Thursday, November 3, 2011


Multiple choice questions with Answers

1)      True or False The high ordered structure of the phospholipid bilayer makes its production and maintenance energetically unfavorable.
Answer - True 
2)      Which of the following statements regarding lipid membranes is not True
A) Membrane lipid diffuse within the plane of the membrane
B)The preferred form of a lipid bilayer in water is a flat sheet with exposed edges.
C) Membrane lipids don’t flip-flop between once monolayer and the other.
D)  Membrane proteins can move around.
                 E) In eucaryotes, some organelles are surrounded by two lipid bilayers
Answer – B

3)      Which of the following phospholipid bilayers would be more fluid?
A)     One with mostly saturated fatty acids
B)     One with only saturated fatty acids
C)     One with no cholesterol
D)     One with mostly unsaturated fatty acids
E)      One with equal amounts of saturated and unsaturated fatty acids
Answer – B

4)      A bacterium is suddenly expelled from a warm human intestine into the cold world outside. Which of the following adjustments might the bacterium make to maintain the same level of membrane fluidity?
A)     Produce lipids with hydrocarbon tails have fewer double bonds.
B)     Produce lipids with hydrocarbon tails that have more double bonds.
C)     Decrease the amount of cholestererol in the membrane.
D)     Decrease the amount of glycolipids in the membrane
E)      Add more protein to the membrane
         Answer – A

5)      True of False when a mouse cell is fused with a human cell, the movement of the respective membrane proteins is restricted to their original locations at the time of fusion.
         Answer – False

6)      Of the following functions, the glycoproteins and glycolipids of animal cell membranes are most important for
A)     The ability of cells to recognize each other
B)     Maintaining membrane fluidity at low temperatures.
C)     Active transport of molecules against their concentration gradients.
D)     Maintaining the integrity of a fluid mosaic membrane
E)      Facilitated diffusion of molecules down their concentration gradients.
        Answer – A

7)      Which of the following would not be a good reason why a cellular membrane needs to contain protein?
A)     Membranes do not form without some proteins.
B)     Proteins are needed to transport some molecules across the membrane
C)     Proteins may be needed to help attach the cell to extracellular structures
D)     Proteins may be needed to anchor the membrane to the cyctoskeleton
E)      All of these are good reasons why cellular membranes need proteins.
      Answer – A

8) An alpha helical protein domain can cross the membrane provided that there is a stretch of 10 or 11 amino acids with hydrophobic side chains
             TRUE

        9) CO2 or O2 are water-soluble molecules that diffuse freely across cell membranes
           Answer- TRUE

      10) Molecules that move against their concentration gradient via………………….require      a protein transporter to cross the membrane
A)     Diffusion
B)     Facilitated diffusion
C)     Active transport
D)     Osmosis
E)      Both B and C are correct
    Answer -  C

11)  Which of the following requires a membrane protein?
A)     Facilitated diffusion
B)     Primary active transport
C)     Secondary active transport
D)     All of these
E)      A and B only
         Answer – D

12) When food molecules are broken down to provide energy and a molecule from outside the cell acts as the final electron acceptor in the process it is called
A)     Fermentation
B)     Glycolysis
C)     Oxidative phosphorylation
D)     Substrate-level phosphorylation
E)      Respiration
Answer - E

        13)The ATP generated during glycolysis is always produce by way of
A)     Fermentation
B)     Glycolysis
C)     Oxidative phosphorylation
D)     Substrate-level phosphorylation
E)      Respiration
Answer – D

14)During the breakdown of sugars carbon dioxide is released during
A)     Glycolysis
B)     The citric acid cycle
C)     Oxidative phosphorylation
D)     Substrate-level phosphorylation
E)      Beta oxidation
Answer - B

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Tuesday, November 1, 2011



Question-   Briefly describe ( or draw) the structure of a phospholipid bilayer and explain the forces holding it  together. Why is it more stable to have membrane close up into a liposome rather than to have exposed edges?
Answer - Phospholipids bilayer - The two layers of phospholipids arranged in such a way that their hydrophobic tails are projecting inwards while their polar head groups are projecting on the outside surfaces.  Phospholipid bilayer structure forms the membrane that surrounds each of your cells and plays an important role in regulating cellular function.

> Vander Waals forces hold the hydrophobic tails of the phospholipid bilayer together and hydrogen bonds keep the hydrophilic heads of opposite the tails together as well as interact with water surrounding the bilayer.
>Because a  liposome encapsulates a region of aqueous solution inside a hydrophobic membrane and dissolved hydrophilic solutes cannot readily pass through the lipids.