Biomolecules — Short Questions

• Carbohydrates are the primary source of energy. Glucose is used by cells to produce energy through cellular respiration.
• Dietary fibre contains undigestible carbohydrates e.g., cellulose. It helps to maintain the proper bowel movements.
• Pentoses (ribose and deoxyribose) are essential parts of nucleic acids (RNA and DNA respectively).
• Plants convert their monosaccharides to disaccharides like sucrose to transport monosaccharides between body parts.

Monosaccharides have sweet taste, disaccharides are less sweet in taste while polysaccharides are tasteless. Therefore the sweetness decreases as the complexity of carbohydrates increases.

1. Pentoses (5C) and hexoses (6 C) are common monosaccharides.
2. Sucrose and maltose are common disaccharides.

Sucrose (Table sugar) is made of two monosaccharides i.e. glucose and fructose.

Starch is a storage polysaccharide found in plants. It is composed of glucose units.

Proteins are made up of monomers called amino acids. Different proteins contain different numbers of amino acids.
Example
Insulin protein has 51 amino acids and haemoglobin has 574 amino acids.
Structure
An amino acid is an organic molecule made of an amino group (NH2), a carboxyl group (COOH), a hydrogen group (H) and a side group (R) are attached to a central atoms.

R
|
H2N – C – COOH
|
H

Lipids are composed of glycerol and fatty acids.
1. Glycerol is an alcohol having three carbons and each carbon has hydroxyl group.

H
|
H – C – OH
|
H – C – OH
|
H – C – OH
|
H
Glycerol

2. Fatty acids are long hydrocarbon chains with carboxyl group (COOH) at the end. Fatty acids may be saturated and unsaturated fatty acids.

H H H H H O
| | | | | ||
H – C – C – C – C – C – OH
| | | | | |
H H H H H

Saturated Fatty Acid

H H H H H O
| | | | | ||
H – C – C – C – C – C – OH
| | | | |
H H H H

Unsaturated Fatty Acid

There are three types of RNA.
a. Messenger RNA (mRNA): Carries the genetic information from DNA to the ribosomes during protein synthesis.
b. Transfer RNA (tRNA): Transfers specific amino acids to the ribosomes, ensuring the correct sequence during protein synthesis.
c. Ribosomal RNA (rRNA): Constitutes the structural and functional components of ribosomes, the cellular machinery for protein synthesis.

DNA contains the hereditary information. This information is in the form of a sequence determines the order of amino acids during protein synthesis. The segment of DNA in which the sequence of nucleotides determines the synthesis of a proteins is called a gene. During reproduction, DNA is passed from one generation to the next. In this way, DNA carries the heredity information to the next generation.

i. Biochemistry and molecular biology

Biochemistry | Molecular Biology
a) Biochemistry is the study of chemical processes that occur within living organisms (e.g. photosynthesis). | a) Molecular biology is the specialized branch of biochemistry that is mainly concerned about the structure and functions of the biomolecules, e.g. carbohydrates, proteins and lipids.
b) Biochemistry is related to both biology and chemistry, that is why biochemistry solves the problems of living organisms by using the knowledge and techniques of chemistry. | b) In molecular biology, the interaction of bio molecules within the cells and biochemical processes like DNA replication, transcription and translation is studied.

ii. Structure of DNA and RNA

Structure of DNA | Structure of RNA
• DNA is made of deoxyribo nucleotides (de-oxy-ribo-nucleotides). | • RNA is single-stranded. Its strand consists of ribonucleotides.
• In this nucleotide, the pentose sugar is deoxyribose while in nitrogenous base may be adenine (A), thymine (T), cytosine (C) or guanine (G). | • A ribonucleotide contains ribose sugar instead of deoxyribose. In a ribonucleotide, the nitrogenous base may be adenine (A) uracil (U) cytosine (C) or guanine (G).

iii. Composition of DNA and RNA

RNA | DNA
• RNA is single stranded. Its strand consists of ribonucleotides. | • DNA is made of deoxyribonucleotides (de-oxy-ribo-nucleotides).
• A ribonucleotide contains ribose sugar instead of deoxyribose. In a ribonucleotide, the nitrogenous base may be adenine (A) uracil (U) cytosine (C) or guanine (G). | • In this nucleotide, the pentose sugar is deoxyribose while nitrogenous base may be adenine (A), thymine (T), cytosine (C), or guanine (G).

iv. Monosaccharides and Disaccharides

Monosaccharides | Disaccharides
Monosaccharides (simple sugars) are made of single sugar molecule. They are easily soluble in water and have sweet taste. They may have 3 to 7 carbon atoms. Pentoses (5 C) and hexoses (6 C) Examples
• Ribose (C5H10C4) and deoxyribose (C5H10O4) are pentoses.
• Glucose, fructose, and galactose are hexoses (C6H12O6). | They are made of two monosaccharides units. They are less soluble in water and are less sweet in taste.
Examples
• Sucrose (table sugar) is made of two monosaccharides i.e., glucose and fructose.
• Maltose is made of two glucose molecules.

v. Glycogen and Starch

Glycogen | Starch
i. Glycogen is the animal starch polysaccharide mainly stored in liver and muscles. | i. Starch is a storage polysaccharide stored in plants.
ii. It is broken down into glucose when energy is needed. | ii. It is composed of glucose units.

vi. Saturated and unsaturated fatty acids

Saturated Fatty Acids | Unsaturated Fatty Acids
Saturated fatty acids have internal carbon atoms bonded with maximum number of hydrogen atoms. They do not have double bonds between carbon atoms. Saturated fatty acids are solid at room temperature.
Example
Palmitic acid.

