Download Protein/Nucleic acid

Macromolecules:
proteins & nucleic acids
Building Blocks
of Life
• Most structurally/functionally diverse
macromolecule group
• Involved in almost everything:
• enzymes : digestive pepsin, amylase
• structure : keratin (hair, feathers)
collagen (connective tissue)
• transport : hemoglobin (O2 transport)
aquaporin (osmosis)
• communication : membrane receptors
(insulin glucose-uptake hormone)
• defense : antibodies
• movement : muscle fibers (actin & myosin)
• storage : seed coat proteins
PROTEINS
• Central C & an H
• Functional groups:
• amino group
• carboxyl group (acid)
H O
H
| ||
—C— C—OH
—N—
|
H
R
• R group (aka side chain)
• Variable; different for each of 20 different
amino acids
• confers unique chemical properties
to each amino acid
Amino acid Monomer
R group
determines
molecule
charge
charge affects
polypeptide
Ex: a point mutation in hemoglobin :
folding
> changes the amino acid,
> changes the charge
> changes the protein shape
> deforming the cell
R Group
Peptide bonds
• Covalent; via dehydration
• Between NH2 (amine) of
one amino acid & COOH
(carboxyl) of another
dehydration
synthesis
H2O
• C–N bond formed
peptide
bond
Polypeptide polymer
Primary (1°) structure
• sequence determined by
gene (DNA)
• change in sequence
can cause a
change in charge
which can cause
change in protein structure
which can cause
change in protien function
sequence -> structure -> function
Secondary (2°) structure
• Folding and coiling
along short sections
of polypeptide
• H bonding between
adjacent R groups
-helix
-pleated sheet
Tertiary (3°) structure
Interactions between distant
amino acids
• hydrophobic clusters
as nonpolar amino acids
avoid watery cytoplasm
• H bonds, ionic bonds,
disulfide bridges
Finally, a Protein
disulfide bridges?
• covalent bonds between sulfhydryl groups (SH)
stabilizes 3-D structure
Keratin protein in hair has many
disulfide bridges – keeps its shape
Quaternary (4°) structure
Collagen
skin &
tendons
Multiple polypeptides
Hemoglobin
Fe containing
protein that
carries O2 in
blood
R groups
hydrophobic interactions
disulfide bridges
(H & ionic bonds)
2° RH groups
bonds
1°
amino acid
sequence
peptide bonds
3°
multiple
polypeptides
hydrophobic
interactions
4°
Recap: protein structure
determined
by DNA
Unfolding a protein
• disrupt bonds & bridges
temperature • pH • salinity
• alters shape
• destroys functionality
many cannot return to
functional shape
Protein denaturation
Nucleic Acids
Information
storage
2006-2007
The genetic material
• stores information
DNA
Genes = template for proteins
• DNA  RNA  proteins  trait
to
• transfers information
template for new cells
template for next generation
protein
to
trait
• Structure
• monomer = nucleotide
• adenine, guanine, thymine,
cytosine, uracil
DNA
• Types
• RNA (ribonucleic acid)
• single helix, ribose, uracil
• DNA (deoxyribonucleic acid)
• double helix, deoxyribose,
thymine
Examples
RNA
3 parts
• nitrogen base
• pentose sugar (5C)
ribose in RNA
deoxyribose in DNA
• phosphate (PO4) group
I’m the
A,T,C,G or U
Nucleotides
• purines
• double ring N base
• adenine (A)
• guanine (G)
• pyrimidines
• single ring N base
• cytosine (C)
• thymine (T)
• uracil (U)
Types of nucleotides
Purine = AG
“Pure silver”
Dehydration synthesis -> covalent bond
aka phosphodiester
between hydroxyl & phosphate groups
polymer ‘backbone’
Nucleic acid
• H-bonds between DNA nucleotide N-bases
• Base-pair rule:
• purine pairs with pyrimidine
A :: T
2 H bonds
G ::: C
3 H bonds
Base Pair rule
o DNA helices are complementary
• via base-pair rule
• can replicate entire molecule
o To reproduce cell via mitosis
o To make gametes via meiosis
“It has not escaped our notice
that the specific pairing we have
postulated immediately suggests
a possible copying mechanism
for the genetic material.”
Copying the Code
James Watson & Francis Crick
1953
.
o Can build RNA complement
• aka transcription of genes
• for eventual translation into protein
Copying the Code