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cell shape, functional
Role of Actin Filaments
Regulation of ___ ___: Actin filaments control cellular morphology.
___ Diversity: Actin involved in various cellular processes.
microvilli, muscle, moving, division
Role of Actin Filaments
Examples:
____: Extensions of intestinal cells aiding nutrient absorption.
___ Cells: Actin filaments contribute to cell contraction.
___ Cells: Actin filaments present at the leading edge.
Cell ____: Form temporary circular rings during division.
nutrient, contraction, leading, rings
Significance of Actin:
Microvilli: Aid in ____ absorption in intestinal cells.
Muscle Contraction: Actin filaments crucial for cell ____.
Cell Movement: Actin present at ___ edge of moving cells.
Cell Division: Actin forms temporary ___, aiding in division.
single, dimers, tubulin, protofilaments
Differences Between Actin Filaments and Microtubules
Structure:
Actin filaments: ___ filaments composed of actin ___.
Microtubules: Tubular structure formed by ___ dimers organized into ___.
ATPases, ATP, GTPases, GTP
Differences Between Actin Filaments and Microtubules
Dimers:
Actin: ____; use ___ for polymerization.
Microtubules: ____; use ___ for polymerization.
plus, minus, plus
Differences Between Actin Filaments and Microtubules
Directionality:
Actin: Grow towards the ___ end, shrink towards the ___ end.
Microtubules: Grow and shrink at the ___ end.
independently, centrosome
Differences Between Actin Filaments and Microtubules
Anchoring:
Actin: Not anchored to a center; grow and shrink ______.
Microtubules: Anchored to the ___; grow towards the plus end.
cortical actin, cortex
Cell Movement
Cell Movement Mechanism
Leading Edge:
Formed by ___ __ underneath the plasma membrane.
___ envelopes the cell.
actin, myosin
Cell Movement
Cell Movement Process:
Leading edge grows towards a direction, stretching the cell.
At the opposite end:
___ depolymerizes.
____ contracts.
lamellipodium, calcium, heterodimers
Cell Movement
Interaction with Extracellular Matrix:
____ attached to substratum via integrins.
Integrins require ___ for interaction.
Integrins are _____.
Lamellipodium, Cortical actin, Contraction, attachment
Cell Movement
Cycle of Movement:
_____ attaches to substratum.
_____ ____ grows and detaches.
_____ at opposite end moves the cell forward.
New ____ forms, and the process repeats.
actin
Actin-Related Proteins (ARPs)
Role in Cell Movement:
Assist in the organization and function of ___ filaments.
mesh, electron
ARPs
Cortical Actin:
Forms ___ underneath the plasma membrane.
Visible in ___ micrographs.
Lamellipodium
ARPs
Cell Movement Observation:
Fish skin cell moving across the field of view.
___ pulls the cell forward.
capping, shrinks
Stabilization of Actin Filaments at Leading Edge:
Plus End: Stabilized by ___ proteins.
Minus End: Actin ___.
globular, linear, dimers, tail
Myosins: Motor Proteins
Structure:
____ head and ___ tail.
Typically exist as ___.
___ dimerizes.
actin, cargo
Myosins: Motor Proteins
Function:
Head interacts with ___.
Tail interacts with ___.
plus
Myosins: Motor Proteins
Movement:
Towards the __ end of actin.
muscle, thick
Special Structural Organization of Muscle-Specific Myosins
Dimerization:
Myosins always dimerized in ___ cells.
____ filaments formed in skeletal and cardiac muscle cells.
tails, heads, tail, tail, bundle, structural
Special Structural Organization of Muscle-Specific Myosins
Organization:
Dimer with dimerized __ and two _.
Multiple dimers organize ___ to ___.
Forms a ___ with strong structural organization.
bundle, tails, heads
Special Structural Organization of Muscle-Specific Myosins
Structural Formation:
Coiled-Coil Dimers:
Heads and tails arranged in a ___.
Central region with ___ and peripheral region with multiple ___.
actin, myosin, interface
Anatomical Structure of Muscle Cells and Sarcomere
Thin Filament (___): Represented in red.
Thick Filament (____): Represented in green.
____: Where myosin heads interact with actin.
minus, capping
Anatomical Structure of Muscle Cells and Sarcomere
Z Disc:
Binds the ___ ends of actin filaments.
Contains ____ protein, including Titan.
Titan, Z disc
Anatomical Structure of Muscle Cells and Sarcomere
____ Protein:
Enormous protein.
Main component of __ __.
myosin, actin, myosin, actin
Anatomical Structure of Muscle Cells and Sarcomere
Striations:
Dark regions: ___.
Very dark: Both ___ and ___.
Light regions: ___.
Z disc, striations
Anatomical Structure of Muscle Cells and Sarcomere
Structural Significance:
_ _ maintains sarcomere integrity.
_____ result from the arrangement of myosin and actin filaments.
stimulation, Action Potential, calcium release,
Muscle Contraction Mechanism
_______: Neuron activates muscle cell.
________ ______: Spreads over muscle cell membrane.
________ _____: Triggered by action potential.
T-tubules
Muscle Contraction Mechanism
Cell Architecture:
__-__ distribute calcium throughout cytosol.
Sarcoplasmic Reticulum
_________ ________ (SR): Major calcium store in muscle cells.
myofibril, actin, myosin, tropomyosin, troponin, motors
Contraction Process:
Calcium interacts with protein filaments in ____.
