Which statement about transmembrane proteins is true?
A) They cross the membrane only once.
B) The signal sequences are always cleaved off.
C) They usually have one or more $\alpha$ helices spanning the membrane bilayer.
D) They are always inserted with the amino terminus on the lumenal side and the carboxyl terminus in the cytosol.

Question

Quizplus · Accepted Answer

Transmembrane proteins usually have one or more alpha helices spanning the membrane bilayer. However, the exact sequence may vary and is not always F1F1F1S1alphaF1F1F10. Choices A, B, and D are not true statements about transmembrane proteins. Some transmembrane proteins may cross the membrane more than once, the signal sequences are not always cleaved off, and the orientation of the protein in the membrane can vary.

Which Statement About Transmembrane Proteins Is True? A) They Cross α\alphaα

Which Statement About Transmembrane Proteins Is True?
A) They Cross $\alpha$