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CHAPTERS 21 AND 22

CHAPTERS 21 AND 22. CONCURRENT ENROLLMENT. NUCLEIC ACID. A biomolecule involved in the transfer of genetic information from existing cells to new cells Living cells can produce exact replicas of themselves RNA (ribonucleic acid) A nucleic acid found mainly in the cytoplasm of cells

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CHAPTERS 21 AND 22

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  1. CHAPTERS 21 AND 22 CONCURRENT ENROLLMENT

  2. NUCLEIC ACID • A biomolecule involved in the transfer of genetic information from existing cells to new cells • Living cells can produce exact replicas of themselves • RNA (ribonucleic acid) • A nucleic acid found mainly in the cytoplasm of cells • Does have a -OH group on the 4th carbon • DNA (deoxyribonucleic acid) • A nucleic acid found primarily in the nuclei of cells • Does not have a -OH group on the 4th carbon, both are β configuration

  3. NUCLEOTIDE • The repeating structural unit or monomer of polymeric nucleic acids( has three parts) • Pyrimidine - two -N– in a heterocyclic, 6 ring • Uracil (found only in RNA), thymine (found only in DNA), and cytosine • Purines - two N– in a heterocyclic, 6 and 5 ring • Adenine an guanine • Look on page 651 • Second a sugar D-ribose or D-deoxyribose • Third is a phosphate derived from phosphoric acid

  4. STRUCTURE OF DNA • AMP - has one phosphate, one sugar and one base • Nucleic acid backbone • The sugar and phosphate chain, each one is linked by a 3' - 5' phosphodiester

  5. SECONDARY STRUCTURE • Do learning check on page 653 as a problem • Watson and Crick based on research by Rosalind Franklin and Wilkins found that all DNA percentages of adenine and thymine were equal to each other, this caused a double helix to form • They run in opposite direction, the two chains attach by hydrogen bonds. Adenine and thymine have two hydrogen bonds. Guanine and cytosine have three hydrogen bonds. • If we had a base sequence of CCAATTG. What is the complementary strand?

  6. DNA REPLICATION • Chromosome • A tightly packed bundle of DNA and protein that is involved in cell division • Gene • An individual section of a chromosomal DNA molecule that is the fundamental unit of heredity • Replication • The process by which an exact copy of a DNA molecule is produced • Semiconservative replication • A replication process that produces DNA molecules containing one strand from the parent and a new strand that is complementary to the strand from the parent • Replication fork • A point where the double helix of a DNA molecule unwinds during replication

  7. PROCESS OF REPLICATION • Step 1 • Unwinding the double helix • Step 2 • Synthesis of DNA segments • Okazaki fragment - a DNA fragment produced during replication as a result of strand growth in a direction away from the replication fork • Step 3 • Closing the nicks • An enzyme called DNA ligase catalyzes this final step • Replication occurs simultaneously at many points on the DNA • Page 660 fig 21.12

  8. PCR • Laboratory technique to mimic replication • Using a buffered solution with DNA polymerase, cofactor MgCl2, the four nucleotide building blocks, and primers the PCR mixture is taken through three steps • Heat for several minutes to unravel the DNA • Cool tube for several minute, this causes the primers to hydrogen bond to the DNA • Tube is heated for several minutes and the DNA polymerase synthesizes a new strand

  9. RNA • RNA differs from DNA in two ways • Sugar unit • RNA has uracil instead of thymine • RNA are single-stranded except in viruses • RNA do contain regions of double-helical loop • Found throughout the cell • Three types of RNA • Messenger RNA (mRNA) - carries genetic information from the DNA in the cell nucleus to the site of protein synthesis in the cytoplasm • Has a short lifetime - usually less than an hour • Ribosomal RNA (rRNA) - constitutes about 65% of the material in ribosomes, the sites of protein synthesis • Ribosome - a sub cellular particle that serves as the site of protein synthesis in all organisms

  10. Continue • Transfer RNA (tRNA) • Delivers individual amino acid molecules to the site of protein synthesis • Anticodon - a three-base sequence in tRNA that is complementary to one of the codons in mRNA • Page 663 fig 21.14 • Central dogma of molecular biology • The well-established process by which genetic information stored in DNA molecules is expressed in the structure of synthesized proteins • There are two steps involved to flow genetic information • Transcription and translation • In eukaryotes the DNA containing the stored information is in the nucleus and protein synthesis is in the cytoplasm

