Exam 3, Set 1

Question 1

Muscle Cell/ Muscle Fiber

Answer 1

A cell that has differentiated for the specialized function of contraction

Question 2

Functions of the muscular system

Answer 2

Heat, Movement, Posture, Structure

Question 3

Myofibril

Answer 3

The long thin contracting protein subunits of a muscle cell that are composed of actin and myosin filaments.

Question 4

Thick Filament

Answer 4

Myosin, essentially a molecule with 2 round heads and chain-like tail.

Question 5

Thin Filament

Answer 5

A polymer of actin with tightly bound regulatory proteins troponin and tropomyosin

Question 6

function and location of myosin heads

Answer 6

Function: Bind and hydrolyze ATP,
Location: attached to elongated tail region

Question 7

Function and location of myosin head binding sites

Answer 7

Function: Facilates binding so cross-bridges can form
Location: on the actin filaments

Question 8

Function and location of actin

Answer 8

Function: Shortens the sarcomere
Location: attached at their plus ends to the Z disc

Question 9

Function and location of troponin

Answer 9

function: sarcomeric Ca2+ regulator
location: attached to the protein tropomyosin and lies within the groove between actin filaments

Question 10

Function and location of tropomyosin

Answer 10

Function: Stabilizes actin filaments but also regulates muscle contraction
Location: in each of the two long-pitch helical grooves of actin

Question 11

Function and location of Ca2+

Answer 11

Function: induces skeletal muscle contraction
Location: the cytosol

Question 12

Sliding filament model of contraction

Answer 12

Within the sarcomere, myosin slides along actin to contract the muscle fiber

Question 13

Excitation-contraction coupling

Answer 13

The rapid communication between electrical events occurring in the plasma membrane of skeletal muscle fibres and Ca2+ release from the SR, which leads to contraction

Question 14

Steps in the process of excitation-contraction coupling

Answer 14

Step 1
AP spreads along the sarcolemma to the T-tubules
Step 2
Calcium is released into the SR

Step 3
Calcium binds to actin and blocking action of tropomyosin is removed

Step 4
Myosin heads attach to begin contraction

Step 5
Calcium is removed and binding sites on actin become blocked again by tropomyosin

Step 6
Muscle relaxes

Question 15

Steps in cross bridge cycling, and the involvement of ATP, cross bridges, and the myosin head ATPase

Answer 15

Step 1
cross bridge formation: myosin head attaches to actin myofilament

Step 2
the power stroke:
ADP and Pi are released from myosin head
Myosin head bends,changes to low-energy state
Shape change pulls actin towards the M line

Step 3
cross bridge detachment: ATP attaches to myosin, breaking cross bridge

Step 4
cocking of the myosin head: attached ADP is hydrolyzed by myosin ATPase —-> ADP + Pi, bringing it back to a high-energy state

Question 16

How a muscle cell obtains the ATP it needs

Answer 16

Using creatine phosphate

Using glycogen (no oxygen)

Using aerobic respiration

Question 17

isotonic Contractions

Answer 17

Tension remains the same in the contraction

Question 18

concentric contractions

Answer 18

total length of the muscle shortens as tension is produced