Overview
This lecture covers the origin of life on Earth, core concepts of biology and biochemistry, cell structure and function, genetics, cell division, evolution, and briefly touches on nervous system function.
Origins of Life & Basic Chemistry
- Earth formed 4.5 billion years ago as a hot, rocky body bombarded by space debris.
- Water arrived via space rocks and condensed as Earth cooled, leading to oceans.
- Hydrothermal vents provided hot, chemical-rich environments where life likely began.
Foundations of Biology
- Biology is the study of life, fundamentally driven by chemical reactions.
- Carbohydrates provide short-term energy; lipids store long-term energy and form membranes.
- Proteins build tissues and serve as enzymes; nucleic acids make up DNA.
Enzymes and Life’s Traits
- Enzymes are protein catalysts that speed up specific chemical reactions (e.g., lactase breaks down lactose).
- Life is defined by metabolism, growth, reproduction, response to stimuli, and being made of cells.
- All living things are cellular: eukaryotes (complex, with organelles) or prokaryotes (simple, no organelles).
Cell Structure & Homeostasis
- Eukaryotes have membrane-bound organelles; prokaryotes do not.
- Taxonomy classifies organisms based on similarities; scientific names use genus and species.
- Homeostasis maintains stable internal conditions vital for enzyme function.
- The cell membrane is a semipermeable phospholipid bilayer, controlling what enters and exits the cell.
Transport & Energy
- Diffusion: particles move from high to low concentration; osmosis is water moving towards higher solute.
- Active transport uses ATP to move particles against gradients.
- ATP stores energy in phosphate bonds, produced via cellular respiration in mitochondria.
Metabolism: Heterotrophs & Autotrophs
- Heterotrophs get glucose by consuming food; autotrophs (like plants) make glucose via photosynthesis in chloroplasts using chlorophyll.
DNA, Genes & Protein Synthesis
- DNA is a double helix of nucleotides (A, T, C, G) that hold genetic information.
- A gene is a DNA segment coding for a protein, influencing traits (e.g., eye color).
- Transcription: DNA is copied to mRNA; translation: ribosomes read mRNA to assemble protein from amino acids.
Genetics & Inheritance
- Humans have about 20,000 genes, mostly non-coding; all somatic cells contain the full genome.
- Chromosomes are condensed DNA, with each cell containing homologous pairs (one from each parent).
- Alleles are gene variants; dominant alleles mask recessive ones.
- Inheritance patterns: simple dominance, incomplete dominance (blending), codominance (both show), and X-linked traits.
Cell Division
- Mitosis creates identical diploid cells for growth/repair; meiosis forms haploid gametes with genetic variation.
- The cell cycle includes checkpoints (e.g., p53, cyclin); apoptosis removes faulty cells.
- Cancer results from uncontrolled cell division, often due to gene mutations.
Mutations & Evolution
- Mutations can be neutral, harmful, or beneficial; natural selection favors traits that improve fitness.
- Bacterial resistance to antibiotics is an example of rapid evolution.
Bacteria, Viruses & Human Systems
- Bacteria are prokaryotes, often beneficial; viruses are non-living entities that require hosts to reproduce.
- Antibiotics work on bacteria, not viruses.
- Bacteria in the gut aid digestion through symbiosis.
Nervous System Basics
- The nervous system uses neurons to transmit electrical signals (action potentials).
- The axon’s membrane potential changes due to ion flow, enabling signal transmission.
- Myelin sheaths speed up signal conduction; neurotransmitters cross the synaptic gap between neurons.
Key Terms & Definitions
- Enzyme — protein catalyst that speeds up specific biochemical reactions.
- Eukaryote — cell with nucleus and organelles.
- Prokaryote — cell without nucleus or membrane-bound organelles.
- Homeostasis — maintenance of stable internal environment.
- Diffusion — passive movement from high to low concentration.
- Osmosis — diffusion of water towards higher solute concentration.
- ATP — main energy carrier in cells.
- Autotroph — organism that produces its own food via photosynthesis.
- Gene — DNA segment coding for a protein.
- Allele — different form of a gene.
- Mitosis — cell division producing identical cells.
- Meiosis — cell division producing gametes with half the chromosomes.
- Mutation — change in DNA sequence.
- Natural selection — process where advantageous traits become more common.
- Neuron — nerve cell transmitting electrical signals.
- Neurotransmitter — chemical messenger between neurons.
Action Items / Next Steps
- Review diagrams of cell structure, mitosis, meiosis, and DNA replication.
- Practice decoding genetic crosses (Punnett squares).
- Memorize key terms and definitions for upcoming quiz.