Exam_Prep_Book_PART_I_Chapter1 Page 1 - 44_test.pdf

The formation of macromolecules was the next step in evolution, achieved by the polymerization of monomeric building blocks. The critical characteristic of the macromolecule from which life evolved was the ability to replicate itself. Only nucleic acids are capable of directing their own self-repl...

The formation of macromolecules was the next step in evolution, achieved by the polymerization of monomeric building blocks. The critical characteristic of the macromolecule from which life evolved was the ability to replicate itself. Only nucleic acids are capable of directing their own self-replication. RNA is capable of catalyzing a number of chemical reactions, including the polymerization of nucleotides, and can serve as a template and catalyze its own replication. RNA is believed to have been the initial genetic system. 1. **RNA's Early Role:** RNA played a big part in the start of life [RNA World]. It mixed with amino acids, which later turned into the genetic code. 2. **DNA Takes Over:** Later on, DNA replaced RNA as our main genetic material. 3. **Genes and Proteins:** Genes are like our body's instruction manuals, written in DNA. They make proteins through transcription [copying DNA into RNA] and translation [turning RNA into proteins]. 4. **First Cell Formation:** The very first cell likely formed when self-replicating RNA was enclosed in a protective [phospholipid] membrane. 5. **Role of Phospholipid Membrane:** This special membrane kept everything inside the cell safe, allowing self-reproduction and further evolution. This membrane consists of water-attracting (hydrophilic) and water-repelling (hydrophobic) components, creating a stable barrier between two watery compartments. 6. **Protein Making:** RNA helps in making proteins, which is vital for life. RNA-directed protein synthesis may already have evolved by this time, in which case the first cell wouldhave consisted of self-replicating RNA and its encoded proteins.