CHAPTER 5 THE STRUCTURE & FUNCTION OF MACROMOLECULES CARBOHYDRATES, LIPIDS, PROTEINS, NUCLEIC ACIDS.
Macromolecules of Life Proteins and Nucleic Acids Chapter 5.
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Transcript of Macromolecules of Life Proteins and Nucleic Acids Chapter 5.
Macromolecules of LifeProteins and Nucleic Acids
Chapter 5
You already know a lot about proteins!
• Biuret – [protein]• Gel Electrophoresis• Enzymes
You’ve been working with them in lab for the past 2-3 weeks!
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
Dehydration removes a watermolecule, forming a new bond
Short polymer Unlinked monomer
Longer polymer
Dehydration reaction in the synthesis of a polymer
HO
HO
HO
H2O
H
HH
4321
1 2 3
(a)
Fig. 5-2b
Hydrolysis adds a watermolecule, breaking a bond
Hydrolysis of a polymer
HO
HO HO
H2O
H
H
H321
1 2 3 4
(b)
Fig. 5-UN1
Aminogroup
Carboxylgroup
carbon
Fig. 5-17Nonpolar
Glycine(Gly or G)
Alanine(Ala or A)
Valine(Val or V)
Leucine(Leu or L)
Isoleucine(Ile or I)
Methionine(Met or M)
Phenylalanine(Phe or F)
Trypotphan(Trp or W)
Proline(Pro or P)
Polar
Serine(Ser or S)
Threonine(Thr or T)
Cysteine(Cys or C)
Tyrosine(Tyr or Y)
Asparagine(Asn or N)
Glutamine(Gln or Q)
Electricallycharged
Acidic Basic
Aspartic acid(Asp or D)
Glutamic acid(Glu or E)
Lysine(Lys or K)
Arginine(Arg or R)
Histidine(His or H)
Fig. 5-17a
Nonpolar
Glycine (Gly or G)
Alanine (Ala or A)
Valine (Val or V)
Leucine (Leu or L)
Isoleucine (Ile or I)
Methionine (Met or M)
Phenylalanine (Phe or F)
Tryptophan (Trp or W)
Proline (Pro or P)
Fig. 5-17b
Polar
Asparagine (Asn or N)
Glutamine (Gln or Q)
Serine (Ser or S)
Threonine (Thr or T)
Cysteine (Cys or C)
Tyrosine (Tyr or Y)
Fig. 5-17c
Acidic
Arginine (Arg or R)
Histidine (His or H)
Aspartic acid (Asp or D)
Glutamic acid (Glu or E)
Lysine (Lys or K)
Basic
Electricallycharged
Peptidebond
Fig. 5-18
Amino end(N-terminus)
Peptidebond
Side chains
Backbone
Carboxyl end(C-terminus)
(a)
(b)
Fig. 5-UN5
Fig. 5-21
PrimaryStructure
SecondaryStructure
TertiaryStructure
pleated sheet
Examples ofamino acidsubunits
+H3N Amino end
helix
QuaternaryStructure
Fig. 5-21a
Amino acidsubunits
+H3N Amino end
25
20
15
10
5
1
Primary Structure
Fig. 5-21b
Amino acidsubunits
+H3N Amino end
Carboxyl end125
120
115
110
105
100
95
9085
80
75
20
25
15
10
5
1
Fig. 5-21c
Secondary Structure
pleated sheet
Examples ofamino acidsubunits
helix
Fig. 5-21f
Polypeptidebackbone
Hydrophobicinteractions andvan der Waalsinteractions
Disulfide bridge
Ionic bond
Hydrogenbond
Fig. 5-21e
Tertiary Structure Quaternary Structure
Fig. 5-21g
Polypeptidechain
Chains
HemeIron
Chains
CollagenHemoglobin
Fig. 5-22a
Primarystructure
Secondaryand tertiarystructures
Function
Quaternarystructure
Molecules donot associatewith oneanother; eachcarries oxygen.
Normalhemoglobin(top view)
subunit
Normal hemoglobin
7654321
GluVal His Leu Thr Pro Glu
Fig. 5-22b
Primarystructure
Secondaryand tertiarystructures
Function
Quaternarystructure
Molecules interact with one another andcrystallize into a fiber; capacity to carry oxygenis greatly reduced.
Sickle-cellhemoglobin
subunit
Sickle-cell hemoglobin
7654321
ValVal His Leu Thr Pro Glu
Exposedhydrophobicregion
Fig. 5-22c
Normal red bloodcells are full ofindividualhemoglobinmolecules, each carrying oxygen.
Fibers of abnormalhemoglobin deformred blood cell intosickle shape.
10 µm 10 µm
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
Normal protein Denatured protein
Denaturation
Renaturation
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
mRNA
Synthesis ofmRNA in thenucleus
DNA
NUCLEUS
mRNA
CYTOPLASM
Movement ofmRNA into cytoplasmvia nuclear pore
Ribosome
AminoacidsPolypeptide
Synthesisof protein
1
2
3
Fig. 5-27ab5' end
5'C
3'C
5'C
3'C
3' end
(a) Polynucleotide, or nucleic acid
(b) Nucleotide
Nucleoside
Nitrogenousbase
3'C
5'C
Phosphategroup Sugar
(pentose)
Fig. 5-27c-1
(c) Nucleoside components: nitrogenous bases
Purines
Guanine (G)Adenine (A)
Cytosine (C) Thymine (T, in DNA) Uracil (U, in RNA)
Nitrogenous bases
Pyrimidines
Fig. 5-27c-2
Ribose (in RNA)Deoxyribose (in DNA)
Sugars
(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
Sugar-phosphatebackbones
3' end
3' end
3' end
3' end
5' end
5' end
5' end
5' end
Base pair (joined byhydrogen bonding)
Old strands
Newstrands
Nucleotideabout to beadded to anew strand