Singer and Nicolson proposed the fluid mosaic model of the c

Singer and Nicolson proposed the fluid mosaic model of the cell membrane The main type of membrane lipids: phospholipids, glycolipids, and sterols could be represented with the respectively membrane lipids phosphoglycerides, cerebrosides and cholesterol. In E. coli the enzyme responsible for creating unsaturated bonds from saturated ones in the fatty adds of the cell membrane is denaturize Substances that can readily pass through the cell membrane are chemically hydrophobic or nonpolar in nature. Transmembrane proteins involved in detecting external stimuli and relaying that Information to the cell are most likely receptor proteins. The current understanding of the membranes of the cell is based on the fluid mosaic model. The ability of some organisms to alter their membrane lipid composition in response to temperature is known as homeoviscous adaptation The technique of transferring proteins from SDS-PAGE gels onto a membrane and using labeled antibodies to identify particular proteins is known as western blot Triglycerides are composed of three fatty acids attached to a molecule of glycerol

Solution

Ans. 1. True. They proposed the model in 1972, and were awarded Nobel prize for it.

Ans. 2. True

Phospholipids = phsophoglycerides

Sterol = cholesterol

Glycolipids are lipids containing covalently linked carbohydrate moieties.

Cerebrosides, also known as, glycosphingolipids, also contain glucose or galactose residues linked to the ceramide (lipid) skeleton. Thus, cerebrosides are also glycolipid in nature because have carbohydrate moieties linked to lipid.

Ans. 3. True

Fatty acid desaturase creates double bond (unsaturation) in fatty acids by removing two H-atoms from adjacent carbo atoms in the chain.

Ans. 4. True

Since the lipid bilayer has a hydrophobic core, small, non-polar or hydrophobic molecules (for example, CO₂) can readily pass through it.

In contrast to it, polar or charged ion/ molecules or large molecules (non-polar as well as polar) can’t pass through the membrane so efficiently.

Ans. 5. True

Receptor proteins need to bind an effector molecule at the extracellular face and transmit the signal to cytoplasmic side of the cell. Thus, it shall be a transmembrane protein, i.e. a protein that spans the lipid bilayer.

Ans. 6. True

Ans. 7. True

Many organism can change the lipid composition of the membrane depending of the environmental temperature. The phenomenon being called “homeoviscous adaptation”.

For example, in winters, the membrane of a plant cell also retains the fluid-nature under freezing conditions. Relatively larger abundance of cis-fatty acids, unsaturated fatty acid in the phospholipids and steroids makes the membrane more fluid because both cis-form and unsaturation makes the chain irregular-shaped and hinders the close packing of hydrophobic core. So, such membrane retain fluidity even at very low temperatures.

Ans 8. True

Western blot detects specific protein through combined use of SDS-PAGE and immunoblotting technique.

Ans. 9. True

Triacylglycerides is a molecule consisting of three fatty acid chains esterified to glycerol.