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.
πͺ As the phosphogen system is exhausted, the muscle tissue begins to mobilize its glycogen stores for the generation of ATP by glycolysis.
πͺ 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].
πͺ Another draw back is that glycolysis generates lactic acid.
πͺ 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
At rest in the skeletal muscle, ________ is the preferred fuel.
(a) glucose
(b) fatty acids
(c) ketone bodies
(d) amino acids
(e) glycerol
(b) fatty acids
Which of the following biochemical changes are observed in the muscles of an athlete some minutes after he/she begins to play?
(a) A high ratio of ATP to ADP
(b) A decreased oxygen consumption as a consequence of an increase in anaerobic glycolysis
(c) Decreased consumption of fatty acids
(d) An increased formation of phosphocreatine
(e) An increased formation of lactate from pyruvate
(e) An increased formation of lactate from pyruvate
Which of the following is false about the purine nucleotide cycle?
(a) occurs in resting muscle
(b) It occurs in active muscle
(c) lt occurs during hypoxia
(d) It occurs during anorexia nervosa (lack of appetite)
(e) B and D are correct
(a) occurs in resting muscle
A sarcomere is a part of muscle fibre between two ________.
(a) I bands
(b) Z lines
(c) A bands
(d) H bands
(e) M lines
(b) Z lines
Which of the following is an invagination of the muscleβs sarcolemma?
(a) Transverse tubules
(b) Microtubules
(c) Triad
(d) Cisternae
(e) Sarcoplasmic reticulum
(a) Transverse tubules
When skeletal muscle shortens in response to stimulation, there is ________.
(a) a decrease in the width of the A band
(b) a decrease in the width of the I band
(c) an increase in the width of the H zone
(d) all the above
(e) A and B
(b) a decrease in the width of the I band
In skeletal muscle, which of the following events occurs before depolarization of the T tubules during excitation-contraction coupling?
(a) Binding of actin and myosin
(b) Binding of Ca2+ to troponin C
(c) Uptake of Ca2+ into the sarcoplasmic reticulum (SR) by Ca2+ - ATPase
(d) Opening of Ca2+ release channels on the SR
(e) Depolarization of the sarcolemma
(e) Depolarization of the sarcolemma
Which of the following sets of ions are critically necessary in the chemical events leading to muscle contraction?
(a) Na+ and K+
(b) Na+ and Ca2+
(c) K+ and Ca2+
(d) Ca2+ and Mg2+
(e) Na+ and Mg2+
(d) Ca2+ and Mg2+
Which of the following statements about creatine phosphate (CP) is correct?
(a) CP is essential in muscle cells for contraction to occur.
(b) CP is stored in muscle cells, unlike ATP.
(c) Like ATP, CP cannot be stored in muscle cells.
(d) CP is converted to creatinine by creatine kinase.
(e) None of the above is correct.
(b) CP is stored in muscle cells, unlike ATP.
Which of the following statements about the control of contraction in skeletal muscles is correct?
(a) In skeletal muscles, contraction is initiated by a nerve impulse opening voltage-gated Ca2+ channels in the sarcoplasmic reticulum.
(b) In skeletal muscles, contraction is initiated by a nerve impulse closing voltage-gated Ca2+ channels in the plasma membrane.
(c) In skeletal muscles, contraction is initiated by a nerve impulse closing voltage-gated Ca2+ channels in the SR.
(d) In skeletal muscles, contraction is initiated by a nerve impulse hydrolysing ATP.
(a) In skeletal muscles, contraction is initiated by a nerve impulse opening voltage-gated Ca2+ channels in the sarcoplasmic reticulum.
The protein of skeletal muscle having ATPase activity is ________.
(a) actin
(b) actinomyosin
(c) myosin
(d) tropomyosin
(e) dystrophin
(c) myosin
Which of the following is false regarding circumstances where glycolysis exceeds oxidative phosphorylation in a skeletal muscle?
(a) lactic acid accumulates
(b) the muscle cell pH decreases
(c) glucose comes from stored glycogen
(d) muscle glycogen is not used for glycolysis
(e) muscle efficiency decreases
(d) muscle glycogen is not used for glycolysis
Which of the following is not true of cardiac muscle?
(a) it is aerobic
(b) it utilizes glucose preferentially
(c) fatty acids are its fuel of choice
(d) utilizes ketone bodies
(b) it utilizes glucose preferentially
Which of the following does not characterize red muscle fibers?
(a) depend on anaerobic oxidation
(b) contain many blood capillaries
(c) glycogen stores are low
(d) contain high concentrations of myoglobin
(e) contain more mitochondria
(a) depend on anaerobic oxidation
Contraction of myofibrils in skeletal muscle is initiated by ________.
(a) release of Ca2+ from the mitochondria
(b) release of Ca2+ from the T tubules
(c) uptake of Ca2+ by the T-tubules
(d) release of Ca2+ from the sarcoplasmic reticulum
(e) uptake of Ca2+ by the sarcoplasmic reticulum
(d) release of Ca2+ from the sarcoplasmic reticulum
The most rapid method to resynthesize ATP during exercise is through ________.
(a) glycogenolysis
(b) glycolysis
(c) tricarboxylic acid cycle
(d) gluconeogenesis
(e) phosphocreatine breakdown
(e) phosphocreatine breakdown
ATP concentration is maintained relatively constant during muscle contraction by
(a) the action of adenylate kinase
(b) the action of creatine kinase
(c) the constant supply of stored fuel
(d) increasing the metabolic activity
(e) all of the above
(e) all of the above
Which of the following proteins does not constitute the I-band?
(a) actin
(b) myosin
(c) troponin
(d) tropomyosin
(e) Z-disk
(b) myosin
Which of the following is not an important role of ATP in skeletal muscle contraction?
(a) Exposure of the myosin binding sites on actin.
(b) Energizing the power stroke of the myosin cross bridge.
(c) Energizing the calcium ion pump which transports calcium ions back into the sarcoplasmic reticulum.
(d) Disconnecting the myosin cross bridge from the binding site on actin at the conclusion of the power stroke.
(e) None of the above.
(e) None of the above.
The end of the rising phase of an action potential occurs when the ________.
(a) potassium channels close
(b) chloride channels open
(c) potassium channels open
(d) A and B
(e) sodium channels close
(e) sodium channels close
In the muscle, the purine nucleotide cycle (PNC) promotes the following except:
(a) Synthesis of fumarate
(b) Catabolism of branched chain amino acids (BCAAs)
(c) Excretion of excess amino groups through the gut and kidney
(e) Synthesis of glutamine
(e) Synthesis of GTP
(b) Catabolism of branched chain amino acids (BCAAs)
Further notes:
The only amino-acid involved is aspartate, and it is not a branched-chain amino acid.
In the muscle, the purine nucleotide cycle (PNC) promotes the following except:
(a) Synthesis of Ξ±-ketoglutarate
(b) Excretion of excess amino groups through the gut and kidney
(c) Synthesis of glutamine
(d) Catabolism of branched chain amino acids (BCAAs)
(e) Synthesis of fumarate
(d) Catabolism of branched chain amino acids (BCAAs)
A resting skeletal muscle ________
(a) uses glucose and FAs for energy
(b) uses lactic acid for energy
(c) may suffer from muscle inefficiency
(d) uses FAs and KBs for energy
(e) uses glucose, FAs and KBs for energy
(e) uses glucose, FAs and KBs for energy
All the enzymes below are part of the purine nucleotide cycle except ________.
(a) adenylosuccinate synthetase
(b) AMP deaminase
(c) adenylosuccinate lyase
(d) myokinase
(e) 5β nucleotidase
(e) 5β nucleotidase
