Cell Biology and Protists - Class IX

In lipid bilayer, lipids are arranged with the polar head towards the outer side and the hydrophobic/ non-polar tails towards the inner side.

RBCs lack a nucleus and may other cell organelles thus they are best suited to study cell membrane without any complication.

In $1935$, Danielli and Davson proposed that cell membrane is made of a double layer of phospholipid molecules sandwiched between two single layers of proteins. The three layers are held together by electrostatic forces while phospholipid layers are kept adhered by vander Waal's forces.

• The fluid mosaic model of the biomembrane or cell membrane was proposed by SJ Singer and GL Nicolson in the year 1972.
  
• According to this model, the protein molecules are embedded in the phospholipid bilayer.
  
• Thus, the proteins are seen as icebergs in the sea of lipids.
  
• The lipid bilayer of the cell membrane provides fluidity, flexibility and elasticity to the membrane. 
  
• So, the correct answer is 'Protein embedded in phospholipid bilayer'.

• The cell membrane or plasmalemma is a phospholipid bilayer that are selectively permeable membranes which separate the interior of the cells (cell organelles and cytoplasm) from the outside environment or the extracellular space.
  
•  A selectively permeable can be defined as a cell membrane which allows only certain molecules or ions to pass through the membrane by active or passive transport.
• So, the correct answer is 'Cell membrane'.

A cell starts at 1 mg (10^-6 kg) and divides 100 times. The total number of cells after 100 divisions is 2^100. The mass of the population is 10^-6 kg * 2^100. Given that 2^10 is approximately 10^3, 2^100 = (2^10)^10 is approximately (10^3)^10 = 10^30. Thus, total mass = 10^-6 kg * 10^30 = 10^24 kg, which matches the given mass of the Earth (10^24 kg). The ratio is therefore 1.

Hybridoma cells are created by fusing a B-lymphocyte (antibody-producing cell) with a myeloma cell (cancerous cell). This fusion allows the resulting cells to produce specific antibodies indefinitely.

The haploid spores are produced from the mass by meiosis, these spores are developed or germinated into flagellated gametes. 

Microorganisms can be observed under microscope using particular stain. To observe Amoeba and Paramecium in a water drop, the drop was taken on a glass slide. If both the organisms were clearly seen, then the stain used must be Methylene blue or thionin. Both these stains are LTP, that is Lipid transfer protein. They are used to observe animal cells like amoeba and paramecium through hybridization membranes like water. This stain makes the nucleus of amoeba and paramecium visible under microscope.

The Paramecium is a unicellular ciliated protozoan. It looks an oval, slipper-shaped micro-organism when observed under a microscope, rounded at the front/top and pointed at the back or bottom. It can also be seen by naked eyes.

Sporozoa do not have flagella, cilia, or pseudopodia and they show gliding movement, amoeboids show movement by pseudopodia, ciliates by cilia and zooflagellates show by flagella, the pellicle is shown by paramecium.