Biomolecules: Important Questions

Biomolecules also called as biological molecules are the molecules which are present in organisms essential for biological processes for cell growth, development, etc. Biomolecules include macromolecules such as Proteins, carbohydrates, lipids, nucleic acids and micromolecules like amino acids, primary metabolites, secondary metabolites and natural products. Among biomolecules, nucleic acids, namely DNA and RNA, have the unique function of storing an organism’s genetic code - the sequence of nucleotides that determines the amino acid sequence of proteins, which are of critical importance to life on Earth.

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Very Short Answer Questions [1 Mark Question]

Ques. Classify the following into one of the appropriate bonds – ester bond, peptide bond, glycosidic bond, hydrogen bond.

1. a) Polysaccharide b) Protein c) Fat d) Water

Ans.

1. Polysaccharide – glycosidic bond
2. Protein-peptide bond
3. Fat – ester bond
4. Water – hydrogen bond

Ques. Name any one sugar, amino acid, fatty acid and nucleotide.

Ans. Sugar – Fructose

Amino acid – Alanine

Fatty acid – Lauric acid

Nucleotide – Guanosine

Ques. Which are the small molecules of the cell?

Ans. Small molecules of the cell are:

1. Minerals
2. Water
3. Amino acids
4. Sugars
5. Lipids
6. Nucleotides.

Ques. Mention functions of the sodium and potassium ions in the human body.

Ans. Sodium ions are primarily required to control the blood volume and blood pressure in the body and potassium ions maintain the function of nerve cells and muscle tissues.

Ques. Why are proteins called biological polymers?

Ans: Proteins are made from monomers like amino acids formed by peptide bonds. They perform various functions such as protection, mechanical support, transportation, and mobility.

Ques. What is the function of ATP in cell metabolism?

Ans. ATP, or Adenosine Triphosphate, is the cell's energy currency. It is a molecule having unstable high-energy bonds.

Ques. How many types of biomolecules are there?

Ans. There are four major classes of biomolecules – Carbohydrates, Proteins, Nucleic acids and Lipids.

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Short Answer Questions [2 Marks Question]

Ques. Can rubber be classified as a primary metabolite or a secondary metabolite? Write a short note on the rubber.

Ans. Rubber is a secondary metabolite. Secondary metabolites are molecules produced by plants which are not essential in their growth. Latex in the rubber tree is produced by the highly specialised cells in phloem called laticifers. Rubber is a terpenoid and because of its high tensile strength, plasticity, and elasticity, it is used across industries. It is a polymeric substance and is a good conductor of electricity.

Ques. What are the sources of Proteins?

Ans. The most common foods which are high in protein are almond, beans, broccoli, chicken, cottage cheese, eggs, fish, milk, oats, pulses, seafood, soy, quinoa and yoghurt.

Ques. What are monosaccharides? Give a few examples.

Ans. Monosaccharides are the simplest carbohydrates that cannot be hydrolyzed into still smaller carbohydrates. The general formula is CnH2nOn. Examples of monosaccharides are Ribose, Glucose, Fructose.

Ques. Why do fats release more energy than carbohydrates on oxidation?

Ans. Like carbohydrates, fats are made up of Carbon (C), hydrogen (H), and oxygen (O) but they contain fewer oxygen molecules than carbohydrates. On oxidation they consume more oxygen releasing more energy.

Ques. Differentiate between nucleotides & nucleosides?

Ans.

Ques. What is metabolism? Mention the role of enzymes in metabolism?

Ans. Metabolism is described as the chemical reactions in the cells which turn food into energy. Enzymes are responsible for directing metabolic pathways. Catalysts are enzymes. Enzymes are organic catalysts that are highly specialised and are created by living cells. Biochemical pathways are the sequences of reactions that occur in cells. Enzymes direct metabolic pathways in the desired direction. They have an active site. The substrate binds to the active site of the enzyme, resulting in the formation of an enzyme-substrate complex.

Ques. What would happen when salivary amylase acts on starch in the mouth and the stomach?

Ans: Salivary amylase converts starch to maltose in the mouth. Amylase activity ceases in the stomach because it cannot function in an acidic environment.

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Long Answer Questions [3 Marks Question]

Ques. Give the functions of lipids?

Ans. Functions of lipids are:

1. They are the main component and help in the manufacturing of the cell membrane that helps the cell to maintain its shape and rigidity and also to protect the cell from the outer environment.
2. The lipids act as the storehouse of energy in the case of the plants and the animals.
3. The lipids are in the form of wax which is the outer coating of various stems, leaves, fruits, birds feathers, etc, and are water repellent thus saving them from exposure to excessive water and making them waterproof.
4. The bile acids are the steroids that help in the digestion of fats inside the stomach.
5. They help in regulating the temperature of the body.
6. The fats act as the chemical messenger and release the hormone prostaglandins.

Ques. Describe Fischer's lock & key model of enzyme action?

Ans: Fischer's lock and key hypothesis of enzyme activity states that if the proper key fits in the right lock, the lock can be opened; otherwise, the lock cannot be unlocked.

To interpret the preceding in the context of enzyme function, it is assumed that molecules have precise geometric forms.

Proteins can operate as enzymes because their form creates a space configuration into which other molecules can fit.

The compounds that are acted on by enzymes are referred to as enzyme substrates. Only substrate molecules with the proper geometric shape can fit into the active site of the enzymes, according to the aforementioned premise.

