31 Years NEET Previous Year Questions: Cell: The Unit of Life - 5 - NEET MCQ

According to fluid mosaic model proposed by Singer and Nicolson (1972, 74), plasma membrane is composed of phospholipid bilayer and protein. Protein molecules occur at places both inside and outside of lipid bilayer. The internal proteins are called intrinsic proteins and the external proteins are called extrinsic proteins.

Acetabularia used in Hammerling’s nucleocytoplasmic experiments is unicellular uninucleate marine green alga.

Centrifuge is an instrument used to create a centrifugal force. The homogenate of the cell organelles is allowed to undergo centrifugation by which different cell organelles get separated. The process is known as differential centrifugation.

Plasma membrane is made up of proteins, lipids and carbohydrates. Carbohydrates are covalently linked to both lipid and protein.

Polyribosomes consists of 4-8 ribosomes which are attached to a single strand of mRNA. This mechanism help in synthesis of several copies of the same protein.

Nucleoproteins  are conjugated proteins. They are deoxyribonucleoproteins and ribonucleoproteins synthesised in cytoplasm of the cell.

A pair of homologus chromosomes lying together in the zygotene stage of Prophase I of first meiotic division is called a bivalent.

Magnification is defind as the power of enlargement. Magnification of compound microscope is the product of magnification of objective lens and magnification of ocular lens. Magnification

Magnification = 400 times.
Magnification is defined as the power of enlargement.
Magnification = 

Fluid mosaic model is the most recent model of a biomembrane proposed by Singer and Nicolson (1972, 74). According to this model, the membrane does not have a uniform deposition of lipids which are present as highly viscous fluid matrix of  two layers of phospholipid moles and proteins arranged in a  symetrical pattern. 

J. Hammerling (1934) conducted experiments using two species of green algae Acetabularia crenulata and A. mediterranea. They differ in the shapes of their caps. The nucleus in both species is situated in rhizoid at the bottom of stalk. If after removing cap, stalk of one species is grafted on rhizoid of the other species, shape of the cap will be determined by nucleus, not by the stalk. This experiment makes clear that the characters of an individual are controlled by nucleus. 

The  resolution is a power of a microscope to distinguish between two particles that are closely situated. Electron microscope has high resolution power due to very low wavelength of electron beam.

The ability to distinguish two close objects is called resolution power.

Fluid Mosaic Model of cell membrane was put forward by Singer and Nicolson.

Ribosomes  were discovered by Robinson and Brown in plant cell and palade in animal cell.

Cell wall shows complete permeability because it helps in the transport of substances in and out of the cell.

Growth of cell wall occurs by two methods :
(i) Intussusception : When the primary wall is stretched, the materials of secondary wall are secreted by protoplam deposited within it.
(ii) Apposition : Materials of secondary wall secreted by protoplam are deposited in the form of thin layer one above the other.

The option ( c)10^-7 mm is correct.

Explanation :- 

The right option (  0.0000001) mm is missing here . Because, 

( 1 A°= 1/( 10)⁷ mm) = 10^-7 mm

Ribosomes are the workhouses of protein biosynthesis, the process of translating messenger RNA (mRNA) into protein. The mRNA comprises a series of codons that dictate to the ribosome the sequence of the amino acids needed to make the protein. Using the mRNA as a template, the ribosome translates each codon of the mRNA, pairing it with the appropriate amino acid. This is done using molecules of transfer RNA (tRNA) containing a complementary anticodon on one end and the appropriate amino acid on the other.Protein synthesis begins at a start codon near the 5’ end of the mRNA.

The inner membrane of mitochondria possess small tennis racket like particles called elementary particle, F0 – F1 particles  or  oxysomes. There are 1 × 104 – 1 × 105 oxysomes in a mitochondria.

All plastids are similar in structure. So they can easily get transformed from one type to another. Depending upon the colours there are three types of plastids- leucoplasts, chromoplasts and chloroplasts.

A covering membrane is absent around nucleolus. Calcium seems to be essential for maintaining its configuration.

Presence of hereditary information in the nucleus was proved by the work of Hammerling on single celled alga Acetabularia.

Glycogen is an animal starch, stored in the liver and is polysaccharide of α-Glucose. About 30,000 glucose molecules joined by 1-4 α-glycosidic bonds and its branches by 1-6 glycosidic bonds. It gives red colour with iodine solution.
• Galactose is a monosaccharide from milk.
• Fructose is a monosaccharide from fruit.
• Sucrose is a disaccharide (Glucose  + Fructose)

X-ray crystallography is a technique to study the binding of specific protein on regulatory DNA. X-ray crystallography or single-crystal X-ray diffraction is an analytical technique which uses the diffraction pattern produced by bombarding a single crystal with X-rays to solve the crystal structure. The diffraction pattern is recorded and then analyzed or “solved” to reveal the nature of the crystal. This technique is widely used in chemistry and biochemistry to determine the structures of an immense variety of molecules, including inorganic compounds, DNA, and proteins.