30+ Biochemistry Important Questions with Answers

Learning objective:

• Introduction to biochemistry
• Carbohydrates
• Classification of carbohydrates – monosaccharides, oligosaccharides and polysaccharides
• Sources and Uses of carbohydrates
• Proteins
• Aminoacids as a building block
• sources and uses of proteins
• Lipids
• Fatty acids
• sources and uses of lipids
• Nucleic acids
• Deoxyribonucleic acid -DNA
• Riboxyribonucleic acid -RNA
• Vitamins
• Types of Vitamins- Fat soluble Vitamins and Water-soluble Vitamins
• sources and uses of vitamins
• Diseases due to the deficiency of vitamins

Biochemistry Question Bank 2022

1. Water can dissolve glucose or sucrose, but it cannot dissolve simple six-membered ring molecules like cyclohexane or benzene. Explain.

Answer:

Five -OH groups are present in a glucose molecule, compared to eight in a sucrose molecule. As a result, water and glucose and sucrose create many H-bonds. They are therefore water-soluble.

Cyclohexane and benzene do not, however, have -OH groups. Since of this, they are insoluble in water because they are unable to establish H-bonds with it.

2. What is meant by dextrose sugar?

Answer:

Monosaccharides that rotate the plane polarized light clockwise are called dextrorotatory sugars or dextrose sugars e.g. Glucose, galactose and mannose.

3. Identify the functional group in an amino acid’s formula and write it down.

Answer:

4. Define a peptide bond.

Answer:

• The bond created by removing the proton (H⁺) from one amino acid NH₂ group and the hydroxyl (OH^–) group from the carboxyl (COOH) group of another amino acid is called a peptide bond.
• Peptide linkage holds two amino acids together in proteins.

5. Name the constituents of lipids.

Answer:

The constituents of lipid are glycerol, fatty acids, and phosphate groups.

6. What purpose does DNA serve?

Answer:

Functions of DNA:

• DNA is the genetic substance that makes up a cell’s nucleus.
• It stores genetic information and transmits it to the organism as it grows.
• For instance, in humans, the fertilized egg transmits the instructions for creating the head, liver, heart, kidney, hands, and legs.
• Each DNA helix is constructed of nucleotides, which are made up of phosphate groups, nitrogenous bases, and deoxyribose sugar (pentose sugar).
• Nitrogenous bases are organized in pairs in a strand.
• Each base pair in a strand represents a code.
• Each code contains genetic data, which is utilized to synthesize proteins.
• DNA is the carrier of genetic information from one generation to the next.

7. Recognize the differences between mono, di, and trisaccharides. Give instances.

Answer:

Monosaccharide:

• Simple carbohydrates include monosaccharides.
• They have three to six carbon atoms.
• They can no longer be hydrolyzed in water due to their simple nature.
• They often have the formula (CH₂O)_n. where n is the total number of carbon atoms, which can only be 3, 4, 5, or 6.

Classification of monosaccharides:

Monosaccharides are further classified into the following groups according to the number of carbon atoms they contain:

• Trioses (monosaccharides having three C atoms)
• Tetroses (monosaccharides having four C atoms)
• Pentoses (monosaccharides having five C atoms)
• Hexoses (monosaccharides having six C atoms)

Hexoses:

• Fructose (C₆H₁₂O₆) and glucose (C₆H₁₂O₆) are the two hexoses.
• As simple sugars with open chain structures, glucose and fructose are both referred to as monosaccharides.

Disaccharides:

Oligosaccharides give two monomers on hydrolysis are called disaccharides. The important point about disaccharides are given below.

• When disaccharides (oligosaccharides) are hydrolyzed, they break down into two monosaccharides.
• As an illustration, the hydrolysis of the disaccharide sucrose yields the two monomers glucose and fructose.
• When lactose (disaccharide) is hydrolyzed, it splits into the two monomers glucose and galactose.
• Maltose is a disaccharide that breaks down into two monomers, glucose and glucose. Below are the reaction schemes.

8. Describe the bond that makes up a protein molecule.

Answer:

• In proteins, the amino acids are linked together by a peptide bond.
• The bond created by removing the proton (H+) from one amino acid NH2 group and the hydroxyl (OH-) from the carboxyl (COOH) group of another amino acid is called a peptide bond.
• Peptide linkage holds two amino acids together in proteins.

