Motor Proteins and Muscles Flashcards
Movement
The ability to move requires a firm structure to provide leverage and a mechanism for moving that structure; these structures rely on both MOTOR PROTEINS and components of the CYTOSKELETON:
- Multicellular: skeleton and muscle
- Unicellula: flagella and/or cilia
Cytoskeleton
cell skeleton; network of filaments that support the PM, gives the cell an overall shape, aids in correct positioning of organelles, provides tracks for vesicle transport, and allows cells to move
- In eukaryotes, there are three types of protein fibers in the cytoskeleton: MICROFILAMENTS, INTERMEDIATE FILAMENTS, MICROTUBULES
- serve as tracks for movement of motor proteins, which use ATP to “walk along” cytoskeletal filaments (microfilaments and microtubules)
Microfilaments
AKA actin filaments because they are composed of ACTIN PROTEIN SUBUNITS; serve as tracks for the motor protein MYOSIN and are involved in many cellular processes that require motion
- Form SACROMERES in muscle cells
- when actin and myosin filaments of a sarcomere slide past each other, muscles contract
Sacromere
organized structures of overlapping filament made up of microfilaments
Microtubules
made up of tubulin proteins and serve as tracks for motor proteins KINESIN + DYNEIN; play roles in cellular structural integrity and cell movement
- cell movement via cilia and flagella
Motor Protein
use ATP to “walk” along specific cytoskeletal tracks; essential for movement of vesicles and other cargoes within cells, as well as for the movement of muscles and cilia/flagella
- Myosin
- Dynein
- Kinesin
Myosin
actin microfilaments; requires for movement of MUSCLE
Dynein
tubulin microtubules; required for movement of CILIA/FLAGELLA
Kinesin
tubulin microtubules; required for movement of VESICLES + OTHER INTRACELLULAR CARGOES
Cilia + Flagella
Structures essential for movement of eukaryotic cilia and flagella:
- ATP
- Dynein motor proteins
- microtubule tracks
Flagella
long, hair-like structures that extend from the cell surface and are used to move an entire cell
- Eukaryotic flagella have different structures and have an independent evolutionary origin from prokaryotic flagella
- EX: Sperm
Cilia
shorter, similar to flagella, usually appear in large numbers on the cell surface
- when cells with motile cilia form tissues, the beating helps move materials across the tissue surface
- EX: cilia of cells in upper respiratory system move dust and particles out through the nostriles
Common Structure: Cilia + Flagella
- 9 pairs of microtubules arranged in a circle, with 2 additional ones in the center (9+2 ARRAY)
- the individual microtubule pairs are physically connected via protein bridges and to the base of the cilium/flagella
- the movement of dynein motor proteins cause the beating of the flagella/cilia
- dynein causes the cell to move in a coordinated fashion
TYPES OF MUSCLEEEEEEEEEEEE
- Skeletal Muscles
- Smooth Muscles
- Cardiac Muscles
Structures Essential for Muscle
- ATP
- Myosin motor proteins
- actin microfilament
Skeletal Muscles
attach to bones/skin and control locomotion and any movement that can be consciously controlled; also called VOLUNTARY MUSCLES
- long, cylindrical; stripped/striated appearance
- the striations are caused by the regular arrangement of contractile proteins (actin + myosin)
Smooth Muscles
occurs in the walls of hollow organs; has no striations, is under automatic control - INVOLUNTARY MUSCLE
- EX: stomach, intestines, bladder, respiratory tract, blood vessels
Cardiac Muscle
found ONLY in the heart; is striated and cannot be consciously controlled (INVOLUNTARY MUSCLE)
Cardiac contractions pump blood throughout the body and maintain blood pressure
- The heart can beat without the nervous system’s input due to PACEMAKER CELLS that spontaneously initiate cardiac muscle contraction
- has INTERCALATED DISKS, which enable rapid passage of AP from one cardiac muscle cell to the next
Skeletal Muscle Structure
each skeletal muscle cell is called a MUSCLE FIBER; structures/molecules important in muscle contraction are:
- Myofibrils
- Sarcomeres
- Myosin
- Actin
- Tropomyosin
- Troponin
Myofibrils
long, cylindrical structures that lie parallel to the muscle fiber; run the entire length of the muscle fiber
- composed of many sarcomeres running along its length, and as they individually contracct, the myofibrils and muscles cells shorten
Sarcomere
Functional units that make up myofibril that cause contraction of a muscle (contractile units)
- give muscle its striated/banded appearance due to the alternating bands of actin + myosin that allow them to contract
- ACTIN AND MYOSIN COMPONENTS
Sarcomere Structure
Each one contains a thick, dark filament of myosin and a thin, light filament of actin
- actin filaments are physically anchored to structures at the end of each sarcomere (Z DISCS)
- the center of the myosin filament is marked by an M-Line
- One sarcomere is the space between 2 consecutive Z-Discs
- THE ACTIN + MYOSIN FIBERS STAY THE SAME LENGTH BY SLIDING PAST EACH OTHER AS THE CELL ITSELF SHORTENS
Myosin
the primary component of thick filaments
- the tail of the myosin molecule connects with the other myosin molecules to form a central region of a thick filament near the M-Line
- the heads align on either side of the filament where the thin filaments overlap
Actin
the primary component of thin filaments
- attached at the Z-Disc and extend toward the M-Line, overlapping with the myosin heads of the thick filament
