28 points) For the following groups of statements (#1-5 circle every letter the

Question

28 points) For the following groups of statements (#1-5 circle every letter the statements may be true (including none of them), so leaving this part blan false that is a TRUE statement. Note that any of k means you think that all statements are 1. During skeletal muscle relaxation: Nebulin returns the sarcomere back to its resting length b. No ATP is needed Calcium is being pumped into the sarcoplasm via the SERCA pump d.) The muscle action potential is traveling down the t-tubules. 2. During the sliding filament theory: a. Rigor state the myosin head is at a 45 degree angle to actin and there is no ATP bound +1 Relaxed state-the myosin head is at a 90 degree angle to actin and there is ATP bound c. Power stroke is initiated when ATP is converted to ADP+P calcium binds to tropomyosin in order to initiate strong binding between myosin and actin 3. In skeletal muscles a. The globular actin is known as F-actin and when two strands come together, it is known as G-actin b. Myosin contains actin binding sites that need to be exposed erroponín T has a strong affinity for Ca2+ Creation of phosphocreatine fuels skeletal muscle contraction 4. In cells and neurons: Diffusion of potassium across the membrane causes depolarization Sodium concentrations are maintained via the sodium-potassium ATPase pump The resting membrane potential is mainly due to sodium leak channels Diffusion of sodium across the membrane can cause excitation to initiate an action potential 2 b) a 5. Smooth muscle contraction: Can be controlled by hormones and neurotransmitterr Is caused by binding of Ach binding to nicotinic acety/choline receptors Involves opening the DHP (Ryanodine) receptor on the SR to release calcium Occurs when calcium binds to calmodulin activating myosin light chain kinase 6. In smooth muscle DAG will inhibit MLCK to initiate contraction D The sodium calcium exchanger facilitates calcium reuptake into the SR Calsequestrin lowers the free calcium levels in the SR d. Epinephrine can activate Gi to inhibit voltage gated calcium channels causing relaxation 7. For skeletal muscles a. c. Isometric contractions causes a change in the skeletal muscle length Slow fibers have high oxidative metabolic capacity Fast fibers are low in red myoglobin Majority of ATP production from oxidative phosporylation

Explanation / Answer

1. Nebulin maintains the alignment of the thin filament in the sacromere. Nebulin inhibits ATPase activity in calcium-calmodulin sensitive manner. It will be responsible for regulating actin myosin interactions. Speed of muscle relaxation is depressed in nebulin skeletal deficient muscles.

ATP is hydrolyzed to ADP and Pi. This action will allow cross-bridging between actin and myosin.

The SERCA pump is responsible for pumping calcium back into the sarcoplasmic reticulum from the sarcoplasm. Muscle Action potential moves down the T tubules and causes release of the calcium ions into the cytosol from the terminal cisternae.

Option a and d.

2. In the Rigor state, the myosin heads are tightly bound to actin at a 450 angle with no bound ATP. During the relaxed state, there is no actin myosin interaction.

Power stroke is the conversion of ATP to ADP and Pi by myosin when its pulls actin. Myosin head and hinge region tilt from a 900 to a 450 angle. Calcium binds to troponin, which releases tropomyosin in muscle contraction.

Option a and c.

3. G-actin are monomers of actin while F-actin are polymers of G actin. Actin has myosin-binding sites that are exposed by binding of calcium to troponin. Troponin C has four sites for calcium binding-two are high affinity and two are low affinity. Troponin T binds to tropmyosin. Muscle contraction obtains its energy from creatine phosphate and glycogen. Creatine phosphate transfers a phosphate group to ADP to form ATP.

Option d.

As per Chegg’s rules, one question needs to be answered.

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