1. Diversity in Living Organisms:

  • Living organisms show wide diversity in nature. A key question is whether all living organisms are made up of the same chemicals (elements and compounds) as non-living things.
  • Elemental Analysis: When scientists analyze plant, animal, or microbial tissues, they find elements like carbon, hydrogen, oxygen, nitrogen, and others. These same elements are present in non-living things (like Earth’s crust). However, the proportions of these elements differ:
    • In Living Organisms: Higher amounts of carbon and hydrogen compared to other elements.
    • In Non-Living Matter: Elements like oxygen, silicon, and magnesium are more abundant.

2. Chemical Analysis of Living Organisms:

  • To study the chemical composition of living organisms, scientists perform a chemical analysis of tissues.
  • The tissue is ground in a special acid (like trichloroacetic acid) to separate compounds into two parts:
    • Filtrate (Acid-soluble pool): Contains thousands of organic compounds.
    • Retentate (Acid-insoluble fraction): Contains substances like proteins, nucleic acids, polysaccharides, and lipids.
  • The organic compounds extracted from living tissues are called biomolecules.

3. Inorganic Elements in Living Organisms:

  • After drying a tissue, scientists burn it to remove all carbon compounds. The remaining ash contains inorganic elements like calcium, magnesium, and compounds like phosphate and sulfate.
  • These inorganic elements are also present in living tissues and play important roles in various biological processes.

4. Classification of Biomolecules:

  • Amino Acids: Organic compounds containing both an amino group (-NH₂) and a carboxyl group (-COOH). These are the building blocks of proteins. There are 20 amino acids commonly found in proteins, each with a unique “R group” (side chain).
  • Lipids: Fatty acids and glycerol are key components of lipids. Fatty acids may be saturated (no double bonds) or unsaturated (one or more double bonds). Lipids form important structures like cell membranes. Some lipids also contain phosphorus, such as phospholipids, which are found in cell membranes.
  • Nucleotides: Found in DNA and RNA. Nucleotides consist of a nitrogenous base (e.g., adenine, thymine), a sugar, and a phosphate group. They are the building blocks of nucleic acids and store genetic information.

5. Metabolites:

  • Primary Metabolites: Essential for the survival of the organism, such as amino acids, sugars, and fatty acids. They play known roles in metabolism.
  • Secondary Metabolites: These are found in plants, fungi, and microbes. Examples include alkaloids (e.g., morphine), flavonoids, and essential oils. While their exact functions are not always clear, many are valuable to humans for medicines, spices, and pigments.

6. Biomacromolecules:

  • Macromolecules: Large molecules with high molecular weights (10,000 daltons or more), such as proteins, nucleic acids, polysaccharides, and some lipids.
  • These macromolecules are polymers made up of smaller units. For example, proteins are polymers of amino acids, and nucleic acids are polymers of nucleotides.

7. Why Lipids Are Classified as Macromolecules:

  • Although lipids are smaller than true macromolecules, they form part of cell membranes and other structures. When cells are broken down, these membrane fragments (which contain lipids) end up in the acid-insoluble fraction, making lipids part of the macromolecular fraction.

8. Composition of Living Cells:

  • The composition of living cells includes:
    • Water: 70-90% of the cell mass.
    • Proteins: 10-15%.
    • Carbohydrates: 3%.
    • Lipids: 2%.
    • Nucleic Acids: 5-7%.
    • Ions: 1%.
  • Water is the most abundant chemical in cells, and it plays a crucial role in biological reactions and maintaining cell structure.

Additional Insights for Competitive Exams:

  • Understanding the chemical composition of living organisms is crucial for biology-based exams, as questions may ask about the types of biomolecules, their functions, and their roles in metabolism.
  • Concepts like primary vs. secondary metabolites, protein structures, and the molecular composition of cells are often tested.
  • Know the types of organic compounds (e.g., amino acids, lipids, nucleotides) and their functions in cells. Also, be familiar with terms like monomers, polymers, and polymerization.

Proteins:

  • Definition: Proteins are made of long chains of amino acids linked by peptide bonds. These chains are called polypeptides.
  • Amino Acids: There are 20 types of amino acids (like alanine, cysteine, proline, tryptophan, and lysine). A protein is a heteropolymer because it’s made from different amino acids, unlike a homopolymer that only has one type of monomer.
  • Essential vs. Non-essential Amino Acids: Some amino acids are essential, meaning they must be obtained through food, while non-essential amino acids are made by the body.
  • Functions: Proteins serve various functions in the body, such as:
    • Transport (e.g., GLUT-4 transports glucose)
    • Fighting infections (e.g., antibodies)
    • Hormones (e.g., insulin)
    • Enzymes (e.g., trypsin)
  • Collagen: The most abundant protein in animals.
  • RuBisCO: The most abundant protein on Earth, found in plants, involved in photosynthesis.

