Gives cell structure - without it, the cell would be a big water balloon with a bunch of smaller balloons inside. 
-Very dynamic! Lengths change constantly.

Description

Many different kinds

Muscle Contraction
Actin and myosin move in opposite directions

1 atp molecule is consumed per step - releasing 7.3 kcal/mole

Work (joule) = Force (newton) x Distance (Meter)

Cell Skeleton

• Movement - cell highway system
• Muscle Contraction
• Locomotion/Cell Motility
• Regulation of Cell Shape, Size, and Shape Chages
• Adhesion between cells and their surroundings
• Cell division
• Response to external mechanical and chemcial stimuli
• Etc. 

• Subunits = actin
• 7-9 nm in diameter
• Flexible polymer
• Functions: Cell Shape, Movement, Muscle, Contraction

• Subunits = tublin (alpha, beta, gamma)
• Hollow cylinder structure
• 25 nm in diameter
• Relatively stiff polymer
• Functions; Cell shape, movement, mitosis

• Rope-like fibers
• Subunits = varies (eg. keratin, vimetin, lamins)

Description

Motor molecule part of thick filament (bc they show up darker in screening images)

Thin Filament

Moving parts of the myosin

• Nucleotides can act as chemical energy storehouses
• ATP - Adenosine triphosphate
• ATP can easily be hydrolyzed to form ADP and release energy

1. Actin and myosin tightly bound (no ATP or ADP bound)
2. ATP binds to myosin head, myosin releases from actin
3. ATP hydrolyzed into ADP+Pi, creates conformational change in myosin, head "cocked"
4. Myosin with ADP+Pi binds to actin, releases Pi, then ADP and creates "power stroke", sliding actin filament and returning to original conformation.