Cellular Metabolism and Genetics Review

Oxidation and ATP Synthase

• Oxidation involves the movement of electrons, which liberates hydrogen ions.

• Hydrogen ions are utilized to power ATP synthase pumps, essential for ATP production.

• ATP synthase pumps are ubiquitous across all explored living organisms, especially in photosynthetic ones (plants, algae).

Conservation of ATP Synthase

• Despite species differences in nucleotide sequences of ATP synthase, the structure and function remain largely conserved, indicating its evolutionary importance.

Photosynthesis vs. Oxidative Phosphorylation

• Photosynthesis uses water as the oxidized substrate and yields NADPH and ATP.

• Oxidative phosphorylation primarily utilizes NADH and FADH, ultimately producing water as a byproduct.

• Light-driven reactions in photosynthesis involve photosystems that excite electrons for transport.

Hydrogen Ions and ATP Synthesis

• The concentration gradient of hydrogen ions across membranes drives ATP synthase.

• For every five hydrogen ions that flow through ATP synthase, one ATP molecule is synthesized.

Calvin-Benson Cycle

• ATP and NADPH generated from light reactions are used in the Calvin-Benson cycle to produce glucose.

• This cycle requires carbon dioxide and utilizes ATP and NADPH to convert ribulose bisphosphate (RuBP) into glucose and regenerate RuBP.

Differences Between Metabolic Pathways

• The Calvin-Benson cycle differs from the Krebs cycle, which is catabolic, as it requires energy investment (ATP/NADPH) to synthesize glucose.

• Non-photosynthetic organisms use glycolysis and oxidative phosphorylation for energy production.

Allosteric Feedback Mechanisms

• Cells regulate enzyme activity using allosteric feedback; excess products inhibit earlier steps to prevent resource waste.

• This process impacts metabolic pathways based on nutrient availability and environmental conditions.

DNA as an Information System

• The nucleic acids (DNA) in cells serve as an information system, guiding cellular functions and responses to nutrient availability.

• Damage to DNA can lead to mutations, impacting the viability and function of cells.

Transcription and Translation Overview

• During replication, a complete copy of DNA (the library) is made for cell division.

• Transcription involves copying a specific gene (photographic image of a book) into mRNA, followed by translation into proteins at the ribosome.

• This process necessitates the recognition of nucleotide sequences and their translation into amino acids via tRNA.

Stability of DNA Structure

• DNA's stable double helix is formed by the pairing of purines (A, G) with pyrimidines (C, T) to maintain optimal width for replication and protection against enzymes that could degrade DNA.

Enzymatic Action During Replication

• Enzymes such as topoisomerase, helicase, and DNA polymerase play crucial roles in unwinding and synthesizing DNA.

• DNA polymerase is responsible for adding new nucleotides and proofreading the strand to maintain fidelity in DNA replication.

Okazaki Fragments

• Lagging strand replication leads to intermittent gaps known as Okazaki fragments, which are later filled by DNA polymerase to ensure continuity.

Role of RNA in Protein Synthesis

• Transcription converts DNA sequences into mRNA; this is followed by translation, wherein tRNA matches the mRNA codons to synthesize chains of amino acids in a precise order, ultimately leading to functional proteins.