Lecture 2: The Molecules of Life (BIOL1010)

Lecture 2 The Molecules of Life Required Reading: Morris text: Chapter 2 (pp. 27-32) Section 2.1 Properties of Atoms Section 2.2 Molecules and Chemical Bonds Objectives: Atoms, Molecules and Chemical Bonds In-class activity Water...

Lecture 2 The Molecules of Life Required Reading: Morris text: Chapter 2 (pp. 27-32) Section 2.1 Properties of Atoms Section 2.2 Molecules and Chemical Bonds Objectives: Atoms, Molecules and Chemical Bonds In-class activity Water Textbook reference sections/pages: Carbon Morris text: Chapter 2 (pp. 32-43) Organic molecules Section 2.3 Water Nucleic Acids Section 2.4 Carbon Section 2.5 Organic Molecules BIOL1010 and 1  Required Reading In-class Activity Socrative Activity – Using your laptop or phone or tablet… – Go to: https://b.socrative.com/login/student/ – Or search Socrative Student – Enter Room Name: BIOLOGYANA and enter your first and last name – Don’t use the notes you made from your reading – see how much you remember! 2 BIOL1010 and  So Much Diversity…So Few Elements What have you learned from your required reading? – The chemistry of life is based on just a few types of molecules, which are made up of just a few elements! Of approx. 100 elements, only about a dozen are found in living organisms – Because of some basic features of chemistry, a huge amount of diversity is generated from a limited number of chemicals and their interactions. 3 BIOL1010 and  Water All life depends on water: – life originated in water – dominant component of almost all living organisms This Photo by Unknown Author is licensed under – covers about 71% of the earth’s surface CC BY-NC often determines the environmental distributions of most species – most biochemical reactions take place in water 4 BIOL1010 and  Water Properties of water: – Water is a polar molecule Partial positive charge (δ+) and partial negative charge (δ-) Due to electronegativity – Polar molecules tend to interact with other polar Figure 2.7 Water molecules have polar molecules; non-polar covalent bonds molecules tend not to interact with polar molecules – Hydrophilic vs. hydrophobic – Water is a good solvent 5 BIOL1010 and  Water – Water is a good solvent E.g. salt dissolved in water 6 BIOL1010 and  Water Special properties of water: – Besides being an excellent solvent, water has special properties due to hydrogen bonds: 7 BIOL1010 and  Water Special properties of water: – Structure Liquid vs. solid water (ice) 8 BIOL1010 and  Water Special properties of water: – Surface tension and cohesion This Photo by Unknown Author is licensed under CC BY This Photo by Unknown Author is licensed under CC BY-SA-NC – Resistance to temperature change 9 BIOL1010 and  Carbon Life as we know it is based on carbon – 90% of total dry mass of a cell is carbon, oxygen, hydrogen and nitrogen – Carbon can combine with many other elements to forma wide variety of specialized molecules 10 BIOL1010 and  Carbon Carbon Atoms Form Four Covalent Bonds When a carbon atom forms orbitals, it behaves as if it has four unpaired electrons – E.g. methane Carbon forms four covalent bonds Bonds can rotate freely around axis Tetrahedron 3-D structure 11 BIOL1010 and  Carbon Other properties that contribute to ability to form diversity of molecules: – Carbon atoms link to other carbon atoms covalently Form chains or rings – Carbon atoms can form double bonds – Can form isomers Same chemical formula; different structure 12 BIOL1010 and  Organic Molecules Proteins – structural support; catalysts In any cell, chemical Nucleic Acids –encode and transmit genetic processes only depend information on a few classes of large carbon-based molecules Carbohydrates - energy Lipids – cell membranes; energy storage; cell signaling molecules 13 BIOL1010 and  Organic Molecules Proteins – Polymers of amino acids held together by peptide bonds – R-groups are variable from one amino acid to another – Peptide bonds (covalent) join carboxyl to amino group to form polypeptide chain Dehydration reaction 14 BIOL1010 and  Organic Molecules Nucleic Acids – Encode genetic information in the nucleotide sequence – Polymers of nucleotides covalently bonded RNA, DNA DNA nucleotide = deoxyribose sugar + phosphate group + base RNA nucleotide = ribose sugar + phosphate group + base 15 BIOL1010 and  Organic Molecules Nucleic Acids – Nucleotide Structure 16 BIOL1010 and  Organic Molecules Nucleic Acids – Base Structure 17 BIOL1010 and  Organic Molecules Nucleic Acids – Putting It All Together Adjacent nucleotides are covalently bonded by phosphodiester bonds – Dehydration reaction In DNA base pairing is complementary via hydrogen bonding 18 BIOL1010 and  Organic Molecules Carbohydrates – polymers of simple sugars linked by glycosidic bonds composed of C, H and O atoms usually in 1:2:1 ratio – simplest carbohydrates are sugars (saccharides) Monosaccharides One simple sugar Disaccharides Two monosaccharides linked Polysaccharides Many monosaccharides linked Complex carbohydrates Long, branched chains of monosaccharides 19 BIOL1010 and  Organic Molecules Carbohydrates – a few examples Disaccharides Monosaccharides Polysaccharide 20 BIOL1010 and  Organic Molecules Lipids – Not polymers but are defined by being hydrophobic – Very diverse group: fats in our diet, part of cell membranes and signaling molecules – E.g.Triacylglycerol 21 BIOL1010 and  Organic Molecules Lipids – Saturated vs. Unsaturated Fatty Acids – Saturated – no double bonds; maximum number of hydrogen atoms attached; straight chains – Unsaturated – contains double bonds between carbon atoms; kinked chains 22 BIOL1010 and  Organic Molecules Lipids – Fatty acids of triacylglycerols do not contain polar covalent bonds – Uncharged molecules and very hydrophobic Form oil droplets within the cell – However, there are areas of transient slightly negative and positive charge in the fatty acids which can weakly bind to each other due to van der Waals forces 23 BIOL1010 and  Organic Molecules Lipids – Because of van der Waals forces, melting points of fatty acids depend on length and level of saturation Longer fatty acid chains, more van der Waals interactions, higher melting point Kinks in fatty acid chains reduce packing, fewer van der Waals interactions, lower melting point – E.g. Butter (saturated) is solid at room temperature – E.g. plant fats and fish oils (unsaturated) are liquid at room temperature 24 BIOL1010 and  Organic Molecules Other types of Lipids – Steroids Ring structure; also hydrophobic – E.g. cholesterol » Component of animal cell membranes; precursor for hormones like estrogen and testosterone – Phospholipids Major component of cell membranes (more on this later) 25 BIOL1010 and