Download Macromolecules of Life

Macromolecules of Life
Proteins and Nucleic Acids
Chapter 5
You already know a lot about
proteins!
You’ve been working with them in lab for the past 2-3 weeks!
• Biuret – [protein]
• Gel Electrophoresis
• Enzymes
Protein Definition
• Consists of one or more polypeptides folded, coiled,
and twisted into a specific 3D shape
• Proteios – “first place”
• There are many different shapes of proteins
depending on its FUNCTION
–
–
–
–
–
–
Enzymes
Cell signaling
Defense
Structural support
Transport
Receptors
Two similar terms
• Protein – already defined
• Polypeptide
– polymer made of repeating subunits of amino
acids (monomer)
– usually refers to a long linear strand of amino acids
that will then get folded into a 3D shape (protein)
Fig. 5-2a
HO
1
2
3
H
Short polymer
HO
Unlinked monomer
Dehydration removes a water
molecule, forming a new bond
HO
1
H
2
3
H2O
4
H
Longer polymer
(a) Dehydration reaction in the synthesis of a polymer
Fig. 5-2b
HO
1
2
3
4
Hydrolysis adds a water
molecule, breaking a bond
HO
(b)
1
2
Hydrolysis of a polymer
3
H
H2O
H
HO
H
Fig. 5-UN1
 carbon
Amino
group
Carboxyl
group
Fig. 5-17
Nonpolar
Glycine
(Gly or G)
Valine
(Val or V)
Alanine
(Ala or A)
Methionine
(Met or M)
Leucine
(Leu or L)
Trypotphan
(Trp or W)
Phenylalanine
(Phe or F)
Isoleucine
(Ile or I)
Proline
(Pro or P)
Polar
Serine
(Ser or S)
Threonine
(Thr or T)
Cysteine
(Cys or C)
Tyrosine
(Tyr or Y)
Asparagine Glutamine
(Asn or N) (Gln or Q)
Electrically
charged
Acidic
Aspartic acid Glutamic acid
(Glu or E)
(Asp or D)
Basic
Lysine
(Lys or K)
Arginine
(Arg or R)
Histidine
(His or H)
Fig. 5-17a
Nonpolar
Glycine
(Gly or G)
Methionine
(Met or M)
Alanine
(Ala or A)
Valine
(Val or V)
Phenylalanine
(Phe or F)
Leucine
(Leu or L)
Tryptophan
(Trp or W)
Isoleucine
(Ile or I)
Proline
(Pro or P)
Fig. 5-17b
Polar
Serine
(Ser or S)
Threonine
(Thr or T)
Cysteine
(Cys or C)
Tyrosine
(Tyr or Y)
Asparagine Glutamine
(Asn or N) (Gln or Q)
Fig. 5-17c
Electrically
charged
Acidic
Aspartic acid Glutamic acid
(Glu or E)
(Asp or D)
Basic
Lysine
(Lys or K)
Arginine
(Arg or R)
Histidine
(His or H)
Fig. 5-18
Peptide
bond
(a)
Side chains
Peptide
bond
Backbone
(b)
Amino end
(N-terminus)
Carboxyl end
(C-terminus)
Fig. 5-UN5
Fig. 5-21
Primary
Structure
Secondary
Structure
 pleated sheet
+H N
3
Amino end
Examples of
amino acid
subunits
 helix
Tertiary
Structure
Quaternary
Structure
Fig. 5-21a
Primary Structure
1
5
H3N
Amino end
+
10
Amino acid
subunits
15
20
25
Fig. 5-21b
1
5
+H
3N
Amino end
10
Amino acid
subunits
15
20
25
75
80
90
85
95
105
100
110
115
120
125
Carboxyl end
Fig. 5-21c
Secondary Structure
 pleated sheet
Examples of
amino acid
subunits
 helix
Fig. 5-21f
Hydrophobic
interactions and
van der Waals
interactions
Polypeptide
backbone
Hydrogen
bond
Disulfide bridge
Ionic bond
Fig. 5-21e
Tertiary Structure
Quaternary Structure
Fig. 5-21g
Polypeptide
chain
 Chains
Iron
Heme
 Chains
Hemoglobin
Collagen
Fig. 5-22a
Normal hemoglobin
Primary
structure
Val His Leu Thr Pro Glu Glu
1
2
3
4
5
7
6
Secondary
and tertiary
structures
 subunit


Quaternary
structure
Normal
hemoglobin
(top view)

Function
Molecules do
not associate
with one
another; each
carries oxygen.

Fig. 5-22b
Sickle-cell hemoglobin
Primary
structure
Secondary
and tertiary
structures
Val His Leu Thr Pro Val Glu
1
2
3
4
5
6
7
Exposed
hydrophobic
region
 subunit


Quaternary
structure
Sickle-cell
hemoglobin

Function
Molecules
interact with
one another and
crystallize into
a fiber; capacity
to carry oxygen
is greatly reduced.

Fig. 5-22c
10 µm
Normal red blood
cells are full of
individual
hemoglobin
molecules, each
carrying oxygen.
10 µm
Fibers of abnormal
hemoglobin deform
red blood cell into
sickle shape.
What Determines Protein Structure?
• In addition to primary structure, physical and
chemical conditions can affect structure
• Alterations in pH, salt concentration,
temperature, or other environmental factors
can cause a protein to unravel
• This loss of a protein’s native structure is called
denaturation
• A denatured protein is biologically inactive
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 5-23
Denaturation
Normal protein
Renaturation
Denatured protein
The Roles of Nucleic Acids
• There are two types of nucleic acids:
– Deoxyribonucleic acid (DNA)
– Ribonucleic acid (RNA)
• DNA directs synthesis of messenger RNA
(mRNA) and, through mRNA, controls protein
synthesis
• Protein synthesis occurs in ribosomes
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 5-26-3
DNA
1 Synthesis of
mRNA in the
nucleus
mRNA
NUCLEUS
CYTOPLASM
mRNA
2 Movement of
mRNA into cytoplasm
via nuclear pore
Ribosome
3 Synthesis
of protein
Polypeptide
Amino
acids
Fig. 5-27ab
5' end
5'C
3'C
Nucleoside
Nitrogenous
base
5'C
Phosphate
group
5'C
3'C
(b) Nucleotide
3' end
(a) Polynucleotide, or nucleic acid
3'C
Sugar
(pentose)
Fig. 5-27c-1
Nitrogenous bases
Pyrimidines
Cytosine (C)
Thymine (T, in DNA)
Uracil (U, in RNA)
Purines
Adenine (A)
Guanine (G)
(c) Nucleoside components: nitrogenous bases
Fig. 5-27c-2
Sugars
Deoxyribose (in DNA)
Ribose (in RNA)
(c) Nucleoside components: sugars
Nucleotide Polymers
• Adjacent nucleotides are joined by covalent
bonds (phosphodiester linkage)
• The nitrogenous bases in DNA pair up and
form hydrogen bonds:
– adenine (A) always with thymine (T)
– guanine (G) always with cytosine (C)
• Forms a double helix
Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings
Fig. 5-28
5' end
3' end
Sugar-phosphate
backbones
Base pair (joined by
hydrogen bonding)
Old strands
Nucleotide
about to be
added to a
new strand
3' end
5' end
New
strands
5' end
3' end
5' end
3' end