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Transcript
Molecules of Life Chapter 3 Molecules Inorganic compound Nonliving matter Salts, water Organic compound Molecules of life Contains Carbon (C) and Hydrogen (H) Carbon backbone Carbon Chemistry Cell is mostly water Carbon is a versatile atom The rest of the cell consists mostly of carbon-based molecules four electrons in an outer shell that holds eight can share its electrons with other atoms to form up to four covalent bonds Structures may vary Organic Molecules Many molecules of life are macromolecules (macromolecules contain many molecules joined together) Monomers: Simple organic molecules that exist individually Polymers: Large organic molecules form by combining monomers Polymer Monomer Carbohydrate Monosaccharide Protein Amino acid Lipids Triglycerides Nucleic acid Nucleotide Polymers Are Built of Monomers All polymers are assembled the same way Covalent bond is formed by removing an hydroxyl group (OH) from one subunit and a hydrogen (H) from another subunit Amounts to the removal of a molecule of water (H2O) Dehydration synthesis Polymers Are Built of Monomers Process of disassembling polymers into component monomers is essentially the reverse of dehydration synthesis Molecule of water is added to break the covalent bond between the monomers Hydrolysis Molecules of Life 4 main classes of biological molecules 1. 2. 3. 4. Carbohydrates Lipids Proteins Nucleic Acids Carbohydrates Carbohydrates Some Functions: Quick fuel Short-term energy storage Structure of organisms Cell to cell recognition Consist of C, H, and O atoms 1:2:1 ratio “Saccharides” 3 major classes: Monosaccharides Disaccharides Polysaccharides Monosaccharides “simple sugars”; “one monomer of a sugar” Dissolve easily in water hydrophilic Glucose C6H12O6 Fructose Form of glucose Disaccharides Short chain of two sugar monomers Two Monosaccharides Lactose, sucrose, maltose Lactose = glucose + galactose Polysaccharide “Complex” carbohydrate Contain many C-H bonds Glycogen Polysaccharide of glucose Storage form of glucose in animals Starch Good for storing energy These bond types are the ones most often broken by organisms to obtain energy Storage form of glucose in plants Cellulose Found in the cell walls of plants Lipids Lipids Cells use lipids to store energy Hydrophobic Functions: Energy Storage Cushioning and Insulation Found in the plasma membrane 3 main types: Fats & Oils Phospholipids Steroids Fats Dietary fat consists largely of the molecule triglyceride Combination of glycerol and three fatty acids Fats Unsaturated fatty acids Have less than the maximum number of hydrogens bonded to the carbons Saturated fatty acids Have the maximum number of hydrogens bonded to the carbons Most animal fats have a high proportion of saturated fatty acids, which can be unhealthy Example: butter Most plant oils tend to be low in saturated fatty acids Example: corn oil Phospholipids Glycerol, two fatty acids and a phosphate group Plasma membrane Nonpolar tail Polar heads Proteins Why Proteins?? VERY important functions in cells Keratin and collagen have structural roles Enzymes speed up chemical reactions of metabolism Responsible for transport of substances within the body Transport substances across cell membranes Hormones that regulate cellular function Insulin Proteins Made from amino acids 20 various kinds Amino acids linked to one another by peptide bonds Two amino acids bound by a peptide bond is a dipeptide Three or more is a polypeptide chain Amino Acids Peptide / Dipeptide Polypeptide Protein Proteins Amino acids are small molecules with a simple basic structure, a carbon atom to which three groups are added an amino group (-NH2) a carboxyl group (-COOH) a functional group (R) The functional group gives amino acids their chemical identity Protein Structure Protein’s final shape and chemical behavior arise from: Chain bends, folds, coils, etc. Proteins Primary structure sequence of amino acids in the polypeptide chain determines all other levels of protein structure Proteins Secondary structure Forms because regions of the polypeptide that are non-polar are forced together folded structure may resemble coils, helices, or sheets Proteins Tertiary structure final 3-D shape of the protein final twists and folds that lead to this shape are the result of polarity differences in regions of the polypeptide Proteins Quaternary structure spatial arrangement of proteins comprised of more than one polypeptide chain Protein The shape of a protein affects its function Changes to the environment of the protein may cause it to unfold or denature Increased temperature or lower pH affects hydrogen bonding, which is involved in the folding process Denatured protein is inactive Nucleic Acids Proteins Denaturing When proteins lose their shape Nucleotides and Nucleic Acids Nucleic acids Can be single stranded or double stranded DNA Deoxyribonucleic acid genetic information RNA Ribonucleic acid used to build proteins Nucleotides and Nucleic Acids Nucleic acids Built by nucleotides Phosphate Pentose sugar Nitrogen-containing base DNA Composition DNA is built from four different kinds of nucleotides One of four bases determines the nucleotide: A - Adenine G - Guanine T - Thymine C – Cytosine DNA consists of two strands of nucleotides twisted into a double helix GAGA….a nucleotide repeat!! Base pairs Bases can only pair up with their corresponding “mate” 2 kinds: A–T G–C Amount of A = T Amount of G = C Can line up in any order DNA Composition Nucleotides linked together by covalent bonds Bases of one strand linked to the other by hydrogen bonds The two strands run in opposite directions DNA into RNA RNA a big player!! Single strand Sugar, phosphate group, and a N-containing base Bases are: A, C, G, and URACIL (U)