Cellular Respiration and DNA: The Building Blocks of Life

Posted on Dec 4, 2024 in Biology

Cellular Respiration

Cellular respiration is the set of biochemical reactions occurring in most cells. Pyruvic acid, produced by glycolysis, is split into carbon dioxide (CO2) and water (H2O), producing 38 molecules of ATP. The general formula is: C6H12O6 + 6O2 —-> 6CO2 + 6H2O, releasing 38 ATP molecules in eukaryotic cells. This process occurs in the mitochondria in three stages:

  1. Oxidation of pyruvic acid
  2. Tricarboxylic acid cycle (Krebs cycle)
  3. Respiratory chain and oxidative phosphorylation of ADP to ATP

Cellular respiration, a part of metabolism (catabolism), releases energy from biomolecules like carbohydrates. Some of this released energy is incorporated into ATP, which fuels endothermic processes like growth and maintenance (anabolism).

Types of Cellular Respiration

Cellular respiration is categorized based on oxygen’s role:

  1. Aerobic Respiration: Uses O2 as the final electron acceptor. Common in bacteria and eukaryotic organisms.
  2. Anaerobic Respiration: Does not use oxygen. Instead, other electron acceptors (e.g., SO42-, which reduces to H2S) are utilized. Characteristic of some prokaryotes, particularly in soil and sediments.

Anaerobic respiration should not be confused with anaerobic fermentation, an internal redox process that doesn’t require O2 or another electron acceptor.

DNA: The Carrier of Genetic Information

Deoxyribonucleic acid (DNA) is the genetic material of all cellular organisms and most viruses. It carries the information for protein synthesis and replication. In most cellular organisms, DNA is organized into chromosomes within the cell nucleus.

DNA Structure and Function

  1. Two DNA strands are held together by bonds between bases, forming base pairs. Genome size is typically based on the total base pairs.
  2. The human genome contains about 3 billion base pairs. During cell division, the genome duplicates.
  3. DNA strands unroll and separate, each directing the synthesis of a new complementary strand. Base pairing is strict: adenine (A) with thymine (T), and cytosine (C) with guanine (G).
  4. Each DNA molecule contains many genes, the physical and functional units of heredity. A gene is a specific nucleotide base sequence carrying the information for building proteins.
  5. The human genome’s 3 billion base pairs are organized into 23 distinct chromosomes. Genes are arranged linearly along these chromosomes.
  6. Most human cells contain two sets of chromosomes, one from each parent. Each set has 22 autosomal and one sex chromosome (X or Y).
  7. Chromosomes contain roughly equal amounts of protein and DNA. Chromosomal DNA averages 150 million bases.
  8. Chromosome abnormalities include extra copies, losses, fusions, and translocations, detectable microscopically (e.g., Down syndrome or trisomy 21).
  9. Subtle changes, detectable only by molecular analysis, are called mutations. Many mutations are linked to diseases like cystic fibrosis, sickle cell anemia, and predispositions to certain cancers and psychiatric illnesses.
  10. Each person has maternal and paternal genes for each trait. Homozygous individuals have identical gene pairs for a trait, while heterozygous individuals have different gene pairs.
  11. In heterozygotes, one gene may dominate (dominant) in expressing the trait over the other (recessive).
  12. Cellular machinery translates genetic codes into amino acid strings, forming proteins.
  13. Over 1100 genetic disorders with identified mutations are associated with distress.