Life Sciences Unit II - Lecture 8

Unit II - Lecture 8

• This lecture covers fundamental life sciences topics, crucial for quizzes and tests.
• All slides are important for assessment.

Lysosome

• Specialized membrane-bound vesicles, primarily in animal cells.
• Contain hydrolytic enzymes to break down biomolecules.
• Structurally, dense granular, enclosed by a lipid bilayer.
• Internal environment has an acidic pH (4.5-5.0), optimal for enzymes.
  • Autophagy: degrades worn-out cellular components.
  • Endocytosis: degrades extracellular substances engulfed by the cell.
  • Exocytosis: expels enzymes, aids in breaking down extracellular material.
  • Often involved in white blood cell function.

Lysosome Enzymes

• Lysosomes contain numerous hydrolases (enzymes).
• Approximately 40 distinct varieties, categorized by substrates.
  • Proteases: hydrolyze proteins, creating amino acids.
  • Lipases: hydrolyze fats into fatty acids and glycerol.
  • Amylases: hydrolyze carbohydrates into simpler sugars.
  • Nucleases: hydrolyze nucleic acids (DNA/RNA).
  • Phosphoric Acid Monoesters: hydrolyze phosphoric acid esters.

Why Lysosomes are Known as Suicidal Bags

• Lysosomes have a potent arsenal of hydrolytic enzymes.
• Primary function: degrade/recycle cellular components (extraneous or aged).
• Vulnerability: Enzymes can rupture lysosomes, releasing them into cytoplasm, damaging the cell (autolysis).
• Important for cellular health/waste removal, but poses risk of cell self-destruction.

Vacuoles

• Membrane-bound organelles, in plants, fungi, some protists, animals, and bacteria.
• Compartments containing water, inorganic/organic molecules, and enzymes.
• Functions:
  • Isolating harmful materials.
  • Containing waste/small molecules/water (especially in plants).
  • Maintaining turgor pressure (shape/buoyancy for plants).
  • Maintaining an acidic internal pH.
  • Exporting unwanted substances.
  • Supporting plant structures (leaves/flowers).
  • Storing proteins needed for germination in seeds.

Centrosome and Centriole

• Centrosome: Organelle containing two centrioles.
• Centrioles: Membraneless cylindrical structures.
• Surrounded by amorphous pericentriolar material (centrosphere/kinoplasm/cytocentrum).
• Commonly called "diplosomes."
• No internal compartment.
• Found in animal cells, except amoeba.
• Absent in higher plants, but found in some stages of certain plants' life cycles.

Centriole Function

• Involved in cell division (mitosis and meiosis).
• Help organize microtubules.
• Involved in the positioning of microtubules.
• Can transform into basal bodies (forming cilia/flagella).

Chromosomes

• 23 pairs
• One from each parent
• Same length, same genes in the same position
• Chromosomes from father & mother are designated

Homologous Chromosomes

• Chromosomes having similar structures
• Same length.
• Same genes.
• Same position.

Alleles

• Specific form of a gene.
• Responsible for variations in expressed genes.
• Occur in pairs.

Mutations and Allele Frequencies

• Mutations in genes can create new phenotypes (like different eye colors).
• Allele frequency shifts over time, but some alleles remain dominant.

Cell Division (Mitosis)

• Stages: Interphase, Prophase, Metaphase, Anaphase, Telophase, Cytokinesis.
• Process where somatic cells divide to produce two genetically identical diploid cells.
• Chromosome number remains the same.

Cell Division (Meiosis)

• Process where sex cells divide to produce four genetically unique haploid gametes or cells.
• Chromosome number is halved.
• Stages: Prophase I, Metaphase I, Anaphase I, Telophase I, Prophase II, Metaphase II, Anaphase II, Telophase II, and Cytokinesis.