtubules
How are cytoskeletal proteins regulated? - ANSWERS-Cell
signaling
- Signal received (hormones, growth factors, etc.)-->
change in signal transduction pathway --> cytoskeleton -->
organization and movement of organelles or cell shape,
movement, contraction
,Microvilli - ANSWERS-Fingerlike extensions of plasma
membrane of apical epithelial cells present in intestines
- Functions to increase surface area for absorption
Overview of the cytoskeletons of an epithelial cell -
ANSWERS-Cytoskeletons help connect the inside of the cell
to the outside of the cell
- Hemidesmosomes function to anchor epithelial cells to
the extra cellular matrix
Actin - ANSWERS-A globular multi-functional protein that
acts as a monomer that forms microfilaments, and is also
involved in movement in other types of cell
- Made up of two types of actin :
1. G-actin (globular)
2. F-actin (filamentous)
- ATP is required to hold together the two different types of
actin monomers (energy-requiring process)
G-actin - ANSWERS-Globular actin
- Act as monomers/building blocks
- Forms helical bundles
- Prevalent in the cytosol
F-Actin - ANSWERS-A fibrous, filamentous actin protein
made of a long chain of G actin molecules twisted into a
helix
- Has 2 ends with differing polarity :
1. (-) end is a stable, static structure; gets capped
,2. (+) end is unstable, dynamic structure that is subject for
change; actin filament grows faster at this end
Actin cytoskeleton - ANSWERS-The actin cytoskeleton is
organized into bundles and networks of filaments, really
important for the movement of cells (filapodia)
- Bundles : stress fibers, actin proteins come together to
form thicker filaments
- Or it can form actin networks : cross-linking pattern, held
together by cross-linking proteins called fascin or filamin
- Eukaryotic cells contain abundant amounts of highly
conserved actin (for movement)
- Microfilaments involved in movement possess cell
surface receptors that can sense stimuli and move the cell
towards it
Fascin - ANSWERS-Cross-linking protein that interacts with
actin proteins and bring them together
- Binds the actin filaments together to form BUNDLES
Filamin - ANSWERS-An actin-binding protein that cross-
links actin filaments into NETWORKS
Actin networks in erthrocytes - ANSWERS-Erthrocytes (red
blood cells); cortical actin cytoskeleton networks are
connected to the plasma membrane by scaffolding
proteins
- This is how erthrocytes get their shape and maintain the
structure and dynamic function of the membrane
, 3 steps in actin polymerization - ANSWERS-1. Nucleation :
G-actin (the globular building block) undergoes nucleation;
binds to ATP and gets activated
2. Elongation : forms F-actin with two different polar ends
3. Steady state : polarity differences; F-actin has a (-) end
and a (+) end
- (-) end is a stable and static structure (anchored), gets
capped (to preserve the end)
- (+) end is unstable and dynamic, can be subject to
change; assembled or disassembled, added to or
subtracted from very quickly
Important actin-binding proteins - ANSWERS-- Severin
- Gelsolin
- CapZ
- Tropomodulin
Gelsolin - ANSWERS-Controls actin networks by severing
filaments; does so by removing the actin cross-linker
protein, also caps (+) end
Actin networks in muscle cells - ANSWERS-The cytoplasmic
protein, dystrophin, links actin filament networks that make
up muscle fiber to the extracellular matrix of the plasma
membrane
- This cell surface process is highly organized and
coordinated
- In a mutation of dystrophin, actin filaments lose the ability
to connect to the plasma membrane; muscle cells can no
longer maintain their shape