  11. TRANSCRIPTION AND TRANSLATION • Transcription • The transfer of genetic information from a DNA molecule to a molecule of messenger RNA • Translation • The conversion of the code carried by messenger RNA into an amino acid sequence of a protein • Transcription: RNA synthesis • RNA polymerase catalyzes the synthesis of RNA • The DNA helix begins to unwind just before the gene that needs to be transcribed (only one DNA strand is transcribed) • One sequence of bases is recognized as the starting point. MRNA is synthesized in the 5' to 3' direction • It runs until it reaches another sequence of bases the is a termination point • The mRNA molecule move away and the DNA rewinds • Example 21.2 page 665

  12. Continue • Intron • A segment of a eukaryotic DNA molecule that carries no codes for amino acids • Exon • A segment of a eukaryotic DNA molecule that is coded for amino acids • Heterogeneous nuclear RNA (hnRNA) • RNA produced when both introns and exons of eukaryotic cellular DNA are transcribed • hnRNA undergoes a series of enzyme-catalyzed reactions that cut and splice the hnRNA to produce mRNA • Page 667 fig. 21.18

  13. GENETIC CODE • There are sequences of three bases in the mRNA, there are 64 possible combinations • Codon • A sequence of three nucleotide bases that represents a code word on mRNA molecules • With very few exceptions a given amino acid is coded by the same codon in every organism • Most amino acids are represented by more than one codon this is called DEGENERACY • No single codon can represent more than one amino acid • 61 out of 64 base triplets represent amino acids, the other three (UAA, UAG, UGA) are signals to chain termination • AUG is the only start codon if it is the first codon in a sequence

  14. TRANSLATION • There are three major stages of protein synthesis • Initiation of the polypeptide chain - ribosomes are made up of a large subunit and a small subunit. The initiation process begins when the mRNA is aligned on the surface of the small subunit • Elongation of the chain - a second site, called the A site (aminoacyl site), is located on the mRNA-ribosome complex next to the P site. The A site is where the tRNA comes to release the amino acid • Termination of the polypeptide - when a stop codon is reached the chain is terminated by a termination factor binding to the stop codon • Page 671-672 • Learning check page 672 • Read pages 673 to 678 some of this will be on the test

  15. NUTRITIONAL REQUIREMENTS • Read pages 684-693 this will be on the test • Cellular respiration • Entire process involved in the use of oxygen by cells • Glucose + O2(g) ---> CO2(g) + H2O(l) + energy • Fig 22.10 page 694 • Metabolism • The sum of all reactions occurring in an organism • Catabolism • All reactions involved in the breakdown of biomolecules • Anabolism • All reactions involved in the synthesis of biomolecules • Metabolic pathway • A sequence of reactions used to produce one product or accomplish one process

  16. CATABOLISM • Three stages • Digestion - large molecules are chemically broken into small ones. Most common reaction is hydrolysis • Small molecules from digestion are degraded to even smaller units -primarily two carbon acetyl portion of acetyl coenzyme A. Some energy is released • The citric acid cycle followed by electron transport and oxidative phosphorylation - COMMON CATABOLIC PATHWAY -ATP is formed (body’s form of energy) • Page 696 fig 22.11

  17. ATP • At the cells pH all protons in ATP are ionized (has a charge of 4-) • Other triphosphates can form from the other bases • A transfer of a phosphate group to water releases energy (this is free energy ∆G) • ATP-ADP cycle • In biological systems, ATP functions as an immediate donor of free energy rather than as a storage form • Mitochondria - a cellular organelle where reactions of the common catabolic pathway occur. Enzymes the catalyze the formation of ATP are found here

  18. Continue • Mitochondrion contains and inner and outer membrane • The inner membrane are called cristae and the space surrounding it is called the matrix. The enzymes are found in the inner membrane. The enzymes to the citric acid cycle are found in the matrix • Read about the following coenzymes: coenzyme A, NAD+, and FAD these will be on the test pages 700-705

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