- Understand the chemical composition of living organisms.
- Analyze the differences in elemental composition between living and non-living matter.
- Identify primary and secondary metabolites in biological systems.
- Classify biomolecules into micromolecules and macromolecules.
- Describe the structure and function of proteins, nucleic acids, polysaccharides, and lipids.
- Explain the role of enzymes in biochemical reactions and their classification.
- Discuss the importance of co-factors in enzyme activity.
- Recognize the significance of metabolic compounds in human welfare.
Biomolecules
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Revision Notes & Summary
TopChapter 9: Biomolecules
9.1 How to Analyse Chemical Composition?
- Living organisms are composed of various chemicals, including elements and compounds.
- Elemental analysis can be performed on plant, animal, or microbial tissues to obtain a list of elements such as carbon, hydrogen, and oxygen.
- The relative abundance of carbon and hydrogen is higher in living organisms compared to non-living matter.
9.2 Primary and Secondary Metabolites
- Primary Metabolites: Compounds essential for normal physiological processes (e.g., amino acids, sugars).
- Secondary Metabolites: Compounds found in plants, fungi, and microbes that do not have identifiable functions but are useful to humans (e.g., alkaloids, flavonoids).
Table 9.3: Some Secondary Metabolites
- Pigments: Carotenoids, Anthocyanins
- Alkaloids: Morphine, Codeine
- Terpenoids: Monoterpenes, Diterpenes
- Essential Oils: Lemon grass oil
- Toxins: Abrin, Ricin
- Drugs: Vinblastin, Curcumin
9.3 Biomacromolecules
- Biomolecules can be classified into micromolecules (molecular weight < 1000 Da) and macromolecules (molecular weight ≥ 10,000 Da).
- Macromolecules include proteins, nucleic acids, polysaccharides, and lipids.
9.4 Proteins
- Proteins are polypeptides formed by amino acids linked by peptide bonds.
- There are 20 types of amino acids, and proteins serve various functions, including:
- Collagen: Intercellular ground substance
- Trypsin: Enzyme
- Insulin: Hormone
- Antibodies: Fight infectious agents
- Receptors: Sensory reception
Table 9.5: Some Proteins and their Functions
| Protein | Functions |
|---|---|
| Collagen | Intercellular ground substance |
| Trypsin | Enzyme |
| Insulin | Hormone |
| Antibody | Fights infectious agents |
| Receptor | Sensory reception |
| GLUT-4 | Enables glucose transport into cells |
9.5 Polysaccharides
- Polysaccharides are long chains of sugars, such as cellulose (homopolymer of glucose) and glycogen (energy storage in animals).
- They can have reducing and non-reducing ends and may form helical structures.
9.6 Nucleic Acids
- Nucleic acids consist of nucleotides and serve as genetic material (DNA and RNA).
9.7 Structure of Proteins
- Proteins have a hierarchy of structures: primary, secondary, tertiary, and quaternary.
9.8 Enzymes
- Enzymes are proteins that catalyze biochemical reactions, requiring optimal conditions for activity.
- They lower the activation energy of reactions and exhibit substrate specificity.
Practice Test – MCQs, True/False
TopMultiple Choice Questions
A.
Amino acids
B.
Nucleotides
C.
Fatty acids
D.
Monosaccharides
Correct Answer: B
Solution:
Nucleic acids are composed of nucleotides, which are the building blocks of DNA and RNA.
Chapter Concept:
Nucleic Acids
A.
Alkaloids
B.
Amino acids
C.
Flavonoids
D.
Essential oils
Correct Answer: B
Solution:
Primary metabolites include amino acids, which are essential for physiological processes.
Chapter Concept:
Biomolecules and Metabolites
A.
Phospholipids are primarily used for energy storage in cells.
B.
Phospholipids form the structural basis of cell membranes due to their amphipathic nature.
C.
Phospholipids are involved in the synthesis of proteins.
D.
Phospholipids serve as enzymes in metabolic pathways.
Correct Answer: B
Solution:
Phospholipids are essential components of cell membranes because they have hydrophilic heads and hydrophobic tails, allowing them to form bilayers that separate the internal environment of the cell from the external environment.
Chapter Concept:
Lipids and Their Functions
A.
Starch is a polymer of eta-glucose, while cellulose is a polymer of eta-glucose.
B.
Starch is a polymer of eta-glucose, while cellulose is a polymer of -glucose.
C.
Starch is a polymer of -glucose, while cellulose is a polymer of eta-glucose.
D.
Both starch and cellulose are polymers of -glucose.
Correct Answer: C
Solution:
Starch consists of -glucose units, forming helical structures, whereas cellulose is composed of eta-glucose units, forming linear chains.
