Biochemistry of Muscle Contraction Flashcards
Describe the structure of myosin.
(1) Head domain: This is also known as the motor domain. It binds to actin filaments and has ATPase activity, which means it can hydrolyze ATP to generate energy for movement.
(2) Neck domain: This acts as a linker and lever arm, transmitting the force generate dby the head domain. It also serves as a binding site for light chains, which are regulatory proteins.
(3) Tail domain: The tail domain varies amond different types of myosin. It can be involved in binding to cargo molecules, forming filaments, or anchoring the myosin to cellular structures.
Myosin molecules typically consist of two heavy chains and four light chains. The heavy chains form a coiled structurein the tail region, while the head and neck regions are involved in the motor activity.
What are two regulatory proteins associated with actin?
troponin and tropomyosin
Explain the creatine phosphate/phosphogen system of ATP generation in muscle tissue.
The enzyme creatine kinase takes a high energy phosphate from creatine phosphate and adds it to ADP to very quickly make ATP available for the cell. This immediate ATP source is used during short and intense activity e.g. sprinting. This supplies the active muscle with ATP anaerobically, as the cardio-respiratory system cannot yet deliver oxygen fast enough to meet the huge demands of the muscle tissue. It is quick but limited.
Explain glycolysis as a means of ATP production in muscle tissue.
As the phosphogen system is exhausted, the muscle tissue begins to mobilize its glycogen stores for the generation of ATP by glycolysis. This system can also be called the Glycogen-Lactic Acid System. It can produce ATP for about 30 to 40 seconds of maximal muscular activity. Glycolysis is fairly fast, but is inefficient [1 glucose only generates 2 ATP]. Another draw back is that glycolysis generates lactic acid. When lactic acid builds up, it lowers the surrounding pH and the proteins in muscle begin to denature, resulting in muscle fatigue.
Discuss oxidative phosphorylation as a means of ATP production in muscle tissue.
After about 40 seconds of maximal activity, the cardio-respiratory system finally catches up to supply enough oxygen to meet ATP generation aerobically. This method takes longer to generate ATP but is much more efficient [1 glucose generates 38 ATP]
