The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge? View Available Hint(s) The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge? ATP bound to a myosin head Troponin bound to tropomyosin Calcium bound to troponin A myosin head bound to actin

D

Question:

The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge? View Available Hint(s) The cross bridge cycle is a series of molecular events that occur after excitation of the sarcolemma. What is a cross bridge?

A. ATP bound to a myosin head

B. Troponin bound to tropomyosin

C. Calcium bound to troponin

D. A myosin head bound to actin

Explanation:

The answer is D

A myosin head bound to actin

During step 2 of the contractile cycle, that is, the hydrolysis of ATP which provide energy for the myosin head to rotate and re-attach to actin

- ATP-binding site on myosin head closes around ATP and hydrolyzes it to ADP + Pi.

- ADP and Pi remain bound to myosin as energy released by ATP hydrolysis rotates the myosin head until it forms a 90 degree angle with the long axis of the filament

- In this position, myosin binds to a new actin that is 1-3 molecules away from where it started

- This cross bridge is weak because tropomyosin is covering the binding site

- Myosin has stored potential energy -- waiting for Ca signal

his week a heat wave will be hitting, and most of the country will be experiencing temperatures above average for july. due to humidity, the temperature outside can feel even warmer than it actually is. this adjusted temperature, often referred to as the “feels like” temperature is called the heat index. the chart shows the heat index, which is calculated based on temperature and relative humidity. use this chart to answer the following questions.  

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