However, under certain conditions, other molecules that are similar to the substrate might potentially bind with the active site of the enzyme. In such instances, molecules may compete with the substrate, causing the process to slow or cease. This is known as competitive inhibition.

Ques. Describe the structure & functions of ATP?

Ans: ATP is the primary and universal carrier of chemical energy in the cell. Living cells capture, store, and transport energy in a chemical form, primarily ATP, and it is ATP that serves as a carrier and intermediate source of chemical energy to those reactions in the cell that do not occur simultaneously. Only when chemical energy is released can these reactions occur. The ATP molecule is made up of a nitrogenous base called adenine, a pentose sugar called ribose, and three inorganic phosphate molecules. Two phosphate bonds have a high energy level and one has a low energy level. The energy released in a living cell is therefore kept in the chemical bonds of the ATP molecule, which then serves as the cell's primary energy generating and energy-demanding material. ATP is broken down into ADP when energy is needed.

ATP = ADP + ip + energy

Ques. What are nucleic acids? Describe the structure of DNA.

Ans: Nucleic acids are linear polymers which are found in nucleus. Hence, the name nucleic acid. The acid-soluble component of live tissue contains nucleic acids. They are of two type Deoxyribonucleic acid and Ribonucleic acid.

Structure of DNA

In 1953 J.D. Watson and F.H.C. Crick working in Cambridge University, England prepared a model of DNA molecule elucidating the structure of DNA molecules.

DNA is a double-stranded helical structure composed of three different parts – nitrogenous base, sugar and phosphate group.

The nucleic acid backbone is made up of alternating pentose sugar and phosphate groups.

The steps consist of nitrogenous bases adenine, guanine, cytosine, and thymine, as well as hydrogen bonds, holding two strands together.

These 4 Nitrogenous bases pair together in the following way: A with T, and C with G. These base pairs are essential for the DNA’s double helix structure, which resembles a twisted ladder.

The two strands of DNA run in opposite directions. These strands are held together by the hydrogen bond that is present between the two complementary bases.

At one end of the strand, 5-c of pentose sugar is free; at the other end, pentose's third carbon is free.

The distance between two chains of the helix is about 20 A and the helix turns over every 34 A. Each mm of the chain consists of about 10 nucleotides.

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Very Long Answer Questions [5 Marks Question]

Ques. Explain briefly four levels of protein structure?

Ans: The four levels of protein structures are primary, secondary, tertiary and quaternary.

Primary Structure: A protein occurs as a long chain of amino acids organized in a certain sequence. For example, the polypeptide is non-functional.

Secondary Structure: The first amino acid is known as N-terminal amino acid, while the last is known as C-terminal amino acid. Every fourth amino acid interacts with another by forming a hydrogen bond, and the polypeptide is folded in a helical shape, as in keratin. When two or more polypeptide chains are joined together by intermolecular hydrogen bonds, a pleated sheet structure is formed.

Tertiary Structure: The polypeptide is stabilised by folding and coating, which results in the creation of ionic bonds, hydrophobic bonds, or disulfide bridges. It is referred to as a tertiary structure. It displays proteins in three dimensions. The biological activity of a protein is determined by its tertiary structure.

Quaternary Structure: These proteins are made up of several polypeptides or subunits, each with its primary, secondary, and tertiary structure. This is referred to as a quaternary structure. Each polypeptide chain serves as a protein component.

Ques. How does the substrate concentration affect the velocity of enzyme reaction?

Ans. Michaelis constant or more appropriately Michaelis - Menten constant (Km) is a mathematical derivation given by Leonor Michaelis and Monde Menten in 1913 with the help of which velocity of reaction can be calculated for any substrate concentration.

Effect of substrate concentration on enzyme action

Km or Michaelis constant is the substrate concentration at which the chemical reaction attains half its maximum velocity. The constant is an inverse measure of the affinity of an enzyme for its substrate, that is the smaller the Km the greater the substrate affinity and vice versa. The value usually lies between 104 – 105 M.

Ques. Explain the functions of amino acids.

Ans. Amino acids are the building blocks for proteins. There are two types of amino acids essential and non-essential amino acids. Their functions are as follow;

Essential amino acids –

1. Phenylalanine helps in maintaining a healthy nervous system and in boosting memory power.
2. Valine acts as an important component in promoting muscle growth.
3. Threonine helps in promoting the functions of the immune system.
4. Tryptophan is involved in the production of vitamin B3 and serotonin hormones. This serotonin hormone plays a vital role in maintaining our appetite, regulating sleep and boosting our moods.
5. Isoleucine plays a vital role in the formation of haemoglobin, stimulating the pancreas to synthesise insulin, and transporting oxygen from the lungs to the various parts.
6. Methionine is used in the treatment of kidney stones, maintaining healthy skin and also used in controlling invaders of pathogenic bacteria.

Non-essential amino acids –

1. Alanine functions by removing toxins from our body and in the production of glucose and other amino acids.
2. Cysteine acts as an antioxidant and provides resistance to our body; it is important for making collagen. It affects the texture and elasticity of the skin
3. Glutamine promotes a healthy brain function and is necessary for the synthesis of nucleic acids – DNA and RNA.
4. Glycine is helpful in maintaining the proper cell growth, and its function, and it also plays a vital role in healing wounds. It acts as a neurotransmitter.
5. Tyrosine plays a vital role in the production of the thyroid hormones -T3 and T4, in synthesising a class of neurotransmitters and melanin, which are natural pigments found in our eyes, hair, and skin.
6. Serine helps in promoting muscle growth and in the synthesis of immune system proteins

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