Lecture 7-Skeletal muscle metabolism Flashcards
What are the three things ATP is needed for in skeletal muscle contraction?
- power stroke
- detachment of myosin from actin
- removal of calcium from the myofibrils into the sarcoplasmic reticulum
How is ATP used in the power stroke?
-splitting of ATP by myosin provides energy for the power stroke
How is ATP used in the detachment of myosin from actin?
-binding (not splitting) of a fresh ATP molecule to myosin permits detachment of the cross bridge, this ATP is then split and the energy is used for the next power stroke
How is ATP used in the removal of calcium from the myofibrils into the sarcoplasmic reticulum?
-active transport of Ca2+ needs ATP
What are the three sources of ATP?
- creatine phosphate
- aerobic (citric acid cycle)
- anaerobic (glycolysis)
How and when is creatine phosphate used for ATP?
-first energy source tapped into -has high energy phosphate group that can be donated to ADP to form ATP need creatine kinase that brings the phosphate over -used for rapid short bursts of energy
How and when is oxidative phosphorylation (aerobic pathway) used for ATP?
-the main source when oxygen present -for longer activity -fueled by glucose derived from muscle glycogen stores or by glucose and fatty acids delivered by the blood -can go on for hours -yields 35 ATPs fro one glucose -fat metabolism (the fatty acids)
What does the aerobic pathway consist of?
-citric acid cycle -oxidative phosphorylation -electron transport chain
How and when is glycolysis used for ATP?
-main source when oxygen not present -pyruvate (the end product) is converted into lactate (lactic acid)when lack of oxygen prevents the pyruvate from entering the aerobic pathway -used for fast short burst of activity, goes before aerobic (citric acid) -supplies 2 ATP per glucose
When do we use which energy source?
-first creatine phosphate (the first 2 mins) -anaerobic (mainly in the first 4 mins) -aerobic (starts 2 mins in) -fat metabolism (8mins)
Why is O2 important in ATP production?
-limiting in maximum exertion -need good circulation for oxygen to get there, depends on the heart, blood pressure - respiratory function -local factors= muscle capillaries
Why do we have fatigue?
-accumulation of lactic acid -accumulation of inorganic phosphate (from the creatine) -depletion of fuel sources -psychological fatigue -neuromuscular fatigue -oxygen debt
What is myoglobin needed for?
-primary oxygen carrying protein in muscle tissue
What are types the two oxidative types of muscle fibres?
-slow twitch (I) –appears red -fast twitch IIa – appears red
What are the two types of glycolytic muscle fibres?
-fast twitch IIx –appears white -fast twitch IIb –appears white
Why is creatine kinase important?
-the enzyme that catalyses the reaction:
