Explain How The Cell Membrane Is Made Out Of Things Called Phospholipids

Structure

The cell membrane is made out of things called phospholipids. Phospholipids have a phosphate ‘head’ and two ‘tails’ made of fatty acids. The head is Hydrophilic and attracts water when the tail is hydrophobic and repels water. This helps them go back into shape when separated.

The Membrane is also made of proteins that can carry out various tasks. Structural proteins give the cell gives the cell support and shape. Receptor proteins communicate. Transport proteins allow certain molecules through the membrane. Glycoprotein are made of sugar and protein and they help with cell to cell communication and transport across membranes.

These can be classified as peripheral, integral and lipid bound. Peripheral proteins sit on top of the phospholipids.

It does not require any energy or ATP to move and is called passive because of that. Molecules that use passive transport go with the concentration gradient until an equilibrium is reached. The concentration gradient is where there is a large concentration of a substance and it moves to an area where there is a low area of that substance until a balance or equilibrium is achieved.

There are three types of passive transport: diffusion, facilitated diffusion and osmosis. Non-polar and small molecules can move in and out of the cell passing through the lipid bilayer using the process of diffusion. Diffusion is where if there is more of one type of molecule around the outside of a cell and less on the inside of the cell it means that more molecules will enter the cell and cause equilibrium. When an equilibrium is reached within the cell and outside the cell the amount of molecules entering and leaving the cell will be equal. Facilitated Diffusion is where a transport proteins starts and assists with the movement. The molecule still always with the concentration gradient and it needs this protein to help it because it is too big or not lipid soluble. There is also osmosis which is the movement of a solvent (most commonly water) to balance the concentration. Water will move from a low concentration of salt (or any other solute) to a high concentration of salt. Or a

-When particles are not lipid soluble or are polar and need help entering (selectively impermeable).

-When the particle is too big to enter or exit.

When transporting small cells into and out of the cell that can’t go through the lipid bilayer they require a transport protein that use ATP to change shape and move the molecule in or out. There are two types of pumps antiport (pumps in both direction) and synport (one direction). When transporting large particle there are two type’s endocytosis (into the cell) and exocytosis (out of).

Endocytosis

Endocytosis is the process in which large particles are taken inside the cell through changing the shape of the cell membrane. There are two main types of this, phagocytosis and pinocytosis. Phagocytosis is where food is taken into the cell and pinocytosis is where liquid drops are taken into the cell. The cell wall in this process moves around the food or liquid to surround it. It is then taken into the cell and breaks off of the membrane creating a vacuole. There is also receptor mediated endocytosis where there are receptors in a pit that trigger the process. This usually occurs when they need more of