Test: Proteins Enzymes And Vitamins


20 Questions MCQ Test Chemistry Class 12 | Test: Proteins Enzymes And Vitamins


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QUESTION: 1

Which of the following is a test for proteins?

Solution:

Biuret solution is used to identify the presence of protein. Biuret reagent is a blue solution that, when it reacts with protein, will change color to pink-purple.

QUESTION: 2

In which structure of protein, the polypeptide chain forms all possible hydrogen bonds by twisting into right handed screw?

Solution:

The correct answer is option D
α helix is one of the most common ways in which a polypeptide chain forms all possible hydrogen bonds (intermolecular and intramolecular hydrogen bond) by twisting into a right-handed screw(helix) with the N−H group of each amino acid residue hydrogen bonded to C=O of an adjacent turn of the helix.
 

QUESTION: 3

Haemoglobin is an example of:

Solution:

The correct answer is A
Haemoglobin is a Quaternary protein because it has 4 polypeptide structures - 2alpha and 2 beta.

QUESTION: 4

The amino acid which is not optically active is:

Solution:

Glycine is the simplest amino acid and is the only amino acid that is not optically active (it has no stereoisomers).

QUESTION: 5

Which one of the following is a water soluble vitamin?

Solution:

The correct answer is Option C
Fat soluble vitamin - A, D, E, K
Water soluble vitamin - Vitamin B complex and C
So, vitamin B is water soluble.
Vitamins which can dissolve in water are called water-soluble vitamins. Water-soluble vitamins include vitamin-C and vitamin-B because they remove the toxins from our body through urine. Therefore, they are not stored in our body and should be taken on a daily basis through the food we eat.

QUESTION: 6

The amino acid which are synthesized in the body are known as:

Solution:

Nonessential amino acids can be synthesized in the body, whereas essential amino acids must be obtained in the diet. Cells in the body can provide the carbon skeleton of the nonessential amino acids.

QUESTION: 7

The enzyme pepsin hydrolyses:

Solution:

The correct answer is Option C
Pepsin hydrolyses proteins to amino acid(polypeptide chains) and initiates protein digestion in the digestion process in humans.

QUESTION: 8

Which of the following statements is correct about Enzymes?

Solution:

The correct answer is option A
 
Higher temperatures  speed up the effect of enzyme activity, while lower temperatures decrease the rate of an enzyme reaction. if the temperature is too high, an enzyme will denature, which causes the shape of the enzyme to change. If the enzyme's shape changes, it cannot bind to the substrate.

QUESTION: 9

Certain organic compounds are required in small amount in our diet but their deficiency causes diseases. The compounds are called:

Solution:
QUESTION: 10

When more than ten amino acids react, then the product formed is called:

Solution:

Small polymers of amino acids (fewer than 50) are called oligopeptides, while larger ones (more than 50) are referred to as polypeptides. Hence, a protein molecule is a polypeptide chain composed of many amino acid residues, with each residue joined to the next by a peptide bond.

QUESTION: 11

Enzymes belong to the class of compounds called:

Solution:

Enzymes are proteins that act as catalysts and help complex reactions occur everywhere in life. These are polypeptides. Chemically, peptide linkage is an amide formed between –COOH group and –NH2 group.

QUESTION: 12

In aqueous solution, the carboxyl group can lose a proton and amino group can accept a proton, giving rise to a dipolar ion known as:

Solution:

The correct answer is Option D
In aqueous solution, the carboxyl group can lose proton and the amino group can accept proton, giving rise to a dipolar ion known as zwitterion. In zwitter ionic form, amino acids show amphoteric behaviour as they react both with acids and bases.

QUESTION: 13

The symptoms of retinol excess are

Solution:

The correct answer is option B
Fibrous Protein
When polypeptide chains run parallel & are held together by hydrogen and disulphide bonds, then ber, rod or wire-like structure is formed. They are shaped like fibers; hence called Fibrous protein These proteins are water-insoluble.
 

QUESTION: 14

Amino acid are connected to each other by:

Solution:

Peptide bonds are formed by a biochemical reaction that extracts a water molecule as it joins the amino group of one amino acid to the carboxyl group of a neighboring amino acid.

QUESTION: 15

The active form of vitamin D is:

Solution:

The correct answer is option B
Calcitriol , is the hormonally active metabolite of vitamin D  which has three hydroxyl groups.Calcitriol increases the level of calcium  (Ca2+) in the blood  by increasing the uptake of calcium from the gut  into the blood, increasing reabsorption of calcium by the kidneys, and possibly increasing the release of calcium into the blood from bone. Vitamin D has a significant role in calcium homeostasis  and metabolism. Its discovery was due to effort to find the dietary substance lacking in children with rickets  (the childhood form of osteomalacia).

QUESTION: 16

Which of the following compounds is a recipient of the one carbon fragments that tetra hydro folate receives and transfers?

Solution:

The correct answer is option B
There are a total 20 amino acids.
out of these 20 amino acids 10 R essential amino acids and 10 R nonessential amino acids.
The amino acids which we can't produce are essential amino acids we have to take that amino acid through our diet.
These 10 Essential amino acids are as follows:-
1) V~ Valine (Val / V)
2) I~ Isoleucine (Ile/ I)
3) P~ Phenylalanine (Phe /F)
4) H~ Histidine (His /H)
5) A~ Arginine (Arg /R){UR ANSWER }
6) L ~ Lysine( Lys /K)
7)L~ Leucine (Leu /L)
8)Me~ Methionine (Met /M)
9) Tryptophan (Trp /W)
10)Threonine (Thr / T)
 

QUESTION: 17

On hydrolysis, proteins give:

Solution:

The correct answer is option  B
Ultimate product of hydrolysis of protein is amino acid. Proteins are polymers made up of several amino acids. These amino acids are linked through peptide bonds. On hydrolysis, peptide bonds are broken and amino acids are released.

QUESTION: 18

Deficiency of which vitamin causes scurvy?​

Solution:

Many people with scurvy, a disease caused by vitamin C deficiency, eventually die of infection due to their poorly functioning immune systems.

QUESTION: 19

When a protein is subjected to physical changes the protein loses its biological activity. This is known as:

Solution:

The correct answer is Option D
This loss of biological activity by the protein is called denaturation. During denaturation, the secondary and the tertiary structures of the protein get destroyed, but the primary structure remains unaltered. One of the examples of denaturation of proteins is the coagulation of egg white when an egg is boiled.

QUESTION: 20

_________ are biocatalysts which speed up the reactions in biosystems.

Solution:

The correct answer is Option A
Biocatalysis refers to the use of living (biological) systems or their parts to speed up (catalyze) chemical reactions. In biocatalytic processes, natural catalysts, such as enzymes, perform chemical transformations on organic compounds.