Polysaccharides:

  • Definition: Polysaccharides are long chains of sugar molecules (monosaccharides), such as glucose, forming complex carbohydrates.
  • Examples:
    • Cellulose: A polymer of glucose; it’s a homopolymer and makes up plant cell walls.
    • Starch: A storage form of energy in plants.
    • Glycogen: A storage form of energy in animals.
    • Inulin: A polymer of fructose.
    • Chitin: Found in the exoskeletons of arthropods.
  • Structure:
    • Polysaccharides can be branched (like glycogen) or linear (like cellulose).
    • Starch can form helical structures that bind iodine (I2), giving a blue color.

Nucleic Acids (DNA and RNA):

  • Building Block: Nucleotides, made of a sugar (ribose or deoxyribose), phosphate group, and a nitrogenous base (adenine, guanine, cytosine, uracil, thymine).
  • Types:
    • DNA: Contains deoxyribose and thymine.
    • RNA: Contains ribose and uracil.
  • Nitrogenous Bases:
    • Purines: Adenine (A) and Guanine (G).
    • Pyrimidines: Cytosine (C), Thymine (T), Uracil (U).

Protein Structure:

  • Primary Structure: Sequence of amino acids in a polypeptide chain.
  • Secondary Structure: Local folding into structures like alpha-helix and beta-pleated sheets.
  • Tertiary Structure: 3D folding of the entire protein, essential for its function.
  • Quaternary Structure: When proteins consist of more than one polypeptide chain (subunit), like hemoglobin which has 4 subunits.

Enzymes:

  • Definition: Most enzymes are proteins that catalyze (speed up) chemical reactions.
  • Active Site: The part of the enzyme where the substrate binds and undergoes a reaction.
  • Enzyme Action:
    1. Substrate Binding: The enzyme binds the substrate at its active site.
    2. Transition State: The substrate forms an unstable transition state, which facilitates the reaction.
    3. Product Formation: The enzyme releases the product and is free to catalyze another reaction.
  • Thermal Stability: Enzymes work best at specific temperatures, usually around 37°C. Some enzymes, like those from thermophilic organisms, can work at very high temperatures.
  • Factors Affecting Enzyme Activity:
    • Temperature and pH: Enzymes have an optimum temperature and pH at which they work best.
    • Substrate Concentration: As substrate concentration increases, enzyme activity increases until a maximum point (Vmax) is reached.

Enzyme Inhibition:

  • Competitive Inhibition: When an inhibitor competes with the substrate for the enzyme’s active site, reducing enzyme activity (e.g., malonate inhibiting succinate dehydrogenase).
  • Non-competitive Inhibition: Inhibitor binds elsewhere, changing the enzyme’s shape, reducing its activity.

Enzyme Classification:

Enzymes are classified into 6 groups:

  1. Oxidoreductases: Catalyze redox reactions (e.g., dehydrogenases).
  2. Transferases: Transfer groups between substrates (e.g., kinases).
  3. Hydrolases: Catalyze hydrolysis reactions (e.g., lipases).
  4. Lyases: Remove groups to form double bonds (e.g., decarboxylases).
  5. Isomerases: Catalyze isomerization reactions (e.g., racemases).
  6. Ligases: Join two molecules using ATP (e.g., DNA ligase).

Co-factors:

  • Prosthetic Groups: Organic molecules tightly bound to the enzyme (e.g., haem in peroxidase).
  • Coenzymes: Organic molecules that temporarily associate with the enzyme (e.g., NAD+).
  • Metal Ions: Required for enzyme function, e.g., zinc in carboxypeptidase.

Key Concepts for Competitive Exams:

  • Protein Functions: Transport, defense, enzymes, and structural roles.
  • Enzyme Kinetics: How enzymes speed up reactions and the effects of substrate concentration, temperature, and pH.
  • Enzyme Inhibition: Understanding different types of inhibition (competitive and non-competitive).
  • Macromolecules: The importance of proteins, nucleic acids, and polysaccharides in biological systems.
  • Thermodynamics of Enzymes: Activation energy, transition states, and how enzymes lower activation energy to speed up reactions.

These notes help in understanding the foundational concepts for competitive exams, particularly in biology and biochemistry.

