All questions of Biomolecules for NEET Exam

Essential Amino Acids

Amino acids are the building blocks of proteins. There are 20 different amino acids that make up proteins, and they can be classified into two groups: essential and non-essential.

- Essential amino acids cannot be synthesized by the body and must be obtained through the diet.
- Non-essential amino acids can be synthesized by the body.

Arginine as an Essential Amino Acid

Arginine is one of the essential amino acids that cannot be synthesized by the body and must be obtained through the diet.

Functions of Arginine

Arginine has several important functions in the body, including:

- Acting as a precursor for the synthesis of nitric oxide, which helps to relax blood vessels and improve blood flow.
- Stimulating the release of growth hormone, which is important for muscle growth and repair.
- Supporting immune function.
- Playing a role in wound healing.

Food Sources of Arginine

Arginine can be found in a variety of foods, including:

- Meat and poultry
- Fish and seafood
- Dairy products
- Nuts and seeds
- Legumes and beans

Conclusion

Arginine is an essential amino acid that plays important roles in the body, including supporting immune function, stimulating growth hormone release, and aiding in wound healing. It can be obtained through a variety of dietary sources, including meat, fish, dairy, nuts, and legumes.

The alpha helix (α-helix) is a common motif in the secondary structure of proteins and is a right hand-helix conformation in which every backbone N−H group hydrogen bonds to the backbone C=O. group of the amino acid located three or four residues earlier along the protein sequence.

Pepsin is an enzyme that is primarily found in the stomach and plays a crucial role in the digestion of proteins. It is secreted by the gastric chief cells in an inactive form called pepsinogen, which is then activated by the acidic environment of the stomach. Once activated, pepsin breaks down proteins into smaller peptide fragments and eventually into individual amino acids, which can be absorbed by the body.

Pepsin acts through a process called hydrolysis, which involves the addition of a water molecule to break the peptide bonds that hold the amino acids together in a protein. This process is essential for the body to obtain the necessary amino acids for various physiological functions, such as the synthesis of new proteins, enzyme activity, and hormone production.

To better understand why the correct answer is option 'C' (proteins to amino acids), let's break down the other options and eliminate them:

a) Polysaccharides to monosaccharides: This process is actually carried out by enzymes called amylases, not pepsin. Amylases are found in saliva and pancreatic secretions and are responsible for breaking down complex carbohydrates (polysaccharides) into simpler sugars (monosaccharides) such as glucose.

b) Glucose to ethyl alcohol: This process is not mediated by pepsin but rather by a different enzyme called yeast. Yeast is able to convert glucose into ethyl alcohol through a process called fermentation.

d) Fats to fatty acids: The digestion of fats involves the action of enzymes called lipases, not pepsin. Lipases break down fats (triglycerides) into fatty acids and glycerol, which can then be absorbed by the body.

In summary, pepsin is specifically responsible for hydrolyzing proteins into amino acids. This process is crucial for the body to obtain the necessary building blocks for protein synthesis and various other physiological functions.

The active form of vitamin D is calcitriol.

Calcitriol, also known as 1,25-dihydroxyvitamin D3, is the active form of vitamin D in the body. It is the biologically active metabolite that is synthesized from calcidiol, also known as 25-hydroxyvitamin D3, which is the storage form of vitamin D.

Explanation:

1. Vitamin D and its forms:
Vitamin D is a fat-soluble vitamin that plays a crucial role in maintaining bone health and calcium homeostasis. It exists in several forms, including vitamin D2 (ergocalciferol) and vitamin D3 (cholecalciferol), which are obtained from dietary sources or synthesized in the skin upon exposure to sunlight.

2. Conversion of vitamin D to its active form:
When vitamin D2 or D3 is ingested or synthesized, it undergoes a series of metabolic conversions in the liver and kidneys to become the active form of vitamin D. The first step involves hydroxylation in the liver, where vitamin D is converted to calcidiol (25-hydroxyvitamin D3) through the action of the enzyme 25-hydroxylase.

