Lecture Notes: The Journey of Life and Biological Basics

Earth's Formation and Early Conditions

• Earth formed 4.5 billion years ago as a mass of flaming rocks.
• Bombarded by meteors containing water, leading to steam and eventual cooling.
• Formation of hydrothermal vents with chemical-rich environments.

Basics of Biology and Chemistry

• Biology is fundamentally chemistry; living organisms are molecular entities.
• Key biological molecules:
  • Carbohydrates: Quick energy.
  • Lipids: Long-term energy storage, form membranes.
  • Proteins: Tissue building.
  • Nucleic Acids: DNA formation.

Enzymes and Life

• Enzymes: Proteins that catalyze chemical reactions.
• Example: Lactase breaks down lactose.

Definition of Life

• Debate among scientists.
• Characteristics: Metabolism, growth, reproduction, response to environment, cellular structure.
• Two main cell types:
  • Eukaryotes: Have membrane-bound organelles like nuclei.
  • Prokaryotes: Lack organelles, DNA freely floats.

Taxonomy and Classification

• Classification into kingdoms based on cellular and structural features.
• Unique scientific names: Genus + Species.

Homeostasis and Cell Membranes

• Homeostasis: Maintenance of stable internal conditions.
• Enzymes require specific conditions to function.
• Cell membrane: Semipermeable phospholipid bilayer.
  • Allows selective molecule passage, controls internal cell environment.

Diffusion and Energy in Cells

• Diffusion: Movement from high to low concentration.
• Use of ATP (energy) to move particles against gradients.

Photosynthesis and Cellular Respiration

• Photosynthesis: Autotrophs (plants) create glucose using light.
• Cellular Respiration: Conversion of glucose into ATP in mitochondria.
• Key molecules: Glucose, ATP, and DNA (both have nucleotide structures).

DNA and Genetic Information

• DNA: Composed of nucleotides with four bases (Adenine, Thymine, Cytosine, Guanine).
• Genes: DNA segments that code for traits.
• Transcription and Translation:
  • DNA is transcribed into mRNA.
  • mRNA is translated into proteins using ribosomes.

Genetic Variation and Inheritance

• Alleles: Different gene versions, can be dominant or recessive.
• Inheritance patterns: Dominance, co-dominance, incomplete dominance.
• Sex chromosomes and X-linked traits.

Cell Division: Mitosis and Meiosis

• Mitosis: Produces identical diploid cells for growth and repair.
• Meiosis: Produces genetically diverse haploid gametes for reproduction.

Mutations and Evolution

• Gene mutations: Changes in base sequence, can affect protein function.
• Chromosomal mutations: Large scale changes, e.g., Down syndrome.
• Natural selection drives evolution; beneficial mutations increase fitness.

Bacteria vs. Viruses

• Bacteria: Single-cell prokaryotes, treatable with antibiotics.
• Viruses: Non-cellular, require hosts to reproduce, not treatable with antibiotics.

Nervous System and Neurons

• Neurons transmit signals via electrical impulses and neurotransmitters.
• Action potentials: All-or-nothing signals for communication.
• Signal transmission: Myelin sheath facilitates faster impulse travel.

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