Transcript Document

Introduction to Biochemistry
What is Biochemitry?Why importance?
How to study Biochemistry?
Demands in this lesson:
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 storage
3. Coordinated motion
4. Mechanical support.
5. Immune protection.
6.Generation and transmission of
impulses.
7.Control of growth and differentiation.
nerve
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 nearultraviolet
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)
NH2
R-C-COOH
H
+ 2
O
C
OH
C
O
OH
Free amino acids are coloured by ninhydrin
(Production)
O
C
O
C
N
C
O
C
C
H
O
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