3. Activation of calcidiol to calcitriol:
The second and final step in the activation of vitamin D occurs in the kidneys. Calcidiol undergoes further hydroxylation by the enzyme 1-alpha-hydroxylase, resulting in the formation of calcitriol (1,25-dihydroxyvitamin D3). This conversion is tightly regulated by various factors, including parathyroid hormone (PTH), calcium levels, and phosphate levels.

4. Biological functions of calcitriol:
Calcitriol acts as a hormone and binds to the vitamin D receptor (VDR) in target tissues, such as the intestines, bones, and kidneys. It regulates the absorption of calcium and phosphate in the intestines, promotes bone mineralization by increasing calcium and phosphate uptake, and helps maintain normal blood calcium levels. Calcitriol also has non-skeletal functions, including modulation of immune responses and cell growth.

Conclusion:
In conclusion, the active form of vitamin D is calcitriol, which is synthesized from calcidiol through the action of 1-alpha-hydroxylase in the kidneys. Calcitriol plays a crucial role in maintaining calcium homeostasis and bone health, as well as other physiological processes in the body.

Because mRNA is called messanger RNA, which carries the information from DNA to synthesis of protein and other essential products in cell.

DNA TO DNA - replication
DNA TO RNA-transcription
RNA TO PROTEIN-translation

Purine is a type of nitrogenous base found in DNA and RNA molecules. The purine bases are adenine and guanine. Among the given options, the purine derivative is:

c) Guanine

Explanation:

- Purine and pyrimidine are two types of nitrogenous bases found in DNA and RNA molecules.
- Purine bases are larger and have a double-ring structure, while pyrimidine bases are smaller and have a single-ring structure.
- Adenine and guanine are purine bases, while cytosine, thymine, and uracil are pyrimidine bases.
- Therefore, among the given options, the purine derivative is guanine.

The structure of nucleotide and nucleoside units are distinguished primarily by the presence (or lack thereof) of this phosphate group. Deoxyribose in DNA differs from the ribose found in RNA in that it has only a hydrogen atom in the same position that ribose has a hydroxyl (-OH) group.

Proteins are polymers of amino acids therefore their hydrolysis gives amino acids

Uracil is not found in DNA , as it Uracil has more base pair affinity to adenine , guanine and cytosine. Instead thymine is present in DNA.

There are two types of pentose sugars- ribose and deoxyribose.The former is present in rna and the latter in dna. In the case of nitrogenous bases uracil is present in rna instead of thymine

Yes. option a is correct as enzymes are proteins and contain amino acids and the correct option is only they have optimum activity at body temperature... hope you got it...

Alpha helix in secondary structure.

A peptide bond is formed (-CONH) between the –NH2 group and the –COOH group of any two adjacent amino acids and it leads to the elimination of a water molecule. The resultant product formed is an amide.

Yes biuret is a blue solution,when it reacts with protein ,its color become pink - purple. molish test & Benedict both are for carbohydrate where as beilstein is for halides

Polypeptide is the correct answer.

Explanation:

When more than ten amino acids react, the product formed is called a polypeptide. A polypeptide is a chain of amino acids joined together by peptide bonds. Peptide bonds are formed through a condensation reaction between the carboxyl group of one amino acid and the amino group of another amino acid, resulting in the release of a water molecule.

Key points:
- Polypeptides are formed by the polymerization of amino acids.
- Amino acids are organic compounds that contain an amino group (-NH2) and a carboxyl group (-COOH) attached to a central carbon atom.
- There are 20 different types of amino acids that can be found in proteins, each with a unique side chain or R-group.
- The order and sequence of amino acids in a polypeptide chain determine the structure and function of the protein.
- Polypeptides can vary in length, ranging from just a few amino acids to thousands of amino acids in length.
- Polypeptides can fold into specific three-dimensional structures, such as alpha helices and beta sheets, which are stabilized by various types of interactions between amino acid side chains.
- These folded structures are critical for the proper functioning of proteins and can determine their enzymatic activity, binding specificity, and overall stability.
- Polypeptides can also undergo post-translational modifications, such as phosphorylation or glycosylation, which can further modify their structure and function.
- Polypeptides can interact with other molecules, such as other polypeptides or small molecules, to form larger protein complexes or perform specific biological functions.
- Polypeptides are an essential component of all living organisms and play critical roles in processes such as metabolism, signaling, and immune response.

