1) The degree of membrane fluidity depends upon the percentage
of unsaturated fatty acids i.e. PUFA (poly unsaturated fatty acids.
The membrane fluidity is to protect the proteins during freezing ,
this is known as freeze tolerance.
2) Membrane proteins can be located entirely within the membrane
i.e cytosol or on the surface of the membrane i.e exposed
externally from the cell surface and attached to the lipid layer
using covalent linkage to phosphatidylinositol of outer layer of
plasma membrane. Hence either of the position is correct.
3) In fluid mosaic model of membrane structure the lipid
bilayers are sandwiched between the monolayer proteins.
Phospholipids are fluid and move laterally. So, they float whereas
proteins move laterally along the membrane. So option D
4) All steroids contains atleast how many rings – four rings
where 3 rings are six membered rings i.e. cyclohexane ring and last
fourth ring is five membered ring i.e cyclopentane ring .
5) The hydroxy group of cholesterol is on third position of A
ring. Hence cholesterol is termed as sterol. This hydroxy group
form hydrogen bonds with phospholipids and sphingolipid carbonyl
oxygen head groups. This sterol is made up of alcohol and
6) Lipoproteins transport cholesterol from the liver to
peripheral tissues. In the spherical lipoprotein complex
unesterified cholesterol is on the surface of sphere along with the
phospholipids and also outer monolayer of proteins called
apoprotein whereas inner core consists of neutral lipids like
triglycerides and cholesterol esters. Hence option A is
7) An important factor in controlling the level of cholesterol
in the bloodstream is the presence of membrane receptors for LDL
(low density protein).
When cells faces low cholesterol levels they stimulate the
increase in cholesterol production via a HMG-CoA reductase and
proteins that increase the uptake of cholesterol from the external
environment via a LDL receptor.
8) The steroid in the body increases the concentration of
glucose is cortisol, a glucocorticosteroid which is produced from
adrenal gland of kidneys (adrenal hormones). It regulates the
energy by opting the correct type and amount of substrate molecules
i.e carbohydrates, proteins and fats.