Chapter Concept:
Biomolecules and Metabolites
A.
Increasing the temperature to 50°C while maintaining the pH at 7.4
B.
Decreasing the pH to 5.0 while maintaining the temperature at 37°C
C.
Increasing the substrate concentration beyond saturation point
D.
Adding a competitive inhibitor that resembles the substrate
Correct Answer: A
Solution:
Increasing the temperature to 50°C can lead to denaturation of the enzyme, significantly decreasing its activity. Enzymes generally function optimally within a narrow temperature range, and high temperatures can disrupt their tertiary structure.
Chapter Concept:
Factors Affecting Enzyme Activity
A.
Oxidoreductases
B.
Lyases
C.
Isomerases
D.
Ligases
Correct Answer: C
Solution:
Isomerases are enzymes that catalyze the rearrangement of atoms within a molecule, resulting in the conversion of one isomer to another, including optical, geometric, or positional isomers.
Chapter Concept:
Enzyme Classification and Cofactors
A.
Proteins
B.
Nucleic acids
C.
Polysaccharides
D.
Lipids
Correct Answer: D
Solution:
Lipids are not considered polymers because they do not consist of repeating monomeric units, unlike proteins, nucleic acids, and polysaccharides.
Chapter Concept:
Biomacromolecules
A.
The sequence of amino acids in the polypeptide chain
B.
The three-dimensional folding of the protein
C.
The arrangement of multiple polypeptide subunits
D.
The formation of alpha-helices and beta-pleated sheets
Correct Answer: A
Solution:
The primary structure of a protein is defined by the linear sequence of amino acids in its polypeptide chain.
Chapter Concept:
Biomacromolecules
A.
Silicon ()
B.
Carbon ()
C.
Calcium ()
D.
Sodium ()
Correct Answer: B
Solution:
Carbon is found in higher relative abundance in living organisms compared to non-living matter such as the earth's crust.
Chapter Concept:
Chemical Composition of Living Organisms
A.
The enzyme's substrate specificity will increase.
B.
The enzyme will become a competitive inhibitor.
C.
The enzyme will lose its ability to bind to its substrate.
D.
The enzyme will catalyze reactions at a higher rate.
Correct Answer: C
Solution:
A structural change in the active site of an enzyme can lead to a loss of substrate binding ability, thereby reducing or eliminating the enzyme's catalytic activity.
Chapter Concept:
Proteins and Their Biological Functions
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Biomolecules
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Locked • AI Weakness TrackerTrue or False
Correct Answer: True
Solution:
Amino acids incorporated into proteins are indeed alpha-amino acids, characterized by having both an amino group and a carboxyl group attached to the same carbon, known as the alpha carbon.
Chapter Concept :
Amino Acids and Peptide Bonds
Correct Answer: True
Solution:
Enzymes are divided into six classes: oxidoreductases, transferases, hydrolases, lyases, isomerases, and ligases. Each class is further divided into multiple subclasses based on specific reactions they catalyze.
Chapter Concept :
Enzyme Classification and Cofactors
Correct Answer: True
Solution:
Primary metabolites are crucial for basic physiological functions, whereas secondary metabolites, such as alkaloids and flavonoids, are not essential for survival but have important ecological roles and applications in human industries.
Chapter Concept :
Biomolecules and Metabolites
Correct Answer: True
Solution:
Amino acids are indeed characterized by having both an amino group and a carboxyl group attached to the α-carbon, making them α-amino acids.
Chapter Concept :
Amino Acids and Peptide Bonds
Correct Answer: True
Solution:
Enzymes generally function in a narrow range of temperature and are denatured by heat, losing their catalytic activity.
Chapter Concept :
Factors Affecting Enzyme Activity
Correct Answer: True
Solution:
Enzymes are proteins that catalyze biochemical reactions by lowering the activation energy, which enhances the rate of the reactions.
Chapter Concept :
Enzyme Function and Kinetics
Correct Answer: True
Solution:
Cofactors are non-protein components that bind to enzymes and are essential for their catalytic activity. They can be metal ions or organic molecules.
Chapter Concept :
Enzyme Classification and Cofactors
Correct Answer: True
Solution:
Analysis of living tissues shows that the relative abundance of carbon and hydrogen is higher in living organisms than in non-living matter such as the earth's crust.
Chapter Concept :
Chemical Composition of Living Organisms
Correct Answer: True
Solution:
Lipids, including fatty acids and phospholipids, are crucial for forming cell membranes and storing energy, primarily because of their hydrophobic characteristics.
Chapter Concept :
Lipids and Their Functions
Correct Answer: True
Solution:
Biomacromolecules are indeed polymers with high molecular weights, crucial for cellular structure and function.
Chapter Concept :
Biomacromolecules
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