H H H H H O
| | | | | ||
H – C – C – C – C – C – OH
| | | | | |
H H H H H

Saturated fatty acid | Unsaturated fatty acids have one or more double bonds between carbon atoms. They are liquid at room temperature.
Example
Oleic acid.

H H H H H O
| | | | | ||
H – C – C – C – C – C – OH
| | | | |
H H H H

Unsaturated fatty acid

vii. Fats and oils

Fats | Oils
Fats contain saturated fatty acids and so are solid at room temperature e.g., animal fats. | Oils contain unsaturated fatty acids and so are liquid at room temperature e.g., plant oils such as olive oil, corn oil, and coconut oil.

Proteins | Lipids | Carbohydrates
(1) One gram of protein has 4 Kcal of energy | One gram of lipids provides 9.1 Kcal energy which is double than carbohydrates or proteins. | 4 Kcal per gram of energy is released when glucose is broken down in the cell.
(2) Proteins can also be used for gaining energy | Lipids act as energy storage in fat cells, liver and in blood. | Carbohydrates are the major source of useable and stored energy in the cells of living organisms.

Biochemistry is the study of different chemical compounds and the chemical processes taking place within the living organisms.
Important Role of Biochemistry
Biochemistry is related to both biology and chemistry. Therefore, biochemistry solves the problems faced by living organisms by using the knowledge and techniques of chemistry. Similarly, knowledge of biochemistry is essential to study the physiology, cell biology and anatomy of organisms because life processes such as photosynthesis, respiration, digestion, inheritance are explained in biochemical terms.

Plant seeds are most common source of proteins like beans, lentils, peas, nuts.

The primary structure of a protein is important because it determines the protein's three dimensional shape, which in turn determines its function.

Keratin in hair and nails and collagen in tissues provide structure to various parts of the body.

Fatty acids in triglycerides can be either saturated or unsaturated. A fatty acid is considered saturated if there are no double bonds between carbon atoms of its chain. On the other hand, an unsaturated fatty acid has one or more double bonds, formed by the removal of hydrogen atoms from the carbon skeleton.

Lipids are organic compounds made up of carbon, hydrogen and oxygen. They have little or no affinity for water (hydrophobic in nature) due to the presence of mostly hydrocarbons. That is why they are insoluble in water but soluble in organic solvents such as alcohol.

Small piece of huge DNA molecule in the chromosome is called gene. Genes actually store and control the hereditary information. Each chromosome is made up of large number of genes.

Molecular biology looks at the molecule related to genetic information, particularly DNA. It seeks to understand how DNA is made, copied and used providing insight into heredity, genetic variations and the basics of life.

Transcription | Translation
It is a process in which specific sequence of DNA nucleotides is copied in the form of messenger RNA (mRNA). It takes place in the nucleus. | The mRNA carries the sequence of its nucleotides to ribosomes. Ribosomes read this sequence and joins specific amino acids, according to it proteins are synthesized. It takes place in the cytoplasm.

Water is essential for the functioning of biomolecules because it acts as a solvent, allowing substances to dissolve causes biochemical reactions. It transports nutrients and to maintain the structure and stability of proteins, DNA, and other biomolecules. Due to its high heat capacity, it acts as environment stabilizer. Water plays key role in hydrolysis and condensation reactions. It plays structural role in plant and animal cells. Without water, the complex processes that support life would not occur.

The amount of carbohydrates, protein, fats, and water in the listed food items may vary slightly depending on method of preparation and product variation:

Amount in grams (approximately)

Food items | Weight (gm) | Carbohydrates | Proteins | Fats | Water
Roti | 40 | 20-25 | 3-4 | 1-2 | 10-15
Burger | 100 | 30-40 | 15-25 | 15-25 | 20-30
Cucumber | 100 | 3-4 | 0.5-1 | 0.1-0.2 | 93-95
Egg | 100 | 0.5-1 | 6-7 | 5-6 | 35-38
Rice | 100 | 28-30 | 2-3 | 0.5-1 | 68-70
Potato fries | 100 | 35-40 | 3-4 | 15-20 | 40-50
Carrot | 100 | 9-10 | 0.9-1 | 0.2-2.3 | 85-88

Amount in percentage (approximately)

Food items | Weight (gm) | Carbohydrates | Proteins | Fats | Water
Roti | 40 | 50-62% | 7-10% | 2-5% | 25-37%
Burger | 100 | 30-40% | 15-20% | .15-25% | 20-30%
Cucumber | 100 | 3-4% | 0.5-1% | 0.1-0.2% | 95%
Egg | 100 | 1% | 12-14% | 10-12% | 70%
Rice | 100 | 28-30% | 2-3% | 0.5-1% | 70%
Potato fries | 100 | 35-40% | 3-4% | 15-20% | 40-50%
Carrot | 100 | 9-10% | 0.9-1% | 0.2-0.3% | 88%