Muscle Biochemistry Flashcards
[6-minute video]: The SERCA Pump [Part 1]
[8-minute video]: The SERCA Pump [Part 2]
[3-minute video]: The SERCA Pump [Part 3]
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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 generated by the head domain. It also serves as a binding site for light chains, which are regulatory proteins.
(3) Tail domain: The tail domain varies among 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 structure in 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.
[Diagram 1] [Diagram 2]
Explain glycolysis as a means of ATP production in muscle tissue. Also point out its drawbacks.
💪 As the phosphogen system is exhausted, the muscle tissue begins to mobilize its glycogen stores for the generation of ATP by glycolysis.
💪 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].
What is the purine nucleotide cycle?
The purine nucleotide cycle is a metabolic pathway that helps to regulate adenosine monophosphate (AMP) levels in muscle cells, producing ammonia and fumarate as byproducts.
Where does the purine nucleotide cycle occur?
It occurs in the cytosol of muscle cells.
What are the main reactions in the purine nucleotide cycle?
(1) Deamination of AMP to IMP [inosine monophosphate aka. inosinic acid], catalysed by AMP deaminase
(2) Formation of adenylosuccinate from IMP and aspartate, catalysed by adenylosuccinate synthetase
(3) Cleavage of adenylosuccinate to AMP and fumarate, catalysed by adenylosuccinate lyase
What is the role of fumarate produced in the purine nucleotide cycle?
Fumarate enters the Krebs cycle, contributing to ATP production via oxidative phosphorylation.
What is the significance of the purine nucleotide cycle during exercise?
It helps maintain energy balance in muscle cells by removing excess AMP and supporting ATP regeneration.
Which of the following is not true about energy systems in a skeletal muscle?
(a) The aerobics system may break a range of fuels such as fats, carbohydrates and proteins to rebuild ATP
(b) The aerobic system is slower in ATP production and has lower capacity to produce ATP
(c) The aerobic system is more reliable in endurance activities
(d) The phosphagen system breaks down phosphocreatine to rebuild ATP
(e) The anaerobic glycolysis system only breaks down carbohydrates to rebuild ATP
(b) The aerobic system is slower in ATP production and has lower capacity to produce ATP
Which of the following is not true about Type 1 muscle fibers?
(a) Contain less myoglobin than Type 2 fibres
(b) Contain more mitochondria than Type 2 fibres
(c) Generate fewer actin-myosin bonds per second than Type 2 fibres
(d) They are slow oxidative
(e) They have less ATPase activity than Type 2 fibres
(a) Contain less myoglobin than Type 2 fibres
________ of the sarcomere remains unaffected during the muscle contraction.
(a) H zone
(b) A band
(c) I band
(d) H band
(e) M band
(b) A band
Which of the following best distinguishes Type 2A and Type 2B muscle fibres?
(a) Their ATPase rate
(b) Their SR pumping capacity
(c) Their glycolytic activity
(d) Their primary ATP production
(e) One is fast oxidative and the other is fast glycolytic
(e) One is fast oxidative and the other is fast glycolytic
Which of the following statements is false about Type 1 muscles?
(a) Their resistance to fatigue is high
(b) Their mitochondrial content is high
(c) They are fast glycolytic
(d) Their diameter is small
(e) Their oxidative capacity is high
(c) They are fast glycolytic
Which of the following statements is true about Type II muscles?
(a) They are geared towards long distance running
(b) Their blood supply is high
(c) Their glycogen reserve is high
(d) Their ATPase rate is slow
(e) Their primary ATP pathway is aerobic
(c) Their glycogen reserve is high
Which of the following statements is not true regarding muscle energy metabolism?
(a) Phosphocreatine has a high energy phosphate bond that provides readily available energy in muscles and nerves.
(b) White fibers generate ATP by short reaction pathways; red fibres use longer pathways towards energy generation.
(c) The presence of creatine kinase in the blood may be an indicator of skeletal muscle damage.
(d) Red muscles have a much more anaerobic metabolism than does the white muscle.
(e) Creatine kinase catalyzes the transfer of a phosphoryl group from phosphocreatine to ADP to form ATP in non-reversible reaction.
(d) Red muscles have a much more anaerobic metabolism than does the white muscle.
Endurance training increases the muscles capacity to ________.
(a) generate energy anaeorobically
(b) burn fat and carbohydrate
(c) contract faster
(d) produce more red blood cells
(e) breakdown phosphocreatine
(b) burn fat and carbohydrate
Which of the following statements is not true regarding muscle metabolism?
(a) Muscle can store glycogen that is hydrolyzed when glucose is absent.
(b) Muscle cells lack the enzyme glucose-6-phosphatase, hence muscle glycogen cannot supply glucose to the circulation and other tissues.
(c) Muscle fuel needs are dependent on activity level.
(d) Muscle can use both glucose and fatty acids and occasionally even amino acids as fuel.
(e) The muscle tissue depends entirely on the liver for its energy supply.
(e) The muscle tissue depends entirely on the liver for its energy supply.
The energy for all forms of muscle contraction is provided by ________.
(a) ADP
(b) Generated in the mitochondria of the cell
(c) ATP
(d) Oxidative phosphorylation
(e) Phosphocreatine
(c) ATP
Which of the following is not true about Type I muscle fibres?
(a) They have less ATPase activity than Type 2 fibres
(b) Generate fewer active-myosin bonds per second than Type 2 fibres
(c) Contain more mitochondria than Type 2 fibres
(d) They are slow oxidative
(e) Contain less myoglobin than Type 2 fibres
(e) Contain less myoglobin than Type 2 fibres
