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CBSE Questions for Class 12 Engineering Chemistry Biomolecules Quiz 15 - MCQExams.com
CBSE
Class 12 Engineering Chemistry
Biomolecules
Quiz 15
The production of starch, and not glucose, is often used as a measure of photosynthesis in leaves because
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starch is immediete product of photosynthesis.
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Glucose formed in photosynthesis soon gets converted into starch
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Starch is soluble in water.
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Sugar can not be tested.
Explanation
Glucose is the immediate product of photosynthesis which is utilized by the plant and extra glucose is stored in form of starch in the leaves. As glucose gets utilized so its presence cannot be detected. But starch is stored in plants and it can be easily detected, hence the production of starch is often used as a measure of photosynthesis in leaves.
So, the correct option is B. 'Glucose formed in photosynthesis soon gets converted into starch'.
State whether the following statements are True or False:
Raffinose is a trisaccharide. On hydrolysis, it gives three molecules of glucose.
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True
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False
Explanation
False-On hydrolysis, it gives three molecules of monosaccharide units one each of glucose, fructose and galactose
State whether the following statements are True or False:
Vitamin C is synthesised in skin cells in sunlight.
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True
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False
Explanation
Given statement is false because Vitamin D is synthesised in skin cells in presence of sunlight.
Ampholyte is :
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$$H_2O$$
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$$Zn(OH)_2$$
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$$H_2NCH_2COOH$$
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all of these
In the table given above the acidic amino acids are______
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I, II
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I, III
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II, III
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I, II & IV
Explanation
$$pka_3$$ value of side-chain determine the nature of the amino acid
Option A is correct.
The metal present in $$Vitamin \ B_{12} $$ is
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Magnesium
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Iron
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Cobalt
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Manganese
Explanation
$$Vitamin \ B_{12} $$
is also referred to as cobalamin because it contains A metal ion (Cobalt).
Hence, Option "C" is the correct answer.
An organic compound answers Molisch's test as well as Benedict's test.But it does not answer Scliwanoffs test.Most probably, it is
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Sucrose
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Protein
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Fructose
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Maltose
Explanation
$$\text{Molisch}$$ test is for identifying $$\text{carbohydrates.}$$ $$\text{Benedict's test}$$ is for $$\text{aldehydes (not aromatic),}$$ and $$\text{scliwanoff's test}$$ is to $$\text{distinguish ketose from aldose.}$$ aldose doesn't show any positive test. so the organic compound may be an $$\text{aldose(carbohydrate with aldehyde group)}$$
$$\text{Hence, correct answer is Option (D).}$$
A carbohydrate that cannot be hydrolysed to simpler forms is called :
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Disaccharide
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Monosaccharide
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Polysaccharide
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Trisaccharide
Explanation
Monosaccharide cannot be hydrolysed to simple forms.
Starch can be used as an indicator for the detection of traces of
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Glucose in aqueous solution
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Proteins in blood
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Iodine in aqueous solution
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Urea in blood
Explanation
Starch solution is colourless but changes its colour in iodine solution.
$$Starch+\underset{(violet)}{Iodine}\rightarrow \underset{(blue-black)}{Starch\,Iodine}$$
Nitrous acid $$(HNO_2)$$ converts amino acids into hydroxy acids with retention of configuration. Estimation of nitrogen gas evolved in the reaction is the reaction is the basis of Van slyke estimation of amino acids.
$$R - \overset{NH_2}{\overset{|}{C}H} - COOH \xrightarrow{HNO_2} R - \overset{OH}{\overset{|}{C}H} - COOH + N_2 \uparrow + H_2O$$
Which of the following amino acids cannot be analysed by Van slyke method?
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Only I
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Only II
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I and III
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I, III, IV
Explanation
Since proline has $$2^{\circ}$$ amino group
Hence, nitrogen gas not evolved.
Option B is correct.
Sugars are
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Optically active polyhydroxy aldehydes
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Optically active polyhydroxy ketones
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Optically active polyhydroxy aldehydes or ketones
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Polyhydroxy aldehydes or ketones which may or may not be optically active
Explanation
$$\text{sugar}$$ may be defined as $$\text{optically active polyhydroxy aldehydes or ketones .}$$ as it contains $$\text{at least one asymmetrical (chiral) carbon}$$ and is, therefore, optically active
The standard compound for determination of configuration in the 'sugar chemistry' is
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Glycolaldehyde
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Glyceraldehyde
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Glucose
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Fructose
Explanation
$$\text{Glyceraldehyde has been chosen as the arbitrary standard for the D and L notation in sugar chemistry Because}$$ $$\text{this has an asymmetric carbon and can exist as a pair of enantiomers}$$
Glucose and fructose form
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Same osazone
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Same acid on oxidation
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Same alcohol when reduced
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Different osazone
Explanation
When $$\text{sugars}$$ react with an $$\text{excess of phenylhydrazine,}$$ a class of compounds known as $$\text{osazone}$$ is formed.
$$\text{Glucose and fructose}$$ differ in the arrangement of atoms around the C−1 and C−2 carbon. When both of them react with three molecules of phenylhydrazine, the formation of osazone crystals makes the difference between the carbon atoms in their chain and hence $$\text{they form the same osazone.}$$
Carbohydrates are
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Hydrates of carbon
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Polyhydroxy aldehydes or ketones
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Polyhydroxy acid compounds
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None of these
Explanation
$$\text{They are organic compounds organized in the form of aldehydes or ketones with multiple hydroxyl groups}$$ coming off the carbon chain.
$$\text{The general empirical structure for carbohydrates is}$$ $$(CH_2O)_n.$$
Which of the following shows the maximum hydrophobic behaviour
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Glycerine
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Stearic acid
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Glucose
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Adenine
Explanation
Adenine has the least tendency to attract with water molecules.
