Cellular Respiration, Protein Synthesis, and DNA Replication: A Comprehensive Guide
Aerobic respiration: goes through the entire cellular respiration process and dumps its electrons to an oxygen molecule that accepts them. Anaerobic respiration: Also goes through the entire cellular respiration process and has all its bonds broken down, however, its final electron acceptor is not oxygen; it’s something else like sulfur or nitrogen. The difference between aerobic and anaerobic cellular respiration is solely based on its final electron acceptor. Fermentation: Is a partial breakdown (incomplete breakdown), it does not have the necessary organelles to undergo full cellular respiration. (Breaks down only one bond C-C and gets 2 ATP). Enzyme Activity Regulation: Two ways of regulating enzymes: 1) Competitive inhibition. (When the substrate binds to the active site but is not a perfect match) 2) Non-competitive (allosteric regulation) the allosteric site of the enzyme can change the active site by altering it if an inhibitor binds to the active site. Has two sites. (Active site and allosteric site). Substrate-level phosphorylation: has to deal with specific enzymes, removes phosphate and gives it to another chemical. à With the help of an enzyme, an organic phosphate is attached to ADP, known as phosphate-level phosphorylation.
Fermentation in detail: From one single energized (by 2 ATP) glucose à you get 2 ATP, 2 NADH, 2 pyruvic acid or pyruvates. Partial breakdown, no organelles C-C-C*C-C-C oxygen not present in fermentation and anaerobic respiration. * Step 1) Glycolysis is the initiation of the breakdown of glucose, whether the next step is fermentation or cellular respiration. Step 2) You break the first bond in glycolysis C-C-C*C-C-C à that glucose goes through a few steps, and at the end from that 6 carbon molecule, you’re going to get 2 3-carbon pyruvates, 2 3-carbon molecules, à electrons given to NAD+ and you get 2 NADH.
Cellular respiration (complete breakdown) (KREBS CYCLE): The Krebs cycle happens in the mitochondria and ETC happens in the inner membrane of the mitochondria. 1. One of the carbons breaks as CO2 à add coenzyme A à more electrons removed. 2 Acetyl CoA’s starts the Krebs cycle, goes through the Krebs cycle in the process you get 2 ATP, 6 NADH, 2 FADH2, 4 CO2 molecules by substrate-level phosphorylation and all carbons come out and form CO2.
ETC: occurs in the mitochondria cristae of eukaryotes and in the cytoplasmic membrane of prokaryotes. A series of protein complexes built in the membrane pump H+ from lower to higher concentration. Each protein oscillates between a reduced state as NADH and FADH2 molecules pass through them. A total of 10 NADH and 2 FADH2 enter this step. Electrons move down the chain from one protein to another, H+ ions disassociating from the carrier molecule gets pumped out to the other side creating a concentration gradient. Protein channels of ETC actively pump H+ ions against the concentration gradient using stored energy in electrons, electrons transferred from one protein to another. Next step H+ are passively channeled back through ATP Synthetase protein into the space they got pumped out from. The transport of H+ is referred to as Chemiosmosis. Net production: 10 NADH and 2 FADH2 à 32 ATP (2 ATP glycolysis, 2 Krebs, 32 ETC)
Protein synthesis; Translation: Step two of protein synthesis is translation where mRNA is processed by ribosomes and translated into protein. 1) Small subunits of ribosomes bind to the beginning or the start codon of mRNA 2) A tRNA molecule with the anticodon to start the codon and carrying the amino acid methionine also binds to the start codon of mRNA 3) Larger subunits of the ribosome bind to the complex, placing the tRNA and the start codon in the P site. 4) Second tRNA with the anticodon and amino acid to the next codon binds to the mRNA at the A site. 5) The two amino acids brought by the two tRNAs will form a peptide bond. The first tRNA (anti-start) will fall off, leaving its amino acids attached to the second tRNA’s amino acid. 6) The ribosome will move down the mRNA by one codon placing the 2nd tRNA and the two amino acids attached to it in the P site and clearing the A site for the third tRNA. 7) Steps 5 & 6 will continue throughout the entire length of mRNA until the last codon, STOP codon, is reached. The polypeptide is synthesized completely at this point and the ribosome subunits will detach and fall off.
Transcription: where the genetic code is copied into a complementary mRNA molecule. 1) DNA molecule in the area of the gene that is being transcribed unwinds, the sense and anti-sense strand separate creating an open reading frame by placing the start codon at the beginning of the frame. 2) RNA polymerase binds to the sense strand of DNA prior to the start codon. RNA polymerase moves along the sense strand creating a complementary mRNA copy of this strand. 3) mRNA remains attached to the RNA polymerase, and when they reach the end of the gene and copy the last codon, (stop codon) they both detach from the sense strand. The open reading frame is closed and then mRNA detaches from RNA polymerase and moves towards the cytoplasm. 4) Before reaching the ribosome, while passing through the envelope it is processed into fragments & removed.
Plasmids: A self-replicating circle of DNA distinct from the chromosomal genome of bacteria. Contains genes normally not essential for cell growth or survival. Can be transferred from one organism to another during certain types of mating. Many types of plasmids: -fertility factor, resistance factor, -bacterium factors, -virulence factors.
DNA Replication. Occurs during the”” phase of interphase 1. Replication starts at sites on the helix called the origin of replication. Origins are small portions of the double helix that unwind. An enzyme called Helicase breaks the DNA hydrogen bonds between two bases of the strands of DNA by”unzippin” & exposing the bases. The exposed bases are called an OPEN FRAME. Special proteins bond to these strands stabilizing them and preventing them from collapsing which creates the replication bubbles. –> Nucleotides A, T & C, G attach to these open frame areas by anabolic reactions provided by the energy present in the DNA by 2 cleaved phosphates that are released. DNA polymerase 3 attaches the nucleotides to two strands of DNA. These enzymes can only add complementary nucleotides at the 3′ prime end of existing nucleotides. The DNA strands are antiparallel and compose of a leading and lagging strand. In the leading strand, helicase runs in the same direction and only 1 primer sequence is required. In the lagging strand, helicase runs in the opposite direction, so multiple primers are required on the new strands are replicated in fragments called Okazaki fragments. Once the entire DNA is replicated another DNA polymerase molecule attaches to DNA replacing the primer sequence with DNA nucleotides. DNA ligase runs along the new nucleotides and assists the formation of covalent bonds to seal the groups. At the end, two DNA molecules will result from replication where each will be composed of an old strand and a complementary strand. This replication method is called semiconservative replication.