Q: The correct order of chemical composition of living tissues/cells in term of percentage of the total cellular mass is

The average composition of a living cell is water \$70-90\%\$; proteins \$10-15\%\$; Nucleic acids \$5-7\%\$;carbohydrates\$3\%\$;lipids \$2\%\$ions \$1\%\$.So, the correct answer is 'H20 > proteins > nucleic acids > carbohydrates> lipids > ions'.

Question 1

If the length of E. coli DNA is $1.36 mm$, can you calculate the number of base pairs in E.coli?

Accepted Answer

Explanation-Here it is given that, the length of the E.coli DNA is 1.36mm.We know the length of the DNA can be calculated by multiplying the number of base pairs into the distance between the basepairs.Thus, from this we can get, Number of base pairs = Length of DNA/ Distance between the base  pairs                                                                                    =1.36 / 0.34 X $10^-9$                                                                                      = 4 X $10^6$ base pairs.Hence, the correct answer is 4X$10^6$ .

Question 2

Explain the factors affecting enzyme activity.

Accepted Answer

Enzymes are biological catalysts that are proteinaceous in nature. The factors affecting the enzyme activity are listed below:1. Substrate concentration:The activity of an enzyme also increases with the increase in substrate concentration. If the substrate concentration increases, then the availability of the active site would decrease. This will affect the activity of an enzyme and limit the reaction rate.2. pHEach enzyme has its optimal pH in which they work. For example pepsin and trypsin work on acidic pH. The enzymes are globular proteinaceous structure, form by the interaction of the hydrogen bond between the side chains of the protein. Any change in the cause deionization of side chain which results in the denaturation of the enzyme.3. Temperature:Each enzyme works on its optimal temperature. Any alteration in temperature affects the activity of an enzyme, and it also leads to denaturation of an enzyme.4. Enzyme cofactor and coenzyme:Each enzyme requires cofactors (inorganic ion or protein organic molecules) for their work. The non-availability of these cofactors decreases the activity of an enzyme.5. Enzyme inhibitors:The inhibitors of an enzyme bind to the active site which affects the activity of an enzyme.

Question 3

List the salient features of double helix structure of DNA.

Accepted Answer

The salient features of double helix structure of DNA are as follows:There are two polynucleotide&#10;chains in a double stranded DNA.The backbone is constituted by sugar phosphate.The two strands possess anti-parallel polarity, means&#10;one chain has polarity 5&#8217;-3&#8217; and the other has 3&#8217;-5&#8217;.The two strands of DNA are joined together by hydrogen&#10;bonds between purines and pyrimidines. Adenine always pairs with Thymine by two&#10;hydrogen bonds and Guanine always pairs with Cytosine by three hydrogen bonds.The two chains are coiled around each other where the pitch of the helix is 3.4 nm and distance between two base pairs is&#10;3.4 A&#176; (as in case of B-DNA)The backbone of DNA double helix is formed by sugars and&#10;phosphates where bases are projecting inwards.

Question 4

Which of the following statement is incorrect? Choose answer:

Accepted Answer

Biomolecules with molecular weights more than one thousand Dalton are called biomacromolecules. These are found in the acid-insoluble fraction. Lipids are not strictly macromolecules as their molecular weights do not exceed 800 Da but form a part of the acid insoluble pool. The molecules in the insoluble fraction with the exception of lipids are polymeric substances. Lipids are indeed small molecular weight compounds and are present not only as such but also arranged into structures like cell membrane and other membranes. So the acid insoluble fraction has only four types of organic compounds, proteins, polysaccharides nucleic acids and lipids but except for lipids none of them are micromolecules.So the correct option is 'The compounds which are found in the acid insoluble fraction are called micromolecules'.

