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