What are Lipids
What are lipids? Lipids are non polar organic compounds such as oils, steroids and waxes. They are soluble in organic solvents but insoluble in water. Now, lets come to Lipid Bilayer Structure and Function.
Lipid membranes have an asymmetric distribution of lipids between two leaflets. Cell membrane composed of polar lipids that self assemble to form a bilayer. Thus, the cell membrane forms an asymmetric structure which means two sides of the membrane are functionally and structurally different.
What are the Functions of Lipids
Lipids in cells have three main functions: energy storage, signal transduction and forming the matrix of biological membranes.
1. Energy storage
2. Signal transduction
Signal transduction means transfer of extracellular signal or message to intracellular response through lipid bilayer.
LIpids are involved in homeostasis and cell signalling as it forms the structural component of cell membrane. Lipids act as signalling molecules.
If extracellular signals are are non-polar/ lipid soluble such as steroid hormones then it can easily pass through the phospholipid bilayer. If extracellular signal is polar/ water soluble/ lipid insoluble such as protein hormones then it cannot pass through lipid bilayer. It uses receptors which are located on cell membranes to enter and then uses second messengers for intracellular response.
3. Forming the matrix of biological membranes
Lipids such as phospholipids involved in forming the matrix of biological membranes. Amphipathic nature of lipids means both hydrophilic and hydrophobic regions are present. Hydrophilic means water loving and Hydrophobic means water fear regions. For example: Detergent is amphipathic in nature. Hydrophobic tails pointing inwards and hydrophilic head pointing outwards which is exposed to water. You can refer to the diagram.
4. Provides insulation
Lipids have a thick fat layer that helps to trap air inside and thus prevents heat loss. Therfore, they are called good thermal insulators.
Why do animals in cold climates have more unsaturated fatty acids
The structure and composition of lipid bilayers varies from one organism to another. This is because all cell membranes have the same structure, but vary from one organism to another. In some organisms, the composition of lipid membranes changes when exposed to different temperatures.
For example, animals in cold climates have more unsaturated fatty acids because Unsaturated fats have kinks in the hydrocarbon tails thus they cannot pack closely together. This makes them liquid at room temperature. Therefore, it prevents fats to solidify. Saturated fats become solid at room temperature. Thus, they replace saturated with unsaturated fatty acids.
History of lipid bilayer structure and function
Concept of cholesterol
In recent years, scientists have developed several concepts in relation to Lipid Bilayer structure and Function in the body. One such concept has been that cholesterol molecules are composed of chains of phospholipids. The idea is that the chains add flexibility to the lipids but constricts them when inside the cell membrane. The constriction reduces the amount of lipids that can be transported into cells and is believed to reduce the risk of atherosclerosis and coronary artery disease.
The research on Lipid Bilayer structure and Function has resulted in the understanding that some lipids have a sulfur-based tail which, when added to a file, produces cholesterol. This study has shown that the tail of the lipid molecule is a protein called cytochrome c. Other researchers have shown that the tails of lipids are not protein at all, but rather simple sugars called F-glycosylated proteins, or F-gradins. These studies have provided an explanation for the health benefits of high-density lipoproteins, or VLDLs.
One of the most interesting results concerning lipid engineering was the discovery that insertion of functional motifs, or ribbons, can alter the functioning of individual sub-membrane proteins. This observation opened up a new avenue for the design of therapeutic proteins that could specifically target defects in protein folding, metabolism, and gene regulation. Although other types of biological molecules have been used in the past, the ribbons generated by litigation are unique in their lipid-functionalizing capabilities. They have revolutionized lipid bilayer research by enabling the generation of therapeutic proteins with multiple functionality goals.
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