Question 5

The correct order of chemical composition of living tissues/cells in term of percentage of the total cellular mass is

Accepted Answer

The average composition of a living cell is water $70-90\%$; proteins $10-15\%$; Nucleic acids $5-7\%$;carbohydrates$3\%$;lipids $2\%$ions $1\%$.So, the correct answer is 'H20  > proteins > nucleic acids > carbohydrates> lipids > ions'.

Question 6

Define the following as related to proteins :(i) Peptide linkage (ii) Primary structure(iii) Denaturation

Accepted Answer

I) Peptide linkage is the peptide bond formed between the amino acids. It is a covalent bond formed between amino group of one molecule and carboxylic acid group of another molecule.II)The primary structure of a peptide or protein is the linear sequence of its amino acid structural units. The primary structure of a protein is reported starting from the amino-terminal (N) end to the carboxyl-terminal (C) end.(III) The process in which proteins or nucleic acids lose the quaternary structure, tertiary structure and secondary structure which is present in their native state known as denaturation. by application of some external stress or compound such as a strong acid or base, a concentrated inorganic salt, an organic sol.

Question 7

Take a living tissue, grind it in trichloroacetic acid using pestle and mortar, and then strain it, you would obtain two fractions: acid-soluble and acid-insoluble fraction. Acid-insoluble fraction does not contain

Accepted Answer

The acid-soluble pool represents roughly the cytoplasmic composition whereas the macromolecules from cytoplasm and organelles become the acid-insoluble fraction. Together they represent the entire chemical composition of living tissues or organisms. Al! the compounds which are found in the add-soluble pool, have their molecular weights ranging from approx. 18 to around 800 daltons (Da). The acid-insoluble fraction, has only four types of organic compounds i.e., proteins, nucleic acids, polysaccharides and lipid.So, the correct answer is 'Flavinoids and alkaloids'.

Question 8

Which of the following factor does not affect an enzyme's activity?

Accepted Answer

Enzyme concentration does not affect the enzyme activity directly as substrate concentration determine it until the presence of the substrate in an excess amount. Enzymes are the assemblage of protein subunits and hence function under specific temperature and pH range only. Presence or absence of cofactors and inhibitors affects the enzyme activity. Thus, the correct answer is option E.

Question 9

For the given DNA sequence, the complementary mRNA sequence is given as below ${5}^{\prime} CGTACGTA{3}^{\prime}$

Accepted Answer

Messenger RNA is a type of RNA which carries information from the synthesis of protein transcribed from a DNA template. In DNA, there are four different bases: adenine (A), guanine (G), cytosine (C) and thymine (T). Each base has its complementary base, which means in the double helical structure of DNA, A will have T as its complimentary and similarly G will have C. mRNA is formed as a complementary strand to one of the two strands of the DNA. Three of the four nitrogenous bases that make up RNA &#8212; adenine (A), cytosine (C), and guanine (G) &#8212; are also found in DNA. In RNA, however, a base called uracil (U) replaces thymine (T) as the complementary nucleotide to adenine. This means that during elongation, the presence of adenine in the DNA template strand tells RNA polymerase to attach a uracil in the corresponding area of the growing RNA strand. The mRNA formed will be complimentary to the DNA strand. During transcription RNA polymerase begins moving down the DNA template strand in the 5' to 3' direction, when it does it strings together complementary nucleotides. Because of complementary base- pairing, this action creates a new strand of mRNA that is organized in the 3' to 5' direction. As the RNA polymerase continues down the strand of DNA, more nucleotides are added to the mRNA, thereby forming a progressively longer chain of nucleotides. This process is called elongation. &#10;&#10;So, the correct answer is option C.

Question 10

What are the functions of proteins?

Accepted Answer

Proteins are the most important nutrient in our food. Functions of proteins:(i) The major structural component of cells which is responsible for the building and repair of body tissues.(ii) Proteins do most of the work in cells and are required for the structure, function, and regulation of the body's tissues and organs.(iii) It helps our body to fight against infections.(iv) It helps in the formation of nails, hair and muscles.