Introduction to Biochemistry • What is Biochemitry?Why importance? • How to study Biochemistry? • Demands in this lesson:
Biochemistry is to study the molecular basis of life. Why is it important and excited ?
1. the chemical or molecular basis of some central processes in biology are understood. 2. common molecular patterns and principles in diverse expressions of life. 3. biochemistry impact on medicine. 4. the development of biochemistry has enabled investigators to resolve the most challenging and fundamental problems in biology and medicine.
1. Active in class 2. Memory on the basic knowledge 3. Answer to the teacher’s question bravely and freely. 4. Not left too much after class 5. No need to preview, but review in time.
Chapter I . Structure and function of proteins • Introduction to protein structure and function • 1. Enzymatic catalysis. • 2. Transport and storage • 3. Coordinated motion • 4. Mechanical support. • 5. Immune protection. • 6.Generation and transmission of nerve impulses. • 7.Control of growth and differentiation.
Chapter I . Structure and function of proteins (Part I) Main contents: Amino acids Peptides and polypeptides Determination of amino acid composition of proteins Determination of amino acid sequence of proteins
Chapter I . Structure and function of proteins 1. Amino Acids----The basic unit of proteins, and Polypeptide
Amino acids • The structure of amino acids and their properties • (a)Amino acids have both acid and base properties • (zwitterion).
(b)Aromatic amino acids absorb light in the near-ultraviolet (c)All amino acids except glycine show asymmetry (d)Coloured by ninhydrin
COOH R C H NH2 Common formula • Common structure formula of L-amino acids
Classification of amino acids • 1. Apolar, hydrophobic R chain; • 2. polar neutral (uncharged) ; • 3. Acidic amino acid; • 4. Basic amino acid.
Amino acids have both acid and base properties 1. Introduction to Henderson-Hasselbach equation (Conception of pH scale and water dissocation, acids dissociation)
2. A simple amino acids with a nonionizable R group gives a complex titration curve with two inflection points. 3. More complex amino acids with an ionizable R group show even more complex titration curves.
Aromatic amino acids absorb light in the near-ultraviolet phenylalanine, tyrosine, and typtophan Quiz: What importiance for this property of amino acids? What can you do applying this property?
All amino acids except glycine show asymmetry Chirality or handedness (take your hand as example) Stereoisomeric pair D: dextrorotatory; L: levorotatory All amino acids constructing proteins are L form. Some D-amino acids: in bacterial cell walls and certain antibiotics.
2. Peptides an polypeptides • peptide bond: partial double-bond character • not rotated freely • Amide plane and amide unit • polypeptides chain • Conception of polypeptides or oligopeptides: • other bond in proteins or polypeptides
Peptides: Short polypeptides chains, up to length of about 20 amino acids, are called peptides; However if they are fragments of whole polypeptide chains, we call it oligopeptides.
3. Determination of amino acid composition of proteins(step?) A. Break down the polypeptide chain into AAs. B. Separate the free AAs. C. Measure the quantities of each amino acids.
Free amino acids are coloured by ninhydrin (Reaction) R-C-COOH + 2 O NH2 OH C H C OH O
Free amino acids are coloured by ninhydrin (Production) O O C C N C C C O H O Ninhydrin coloured by red
Structure and function of proteins Part II .The Three-Dimensional Structure of Proteins Contain: (1)Primary structure (2)secondary structure -helix; -pleated sheet -blend(turn); random coil one special structure: motif (eg.Zinc finger)
(3) Tertiary structure special structure: domain (4) Quaternary structure subunit
(5) Bonds in the protein structure (6) Relationship of structure