Illustration of Peptide Bond:

• The following is a description of how peptide bonds form:

• One amino functional group is on the left side and one carboxyl functional group is still present, as can be seen in the final molecule.
• Through peptide linkages, these functional groups can interact with additional amino acids.
• Therefore, thousands of amino acids are connected to one another by peptide bonds in this manner to form long chain polymers known as proteins.

9. Describe the lipids’ applications and origins.

Answer:

Origins of Lipids:

Animals:

• The majority of marine creatures, like whales and salmon, are excellent sources of lipids.
• An oil known as “cod liver oil” is extracted from salmon and whales.
• Animal milk also contains a significant amount of fat.
• Butter and ghee can be made from animal fat.

Plants:

The majority of plants are abundant sources of lipids, such as the oil-rich seeds of sunflower, corn, cotton, olive, coconut, and ground nut.

Applications of Lipids:

• A fatty layer is present under mammalian skin that protects the inner organs from shocks because fat acts as an insulator
• A fatty layer is present around our heart and kidneys to protect them from injury.
• Some important vitamins, such as vitamin-A, vitamin D, and vitamin-E, are essential for our body and can be obtained from lipids.
• Fats are the primary source of energy; they offer twice as much energy as carbohydrates. As a result, the body stores energy as fat and oil for later use. In the future, when a body experiences an energy crisis, these fats and oils will give the body enough energy to survive.
• The majority of commonly used items, including soap, detergents, polishes, paints, and cosmetics, are made from fats and oils. The oil can be turned into ghee by the hydrogenation process in the presence of a catalyst.
• Cholesterol, a lipid, is crucial for the production of hormones, bile acid, and vitamin D.

10. Give examples of proteins’ origins and applications.

Answer:

Origins of Protein:

Animals:

• The majority of animals possess essential amino acids, which are needed by our bodies but cannot be produced by them.
• Meat, fish, eggs, milk, and cheese all provide significant quantities of essential amino acids.

Plants:

Protein is mostly obtained from plants; for example, beans and pulses are excellent providers of the amino acid.

Applications of Protein:

• Because our muscles, nails, hair, skin, and other protein-based tissues are made up of essential amino acids, we consume them as part of a healthy diet.
• In addition, protein is necessary for the survival of the cells and protoplasm that make up our bodies.
• When we heated tendons and bones in water, we found a protein called gelatin, used in bakery ingredients. We need protein in our diet on a daily basis because it gives us both physical and mental strength.
• We know that enzymes operate as catalysts in biological reactions and that the majority of the enzymes in our bodies are protein-based.
• Antibodies, which are defence cells in our bodies that protect us from germ attacks, are also proteins in nature.
• In conclusion, both animals and humans must consume protein in order to survive.

11. List the origins and applications of carbohydrates.

Answer:

Origins of Carbohydrates:

Monosaccharides:

Monosaccharides like glucose, fructose, and galactose are found in plants, fruits, cereals, and honey.

Disaccharides:

Disaccharides like sucrose, lactose, and maltose are present in milk, sugarcane, and oranges correspondingly.

Polysaccharides:

Cellulose and starch are polysaccharides, found in plants and animals e.g.

• Cellulose (Cotton)
• Starch (Cereals, barley, wheat, rice, maize and sweet potato)

Applications of Carbohydrates:

• Carbohydrates are the source of food for both animals and human beings.
• Our bodies employ carbohydrates to store energy for later use, such as 1g of glucose equals 15.6 kJ.
• A disaccharide called sucrose is used as table sugar.
• Glycogen is the type of glucose that animals store for later uses. In the future, if we run out of energy, this glycogen will turn back into glucose and supply our body with energy.
• Starch is the type of glucose that plants store for later use. This starch converts back into glucose when plants in the future experience an energy shortage, giving them the energy they need to survive.
• Starch can be converted into rectified alcohol by the fermentation process.
• Dextrin and wallpaper glue are both adhesives that can be made from starch.
• As a carbohydrate, cellulose is a source of food for termites, cows, goats, and sheep, among other creatures.
• Plants use cellulose as a structural component.

12. Make a distinction between oil and fat.

Answer:

Fat:

At room temperature, a solid lipid is known as fat.

Oil:

At room temperature, a liquid lipid is known as oil.

