Overview
This lecture covers key concepts in cellular energetics (ATP, photosynthesis, respiration), cell division (mitosis and meiosis), patterns of inheritance, DNA replication, protein synthesis, and genetic variation, highlighting processes, structures, and foundational mechanisms in biology.
ATP, Cellular Energetics, and Respiration
- ATP is the primary energy currency in cells, produced mainly by cellular respiration.
- Cellular respiration involves glycolysis, the Krebs cycle, and oxidative phosphorylation.
- Oxidative phosphorylation occurs in mitochondria and creates most cellular ATP.
- Photophosphorylation in plants uses light energy to generate ATP.
- ATP releases energy when hydrolyzed to ADP and inorganic phosphate.
- Oxygen is essential as the final electron acceptor in cellular respiration.
Photosynthesis
- Photosynthesis occurs in chloroplasts and involves light-dependent and light-independent (Calvin cycle) reactions.
- The photosynthesis equation: 6CO2 + 6H2O + light → C6H12O6 + 6O2.
- Gas exchange in leaves occurs via stomata; chloroplasts are mainly in leaf cells.
- Photosystems II and I capture light energy and transfer electrons.
- Light reactions occur in thylakoid membranes, producing ATP, NADPH, and O2.
- The Calvin cycle in the stroma uses ATP, NADPH, and CO2 to make sugars.
- Carbon fixation incorporates CO2 into organic molecules.
- Photosynthetic pigments absorb blue and red light; green is reflected.
Cell Division: Mitosis and Meiosis
- Mitosis produces two diploid, genetically identical daughter cells for growth, repair, and asexual reproduction.
- Meiosis creates four haploid gametes with genetic variation for sexual reproduction.
- Cell cycle phases: G1 (growth), S (DNA synthesis), G2 (prep for division), M (mitosis/cytokinesis).
- Checkpoints (G1, G2, M) regulate cell cycle and prevent damaged cell division.
- Genetic diversity in meiosis arises from crossing over, independent assortment, and random fertilization.
- Nondisjunction causes chromosomal disorders (e.g., Down, Turner, Klinefelter, Edwards syndromes).
Inheritance Patterns and Genetics
- Mendel used pea plants to study inheritance; established laws of segregation and independent assortment.
- Alleles are alternative gene versions; genotype is genetic makeup; phenotype is expressed traits.
- Codominance, incomplete dominance, and polygenic inheritance show varied inheritance patterns.
- Linked genes are inherited together; pedigrees trace traits through generations.
- Sex determination in humans is via X and Y chromosomes.
DNA Replication and Protein Synthesis
- DNA is a double helix; replication is semiconservative and requires DNA polymerase and ligase.
- RNA types: mRNA (messages), tRNA (amino acid transfer), rRNA (ribosomes).
- Protein synthesis: transcription (DNA to RNA) and translation (RNA to protein via ribosomes).
- Mutations: silent (no effect), missense (amino acid change), nonsense (stop codon), frameshift (reading frame change).
Key Terms & Definitions
- ATP — energy-carrying molecule in cells.
- Photosynthesis — process by which plants convert light energy to chemical energy.
- Cell Cycle — ordered sequence of cell life and division events.
- Mitosis — division of a nucleus to produce identical cells.
- Meiosis — division to produce haploid gametes with genetic variation.
- Allele — alternative form of a gene.
- Genotype — genetic composition of an organism.
- Phenotype — observable traits of an organism.
- Codon — three-base sequence on mRNA for an amino acid.
- Mutation — change in DNA sequence or structure.
Action Items / Next Steps
- Review diagrams of cell division (mitosis and meiosis).
- Practice genetics problems involving Punnett squares and inheritance patterns.
- Complete assigned readings or online labs and quizzes related to photosynthesis and respiration.