Peptides to
Proteins
• What are
proteins?
• Why are proteins important?
• How are proteins made?
• How do proteins fold?
What are PROTEINS?
Proteins are large, complex molecules
that serve diverse functional and
structural roles within cells.
Proteins are the ACTION FORCE
in the cell.
Enzyme
Defense
Protease
Antibody
Fights
Viruses
Degrades
Protein
Proteins can be functionally classified.
Motion
Actin
Transpor
t
Hemoglobin
Contracts Muscle Fibers
Carries O2
Regulation
Insulin
Controls Blood Glucose
Support
Keratin
Forms Hair
and Nails
Proteins are chains of amino acids.
O
C
OH
N
H
H
Short chains of amino acids are called
peptides.
Proteins are polypeptide molecules that
contain many peptide subunits.
N
H
H
Amino acids have an amino group,
carboxyl group, R group and hydrogen.
R
NH2
C
H
Amino Acid 1
COOH
Each amino acid has unique chemical
properties.
Glycine
Histidine
Glutamine
Glutamate
Lysine
Cysteine
Aspartate
Asparagine
Arginine
Isoleucine
Methionine
Serine
Leucine
Proline
Alanine
Threonine
Tryptophan
Phenylalanine
Valine
Tyrosine
Peptide bonds form by
dehydration synthesis
R
R
NH2
C
H
Amino Acid 1
H N
C
O
OH
H
C
COOH
H
Amino Acid 2
H2O
R
R
C
COOH
NH2
C
H
Amino Acid 1
H
Amino Acid 2
Gene
3’
Nucleus
Messenger
Ribonucleic Acid
(mRNA)
Trp
tRNA
Ala
tRNA
Met
Met
Large
Subunit
Ribosome
Met
5’
Amino Acidtransfer
RNA
tRNA
Ala
Empty tRNA
Trp
Empty tRNA
A
U
G
G
C
C
U
G
G
U
A
G
Small Subunit
Cytoplasm
Ribonucleotides
Codon 1
A
U
G = Methionine
Codon 3
U
G
G = Tryptophan
Codon 2
G
C
C
Codon 4
U
A
G = Stop
= Alanine
A
G
C
U
is the synthesis of proteins in the cell.
Primary
There are 4 basic
Secondary
Tertiar
y
Quaternary
L
V
M
H
G
I
Q
Y
P
S
E
C
K
T
F
The primary structure is the
sequence of amino acids.
N
R
A
P
D
The secondary structure is primarily composed of
alpha helices and beta-pleated sheets.
Folding Back and
Coiling
Alpha Helix
Primary Structure
Beta-Pleated Sheet
The tertiary structure is the protein’s 3D
shape.
The quaternary structure is the assembly
of folded subunits.
Proteins must reach their final shape to
perform their vital functions
Improperly
Folded
Properly Folded
Summary
• Proteins are biological workhorses that
carry out most of the functions within
the cell.
• Proteins are large biological molecules
that serve diverse functional and
structural roles within cells.
• Proteins are synthesized during the
translation process.
Summary cont’d…
• Proteins are composed of amino acids
that are covalently linked by peptide
bonds.
• Proteins have four basic levels of
structure. However, proteins must fold
correctly in order to function properly.
THE END!