Question

How do ions cross the lipid layer?

Answer 1

A biological membrane containing two layers of lipid molecules is a bilayer of lipid. The hydrophilic head and hydrophobic tail are present in each lipid molecule, or phospholipid.

Complete answer:
The key function of the cell membrane is to create a favourable environment inside the cell. This is done by regulating the movement of molecules and ions into or out of the cell. Ions are charged atoms where there is a difference between the number of protons and the number of electrons. The cell membrane uses proteins to help ions navigate the cell membrane.
A double layer of phospholipids is made up of a cell membrane. Each phospholipid molecule contains a phosphate head and two lipids or fatty tails. The phosphates form the inner and outer limits of the membrane, while the space between them is filled by the lipid tails. Lipids are hydrophobic, indicating that water and water-dissolved compounds, such as sodium, potassium and calcium ions, are repulsed. The cell membrane is peppered with transmembrane proteins, which form pores that can allow ions and other molecules to escape the lipid barrier.
Ion channels are a class of transmembrane proteins that allow a high rate of ion flow driven by an electrochemical gradient across the cell membrane. The gradient in which ions travel from higher concentration regions to lower concentration regions is caused by variations in the concentration of ions on either side of the membrane. Different channels are specialized for different ions, although more than one form of ion may be treated by certain channels. Ion channels are shaped like small gates that open or close to allow an ion to pass through. The channels are passive and do not tap the cell's energy to act.
Ion pumps are proteins that, with or without the help of the concentration gradient, spend energy to allow ions to bypass the lipid bilayer. Pumps made from enzymes known as ATPases that release energy from the cell's primary energy molecule, adenosine triphosphate, or ATP, are used in primary active transport. The protein uses the energy released to change its shape, translocating the ion from one side to the other. By moving ions against the concentration gradient, primary active transport helps control the sodium and potassium levels of the cells.

Note:
Secondary transport is another known method. Simultaneous transport of two different substances is part of secondary active transport. One substance is transported down the concentration gradient, providing the energy available for the second substance to be transported against the gradient. Antiport proteins transfer two substances in opposite directions. For example, for each of the calcium ions exported, the sodium-calcium antiport allows three sodium ions to enter the cell. Both materials are moved in the same direction by the Symport proteins. ATP does not use active secondary transport.