Hence it has the maximum hydrophobic behavior.
Which of the following is not present in nucleic acids
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Uracil
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2-aminopyridine
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Thymine
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Adenine
Explanation
The answer is (B). 2-aminopyridine is not present in nucleic acid and as cytosine, Adenine, Thymine and GUANINE are the four main bases found in nucleic acid. Adenine and Guanine are purines while thymine and cytosine are pyrimidines. They together form triple bonded histones of DNA.
2-Aminopyridine is an organic compound with the formula $$H_2NC_5H_4$$N. It is one of three isomeric aminopyridines
Ascorbic acid is a
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Vitamin
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Enzyme
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Protein
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Carbohydrate
Explanation
$$\text{Ascorbic Acid is a natural water-soluble vitamin (Vitamin C).}$$ Ascorbic acid is a potent reducing and antioxidant agent that functions in fighting bacterial infections, in detoxifying reactions, and in the formation of collagen in fibrous tissue, teeth, bones, connective tissue, skin, and capillaries.
Which $$\alpha$$ amino acid can cross link peptide chains
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Serine
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Cysteine
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Protein
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Carbohydrate
Explanation
the correct answer is B.
$$\text{In some proteins, the linear polypeptide chain is cross-linked. The most common cross-links are disulfide bonds,}$$ $$\text{formed by the oxidation of a pair of cysteine residues }$$
Which carbohydrates has highest abundance in human blood
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d-fructose
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d-glucose
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Sucrose
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Lactose
Explanation
$$\text{Blood sugar, or glucose, is the main carbohydrates found in blood.}$$The human body contains approximately 5 liters of blood. This amounts to 4 grams of sugar in the blood,
The optically inactive amino acid is
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Lysine
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Glycine
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Arginine
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Alanine
Explanation
All amino acids have an amine and a carboxyl group They also have a functional group which is unique to each of them. $$\text{Depending on the polarity of the functional group the amino acid can be rendered optically inactive or active.}$$ $$\text{The simplest of all amino acids, Glycine which has H as a functional group lacks optical acitivity,}$$ as the saturated alpha carbon is unsubstituted. Others among the 20 amino acids have D or L stereoisomers. So, the correct answer is 'Glycine'.
Galactose is converted into glucose in
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Mouth
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Stomach
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Liver
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Intestine
Explanation
$$\text{In the liver, galactose is converted to glucose-6-phosphate in order to enter the glycolytic pathway.}$$
Which substance is not present in nucleic acid
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Cytosine
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Adenine
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Thymine
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Guanidine
Explanation
The answer is (D). $$\text{Guanidin is not present in nucleic acid}$$ and as $$\text{cytosine, Adenine, Thymine and Guanine}$$ are the four main bases found in nucleic acid. Adenine and Guanine are purines while thymine and cytosine are pyrimidines. They together form triple bonded histones of DNA. $$\text{Guanidine is another compound which has a chemical formula }$$$$HNC.$$
Vitamin A is present in
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Cod liver oil
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Carrot
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Milk
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In all of these
Explanation
Concentrations of vitamin A are highest in liver and fish oils. Other sources of vitamin A are milk and eggs, which also include some provitamin A Most dietary provitamin A comes from leafy green vegetables, orange and yellow vegetables(Carrot), tomato products, fruits, and some vegetable oils.
In RNA , nitrogen bases are
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Adenine and guanine and cytosine and thymine
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Adenine and guanine and thymine and cytosine
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Adenine and thymine and guanine and cytosine
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Adenine and guanine and uracil and cytosine
Lysine, is ________
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$$\alpha$$- Amino acid
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Basic amino acid
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Amino acid synthesised in body
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$$\beta$$- Amino acid
Which of the following is the correct statement?
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Starch is a polymer of $$\alpha-$$glucose.
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Amylose is not a component of starch.
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Proteins are composed of only one type of amino acid.
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In the cyclic structure of fructose, there are five carbon atoms and one oxygen atom.
Which of the following vitamins is water soluble
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Vitamin $$E$$
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Vitamin $$D$$
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Riboflavin
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Retinol
Explanation
Riboflavin (vitamin $$B_2)$$ is water soluble vitamin. All other vitamins (vitamins $$K$$) and retinol (vitamin $$A$$) are fat soluble vitamins.
Hence option (C) is correct.
Nucleic acid are
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Small molecules
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dipepetides
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Long chain polymers of nuceotides
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Polypeptides
Explanation
Nucleic acid are Long chain polymers of nucleotides hence they are also called polynucleotides.
Hence option (C) is correct.
Nuclei acids are polymers of ________.
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nucleosides
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nucleotides
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bases
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sugars.
Explanation
Nuclei acids are long chain polymers of $$\textbf{nucleotides}$$ hence, are also called polynucleotides.
Hence option (B) is correct.
In what respect enzymes are different from catalysts?
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High diffusion rate
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Active at high temperature
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Protein nature
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Used in the reaction
Explanation
Catalysts are inorganic substances or elements the increase the rate of reaction, while converting reactants into products. Enzymes are organic molecules, proteins, which may or may not be attached to an inorganic moiety, and are called bio-catalysts.
So, the correct answer is '
Protein nature'
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