Lecture 41 Flashcards
(23 cards)
True or False:
Myosin is an enzyme?
True
Thick filaments are primarily made up of ____ and thin filaments are primarily made up of ___, ___. and _____.
- Myosin
- Actin
- Troponin
- Tropomyosin
What part of the thin filament will bind calcium?
Troponin
Where is the enzymatic activity of myosin contained? What does this activity entail?
- Head
- Binds actin and splits ATP
What happens to intracellular Ca2+ concentration upon muscle contraction?
Released from SR and rises
How does a rise in Ca2+ concentration aid in muscle contraction?
- Ca2+ binds to troponin allowing myosin/actin interaction (myosin binds troponin) creating a crossbridge
- Release of ADP + P from myosin (power stroke) pulls z-line toward center of sarcomere
How is muscle contraction stopped?
- Binding of new ATP to myosin allows release of actin from myosin
- Finally ATP is hydrolyzed to ADP + P by myosin in preparation for another contraction signal
1 myosin head splits ____ ATP molecule at a time using the enzyme ____
- 1
- Myosin ATPase
____ is a major high energy phosphate reservoir in muscle
Creatine phosphate
How does creatine phosphate enable muscle contraction?
-Creatine phosphokinase transfers phosphate from creatine phosphate to ADP to make more ATP to fuel muscle contraction
How is creatine phosphate regenerated in a resting muscle cell?
-Resting cell builds ATP back up and re-phosphorylates creatine
How can creatine be used clinically?
Elevated plasma levels of creatine phosphate indicate muscle cell damage (leaking out from broken muscle cell)
How does myokinase work?
Uses 2 ADP to make 1 ATP + 1 AMP
-AMP signals pathways to produce energy (AMPK; phosphofructokiase) –> need to regenerate ATP
How is vasodilation signaled in muscle contraction?
-Myokinase is generating AMP. Nucleotidase can remove a phosphate from AMP and generate adenosine which is a signal for increased vasodilation.
During prolonged muscle contraction some ATP is lost to generation of what waste product?
Uric Acid
Explain the use and re-synthesis of ATP for muscle contraction over the course of exercise.
- Initially muscle reserve ATP is used quickly
- Creatine phosphate is used to rephosphorylate ADP
- After this begins to be depleated anaerobic glycolysis from phosphorylase kinase and PFK stim generates more ATP
- Eventually a shift to aerobic glycolysis happens which allows glycogen supply of muscle as well as FFA to provide energy
How does exercise enhance glucose uptake?
-stimulates GLUT4 translocation to cell surface and thus increased glucose uptake
How does exercise affect insulin sensitivity?
- Enhances
- Lower amounts of insulin will accomplish same metabolic activity
During initial exercise periods most of fuel is being provided by ____. Over time ____ is depleted from the muscle and ____ will provide most of the energy.
- Glucose
- Glycogen
- Fatty Acids
Over prolonged exercise indicate what will happen to each:
- Blood glucose
- Lactate concentration
- Fatty acid production and use
- Insulin production
- Glucagon production
- Hormone (cortisol, epinephrine, norepinephrine)
- Glycogenolysis
- Lipolysis
- Remains same
- Constant
- Increased
- Decreased
- Increased
- Increased
- Increased
- Increased
In general why is anaerobic glycolysis occurring in a resting muscle?
-Regenerate ATP to rephosphorylate creatine to make creatine phosphate
Spontaneous breakdown of creatine generates ____.
Creatinine
How does the body deal with creatinine? How is this clinically important?
- Filtered out and excreted
- High creatinine levels may indicate kidney problems
