Which statement accurately describes the relationship between air pressure, air density, or altitude? As altitude increases, pressure increases. As altitude increases, air density increases. Air pressure and density are lowest at sea level. Denser air exerts more pressure than less dense air.

What is the significance of the protein-lined pits? a. protein attracts other proteins needed for atp synthesis within the cell. b. protein-lined pits are able to transport one molecule at a time down the concentration gradient within the cell. c. the polarity of proteins allows other polar molecules to attach and be transported in the cell by transport channels. d. receptors within the pits allow ligands to fuse and be transported into the cell by endocytosis.