Intergration

• Nitrogen Metabolism involves the dynamics of protein metabolism, digestion of dietary proteins, and protein turnover.
• Digestion of dietary proteins provides amino acids for protein biosynthesis and nitrogen for nitrogen-containing compounds.
• Excess amino acids are not stored for later use and are degraded by the body for some useful function.
• Nitrogen Metabolism also involves the integration of metabolism, the structure of nucleic acid, and central dogma of molecular biology.
• Mutation is a part of Nitrogen Metabolism.
• Glycogen metabolism is regulated through a hormone-triggered cascade of reactions.
• PPP provides NADPH for reductive biosynthesis and ribose-5-P for nucleotide biosynthesis.
• Glycolysis and gluconeogenesis are reciprocally regulated.
• Glucose-6-P dehydrogenase is the major regulatory point in glycolysis.
• Glycolysis is activated when energy level is high where glycolysis is inhibited.
• Glucose-6-P dehydrogenase is activated by high [NADP+].
• Glycogen synthesis and degradation are reciprocally regulated.
• Ionizing radiation causes the formation of Pyr dimers, such as T-T dimers.
• Base analogues can substitute for bases in DNA because of their structural similarity, for example, 5-bromouracil can substitute for thymine.
• Missense means the original amino acid is replaced with another one, as seen in sickle-cell anemia.
• HNO2 causes C → U or C → G to U → A.
• Intercalating agents are flat molecules that insert themselves between adjacent bases in the double helix causing distortion at the point of insertion, examples include Benzo[a]pyrene and Aflatoxin.
• Same sense changes the codon to a different one coding for the same amino acid.
• Non-sense changes a codon to a stop codon.
• Frame shift mutations are caused by mutagens, which can be physical agents like ionizing radiation or chemical agents like HNO2.
• tRNA is the carrier of the activated amino acid, an adaptor that links the codons and amino acids, and each amino acid has a specific tRNA used for activation.
• In the activation of amino acids, ATP is converted to amino acyl-AMP and ATP, and amino acyl-tRNA is converted to amino acyl-tRNA and ATP.
• Activation of amino acids involves the conversion of amino acid + ATP to amino acyl-AMP + PP i and amino acyl-tRNA + ATP to amino acyl-tRNA + AMP, catalyzed by amino acyl-tRNA synthetase.
• Amino acid - tRNA synthetase is the enzyme that catalyzes the activation of amino acids.
• In the formation of initiation complex, mRNA and small ribosomal subunit (30S) bind to each other, facilitated by initiation factor 3 (IF3), and the first charged tRNA binds to the mRNA, hydrolyzing GTP, facilitated by initiation factor 2 (IF2).
• In elongation, the polypeptide chain moves from the tRNA in the P-site to the amino acid attached to the tRNA in the A-site, catalyzed by peptidyl transferase, and translocation is promoted by another elongation factor EF-G and requires GTP hydrolysis, placing empty tRNA in the E-site and moving the growing polypeptide chain onto the P-site.
• In DNA replication, high fidelity is observed due to the proofreading ability of DNA polymerase, but errors may still arise and if not repaired there will be mutations.
• The enzyme catalyzing activation is also specific for a given amino acid.
• Mutation is a change in the genetic material that can be caused by errors in DNA replication or mutagens.
• Types of DNA mutation include point mutations, which are changes in single nucleotide or few adjacent nucleotides, and frameshift mutations, which are insertion or deletion of base that causes adjustment in the reading frame during translation.
• The steps in translation include initiation, elongation, and termination.
• Termination involves the recognition of stop codons in the A-site, binding of release factor (RF) in the A-site, and dissociation of the translation machinery.
• Naming of nucleotides involves combining a nucleoside and phosphate, with sugar being 2-deoxyribose and base being adenine.
• TAG mobilization and breakdown is the process of converting triglycerides into free fatty acids and glycerol.
• Nucleosides are composed of sugar and base only.
• Nucleic acids are biopolymers of nucleotides linked together by phosphodiester bonds.
• During starvation, priorities of metabolism are to provide sufficient glucose to the brain and RBCs and to preserve protein for muscle action.
• Upon formation of a nucleotide, two water molecules are liberated.
• Gluconeogenesis by liver occurs after 3 days of starvation.
• Nucleotides serve as repeating units/ precursors of nucleic acids, energy currencies in metabolism (ATP and GTP), and components of co-enzymes and reductants (FAD, NADH, NADPH).