These all are the notes of chapter 9. And important questions are below HERE. *#THANKS FOR VISITING, VISIT AGAIN #*😊

1. What are living organisms made of?

Answer:
Living organisms are made of the same elements (like carbon, hydrogen, oxygen, and nitrogen) as non-living things, but in different amounts. For example:

  • Living organisms have more carbon and hydrogen.
  • Non-living things like rocks have more oxygen, silicon, and magnesium.

2. What are biomolecules?

Answer:
Biomolecules are organic compounds found in living organisms. They are divided into two groups:

  1. Acid-soluble (small molecules): Amino acids, sugars, and lipids.
  2. Acid-insoluble (large molecules): Proteins, nucleic acids, polysaccharides, and some lipids.

3. What are primary and secondary metabolites?

Answer:

  • Primary Metabolites: Essential for survival, like amino acids, sugars, and fatty acids.
  • Secondary Metabolites: Found in plants, fungi, and microbes, such as alkaloids (e.g., morphine), pigments, and essential oils. These are not essential for survival but are useful (e.g., medicines, spices).

4. What are macromolecules? Why are lipids included?

Answer:
Macromolecules are large molecules like proteins, nucleic acids, and polysaccharides. Lipids are included because they form cell membranes, although they are smaller than other macromolecules.

5. What is the composition of living cells?

Answer:
Living cells are made up of:

  • Water: 70-90% (most abundant).
  • Proteins: 10-15%.
  • Carbohydrates: 3%.
  • Lipids: 2%.
  • Nucleic acids: 5-7%.
  • Ions: 1%.

6. What are proteins and their functions?

Answer:

  • Proteins are made of amino acids linked by peptide bonds.
  • There are 20 types of amino acids, classified as essential (from food) or non-essential (made by the body).
    Functions of Proteins:
  • Transport (e.g., hemoglobin for oxygen).
  • Defense (e.g., antibodies).
  • Hormones (e.g., insulin).
  • Enzymes (e.g., trypsin).
  • Structural support (e.g., collagen in skin).

7. What are polysaccharides and their types?

Answer:
Polysaccharides are long chains of sugar molecules. Examples:

  • Cellulose: Provides strength to plant cell walls.
  • Starch: Stores energy in plants.
  • Glycogen: Stores energy in animals.
  • Chitin: Found in insect exoskeletons.

8. What are nucleic acids, and what do they do?

Answer:
Nucleic acids like DNA and RNA store genetic information.

  • DNA: Contains the genetic code.
  • RNA: Helps make proteins.

Structure: Made of nucleotides, each containing:

  1. A sugar (ribose or deoxyribose).
  2. A phosphate group.
  3. A nitrogen base (adenine, guanine, cytosine, thymine, or uracil).

9. What are enzymes, and how do they work?

Answer:
Enzymes are proteins that speed up chemical reactions without being used up.

  • They work by binding to a substrate at the active site, forming a product.
  • Enzymes lower the activation energy needed for reactions.

10. What factors affect enzyme activity?

Answer:

  1. Temperature: Work best at an optimum temperature (around 37°C in humans).
  2. pH: Each enzyme has an optimum pH (e.g., stomach enzymes work in acidic pH).
  3. Substrate Concentration: Enzyme activity increases with more substrate until it reaches a maximum.

11. What are inhibitors, and how do they affect enzymes?

Answer:
Inhibitors slow down enzyme activity.

  • Competitive inhibitors: Compete with the substrate for the active site.
  • Non-competitive inhibitors: Bind elsewhere on the enzyme, changing its shape.

12. How are enzymes classified?

Answer:
Enzymes are grouped based on their functions:

  1. Oxidoreductases: Catalyze redox reactions (e.g., dehydrogenases).
  2. Transferases: Transfer groups (e.g., kinases).
  3. Hydrolases: Break down molecules with water (e.g., lipases).
  4. Lyases: Remove groups to form double bonds (e.g., decarboxylases).
  5. Isomerases: Rearrange molecules (e.g., racemases).
  6. Ligases: Join molecules using ATP (e.g., DNA ligase).

13. What is the difference between primary and secondary structures of proteins?

Answer:

  • Primary Structure: The sequence of amino acids.
  • Secondary Structure: Folding into alpha-helices or beta-sheets.
  • Tertiary Structure: 3D shape of the protein.
  • Quaternary Structure: Combination of multiple polypeptide chains (e.g., hemoglobin has 4 chains).

14. What are the functions of biomolecules like proteins, lipids, and nucleic acids?

Answer:

  • Proteins: Structure, transport, enzymes, hormones.
  • Lipids: Energy storage, cell membranes, hormones.
  • Nucleic Acids: Genetic information storage and protein synthesis.