Calcium triggers interaction between ___ and ___ filaments.
____ moves off myosin binding sites on actin.
___ binds to calcium, facilitating tropomyosin movement.
Myosin ___ interact with actin, causing muscle fiber contraction.
Calcium Reabsorption:
Muscle Contraction
______ ____: Pump returns calcium to sarcoplasmic reticulum
relaxation
Muscle Contraction
______: Without calcium, myosin releases actin and filaments slide back.
Tropomyosin, Binding, Hydrolysis, Actin, Sliding, Contraction, Relaxation
Steps of Muscle Contraction
1. ____ Movement:
2. ATP ____:
3. ATP _____:
4. Binding to ___:
5. ____ Movement:
6. ___ and ___:
troponin, actin, myosin
Steps of Muscle Contraction
1. Tropomyosin Movement:
___ bound to calcium undergoes conformational change.
Moves away, allowing ___ and ___ interaction.
2. ATP Binding:
ATP binds to myosin head.
Myosin head becomes bound to ATP.
3. ATP Hydrolysis:
ATP hydrolysis occurs.
Myosin head moves, bound to ADP and phosphate.
4. Binding to Actin:
Myosin head binds to actin.
Detaches and binds ATP again.
5. Sliding Movement:
Myosin slides along actin filament.
Sarcomere contracts as myosin moves.
6. Contraction and Relaxation:
Cycle repeats until calcium is depleted.
Resulting in muscle contraction and relaxation.
myosin, ATP
Steps of Muscle Contraction
1. Tropomyosin Movement:
Troponin bound to calcium undergoes conformational change.
Moves away, allowing actin and myosin interaction.
2. ATP Binding:
ATP binds to ___ head.
Myosin head becomes bound to ___.
3. ATP Hydrolysis:
ATP hydrolysis occurs.
Myosin head moves, bound to ADP and phosphate.
4. Binding to Actin:
Myosin head binds to actin.
Detaches and binds ATP again.
5. Sliding Movement:
Myosin slides along actin filament.
Sarcomere contracts as myosin moves.
6. Contraction and Relaxation:
Cycle repeats until calcium is depleted.
Resulting in muscle contraction and relaxation.
hydrolysis, myosin, ADP, phosphate
Steps of Muscle Contraction
1. Tropomyosin Movement:
Troponin bound to calcium undergoes conformational change.
Moves away, allowing actin and myosin interaction.
2. ATP Binding:
ATP binds to myosin head.
Myosin head becomes bound to ATP.
3. ATP Hydrolysis:
ATP ____ occurs.
___ head moves, bound to ___ and ___.
4. Binding to Actin:
Myosin head binds to actin.
Detaches and binds ATP again.
5. Sliding Movement:
Myosin slides along actin filament.
Sarcomere contracts as myosin moves.
6. Contraction and Relaxation:
Cycle repeats until calcium is depleted.
Resulting in muscle contraction and relaxation.
myosin, ATP
Steps of Muscle Contraction
1. Tropomyosin Movement:
Troponin bound to calcium undergoes conformational change.
Moves away, allowing actin and myosin interaction.
2. ATP Binding:
ATP binds to myosin head.
Myosin head becomes bound to ATP.
3. ATP Hydrolysis:
ATP hydrolysis occurs.
Myosin head moves, bound to ADP and phosphate.
4. Binding to Actin:
___ head binds to actin.
Detaches and binds ___ again.
5. Sliding Movement:
Myosin slides along actin filament.
Sarcomere contracts as myosin moves.
6. Contraction and Relaxation:
Cycle repeats until calcium is depleted.
Resulting in muscle contraction and relaxation.
actin, sarcomere
Steps of Muscle Contraction
1. Tropomyosin Movement:
Troponin bound to calcium undergoes conformational change.
Moves away, allowing actin and myosin interaction.
2. ATP Binding:
ATP binds to myosin head.
Myosin head becomes bound to ATP.
3. ATP Hydrolysis:
ATP hydrolysis occurs.
Myosin head moves, bound to ADP and phosphate.
4. Binding to Actin:
Myosin head binds to actin.
Detaches and binds ATP again.
5. Sliding Movement:
Myosin slides along ___ filament.
____ contracts as myosin moves.
6. Contraction and Relaxation:
Cycle repeats until calcium is depleted.
Resulting in muscle contraction and relaxation.
calcium, relaxation
Steps of Muscle Contraction
1. Tropomyosin Movement:
Troponin bound to calcium undergoes conformational change.
Moves away, allowing actin and myosin interaction.
2. ATP Binding:
ATP binds to myosin head.
Myosin head becomes bound to ATP.
3. ATP Hydrolysis:
ATP hydrolysis occurs.
Myosin head moves, bound to ADP and phosphate.
4. Binding to Actin:
Myosin head binds to actin.
Detaches and binds ATP again.
5. Sliding Movement:
Myosin slides along actin filament.
Sarcomere contracts as myosin moves.
6. Contraction and Relaxation:
Cycle repeats until ___ is depleted.
Resulting in muscle contraction and ___.
