Question

by which of the following mechanisms can a cell transport a substance from a lower to a higher concentration?
aquaporins
simple diffusion
osmosis
facilitated transport
active transport
question 7 (1 point)
simple staining is often necessary to improve contrast in which microscope?
compound light microscope
phase - contrast microscope
electron microscope
darkfield microscope

Explanation:

1. For the first question, active transport is the process by which cells move substances against their concentration gradient (from lower to higher concentration), requiring energy. Aquaporins are channels for water transport, simple diffusion and osmosis (a type of diffusion for water) move substances down - their concentration gradient, and facilitated transport also moves substances down their concentration gradient with the help of transport proteins.
2. For the second question, a compound light microscope uses visible light to view specimens. Simple staining is often necessary to improve contrast because the specimens are usually color - less and transparent, making them difficult to see clearly without staining. Phase - contrast microscopes, electron microscopes, and darkfield microscopes have different mechanisms to enhance contrast without the need for simple staining in most cases.

Answer:

1. E. active transport
2. A. compound light microscope