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Principles of Biology Chapter 3
Chapter 3 Molecules of Life
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Carbon is essential to life Cells are mostly carbon molecules & water Carbon is the basic building block of the 4 macromolecules
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Carbohydrates, lipids, proteins, DNA Carbon
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Can form very large molecules 4 bonds
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Basis of Organic chemistry
Fig. 3.2
Carbon skeletons
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Can be very large and varied
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Linear or branched
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Bonded to carbon atoms or other molecules
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Hydrocarbon
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Simplest organic molecule
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Methane Gasoline
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Consists of carbon and hydrogen atoms
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Unique 3-D shape
Fig. 3.3
Fig. 3.5
Functional groups
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Attached to hydrocarbon skeleton Participate in chemical reactions
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OH - called hydroxyl or alcohol group
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Sugars and alcohols
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Carbonyl - O = C (double bond to carbon)
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Found in sugars
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NH 3
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- amino group found in proteins COOH - carboxyl group
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Found in amino acids, fatty acids and vitamins
Fig. 3.6
Synthesis and digestion
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Macromolecules - very large Polymers - many (repeating)parts
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Monomer - one unit Dehydration synthesis -builds
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Bonds monomers together
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Release water molecule Digestion - breaks
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Aka hydrolysis ( water breaking)
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Adds water ions to the broken ends
Carbohydrates
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Monosaccharides
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One sugar unit- molecular formula of CH 2 O
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Glucose - C 6 H 12 O 6
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Fructose - C 6 H 12 O 6
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Honey has both monosaccharides
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In aqueous solutions forms rings Main fuel for cellular work
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Can used to make other molecules
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Can be chained together
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Disaccharides - two sugar units
Fig. 3.9
Fig. 3.10
Fig. 3.11
Polysaccharides
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Complex sugars - many sugar units
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Starch
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Glucose chain molecules
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Energy storage in plants
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Glycogen
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Glucose chain molecule
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Energy storage in animals Cellulose
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Glucose chain molecule
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Structural molecule in plant cell walls
Lipids
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Hydrophobic
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Water hating Fats and steroids Fats
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Glycerol molecule and 3 fatty acids
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Triglyceride
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Store twice as much energy as carbs
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Cushion and insulate
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Saturated - no double bonds- all possible H
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Unsaturated- double bonds - fewer H atoms
Fig. 3.14
Steroids
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Lipids because they are hydrophobic Carbon chains form 4 fused rings Cholesterol
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Form other steroids from it
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Make into sex hormones
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Estrogen
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Testosterone
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Component of cell membranes
Fig. 3.15
Anabolic steroids
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Mimic testosterone First used for anemia / muscle disease Abused by athletes Misuse can cause
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Facial bloating/acne
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Violent mood swings
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Liver damage
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Increase cholesterol levels
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Reduce sex drive and fertility
Phospholipids
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Two regions with opposite properties Phosphate ‘head’ is polar
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Hydrophillic water loving Fatty acid tails are non-polar
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Hydrophobic - water fearing Forms plasma membrane
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Phosphate group faces out
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Watery environment inside/outside cell - Tails face each other - Form barrier
Fig. 3.18
Proteins
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Greek word meaning “first place” Polymer of amino acids Have thousands of proteins in us Monomer
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Amino acid
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Central carbon Amine group Carboxyl group Hydrogen “R” group - remainder - what differs from amino acid to amino acid
Proteins
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Amino acids linked by peptide bonds Forming a polypeptide (aka protein)
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Chain of amino acids
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100 or more
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Primary structure
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Order of amino acids
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20 different amino acids
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Change in order can cause disease
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Sickle cell anemia One amino acid changed
Fig. 3.20
Fig. 3.21
Protein structure
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Secondary and tertiary structure
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Twisting and folding
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Bonding between different parts of molecule
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3-D shape
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Quaternary structure
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Interaction between more that one polypeptide
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All this leads to a particular shape that allows the protein to do its job
Fig. 3.19
Protein shape
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Must twist, fold, and coil correctly to function
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Hydrophobic region inside Hydrophilic regions outside in watery environment of cell
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3-D shape is critical Denaturation
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Caused by change in pH or temperature
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Changes 3-D shape - non functional
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Shape determines function
Fig. 3.22
Enzymes
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Enzymes are a kind of protein
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Many different enzymes in our bodies
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Metabolism is the sum total of all chemical reactions in an organism
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Most require a specific enzyme to happen
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Catalyst - stimulate a reaction to occur
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Reactions require a input of energy to get started - activation energy Enzymes lower the energy required Result is that chem rxns are effective
How is structure determined?
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Order of amino acids specified by a gene - recipe for a polypeptide Proteins include
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Structural
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Storage
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Contractile
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Transport
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Defensive
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Signal proteins
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ENZYMES!
Nucleic acids
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DeoxyriboNucleic Acid - DNA DNA is a recipe book for proteins Genes direct the order of amino acids Two types of nucleic acids
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DNA
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RNA - RiboNucleic Acid
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Chemical code
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Nucleic acid to protein language
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RNA helps with this process
Fig. 3.26
Nucleic acids
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Polymer
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Repeating unit is a nucleotide consisting of:
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Sugar Phosphate Base
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Adenine - A Cytosine - C
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Guanine - G Thymine - T (only in DNA) Uracil - U (only in RNA)
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Dehydration synthesis makes the polymer
Fig. 3.27
DNA
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One strand has 100’s to 1000’s of genes DNA double helix
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2 strands Bonded to each other by hydrogen bonds A pairs with T, vice versa C pairs with G, vice versa RNA is a single strand of nucleotides Replication (DNA copying)
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Strands separated New complementary nucleotides join
Fig. 3.29