13. Describe vitamins in detail.

Answer:

Vitamins:

Background:

• F.G. Hopkins, a British scientist, used experiments to demonstrate that our body also needs other nutrients besides carbs, proteins, and fats for survival and good health.
• A Latin phrase called vita, which means life, was coined by a Polish biochemist (Casmir funk) to describe these deficient elements.
• Thus, vitamins are essential growth elements, to put it briefly.

Definition:

Vitamins are necessary growth factors. The body cannot synthesize vitamins, which are organic molecules, thus our bodies need to consume them every day for health, growth, and life.

Examples of Vitamins:

• Vitamin A, which is present in our eyes, helps us see by transporting visual data from the eye to the brain. It also provides the cornea of the eye with a moist nature.
• Vitamin C strengthens our immune system and aids in blood production.
• The control of nerve impulse transmission and the synthesis of haemoglobin are both aided by vitamin B. Additionally, about 100 enzymes are activated by vitamin B.
• Vitamin D strengthens bones and teeth. It controls the amount of Ca in our blood.

Classification of Vitamins:

The solubility of vitamins determines which of two categories they fall into. Below are the two categories:

1. Fat soluble vitamins
2. Water soluble vitamins

Fat Soluble Vitamins:

• The term “fat-soluble vitamins” refers to vitamins that are soluble in fat.
• Fat-soluble vitamins should only be used in accordance or as directed by your doctor because excessive intake can have negative effects, such as vitamin-A overdose causes:
• Irritability
• Dry skin
• The pressure inside head or headache

Overdose of vitamin D cause:

• Bone pain
• Joint pain
• Kidney pain
• Loss of weight

Examples of fat-soluble vitamins are; vitamin-A, vitamin D, vitamin E and vitamin K.

Water Soluble Vitamins:

• Water-soluble vitamins are those that are soluble in water.
• Any excess water-soluble vitamins you consume will be expelled by your body.
• However, even at excess doses, they are not hazardous.

Examples of water-soluble vitamins are; vitamin B and vitamin C.

14. Why are vitamins crucial to our health?

Answer:

Our bodies require vitamins as development factors. The significance of each vitamin is described in depth below. However, their absence results in a number of illnesses, which are listed below in further detail:

Significance of vitamins:

Vitamin-A:

Vitamin A is crucial for healthy skin and vision.

Vitamin-B:

The creation of energy, nerve modulation, and skin health all depend on vitamin B.

Vitamin-C:

Blood vessels, gum strength, wound healing, and cold prevention all benefit from vitamin C.

Vitamin-D:

Bone and teeth gain strength from vitamin D.

Vitamin-E:

Antioxidants include vitamin E.

Vitamin-K:

Vitamin K promotes blood coagulation.

Diseases brought on by vitamin deficiencies:

Vitamin-A:

Deficiency of vitamin-A causes night blindness and dryness of the skin.

Vitamin-B:

Anaemia, gum disease, tongue irritation, and skin problems are all brought on by vitamin-B deficiency.

Vitamin-C:

Deficiency of vitamin-C causes scurvy.

Vitamin-D:

Osteomalacia and rickets are brought on by vitamin D deficiency.

Vitamin-E:

Deficiency of vitamin-E causes sterility and hemolysis of red blood cells (RBC’s)

Vitamin-K:

Delay in blood clotting haemorrhage is brought on by vitamin K deficiency.

15. What significance do nucleic acids have?

Answer:

Nucleic acids are nucleotide polymers. They are found in every living cell. They work as brains for a cell. They are of two types given below:

1. DNA
2. RNA

Significance of DNA:

• DNA is the genetic substance that makes up a cell’s nucleus.
• It stores genetic information and transmits it to the organism as it grows.
• For instance, in humans, the fertilized egg transmits the instructions for creating the head, liver, heart, kidney, hands, and legs.
• Each DNA helix is constructed of nucleotides, which are made up of phosphate groups, nitrogenous bases, and deoxyribose sugar (pentose sugar).
• Nitrogenous bases are organized in pairs in a strand.
• Each base pair in a strand represents a code.
• Each code contains genetic data, which is utilized to synthesize proteins.
• DNA is the carrier of genetic information from one generation to the next.

Significance of RNA:

RNA receives genetic information from DNA. After reading the information, RNA quickly makes protein.

