Chapter 2: The Chemistry of Cells Student Guide PDF

Chapter 2 The Chemistry of Cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.  Atoms, Bonds, and Molecules Matter - all materials that occupy space and have mass Matter is composed of atoms. Atom – simplest form of matter not divisible int...

Chapter 2 The Chemistry of Cells Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display.  Atoms, Bonds, and Molecules Matter - all materials that occupy space and have mass Matter is composed of atoms. Atom – simplest form of matter not divisible into simpler substances – composed of protons, neutrons, and electrons Element – pure substances with a characteristic number of protons, neutrons, and electrons and predictable chemical behaviors 2 Insert Figure 2.1 Models of atomic structure 3  Characteristics of Elements Atomic number – number of protons Mass number – number of protons and neutrons Isotopes – variant forms of an element that differ in mass number Atomic weight – average of the mass numbers of all of the element’s isotopic forms Electron orbitals – volumes of space surrounding the atomic nucleus where electrons are likely to be found 4 Insert figure 2.2 Periodic table 5  Molecules and Bonds Molecule – distinct chemical substance that results from the combination of two or more atoms Compounds – molecules that are combinations of 2 or more different elements Chemical bonds – when 2 or more atoms share, donate or accept electrons to form molecules and compounds – 3 types: covalent, ionic, and hydrogen 6  3 Types of Chemical Bonds 1. Covalent bonds – electrons are shared among atoms – polar covalent bonds– unequal sharing – nonpolar covalent bonds– equal sharing 2. Ionic bonds – electrons are transferred to one atom forming positively charged cations and negatively charged anions 3. Hydrogen bonds – weak bonds between hydrogen and other atoms 7 Insert Figure 2.3 3 Types of Chemical Bonds 8 Insert figure 2.4 Covalent bonds 9 Insert figure 2.5 H2O – a polar molecule 10 11 Insert figure 2.7 Ionization 12 Insert figure 2.8 H-bonding in H2O 13  Electron Transfer and Oxidation- Reduction Reactions Energy exchanges in cells is a result of the movement of electrons from one molecule to another. Oxidation – the loss of electrons Reduction – the gaining of electrons Redox reactions – essential to biochemical processes 14 Insert figure 2.9 Redox reaction 15  Solutions: Mixtures of Molecules Solution – a mixture of one or more substances called solutes, dispersed in a dissolving medium called a solvent - Solutes – Na+ & Cl Insert figure 2.7 ionization Solvent – H2O 16  Most biological activities occur in aqueous (water-based) solutions. Hydrophilic molecules – dissolve in water Hydrophobic molecules – repel water Amphipathic molecules -have both hydrophilic and hydrophobic properties 17 Insert figure 2.12 Ions in solution 18  Acidity, Alkalinity, and the pH Scale Ionization of H2O releases hydrogen ions + - [H ] and hydroxyl ions [OH ] pH scale – ranges from 0 to 14, expresses the concentration of H+ ions pH is the negative logarithm of the concentration of H+ ions. pH 6 = 0.000001 moles H+/ l pH 9 = 0.000000001 moles H+/ l 19 Insert figure 2.13 pH scale 20 The Chemistry of Carbon and Organic Compounds Organic chemicals – compounds containing both carbon and hydrogen atoms 21  Carbon is the fundamental element of life – contains 4 atoms in its outer orbital – can form single, double, or triple covalent bonds – can form linear, branched, or ringed molecules 22 Insert figure 2.14 Carbon bonding 23  4 Families of Macromolecules 1. Carbohydrates – monosaccharides, disaccharides, polysaccharides 2. Lipids – triglycerides (fats and oils), phospholipids, steroids 3. Proteins 4. Nucleic acids – DNA, RNA 24  Carbohydrates Sugars and polysaccharides – general formula (CH2O)n Monomer – monosaccharide (glucose, fructose) Polymer –polysaccharide (starch, cellulose, glycogen) Subunits linked by glycosidic bonds Functions – structural support, nutrient and energy stores 25 Insert figure 2.15 Carbohydrates 26  Lipids Long or complex, hydrophobic, C - H chains Triglycerides, phospholipids in membranes, steroids like cholesterol Functions – triglycerides – energy storage – phospholipid – major cell membrane component – steroids – cell membrane component 27 Insert figure 2.18 triglycerides 28 Insert figure 2.19 phospholipids 29 Insert figure 2.20 Cell membrane 30  Proteins Predominant molecules in cells Monomer – amino acids – 20 Polymer – peptide, polypeptide, protein Subunits linked by peptide bonds Fold into very specific 3-D shapes Functions - support, enzymes, transport, defense, movement 31 Insert figure 2.22 Protein structure 32  Nucleic Acids DNA and RNA Monomer – nucleotide DNA – deoxyribonucleic acid – A,T,C,G – nitrogen bases – double helix – function - hereditary material RNA – ribonucleic acid – A,U,C,G – nitrogen bases – function - organize protein synthesis 33 Insert figure 2.23 Nucleic acid structure 34 35 ATP: The Energy Molecule of Cells Adenosine triphosphate – nucleotide - adenine, ribose, three phosphates Function – transfer and storage of energy Insert figure 2.27 a ATP molecule 36 50