药学英语-生物化学Biochemistry

Biochemistry Biochemistry is the application of chemistry to the study of biological processes at the cellular and molecular level It emerged as a distinct discipline around the beginning of the 20th century when scientists combined chemistry physiology and biology to investigate the chemistry of living systems Generally speaking it is concerned with the chemistry of those compositions such as protein fat saccharide and nucleic acid found in living organisms and their metabolic process Principles of BiochemistryCells basic structural units of living organisms are highly organized and constant source of energy is required to maintain the ordered state Living processes contain thousands of chemical pathways Precise regulation and integration of these pathways are required to maintain life Certain important pathways e g Glycolysis is found in almost all organisms All organisms use the same type of molecules carbohydrates proteins lipids Unstaurated fatty acids contain one or more double bonds in hydrocarbon chains triglycerides are esters of glycerol with three long chain fatty acids Compound lipid 复合脂 with additional groups other than fatty acids and alcohols including phospholipid glycolipid sphingolipid 鞘脂 Each glycerophospholipid includes a polar region glycerol carbonyl O of fatty acids Pi the polar head group X apolar hydrocarbon tails of fatty acids R1 R2 A lipid bilayer with associated proteins Roles of Lipids Structural elements phospholipid Energy storage fatty acids Hormones sex hormones e g Estrogen biological membrane Protective cushion and structural support Important sources for lipid soluble vitamins 4 Nucleic acid Nucleic acids are large molecules found in the nuclei of cells that contain all the information needed to direct the activities of a cell and its reproduction All of the genetic information in the cell is called the genome Every time a cell divides the information in the genome is copied and passed on to the new cells Flow of genetic information DNA Transcription RNA Translate Protein 4 1 Nucleic acids are Molecules that store information for cellular growth and reproduction Deoxyribonucleic acid DNA and ribonucleic acid RNA Large molecules consisting of long chains of monomers called nucleotides 核苷酸 4 2 nucleotides The nucleic acids DNA and RNA consist of monomers called nucleotides that consist of a Pentose Nitrogen containing base Phosphate Pentose Sugars The pentose five carbon sugar In RNA is ribose In DNA is deoxyribose with no O atom on carbon 2 Nitrogen Bases The nitrogen bases in nucleic acids consist of the Pyrimidines Cytosine 胞嘧啶 Thymine 胸腺嘧啶 and Uracil 尿嘧啶 Purines Adenine 腺嘌呤 and Guamine 鸟嘌呤 4 3 DNA Double Helix In DNA nucleotide monomers form polynucleotides by phosphodiester bond There are two strands of nucleotides that wind together in a double helix Two hydrogen bonds form between the complementary base pairs A T Three hydrogen bonds form between the complementary base pairs G C Genetic information is carried by the sequence of base pairs DNA Double Helix Structure Before a cell divides it has to replicate its DNA so that the daughter cell receives a copy of the genome The DNA helix consists of two complementary DNA strands Therefore each of the two strands serves as a template for the construction of the other strand This process is called semiconservative replication DNA replication involves An enzyme helicase 解旋酶 unwinds the parent DNA at several sections At each open DNA section DNA polymerase reads an intact DNA strand as a template and catalyze the formation of phosphodiester bond between nucleotides Pairing of the bases between parent strand and the new complementary strands Producing two new DNA strands that exactly duplicate the original DNA Important morpheme vivi vit bio life alive vivisect in vivo in vitro vitamin antibiotics necr o mort death necrosis necrotomy mortality gluc o glyc o sacchar o ose sugar glucose glycogen polysacchride latose rib o kary o nucle nucleus ribose eukaryocyte ribozyme endonuclease exonuclease Endonucleases are enzymes that cleave the phosphodiester bond within a polynucleotide chain in contrast to exonucleases which cleave phosphodiester bonds at the end of a polynucleotide chain amyl o starch amylase lact o milk lactose lactic acid lactobacilli protein o prote o protein proteoglycan proteinuria pepid o peptide polypeptide oliogpeptide peptidase endopeptidase exopeptidase amin o amino aminotransferase vitamin enzym o zym o ase enzyme metalloenzyme proenzyme zymogen isomerase isozyme co h