• Describe the value of agricultural and nutritional science.

Answer:

• We are aware of the daily population growth.
• Crop productivity, processing, and sustainability are all covered by the agricultural sciences because humans need to eat.
• The nutritional sciences are important because they study how people and other animals eat, digest, and use their food.

16. Describe how vegetable oil is hydrogenated.

Answer:

• The process known as hydrogenation can turn plant-derived oils, which are liquid at ambient temperature, into ghee, which is solid at room temperature.
• Hydrogen addition is known as hydrogenation.
• The double covalent bond between the carbon atoms in oils causes them to be unsaturated by nature.
• By adding an H₂ molecule, this unsaturated oil can be transformed into ghee (saturated substance).
• Below is a general reaction diagram for hydrogenating oil.

17. Enlist the commercial applications of enzymes.

Answer:

Commercial uses of enzymes:

Proteins are the foundation of enzymes. They function as biological catalysts. Commercial applications for enzymes include:

• Food baking,
• Brewing,
• Stain-removal detergents,
• Fermented goods,
• Pharmaceuticals,
• Textiles,
• Leather processing,
• Chemical manufacturing,
• Food and beverage production
• Biofuels.

18. Describe how dextrose is employed in drips.

Answer:

• When patients are unable to consume carbohydrates orally owing to dehydration or for other reasons, doctors inject them with dextrose intravenously using drips.
• Drips have a dextrose sugar content of 5% m/v.

Note:

 A 100 cm³ solution is prepared when 5g of dextrose sugar dissolves in a 5 percent m/v ratio of water.

19. Sort the following vitamins that are water-soluble.

Vitamin-A,   Vitamin-C,    Vitamin-E,    Vitamin-B

Answer:

Water soluble vitamins:

• Water soluble vitamins are vitamin-B and vitamin-C.
• While vitamin-A and vitamin-E are fat soluble vitamins.

20. Compare the constituents that both proteins and carbohydrates include.

Answer:

Protein Components	Carbohydrate Components
Amino acids, which are made up of  H atom, an amino group, a carboxyl group, and an alkyl group, are the protein’s basic building blocks.	Carbohydrates are made up of tiny units known as monomers, such as glucose, fructose, and galactose. These monomers solely include the atoms C, H, and O.
Peptide bonds hold amino acids together.	Glycosidic linkages hold carbohydrate monomers together.

21. What is the name of the chemical interaction that two amino acids make when a protein is created?

Answer:

Peptide bonds are the name of the bond that develops between two amino acids during the synthesis of proteins.

22. How many water molecules must be present for a disaccharide to transform into a monosaccharide? Use a chemical equation as an example.

Answer:

• To hydrolyze into two monomer units, disaccharide needs one water molecule.
• Sucrose, lactose and maltose are disaccharides and they need one water molecule to hydrolyze into its respective monomers.
• The illustration is given below:

23. Each of the molecules below should have a drawing of its structure.

1. An amino acid having –CH₃ as R group
2. A protein with two amino acids

Answer:

a)

b)

24. Differentiate between RNA and DNA?

Answer:

Deoxyribonucleic acid (DNA)

• DNA is the genetic substance that makes up a cell’s nucleus.
• It stores genetic information and transmits it to the organism as it grows.
• For instance, in humans, the fertilized egg transmits the instructions for creating the head, liver, heart, kidney, hands, and legs.
• DNA has a double helix structure, which is a spiral made of two strands that spiral over one another with the aid of hydrogen bonds.
• J. Watson and Francis Crick discovered the structure of DNA in 1953.
• They won the Nobel Prize for their efforts.
• Each DNA helix is constructed of nucleotides, which are made up of phosphate groups, nitrogenous bases, and deoxyribose sugar (pentose sugar).
• Nitrogenous bases are organized in pairs in a strand.
• Each base pair in a strand represents a code.
• Each code contains genetic data, which is utilized to synthesize proteins.
• DNA is the carrier of genetic information from one generation to the next.

Ribonucleic acid (RNA):

• RNA is a single-stranded structure.
• Additionally, it is a polymer of nucleotides that contain phosphate group, ribose sugar, and nitrogenous bases (in RNA ribose sugar and in DNA deoxyribose sugar).
• DNA transmits genetic data to RNA. RNA reads the data and immediately produces protein.

