September 11, 2023 Flashcards
What are ATPases
are a class of enzymes that breakdown ATP to provide useful cellular energy
what is catabolism
refers to the break down complex molecules into simpler ones, releasing energy in the process
what is the job of metabolism
Energy Production: Metabolism’s most well-known role is to generate energy. It breaks down molecules like carbohydrates, fats, and proteins to release energy in the form of adenosine triphosphate (ATP).
This energy is used for various cellular processes, including muscle contraction, active transport of molecules, and the synthesis of other molecules.
what system takes care of the immediate source of energy
ATP-PC system
ATP-Phosphocreatine system
what is ATP-PCr
ATP-PCr, or adenosine triphosphate-phosphocreatine system, is a system within the body that plays a crucial role in providing short bursts of energy during high-intensity, short-duration activities, such as sprinting, weightlifting, and jumping.
It is one of the energy systems used by muscle cells to regenerate adenosine triphosphate (ATP), which is the primary molecule that provides energy for cellular processes.
how does the ATP-PC system work during exercise
Calcium indirectly activates Myosin ATPase
Phosphocreatine and ADP combine together to form Creatine and ATP (this is done with the enzyme Creatine Phosphokinase (CPK)
What is the role of Creatine Phosphokinase
CPK plays a crucial role in energy metabolism, particularly in the transfer and regulation of phosphate groups between molecules involving creatine.
where can Creatine Phosphokinase be found
an enzyme found in various tissues of the body, with the highest concentrations found in muscles and the brain.
How does the ATP-PC system work during recovery from exercise
Once you stop exercises, there is no more calcium to activate Myosin ATPase, which means ATP is not being broken down
ATP from the mitochondria mixed with creatine push the reaction back in the other direction
This causes phosphocreatine to go back up to resting levels
what activates myosin ATPase
Calcium Ion Release: Muscle contraction is initiated by the release of calcium ions (Ca2+) from the sarcoplasmic reticulum, a specialized organelle in muscle cells. When an action potential (nerve impulse) reaches the muscle cell, it triggers the release of calcium ions into the muscle cell’s cytoplasm.
single celled myoblasts →
multi-nucleated myotubes →
Muscle cells →
Muscle fibres →
Myofibres
Single fibres constrain myofibrils and have resident satellite cells which help to regenerate muscle
Myofibrils consist of
repeating sarcomeres with sarcoplasmic reticulum
Sarcomere:
the contractile unit; z-line; thick filament; thin filament
what is excitation-contraction coupling in skeletal muscle
Excitation-contraction coupling is the process by which a muscle cell (muscle fiber) is stimulated to contract
what are the key steps in excitation-contraction coupling in skeletal muscle:
1.Motor Neuron Stimulation: The process begins when a motor neuron releases a neurotransmitter called acetylcholine (ACh) at the neuromuscular junction, a synapse between the motor neuron and the muscle fiber. ACh binds to receptors on the sarcolemma, causing a change in membrane potential and initiating an action potential.
2.Propagation of Action Potential: The action potential travels along the sarcolemma and into the muscle fiber through a specialized network of tubules called the transverse (T) tubules. These tubules penetrate deep into the muscle fiber, allowing the action potential to reach all parts of the muscle quickly.
3.Release of Calcium Ions: As the action potential spreads into the T tubules, it triggers the opening of voltage-gated calcium channels in the sarcoplasmic reticulum (SR), a network of membranous sacs surrounding the myofibrils inside the muscle fiber. Calcium ions (Ca2+) stored in the SR are released into the cytoplasm of the muscle fiber.
4.Binding of Calcium to Troponin: The released calcium ions bind to troponin, a protein associated with the actin filaments in the muscle fiber. This binding causes a conformational change in troponin, which moves tropomyosin, another protein, away from the myosin-binding sites on the actin filaments, exposing these binding sites.
5.Cross-Bridge Formation: With the myosin-binding sites exposed, myosin heads (protein projections from myosin filaments) bind to the actin filaments, forming cross-bridges.
6.Power Stroke and Muscle Contraction: ATP is hydrolyzed to ADP and inorganic phosphate (Pi) by myosin ATPase, releasing energy that powers the swiveling motion of the myosin heads (power stroke). This motion pulls the actin filaments toward the center of the sarcomere, causing muscle contraction.
7.Reuptake of Calcium: When the action potential ends, calcium ions are actively pumped back into the SR by calcium pumps, lowering the cytoplasmic calcium concentration. This process is energy-dependent and restores the low calcium levels needed for muscle relaxation.
8.Cross-Bridge Detachment and Muscle Relaxation: Muscle relaxation occurs when ATP binds to myosin, causing the myosin heads to detach from actin. Tropomyosin returns to its blocking position, covering the myosin-binding sites on actin, preventing further cross-bridge formation.
9.Recovery: The muscle cell returns to its resting state, ready for the next action potential and contraction cycle.
what is an isoform
An isoform is a variant or different form of a particular protein
how much time after exercise(whether it be mild, moderate or severe) does PCr recover by 90%
2min
PCr is used rapidly and restored rapidly, while ATP stays relatively constant even during high intensity exercise. True or false and how
true
PCr donates phosphate to maintain ATP during exercise
are ATP and PCr available for immediate use?
yes
how much more PCr is there then ATP
3-4 times more
does PCr utilization depend on exercise intensity
yes
what does PCr restoration depend on
O2 delivery
