Contraction of Muscle

Question 1

Describe the structure of a muscle.

Answer 1

Muscle fiber= cell with multiple nuclei surrounded by sarcolemma membrane
Muscle fibers are made up of myofibrils.
Myofibrils are made up of sarcomeres from Z disc to Z disc and surrounded by sarcoplasm

Question 2

What are the parts of a sarcomere?

Answer 2

Z disc to Z disc. M line cuts in half

Thick myosin filaments (anchored to Z disc by titin) sandwiched between thin actin filaments.

Question 3

In what way do actin and myosin interact to contract the muscle?

Answer 3

Sliding…relaxed state means small overlap between actin and myosin…contraction means myosin head is on actin to shorten sarcomere= lots of overlap between actin and myosin

Question 4

What are the components of the actin filament?

Answer 4

F-actin: double stranded helix with ADP bound to each G actin, making active sites for myosin heads to bind to.
Tropomyosin: covers active site to prevent interaction with myosin
Troponin: complex of 3 proteins: I (binds actin), T (bind tropomyosin), C (binds Ca+2)

Question 5

Describe the myosin molecule.

Answer 5

Two heavy chains make up the tail, two light chains make up the head which is the site of ATPase activity.

Question 6

Describe muscle contraction.

Answer 6

“Walk Along” Theory
Ca binds to troponin–>uncovering of active sites on actin by tropomyosin–> Myosin head attached to actin–>ATP used to hydrolyze myosin head from actin–>myosin head cocked with ADP+P bound–>attaches to new site and relaeses ADP with power stroke.