《生物化学》课程PPT教学课件（留学生）Chapter 01 Amino Acids（structure of amino acid、acid/base properties of amino acid）

BIOCHEMISTRYANDMOLECULARBIOLOGYChapter 1AminoAcidsDepartment of Biochemistryand Molecular Biology,MedicineSchool

Department of Biochemistry and Molecular Biology, Medicine School BIOCHEMISTRY AND MOLECULAR BIOLOGY Chapter 1 Amino Acids

BIOCHEMISTRYANDMOLECULARBIOLOGYOutline*overview*structure of amino acid*acid/base properties of amino acid*other applications ofthehenderson-hasselbalchequationDepartment of Biochemistry and Molecular Biology,Medicine School

Department of Biochemistry and Molecular Biology, Medicine School BIOCHEMISTRY AND MOLECULAR BIOLOGY Outline *overview *structure of amino acid *acid/base properties of amino acid *other applications of the henderson-hasselbalch equation

2.Structureof aminoacidOpticalpropertiesofaminoacids

2 . Structure of amino acid Optical properties of amino acids

BIOCHEMISTRYANDMOLECULARBIOLOGY2.Structureof aminoacidOpticalpropertiesofaminoacidsGlycine is the exception because its α-carbonhas two hydrogen substituents and therefore isoptically inactiveDepartment of Biochemistry and Molecular Biology,Medicine School

Department of Biochemistry and Molecular Biology, Medicine School BIOCHEMISTRY AND MOLECULAR BIOLOGY Glycine is the exception because its α-carbon has two hydrogen substituents and therefore is optically inactive. 2 . Structure of amino acid Optical properties of amino acids

BIOCHEMISTRYANDMOLECULARBIOLOGY2.Structureof aminoacidOpticalpropertiesofaminoacidsAmino acids that have an asymmetric center at the α-carbon can exist in two forms, designated D and Lthat are mirror images of each other.Department of Biochemistry and Molecular Biology,Medicine School

Department of Biochemistry and Molecular Biology, Medicine School BIOCHEMISTRY AND MOLECULAR BIOLOGY Amino acids that have an asymmetric center at the α- carbon can exist in two forms, designated D and L, that are mirror images of each other. 2 . Structure of amino acid Optical properties of amino acids

BIOCHEMISTRYANDMOLECULARBIOLOGY2.Structureof aminoacidOpticalpropertiesofaminoacidsAll the amino acids found in proteins are of the L-configurationHowever, D-amino acids are found in some antibiotics and inbacterial cell wall.Department of Biochemistry and Molecular Biology,Medicine School

Department of Biochemistry and Molecular Biology, Medicine School BIOCHEMISTRY AND MOLECULAR BIOLOGY 2 . Structure of amino acid Optical properties of amino acids All the amino acids found in proteins are of the L-configuration. However, D-amino acids are found in some antibiotics and in bacterial cell wall

BIOCHEMISTRYANDMOLECULARBIOLOGYEHN00NH3COOHHamino acid-D-amino acidDepartment of Biochemistry and Molecular Biology,Medicine School

Department of Biochemistry and Molecular Biology, Medicine School BIOCHEMISTRY AND MOLECULAR BIOLOGY L- amino acid D- amino acid

BIOCHEMISTRYANDMOLECULARBIOLOGY3.Acid/basepropertiesofaminoacids1) The isoelectric point (pl)Demonstration ofbufferingA buffer is a solution that resists change in pH following theadditionofacidorbaseA buffer can be created by mixing equal concentrations of a weakacid(HA) and its conjugate base(A).Department of Biochemistryand Molecular Biology,Medicine School

Department of Biochemistry and Molecular Biology, Medicine School BIOCHEMISTRY AND MOLECULAR BIOLOGY 3.Acid/base properties of amino acids Demonstration of buffering A buffer is a solution that resists change in pH following the addition of acid or base. A buffer can be created by mixing equal concentrations of a weak acid(HA) and its conjugate base(A- ). 1) The isoelectric point (pI)

ABIOCHEMISTRYANDMOLECULARBIOLOGY3.Acid/basepropertiesof aminoacidsConsider therelease of a proton by a weak acidrepresented by HA:HAH++A-WeakprotonsaltformoracidconjugatebaseDepartment of Biochemistry and Molecular Biology,Medicine School

Department of Biochemistry and Molecular Biology, Medicine School BIOCHEMISTRY AND MOLECULAR BIOLOGY Consider the release of a proton by a weak acid represented by HA: HA H+ + A￾Weak proton salt form or acid conjugate base 3.Acid/base properties of amino acids

BIOCHEMISTRYANDMOLECULARBIOLOGY3.Acid/basepropertiesofaminoacidsAmino acids they contain weakly acidic α-carboxyl groups andweakly basic α-amino groupThus,amino acids can potentially act as buffers.The quantitative relation between the concentration of a weak acid(HA) and its conjugate base (A-) is described by the HendersonHasselbalchequationDepartment of Biochemistry and Molecular Biology,Medicine School

Department of Biochemistry and Molecular Biology, Medicine School BIOCHEMISTRY AND MOLECULAR BIOLOGY 3.Acid/base properties of amino acids Amino acids they contain weakly acidic α-carboxyl groups and weakly basic α-amino group. Thus , amino acids can potentially act as buffers. The quantitative relation between the concentration of a weak acid (HA) and its conjugate base (A- ) is described by the Henderson￾Hasselbalch equation