Question

Which of the following statements are true and which are false regarding cell structure and function? T = true and F = false.

A) proteins can be imported into the nucleus without being unfolded.

B) ribosomes can be either free or bound, dependent upon the whether the protein they are translating has an ER signal sequence.

C) All cells in the human body can participate in both constitutive and regulated secretion.

D) Proteoglycans, as part of the extracellular matrix (ECM), are anionic, which attracts Na⁺ ions, which attracts water, causing the ECM to swell.

Answer 1

Nuclear pore complexes allow transport of molecules across nucleus and proteins to be imported should be recognised by this complex. Fully folded proteins are recognised by this complex.So Statement A is false

Signal peptide is sequence of hydrophobic amino acids.when this sequence sticks out of ribosome,it is recognised by a protein complex called Signal Recognition Particle.This complex takes ribosome to endoplasmic reticulum.So statement B is true.

All cells have constitutive secretory pathway but some specialised cells have special regulated secretion pathway.So statement C is false.

Proteoglycans are covalently bonded to glycosaminoglycans and due to ionic character of glycosaminoglycans , proteoglycans have negative charges which makes to swell extracellular matrix.

So statement D is true