Objectives 5 & 6 Flashcards
What are Sarcomeres made up of?
Composed of Myofilaments – made up of contractile proteins
What are Sarcomeres?
- The smallest contractile unit of a muscle
- The region of a myofibril between two successive Z discs
What are two types of myofilaments?
Thick (myosin)
Thin (actin)
What is myosin?
A thick myofilament
What is actin?
A think myofilament
Describe the banding pattern of thick (myosin) myofilaments
Thick filaments - extend the entire length of an A band
Describe the banding pattern of think (actin) myofilaments
Thin filaments - extend across the I band and partway into the A band
What is the Z-disc?
The Z disc (z-line) is a coin-shaped sheet of proteins (connectins) that anchors the thin filaments and connects myofibrils to one another
What is the H-zone?
The H-zone is the lighter, mid-region where filaments do not overlap
What are M lines?
M lines are lines of protein that hold adjacent thick filaments together
What are the Thick Filaments of the ultrastructure made up of?
Thick filaments are composed of the protein myosin
Describe the structure of the myosin molecule
Each myosin molecule has a rod-like tail and two globular heads
What is the tail of the myocin molecule made up of?
Two interwoven, heavy polypeptide chains.
What are the two globular heads of the myosin molecule made up of?
two smaller, light polypeptide chains that act as cross bridges during contraction
- containing binding sites for actin, binding sites for ATP and ATPase enzymes
Describe the ultrastructure of Thin (actin) Filaments
Thin filaments are twisted double strands of the protein actin