25. An essential reaction in the food industry is hydrogenation. Please explain this statement.

Answer:

Yes, hydrogenation is a crucial process in the food sector because it allows us to change ghee, an unsaturated substance with a high fat and calorie content, into oil, a saturated substance with a lower fat and calorie content.

26. List the vitamins’ origins.

Answer:

Origins of Vitamins:

Vitamin-A:

Green vegetables, milk, butter, fish oil, and eggs all contain vitamin A.

Vitamin-B:

Meal, bread, rice, yeast, liver, soybeans, and green vegetables all contain vitamin B.

Vitamin-C:

Oranges, lemons, tomatoes, and green vegetables all contain vitamin C.

Vitamin-D:

Fish oils, milk, butter, and eggs all contain vitamin D.

Vitamin-E:

Meal, bread, rice, eggs, butter, and green vegetables all contain vitamin E.

Vitamin-K:

Green vegetables and liver both contain vitamin K.

27. Indicate the roles of each vitamin.

Answer:

Roles of vitamins:

Vitamin-A:

Vitamin A is crucial for healthy skin and vision.

Vitamin-B:

The creation of energy, nerve modulation, and skin health all depend on vitamin B.

Vitamin-C:

Blood vessels, gum strength, wound healing, and cold prevention all benefit from vitamin C.

Vitamin-D:

Bone and teeth gain strength from vitamin D.

Vitamin-E:

Antioxidants include vitamin E.

Vitamin-K:

Vitamin K promotes blood coagulation.

28. List the illnesses brought on by vitamin deficiencies.

Answer:

Illnesses brought on by vitamin deficiencies:

Vitamin-A:

Deficiency of vitamin-A causes night blindness and dryness of skin.

Vitamin-B:

Anaemia, gum disease, tongue irritation, and skin problems are all brought on by vitamin-B deficiency.

Vitamin-C:

Deficiency of vitamin-C causes scurvy.

Vitamin-D:

Osteomalacia and rickets are brought on by vitamin D deficiency.

Vitamin-E:

Deficiency of vitamin-E causes sterility and hemolysis of red blood cells (RBC’s)

Vitamin-K:

Delay in blood clotting haemorrhage is brought on by vitamin K deficiency.

29. Define and depict the chemical makeup of a nucleotide.

Answer:

Nucleotides are the building blocks of nucleic acids e.g. DNA and RNA. Nucleotides are composed of:

1. Pentose sugar (either ribose or deoxyribose)
2. Nitrogenous bases
3. Phosphate group

Illustration of chemical structure of nucleotide:

30. How are amino acids classified?

Answer:

Basic and non-essential amino acids are the two categories of amino acids.

Asparagine, glycine, and other non-essential amino acids can be made by the body.

The body cannot synthesise essential amino acids, thus they must be obtained from the diet. lysine and histidine, for instance.

31. What do you know about proteins’ secondary structures?

Answer:

The shape that a lengthy polypeptide chain can survive in due to regular folding of the polypeptide chain’s backbone as a result of hydrogen bonding between > C = O and the polypeptide chain, – NH group, is known as the secondary structure of a protein.

32. The two forms of secondary structures that are seen in proteins are -helix and -pleated sheet structures. A protein’s -helix structure is stabilized by:

• Hydrogen bonding 
• Van der Waals forces are 
• Peptide bonds 
•  Interactions between dipoles

The first is hydrogen bonding.

The normal folding of the polypeptide chain’s backbone causes the -helix and -pleated sheet structures to form due to hydrogen bonding between the peptide bonds >C—O and —NH— group.

One of the most typical ways for a polypeptide chain to create all potential hydrogen connections is by twisting into a right-handed screw shape, or helix, with each amino acid residue’s -NH group hydrogen bonding to the >C=O of a neighbouring turn.

33. Name the reagents used to check the reducing nature of carbohydrates.

Answer:

The reducing nature of sugars can be verified using Tollen’s reagent and Fehling’s solution.

34.  Which of the B group vitamins can our bodies store?

(i) Vitamin B1

(ii) Vitamin B12

(iii) Vitamin B6

(iv) Vitamin B2

Answer: (ii) Vitamin B12

Reason: Since water-soluble vitamins are eliminated in urine and cannot be kept by the body, they must be frequently ingested (except for vitamin B12).

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