Singer and Nicolson proposed the fluid mosaic model of the cell membr.pdf

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.

1. 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

2. 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.