Reading...
Play button
Play button
Use LEFT and RIGHT arrow keys to navigate between flashcards;
Use UP and DOWN arrow keys to flip the card;
H to show hint;
A reads text to speech;
17 Cards in this Set
- Front
- Back
|
What does muscle do to contract?
|
it is a major biochemical transducer that converts chemical energy (from ATP) into mechanical energy (contraction)
skeletal = striated , voluntary, multinucleate muscle fibers surrounded by an electrically excitable membrane (sarcolemma) |
|
|
what is a sarcomere?
|
basic functional unit of muscle contraction
between Z lines composed of thick and thin filaments |
|
|
What are the 4 major proteins involved in muscle contraction
|
myosin - ATPase activity in presence of Ca2+
actin - F-actin polymer tropomyosin - fibrous protein in grooves of actin - stabilizes actin subunits troponin - binds to tropomyosin and modulates interaction between actin and myosin |
|
|
process of initiating muscle contraction
|
AP sends electrical signal along T tubules
causes release of Ca2+ from SR (main Ca2+ storage) release of Ca2+ into cytoplasm initiates muscle contraction contractile events require lots of ATP! myosin catalyzed ATPase |
|
|
what are the different fuel sources that the muscle uses to regenerate ATP
|
creatine phosphate
glycogen (anaerobic and aerobic glycolysis) oxidation of FAs and Kbs oxidation of specific AAs (mainly BCAAs) can get these from the muscle itself or from the blood stream |
|
|
How does creatine phosphate regenerate ATP?
How is it created? |
created by enzyme creatine kinase (uses ATP to ADP)
degraded by same enzyme (reaction is in an equilibrium/reversible and depends on amount of ATP present) usually formed in the intermembrane space of mitochondria and is used to regenerate ATP in cytoplasm |
|
|
What else is made from creatine phosphate other than ATP?
|
creatinine (nonenzymatically)
end product of creatine so excreted by kidney good measure of muscle mass and renal function |
|
|
What is malonyl coA and why is it important in the muscle?
|
formed from acetyl coA and CO2 by acetyl coA carboxylase 2 (different from ACC1 in liver)
degraded by malonyl coA decarboxylase malonyl coA is an important intermediate in fatty acid synthesis it also blocks the carnitine transport system (necessary for fatty acid oxidation) in muscles when AMP is high it increase AMP kinase activity AMP kinase will inhibit ACC2 and activates mCoADC end up with decreased levels of malonyl coA therefore increasing fatty acid oxidation for more energy production important in relationship of carbohydrate metabolism and lipid metabolism in muscle |
|
|
what is adenylate kinase
|
enzyme that uses one ADP to phosphorylate a second ADP
makes an ATP molecule but also makes AMP |
|
|
What does AMP do?
|
increases fatty acid oxidation (by decreasing levels of malonyl coA)
also activates muscle glyocgenolysis positively regulates levels PFK1 (glycolysis) promotes enzymes involved in production of ATP |
|
|
What fuels do muscle cells use at rest?
|
balance still between glucose, AAs, and FAs depending on serum levels
|
|
|
What happens in an at rest muscle cell when energy levels are adequate?
|
intermediates get backed up including citrate
citrate can leave mitochondria and give off acetyl coA and can make malonyl coA which will inhibit carnitine transport system and therefore fatty acid oxidation |
|
|
What fuels are used by muscle cells during starvation?
|
blood glucose and insulin levels decrease so there are less GLUT 4 transporters in muscle cells
muscle cells take up less glucose FATTY ACIDS are preferred use of fuel glycolysis and glycogenolysis are decreased ketone bodies can be used too |
|
|
What happens during exercise in terms of fuel utilization in muscle?
|
at first use creatine phosphate
ATP is synthesized from both glycolysis and oxidative phosphorylation anaerobic glycolysis is important in the initial onset of exercise (can be from glycogen) - end product will be lactate when blood flow increases and oxygen becomes available - aerobic oxidation will take over (from glucose and FA and AA oxidation) glycogenolysis and glycolysis are both activated due to their sensitivities to AMP over time, more energy is derived from Fatty acids |
|
|
How is blood glucose for the brain maintained for the first 40 min during mild/moderate exercise?
after that? |
by liver glycogenolysis at first
then gluconeogenesis takes over and will be the major contributor |
|
|
What is the purine nucleotide cycle and why is it important during exercise in muscle?
|
it is increased during exercise
produces ammonia which buffers the protons from lactate also produces a CAC intermediate which can be used for energy |
|
|
aspects of contraction
|
Relaxation phase – myosin head hydrolyzes ATP to ADP and P, resulting in energized complex
Contraction – muscle is stimulated (involving Ca++, troponin, tropomyosin and actin) and actin and allows binding to myosin head Formation of complex causes release of P and initiates the power stroke, followed by release of ADP and a conformational change in myosin head, pulling actin toward the center of the sarcomere Another molecule of ATP binds to the myosin head forming an actin-myosin-ATP complex Myosin ATP has low affinity for actin and actin is released |
