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.

Thursday, October 27, 2011

We help in multiple choice tests/assignments


5. Which of the following correctly matches an organelle with its function?
a. mitochondrion . . . photosynthesis
b. nucleus . . . cellular respiration
c. ribosome . . . manufacture of lipids
d. lysosome . . . movement
e. central vacuole . . . storage


ANSWER -  Central vacuole . . . storage

Monday, October 24, 2011

mrcapable1's Question

Eukaryotic cells are complex in organization and structure, especially when you consider their small size. Consider the organelle contents of the typical eukaryotic cell. Select two organelles and compare them relative to structure and function. Describe what would be the specific probable effects on the cell if each of these organelles were lost. 


ANSWER - We choose MITOCHONDRIA and  CHLOROPLAST


SIMILARITIES  -   Both have originated from endosymbiotic bacteria
                                   Both have double outer membrane
                                   They both have their own DNA. 
                                   Both reproduce independently
                                   Both have ribosomes capable of synthesizing  proteins


DIFFERENCES -  MITOCHONDRIA                      CHLOROPLAST
                       Present in all Eukaryotes            Present in Plants , algae
                       Size is 0.5 to 10 micrometers     Size is  2 to 10 micrometers
               Breaks glucose to release energy    Builds up glucose to store energy
                         Carries out respiration              Carries out  Photosynthesis. 


>If mitochondria is removed from the cell, it can not carries out respiration and food presnt in cell can not be used to release energy. Cell will die.


>If chloroplast is absent from the plant cell , there will be no food synthesis by photosynthesis.No food ,no energy and eventually cell will die

Friday, October 21, 2011

Jessy Andrew's question

A flowering plant in a clay pot is placed in a window that has light shining through it most the day. The plant is provided with sufficient water and fertilizer.
  1. Describe daily and nightly events that occur in the plant's metabolism.
ANSWER-  In daylight plants carries out 
1.Photosynthesis, process in which light energy is captured, converted and stored in simple sugar molecule. This process occurs in chloroplasts in the leaves  It is a backbone process, in the sense that all life on earth depends on it’s functioning. 
6CO2 + 12 H2O + light energy -> C6H12O6 + 6O2 +6H2O
carbon        water                              glucose     oxygen   water
2.Respiration, process in which energy , CO2 , H2O is released from the glucose which was made through photosynthesis.
C6H12O6 + 6O2   -> 6CO2 + 12 H2O +energy

At nights only respiration is carried out by plants. It is said that plants release CO2 through respiration at night that is because in day plants take up much more carbon dioxide in photosynthesis than they give off in respiration.So overall we see that plants take up CO2 in day and releases in night.


  1. Describe the changes that would occur in the plant is you rotated it 180o degrees.
ANSWER-  If we rotate the the plants to 180 degrees , it will change the direction of the leaves .Leaves would change the direction and go towards the light and roots will go towards the gravity.

Sunday, September 19, 2010

Sample for our assignment/learning topic help ! Epethilial tissue

EPETHILIAL TISSUE
Epethilial tissue covers the whole surface of the body.It covers body surfaces and lines hollow organs, body cavityies and ducts.It also forms glands
An epethilial tissue consist of cells arranged in continuos sheets, in either single or multiple layers.As cells are closely packed and are held tightly together by many cell junctions, there is little intercellular space between adjacent plasma memberanes.
Epethilial tissue may be divided inti two types :

  1. Covering and lining epethilium : It forms the outer covering of skin and some internal organs.It also forms the inner lining of blood vessels, ducts and body cavities, and the interior of respiratory tract, digestive tract, urinary tract and reproductive tract. Epithelial tissue that occurs on surfaces on the interior of the body is known as endothelium 
  2. Glandular epethilium : It makes up the secretin portion of the glands such as thyroid gland, adrenal gland and sweat gland.
The covering and lining epethilium tissue is further classified according to two characteristics like the arrangement of cells into layers and the shapes of the cells.

According to arrangement of cells into layers :

SIMPLE EPETHILIUM : Layer of cells that functions in diffussion, osmosis, filteration, secretion, absorption.It may be:

  1. Simple squamous (pavement) epithelium
Description : Single layer of flat cells, Centrally located nucleus.
Location : Lines heart, Blood vessels,Lymphatic vessels, Air sacs of lungs. Glomerular (Bowman's capsule) of kidney, Inner surface of tympanic membrane( Ear drum),
Functions : Filtration, diffussion ,Osmosis and Secretion into serous memberanes





      2.  Simple Cuboidal Epithelium

Description : Single layer of cube shaped cells, Centrally located nucleus.
Location : Covers the surface of ovary, Lines anterior surface of capsule of lens of eye, Lines kidney tubules and smaller ducts of many glands, Makes up secretion portion of thyroid gland and duct of pancreas.
Functions : Secretion and Absorption.



      3   Simple Columnar Epithelium
Description : One or more layers, Elongated and Column-shaped and Elongated nuclei  located near the base of the cells.Goblet cells (unicellular glands) are found between the columnar epithelial cells of the duodenum. They secrete mucus or slime, a lubricating substance which keeps the surface smooth. 
Location : Lining of the stomach and intestines, Specialised for sensory reception such as in the nose, ears and the taste buds of the tongue.
Functions : Secretion and Absorption.



     4. Ciliated Columnar Epithelium
Description : simple columnar epithelial cells, in addition, they posses fine hair-like outgrowths, cilia on their free surfaces.
Location : Air passages like the nose,Uterus and Fallopian tubes of females
Functions : Capable of rapid, rhythmic, wavelike beatings in a certain direction



STRAITED EPETHILIUM
  
       1.   Stratified squamous epithelium.
Description : Several layers of cells cuboidal to columnar shape in deep layers.
Location : Keratinized variety forms superficial layer of skin, nonkeratinized variety lines wet surface such as lining of mouth , eosophagus.
Function : Protection.


       2. Straitified cuboidal epethilium
Description : Two or more layers of cells in which the cells in the apical layer is in cube shaped.
Location : Ducts of adult sweat glands and esophageal glands and part of male urethera.
Function : Protection, Limited secretion and Absorption.


         3. Straitified columnar epethilium
Description : Several layers of irregularly shaped cells, only the apical layer has columnar cells.
Location : Lines part of Urethra, Large excretory ducts of some glands such as esophagus glands, small areas of anal mucous membrane, and par of the conjunctiva of the eye.
Function : Protection

     4. Transitional epethilium
Description : Appearance is variable (transitional), shape of cells in apical layer ranges from sqamous (when stretched ) to cuboidal (when relaxed).
Location : Lines urinary bladder and portions of ureters and urethra.
Function : Permts distension.




GLANDULAR EPETHILIUM

     1.Endocrine glands
Description : Secretory products (hormones) diffuse into blood after passing through interstitial fluid.
Location : Pituitary glan at base of brain, Pineal gland in brain, Thyroid and Parathyroid gland near larynx, Adrenal glands superior of kidneys.
Function : Produce hormone that regulate various body activities.
    2. Exocrine glands
Description : Secretory products released into ducts.
Location : Sweat, Oil and Earwax glands of the skin, Digestive glands such as salivary glands and pancreas.
Function : Produce substance such as Sweat , Oil earwax , Saliva and Digestive enzymes.