Metabolism the sum of all chemical activity in the cell thousands of individual reactions Catabolism takes molecules and breaks them down o Releases energy o Final products used as precursors for new molecules Biosynthesis takes precursors and makes macromolecules How do we get the energy from our food to use in biosynthesis o The carbon and hydrogen in food molecules are not in most stable form which makes them reactive o Most stable form of carbon is CO2 and most stable form of hydrogen is H2O o So in a series of steps reactions large organic molecules like glucose are successively broken down to CO2 and H2O by combining with oxygen The C and H are oxidized called oxidation reaction Options Use energy now Harness and use later Lose as heat keep to a minimum o Spread out over multiple reactions 20 to harness more of the energy not dissipated as heat o Each oxidation reaction is controlled by a specific enzyme Dna synthesis is exergonic because dNTPs have closely spaced phosphate groups repulsion high potential energy enough to make the bond as two phosphate are cleaved off Origin fo replication bacteria only have one eukaryotes have a ton DNA replication happens in both directions replication bubbles grow in both directions Helicase breaks hydrogen bonds between base pairs Single stranded binding protiens attach and prevent two strands from snapping back Topoisomerase keeps the DNA from being tightly wound ahead of helicase DNA Polymerase only works from 5 to 3 requires a 3 end to extend from and a single stranded template Primer is a short sequence of rna nucleotides that provides 3 o Added by primase type of RNA polymerase Only leading strand can be synthesized in a direction that follows the direction of the moving replication fork o Many primers to make short okazaki fragments o Dna polymerase 1 attahces to 3 end removes RNA primer o Dna ligase attaches adjacent fragments Lagging strand get degraded telomeres short stretches of base that repeat over and over Telomerase catalyzes synthesis of DNA from RNA template it contains Somatic cells don t have telomerase limit cell divisions Cancer cells have telemorase
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