Proteins Enzymes & Vitamins - Free MCQ Practice Test with solutions, NEET

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.

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.
 

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

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

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.

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.

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

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.

Certain organic compounds are essential for our health. These compounds are needed in small amounts in our diet, but their deficiency can lead to various diseases. The most notable of these are:

• Vitamins: Vital for numerous bodily functions, including vision, skin health, and immune function.
• Proteins: While they are crucial for growth and repair, they are not classified as organic compounds that are required in small amounts.
• Amino acids: These are the building blocks of proteins but are not necessary in their own right as organic compounds.
• Carbohydrates: They provide energy, but they are not categorized as essential organic compounds needed in small quantities.

Among these, vitamins stand out as the key organic compounds whose lack can cause significant health issues.

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.

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.

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.

Option D is correct: all of these.

Retinol (vitamin A) in excess causes hypervitaminosis A, which arises from chronic high intake of vitamin A.

Bone fragility is seen because prolonged excess of vitamin A alters bone remodelling, increasing bone resorption and raising the risk of bone pain and fractures.

Weakness and generalised fatigue are common systemic symptoms associated with vitamin A toxicity.

Dry skin (xerosis), along with hair loss and mucocutaneous dryness, are typical dermatological features of retinol excess.

All the listed features are recognized consequences of retinol overdose; therefore all of these is the correct choice.

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.

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).

Formaldehyde  is a recipient of the one carbon fragments that tetra hydro folate receives and transfers 

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.

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

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.

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.