Question

A scientist isolated the plasma membrane from some animal cells and put them in a solution of chemicals that stabilized the membranes. When she added a small amount of a salt solution, she discovered that although the membranes seemed intact, the amount of protein in the stabilizing solution had increased. These new proteins in the stabilizing solution were probably
(a) Peripheral proteins
(b) Integral proteins
(c) Lipid-anchored proteins
(d) Trimeric G proteins

Answer 1

These proteins are formed from amino acids that interact with the surface of the lipid bilayer of cell membranes and do not enter into the hydrophobic space within the cell membrane.

Complete answer:
In the above-mentioned experiment performed by the scientist, the new proteins in the stabilizing solution were probably the peripheral proteins.
-The cell membranes or plasma membrane are a delicate two-layered structure made up of lipids and proteins, and it is semi-permeable to control the entry and exit of the cell. It differentiates with the interior of the cell from the outside environment. The lipids are specialized lipids called phospholipids.
-The extrinsic or peripheral proteins are present on the two surfaces of the plasma membrane, more towards the cytosol of the cell than on the external face. Peripheral proteins can be separated by mild treatment with high ionic strength. They are soluble in aqueous solutions and are usually free of lipids, which means they are not associated with liquid.
-The plasma membrane is mainly composed of phospholipids, cholesterol, and galactolipids. The proportion of these components varies in different cell membranes.
- According to the fluid mosaic model of the plasma membrane, the lipid molecules are present in the viscous bilayer and protein molecules are present on both sides; the inside and on the outside of the lipid bilayer.
- More than 70% of the membrane protein is represented by the integral proteins of the protein present on the inner side of the lipid bilayer.
-These proteins are insoluble in water and are associated with lipids that are attached to oligosaccharides to form glycoproteins. They pass into the lipid bilayer to different depths and develop hydrophobic bonds with lipid molecules. Throughout the lipid bilayer, some of the integral proteins are present.
So, the correct answer is, 'Peripheral proteins'.

Note: -A phospholipid is made up of a hydrophilic, phosphate head which is water-loving, along with two hydrophobic, water-fearing, fatty acid tails.
-the integral or intrinsic proteins are insoluble in water whereas the extrinsic or peripheral proteins are soluble in water.
-The cell membranes or plasma membrane are a delicate two-layered structure made up of lipids and proteins, and it is semi-permeable to control the entry and exit of the cell.