Autotrophs Photosynthesis The process that feeds the biosphere Directly or Indirectly photosynthesis nourishes the entire earth Can classify life in two groups sustain themselves without eating anything from other organisms producers of biosphere produce organic molecules from CO2 Almost all plants are photoautotrophs make organic molecules from CO2 and H2O Heterotrophs obtain organic material from other organisms Consumers of biosphere Depend on photoautotrophs for organic molecules and also O2 Converts light energy to the chemical energy of food happens in the chloroplasts structural organization of chloroplasts allows for photosynthesis leaves are the major location of photosynthesis green color is from pigment chlorophyll light energy absorbed by chlorophyll drives synthesis of organic molecules in chloroplast CO2 enters and O2 exits through holes in the leaf called stomata chloroplasts are found mainly in mesophyll cells of leaf Chlorophyll is in the membranes of the thylakoids Veins deliver water from the roots typical mesophyll has 30 40 chloroplasts Photosynthesis is a redox process h2o is oxidized co2 is reduced starts with the spliting of water chloroplasts split water into hydrogen and oxygen and incorporate the electrons of hydrogen into small sugars photosynthesis has two parts split water reduce NADP to NADPH Generate ATP by photophosphorylation the light reactions in the thylakoids The calvin cycle forms sugar from co2 using ATP and NADPH begins with xation of co2 by rubisco into organic molecules The Light Reactions The light reactions convert solar energy to the chemical energy of ATP and NADPH Light is a form of energy that travels in waves wavelength determines the type of electromagnetic energy visible light consists of wavelengths that drive photosynthesis Excitation of chlorophyll by light When a pigment absorbs light energy it goes from a ground state to an excited state which is unstable When the excited electrons fall back down photons are given o with an afterglow called uorescence Photosytems A reaction center complex associated with light harvesting complexes Consists of a reaction center protein complex surronded by light harvesting complexes A primary electron accepter within the reaction center accepts an electron from chlorophyll a Solar power is used to transfer electrons from chlorophyll to primary acceptor Calvin Cycle Uses ATP and NADPH to convert CO2 to sugar Regenerates it s starting material after CO2 enters the cycle Builds sugar by using energy of ATP and the reducing power of electrons carried by NADPH Carbon enters speci cally as CO2 and leaves as glyceraldehyde 3 phosphate G3P To make one G3P 3 CO2 must be red Consists of three phases Carbon xation Reduction Rubisco Regeneration Can bind O2 with catalytic e ciency plants in hot arid climates close stomata to prevent dehydration Conseqence increased levels of O2 and decreased levels of CO2 therefore rubisco binds O2 and O2 is used instead of CO2 This is called photorespiration Photorespiration consumes O2 and organic fuels Does not produce ATP releases CO2 How do plants get around photorespiration Spacial seperation of CO2 xation temporal time seporation of CO2 xation C4 plants CAM Gri th Demonstrations of bacterial transformation Strephcoccous pnemoniac called Rough R Can be phagocytozed Non pathogenic not harmful Pathogenic smooth S caused pnemonia secretes a peptido glycan protein glucose Forms a slimy capsule Cannot be phagocytosed Control pathogenic inject live smooth Control non p R live S heat killed Exam question Mix live rough heat killed smooth If the percent G is 27 what is the percent T G 27 C 27 54 added 100 54 46 46 2 23 A 23 T 23 Died before Nobel prize could be given Rosalind Franklin the 8th day of creation Proteins and enzymes that function in DNA replication Helicase untwists double helix single strand binding protein prevents from going back to double helix primase makes a primer starting point for polymerase Topoisomerase relieves the strain of twisting caused by unwinding ligase ligats or joins together nuceic acids Polymerases only extend in a 5 prime to 3 prime direction initiation elongation Stages of replication tolamerase adds back sequences to tilamerase so they are the original young appearing link gerald heritiability and disease beadle and tatum 1 enzyme 1 protein Principles of transcription and translation RNA is the intermediate between genes and the proteins for which they code Transcription is the synthesis of RNA using DNA as a template Translation is the synthesis of a polypeptide using mRNA as a template In Eukaryotes the nucleus separates transcription and translation RNA transcripts are modi ed to yield nished mRNA Ribosomes are the site of translation produces messanger RNA mRNA The genetic Code how are the instructions for assembing amino acids encoded into DNA 20 amino acids but only 4 bases How many bases correspond to an amino acid 3 codons are triplets of bases that code for an amino acid Codone 3 nucleotide word Smallest unit of uniform length that can code for all amino acids During transcription 1 of the 2 DNA strands is used as a template for the ordering of sequence in an mRNA transcript During translation codons are read in a 5 to 3 direction Each codone speci es an amino acid The codon code 61 code for amino acids 3 code for STOP signal an end to translation all 64 codons deciphered in the 60s Must be read in the correct frame code is universal redundant unambiguous Transcription RNA synthesis catalized by an enzyme called RNA polymerase II transription follows the same base pairing rules as DNA except Uracil subsitutes for thymine The sequence on DNA when RNA pol II attacks is called the promoter stretch of DNA transcribed is called the transcription unit Three stages of transcription Initiation initiation elongation termination Promoters signal the initiation of RNA sythensis Transcription factors mediate the binding of RNA pol II and the initiation of transcription the completed assembly of transcription factors and RNA pol II bound to the promoter the initiation complex A promoter element called the TATA box is crucial in forming the initiation complex in eukaryotes elongation Termination as polymerase moves along the DNA it untwists the double helix 10 20 base pairs at a time transcription progresses at a rate of 40 nucleotides per second a gene can be transscribed simotaneously by multiple RNA polymerases who took the rst
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