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Principles of Biology Chapter 3 Chapter 3 Molecules of Life • Carbon is essential to life • Cells are mostly carbon molecules & water • Carbon is the basic building block of the 4 macromolecules – Carbohydrates, lipids, proteins, DNA • Carbon – Can form very large molecules - 4 bonds – Basis of Organic chemistry Fig. 3.2 Carbon skeletons • Can be very large and varied – Linear or branched – Bonded to carbon atoms or other molecules • Hydrocarbon – Simplest organic molecule • Methane • Gasoline – Consists of carbon and hydrogen atoms • Unique 3-D shape Fig. 3.3 Fig. 3.5 Functional groups • Attached to hydrocarbon skeleton • Participate in chemical reactions – OH - called hydroxyl or alcohol group • Sugars and alcohols – Carbonyl - O = C (double bond to carbon) • Found in sugars – NH3 - amino group found in proteins – COOH - carboxyl group • Found in amino acids, fatty acids and vitamins Fig. 3.6 Synthesis and digestion • Macromolecules - very large • Polymers - many (repeating)parts – Monomer - one unit • Dehydration synthesis -builds – Bonds monomers together – Release water molecule • Digestion - breaks – Aka hydrolysis ( water breaking) – Adds water ions to the broken ends Carbohydrates • Monosaccharides – One sugar unit- molecular formula of CH2O – Glucose - C6H12O6 – Fructose - C6H12O6 – Honey has both monosaccharides • In aqueous solutions forms rings • Main fuel for cellular work – Can used to make other molecules – Can be chained together • Disaccharides - two sugar units Fig. 3.9 Fig. 3.10 Fig. 3.11 Polysaccharides • Complex sugars - many sugar units • Starch – Glucose chain molecules – Energy storage in plants • Glycogen – Glucose chain molecule – Energy storage in animals • Cellulose – Glucose chain molecule – Structural molecule in plant cell walls Lipids • Hydrophobic – Water hating • Fats and steroids • Fats – Glycerol molecule and 3 fatty acids – Triglyceride – Store twice as much energy as carbs – Cushion and insulate – Saturated - no double bonds- all possible H – Unsaturated- double bonds - fewer H atoms Fig. 3.14 Steroids • Lipids because they are hydrophobic • Carbon chains form 4 fused rings • Cholesterol – Form other steroids from it – Make into sex hormones • Estrogen • Testosterone – Component of cell membranes Fig. 3.15 Anabolic steroids • • • • Mimic testosterone First used for anemia / muscle disease Abused by athletes Misuse can cause – Facial bloating/acne – Violent mood swings – Liver damage – Increase cholesterol levels – Reduce sex drive and fertility Phospholipids • Two regions with opposite properties • Phosphate ‘head’ is polar – Hydrophillic water loving • Fatty acid tails are non-polar – Hydrophobic - water fearing • Forms plasma membrane – Phosphate group faces out – Watery environment inside/outside cell - Tails face each other - Form barrier Fig. 3.18 Proteins • • • • Greek word meaning “first place” Polymer of amino acids Have thousands of proteins in us Monomer – Amino acid • • • • • Central carbon Amine group Carboxyl group Hydrogen “R” group - remainder - what differs from amino acid to amino acid Proteins • Amino acids linked by peptide bonds • Forming a polypeptide (aka protein) – Chain of amino acids – 100 or more • Primary structure – Order of amino acids – 20 different amino acids – Change in order can cause disease • Sickle cell anemia • One amino acid changed Fig. 3.20 Fig. 3.21 Protein structure • Secondary and tertiary structure – Twisting and folding – Bonding between different parts of molecule – 3-D shape • Quaternary structure – Interaction between more that one polypeptide • All this leads to a particular shape that allows the protein to do its job Fig. 3.19 Protein shape • Must twist, fold, and coil correctly to function • Hydrophobic region inside • Hydrophilic regions outside in watery environment of cell • 3-D shape is critical • Denaturation – Caused by change in pH or temperature – Changes 3-D shape - non functional • Shape determines function Fig. 3.22 Enzymes • Enzymes are a kind of protein – Many different enzymes in our bodies • Metabolism is the sum total of all chemical reactions in an organism – Most require a specific enzyme to happen – Catalyst - stimulate a reaction to occur • 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? • Order of amino acids specified by a gene - recipe for a polypeptide • Proteins include – Structural – Storage – Contractile – Transport – Defensive – Signal proteins – ENZYMES! Nucleic acids • • • • DeoxyriboNucleic Acid - DNA DNA is a recipe book for proteins Genes direct the order of amino acids Two types of nucleic acids – DNA – RNA - RiboNucleic Acid • Chemical code – Nucleic acid to protein language – RNA helps with this process Fig. 3.26 Nucleic acids • Polymer – Repeating unit is a nucleotide consisting of: • Sugar • Phosphate • Base – – – – – Adenine - A Cytosine - C Guanine - G Thymine - T (only in DNA) Uracil - U (only in RNA) • Dehydration synthesis makes the polymer Fig. 3.27 DNA • One strand has 100’s to 1000’s of genes • DNA double helix – – – – 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) – Strands separated – New complementary nucleotides join Fig. 3.29