Structure and function of phospholipids

• A phospholipid is similar to a triglyceride, both being types of lipids, and has a similar structure to the triglycerides.
• A phospholipid is made up of two main components: a molecule at the start called glycerol, which is a type of alcohol, and three fatty acids.
• One of the fatty acids in a phospholipid is replaced by a phosphate molecule.
• The joining of the phosphate group onto the glycerol is a condensation reaction between a hydroxyl group on the phosphoric acid and an oh group on the glycerol.
• The total molecule, including the phosphoric acid, is called the phospholipid.
• The phosphoric acid becomes a phosphate group which is now linked by a covalent bond to the glycerol, forming a molecule of water.
• The phosphate group, which is now joined to the glycerol, is called the head of the phospholipid, and the fatty acid chains are known as the tails.
• When a phospholipid is surrounded by water on all sides, the hydrogen ions which are found in the phosphate group start dissociating from that phosphoric acid, causing the phosphate group to have a negative charge.
• The phospholipid bilayer acts as a barrier, controlling the substances entering and exiting the cell.
• The phospholipid bilayer in membranes allows the cell membrane to carry out important roles and have important properties.
• The partial permeability of the membrane also allows it to act as an electrical insulator, preventing certain ions from passing through these parts of the neuron.
• The phospholipid bilayer can provide electrical insulation, preventing certain ions from entering or leaving, keeping the ions and the charge concentrations correct in and outside of the membrane.
• Only certain small non-polar molecules like oxygen and carbon dioxide can easily pass through the membrane.
• When ions are dissolved in water, they're surrounded by water molecules and if water can't get through, these ions can't get through either, keeping the charge in the right proportions inside and outside.
• The area in the middle of the phospholipid bilayer, a non-aqueous environment, is excluded from water due to the fatty acid tails.
• The phospholipid bilayer insulates against charge because the charged ions cannot pass through it.
• Oxygen and carbon dioxide can enter cells when needed for respiration and leave the cell as a waste product because they're both small and non-polar.
• The partial permeability of the membrane allows it to control what enters and leaves the cell and what can't enter or leave the cell.
• The phospholipid bilayer acts as an electrical insulator in neurons, preventing electricity and charged particles from passing through these parts of the neuron.
• Molecules with a charge are referred to as hydrophilic, as they are attracted to water due to having a charge.
• Phospholipids can also form a monolayer called a mycel or a micelle, where the sphere-shaped structure is surrounded by a watery solution.
• In a mycel or a micelle, the hydrophilic heads face the water because they have a negative charge, while the hydrophobic tails cluster away from the water in the core of the micelle.
• The phospholipid bilayer is an integral part of all membranes in a cell, especially eukaryotic cells like our own.
• The fatty acid tails attached to the glycerol are not polar and are referred to as hydrophobic, as they are repelled by water due to not having any charge or polarity.
• Two 'o's have lost their 'h's, resulting in each having a negative charge.
• In a cell, especially eukaryotic cells like our own, we have a cell surface membrane which is the ultimate barrier of the cell and also have organelles inside with their own membranes like the golgi and lysosome, both of which involve phospholipid bilayers.
• The phospholipid head is hydrophilic and likes water, as it has a negative charge.
• Phospholipids may form a layer on the surface of the water due to the hydrophilic heads facing the water and the hydrophobic tails facing away.
• If we have an aqueous environment inside and outside, the hydrophilic heads face outwards because they can be attracted to the water, while the hydrophobic tails face away from the water because they don't want to be associated with the water.
• Phospholipids can form a bilayer, where the layers mirror each other and the watery environments are on either side.
• The phosphate group has a negative charge due to the loss of positive charge from the oxygens.
• In a phospholipid bilayer, the hydrophilic heads form two rows on the outside facing the watery environment, while the hydrophobic tails are sheltered in the middle.