What is Biochemitry?Why importance?

How to study Biochemistry?

Demands in this lesson:

Introduction to Biochemistry

Biochemistry is the study of the molecular basis of life.

Why important and excited about Biochemistry?

1. the chemical basis of some central processes in biology are now understood.

2. there are some common molecular patterns and principles that underlie the diverse expressions of life.

3. biochemistry is making an increasing impact on medicine.

4. the rapid development of biochemistry in recent years has enabled investigators to tackle some of 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.

Interest and Great passion

Memorize the basis

Indulging in the understanding

Combining the theory and practice

Chapter I . Structure and function of proteins

Introduction to protein structure and function

1. Enzymatic catalysis. 2. Transport and storage3. Coordinated motion4. 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 contains:

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

(b)Aromatic amino acids absorb light in the near-ultraviolet

(c)All amino acids except glycine show asymmetry

(d)Coloured by ninhydrin

•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

NH2

H

C

O

C

O

OH

OH

Free amino acids are coloured by ninhydrin

(Production)

C

O

C

O

C

O

C

OH

N C

Ninhydrin coloured by red

4. Determination of amino acids sequence of proteins (steps?)

(1) purification of protein;

(2)cleavage of all disulfide bonds

(3)determination of the terminal amino acid residues

(4)specific cleavage of polypeptide chain into small fragments in at least two different cleavage methods.

(5) Independent separation and sequence determination of peptides produced by the different cleavage methods.

(6) Reassembly of the individual peptides with appropriate overlaps to determine the overall sequence.

COOH

R C H

NH2

Common formula