Question

19. The degree of membrane fluidity depends on . the percentage of lipids that contain choline b. the percentage of glycolipids c. the percentage of faty acids d the percentage of unsaturated farty acids Membeane proteins can be located a. entirely within the membrane b on the surface of the membeane c. in either position d. the position cannot be determined 20. 21. Which property has not been observed for membrane proseins? a energy storage b. transport of substances into and out of the eell e. eatalysis (enzymatic activity) d. acting as a receptor 22. In the fluid mosaic model of membrane structure a. the proteins are specifically bonded to the lipids b. the proteins "float in the lipid bilayer c. the proteins are sandwiched between the lipid molecules d. the lipids are sandwiched between the protein molecules All steroids coetain at least how many rings? b. 2 d. 4 23. The hydroxy group of cholesterol is on ring a. A b. B с.С d. D 24. to the peripheral tissues. In the spherical lipopeotein complex 25. Lipoproteins transport cholesterol from the liver to the peripheral tissues. In the spherical a. unesterified cholesterol is on the surface of the sphere b. esterified cholesterol is on the surface of the sphere e phospholipids are not present d. linoleic acid is not an important constitoent An important factor in controlling the level of cholesterol in the bloodstream is the presence of membrane receplors for a cholesterol b. cholesterol esters c. atherosclcrosis d. LDLs 26. Which steroid in the body increases the concentration of glucose? 27. b. aldosterone s. cortisol d. estradiol

Answer 1

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 steroid.

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 correct.

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.