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8/2/2019 Lecture Carbon Molecules, Proteins, And DNA
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Carbon Molecules,
Proteins, and DNA
Emphasis: Proteins and DNA
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Importance of Carbon
Carbon permeates the world of lifefrom theenergy-requiring activities and structural
organization of cells, to physical and chemicalconditions that span the globe and influenceecosystems everywhere.
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Organic Compounds
Hydrogen and other elementscovalently bonded to carbon
Carbohydrates
Lipids
Proteins
Nucleic Acids
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Carbons Bonding Behavior
Outer shell of carbonhas 4 electrons; canhold 8
Each carbon atomcan form covalentbonds with up to 4
atoms
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Methane: Simplest Organic
Compound
Structural formula
Ball-and-stickmodel
Space-fillingmodel
HH
H
H
C
Figure 3.2Pa e 36
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Bonding Arrangements
Carbon atoms canform chains or rings
Other atoms projectfrom the carbonbackbone
Glucose(ball-and-stick model)
In-text figurePage 36
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Hemoglobin Molecular Models
Ball-and-stick model Space-filling model
Ribbon modelFigure 3.3Pa e 37
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Functional Groups
Atoms or clusters of atoms that are covalentlybonded to carbon backbone
Give organic compounds their differentproperties
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Examples of Functional Groups
Methyl group - CH3
Hydroxyl group - OHAmino group - NH3
+
Carboxyl group - COOH
Phosphate group - PO4-
Sulfhydryl group - SH
Memorize!
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Condensation Reactions
Form polymers from subunits
Enzymes remove -OH from one molecule, H
from another, form bond between twomolecules
Discarded atoms can join to form water
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Amino Acid Structure
Aminogroup
Carboxylgroup
R group
tryptophan(trp)
Radical
Amino group
Acid
Central carbon
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Protein Synthesis
Peptide bond
Condensation reaction links amino group of one
amino acid with carboxyl group of next
Water forms as a by-product
Fig. 3.18aPa e 45
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Peptide bond forms.Water forms as a by-product.
Another peptide bond forms.Water forms as a by-product.
Another peptide bond forms.Water forms as a by-product.
newly formingpolypeptide chain
Another peptide bond forms.Water forms as a by-product.
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Primary Structure
Sequence of amino acids
Unique for each protein
Two linked amino acids = dipeptide
Three or more = polypeptide
Backbone of polypeptide has N atoms:
-N-C-C-N-C-C-N-C-C-N-
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Second and Third Levels
Hydrogen bonding
produces helix or
sheet
Domain formation
Secondarystructure
Tertiary structure
Figure 3.19aPa e 46
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Fourth Level Structure
Some proteins are
made up of more
than one
polypeptide chain
HLA-A2 quaternary structureFigure 3.20Pa e 47
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Hemoglobin
alpha chain
beta chain alpha chain
beta chain
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One Wrong Amino Acid
Single amino acid change in beta chain cancause sickle-cell anemia
HbS
valine histidine leucine proline threonine glutamatevaline
Fig. 3.21c,dPa e 48
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Sickle Cell Anemia
Caused by two mutated copies (HbS) of Hbgene
Low oxygen causes red blood cells to clump
Clumping prevents normal blood flow
Over time, may damage tissues and organsthroughout the body
The gene defect is a known mutation of asingle nucleotide (A to T) of the -globingene, which results in glutamic acid beingsubstituted by valineat position 6.
http://en.wikipedia.org/wiki/Sickle-cell_disease
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Sugar
At least one
phosphate group
Nitrogen-containing
base
Nucleotide Structure
ATP
Figure 3.23a
Page 50
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Nucleotide Functions
Energy carriers
Coenzymes
Chemical messengers
Building blocks for nucleic
acids
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DNA
Double-stranded
Sugar-phosphatebackbone
Covalent bonds inbackbone
H bonds between
bases
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DNA Structure Video
http://www.youtube.com/watch?v=qy8dk5iS1f0
http://www.youtube.com/watch?v=qy8dk5iS1f0http://www.youtube.com/watch?v=qy8dk5iS1f0http://www.youtube.com/watch?v=qy8dk5iS1f0http://www.youtube.com/watch?v=qy8dk5iS1f08/2/2019 Lecture Carbon Molecules, Proteins, And DNA
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RNA
Usually single strands
Four types of nucleotides
Unlike DNA, contains the base uracil in place of
thymine
Three types are key players in protein synthesis
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