Muscle cells have an abundant, modified smooth ER called the sarcoplasmic reticulum.

The release and reuptake of Ca2+ by the sarcoplasmic reticulum trigger myofibril contraction and relaxation, respectively

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#Id: 7747

#XL - Q Biochemistry

Size of atom or atomic radii can be estimated by effective nuclear charge

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#XL - Q Biochemistry

The noble gases are left out of the trends in atomic radii because there is great debate over the experimental values of their atomic radii.

The SI units for measuring atomic radii are the nanometer (nm) and the picometer (pm). 1 nm = 1 X 109 m; 1 pm = 1 X 10-12 m.

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#Id: 7745

#XL - Q Biochemistry

The noble gases are left out of the trends in atomic radii because there is great debate over the experimental values of their atomic radii.

The SI units for measuring atomic radii are the nanometer (nm) and the picometer (pm). 1 nm = 1 X 109 m; 1 pm = 1 X 10-12 m.

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#Id: 7744

#XL - Q Biochemistry

An ionic radius is one-half the distance between the nuclei of two ions in an ionic bond.

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#Id: 7743

#XL - Q Biochemistry

A covalent radius is one-half the distance between the nuclei of two identical atoms.

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#Id: 7742

#XL - Q Biochemistry

Atomic radii: The atomic radii of an atom depends on its position in the periodic table.

We can never determine the atomic radius of an atom because there is never a zero probability of finding an electron, and thus never a distinct boundary to the atom.

All that we can measure is the distance between two nuclei (internuclear distance).