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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#Section 2: General Biology

The amino group at C-2 bears a fatty acid in amide linkage.

The fatty acid is usually saturated or monounsaturated, with 16, 18, 22, or 24 carbon atoms.

Ceramide is the parent compound for this group.

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#Section 2: General Biology

A typical membrane lipid of archaea.

Diphytanyl moieties are 8 five-carbon isoprene groups condensed end-to-end.