In conclusion, when more than ten amino acids react, the product formed is called a polypeptide, which is a chain of amino acids joined together by peptide bonds. Polypeptides are the building blocks of proteins and are essential for the structure and function of biological systems.

Certain organic compounds are required in small amount but their deficiency causes diseases. The compounds are called Vitamins. Most of the vitamins cannot be synthesised in our body but plants can synthesise almost all of them, so they are considered as essential food factors.

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.

Denaturation
Denaturation is the process by which proteins or nucleic acids lose their structure due to external factors such as heat, pH changes, or chemicals. Let's analyze the statements given in the question:

Statement (a) - Correct
- Denaturation of proteins causes the loss of secondary and tertiary structures of the protein. This is true as denaturation disrupts the non-covalent interactions that maintain the protein's folded structure, leading to the loss of secondary and tertiary structures.

Statement (b) - Incorrect
- Denaturation does not lead to the conversion of double-stranded DNA into single strands. DNA denaturation involves the separation of the two strands of DNA, but it does not convert double-stranded DNA into single strands.

Statement (c) - Correct
- Denaturation affects the primary structure of proteins, causing it to become distorted. The primary structure refers to the sequence of amino acids in a protein, and denaturation can disrupt this sequence, leading to distortion.
Therefore, the correct statements about denaturation are (a) and (c). Denaturation primarily affects the secondary and tertiary structures of proteins while also impacting the primary structure by causing distortion.

Vitamin B is a water soluble vitamin. They must be regularly supplied in diet because they are readily excreted in urine. Vitamin A, D, E and K are fat soluble vitamins. Whereas, vitamin B and C are water soluble.

Nonessential amino acids are mainly synthesized from glucose (alanine, arginine [from the urea cycle in hepatic cells], asparagine, aspartate, cysteine, glutamate, glutamine, glycine, proline, and serine), except for tyrosine, which is synthesized from phenylalanine.

Vitamin C (ascorbic acid) short-term deficiency can lead to weakness, weight loss and general aches and pains. Longer-term depletion may affect the connective tissue. Persistent vitamin C deficiency leads to scurvy.

Enzymes belong to the class of compounds called polypeptides.

Enzymes are biological catalysts that are responsible for facilitating chemical reactions in living organisms. They play a crucial role in various physiological processes such as metabolism, digestion, and DNA replication. Enzymes are highly specific in their actions and can accelerate the rate of chemical reactions by lowering the activation energy required for the reaction to occur.

Enzymes are classified as polypeptides for the following reasons:

1. Structure: Enzymes are composed of long chains of amino acids linked together by peptide bonds. These chains fold into specific three-dimensional structures that are critical for their catalytic activity. The amino acid sequence and arrangement determine the enzyme's shape and function.

2. Protein nature: Enzymes are a type of protein. Proteins are organic compounds made up of polypeptides, which are linear chains of amino acids. Therefore, enzymes are classified as polypeptides due to their proteinaceous nature.

3. Synthesis: Enzymes are synthesized in living cells through a process called protein synthesis or translation. During translation, the genetic information encoded in DNA is transcribed into messenger RNA (mRNA), which serves as a template for the synthesis of proteins. The mRNA carries the instructions for the specific sequence of amino acids that make up the enzyme.

4. Function: Enzymes exhibit catalytic activity due to their specific three-dimensional structure. They bind to substrates, which are the molecules upon which they act, and facilitate the conversion of substrates into products. The specific amino acid sequence and arrangement in the enzyme determine its ability to recognize and bind to the substrate, leading to the catalytic reaction.

In conclusion, enzymes belong to the class of compounds called polypeptides because they are composed of long chains of amino acids linked together by peptide bonds. This polypeptide nature is crucial for their structure, synthesis, and catalytic function in living organisms.