When would cells need energy to move particles across a membrane?

Answer 1

Active transport over a membrane is called active because it requires conformal changes of the proteins involved, provided whatever you want to bring across is not hydrophobic enough to simply dissociate over the membrane.

There are different types of carriers in biological membranes. The non-active ones are constantly open pores (for water, for example), which require no energy to stay open.

However, the other methods of providing movement across the membrane come as either pores that can change their state from closed to open, or as carriers or pumps which actively transport a substance across the membrane by allowing it to attach to them (or diffuse close to them) and then changing their conformation to wield the substance to the other side of the membrane (or to open a pore). Usually, the carrier or pump is in its normal conformation in the first place because of electric and covalent forces that keep it in this functional shape. To change and wield or pump a substance across the membrane (or to open a pore), these forces need to be overcome. That requires energy (usually provided by splitting phosphate off an ATP molecule). Some carriers also simply need the energy to get back into their original shape (if the substance that attaches to them adds different chemical forces to the original carrier that already suffice to cause a conformational change).

Answer 2

If a cell has more nutrients contained within it than surrounding it, the nutrients inside will diffuse out, in accordance with the concentration gradient. Active transport is used to draw in additional nutrients, even when the the cell has many more nutrients that it's external vicinity.

This is used practically in plant root hair cells, as the cells require more nutrients for the plant than is averagely distributed in a cell-sized area of surrounding soil. If this were not used, the plants would quickly reach a vastly insufficient maximum nutrient level, much to the detriment of the plant.

Answer 3

Transport mechanisms that require energy in the form of ATP are described as active transport. This includes pinocytosis, endocytosis and exocytosis. This usually happens when particles are moved against their concentration gradient.

Answer 4

A molecule would be actively transported when an equal concentration of solutes exist on either side of the cell membrane.

Answer 5

whenever a solute needs to be moved from low concentration to high concentration through a phospholipid bilayer membrane

Answer 6

When they have to move these particles from a region of their lower concentration to a region of their higher concentration. This process is called active transport.

Answer 7

yes

Answer 8

active type