Chapter 2 Chemical and Biochemical Foundations, Part 1 PDF

POWERPOINTS TO ACCOMPANY Chapter 2 Chemical and Biochemical Foundations, Part 1 Advanced Physiology and Pathophysiology: Essentials for Clinical Practice Nancy C Tkacs, Randall L Johnson, and Linda L Herrmann 1...

POWERPOINTS TO ACCOMPANY Chapter 2 Chemical and Biochemical Foundations, Part 1 Advanced Physiology and Pathophysiology: Essentials for Clinical Practice Nancy C Tkacs, Randall L Johnson, and Linda L Herrmann 1 © Springer Publishing Company, LLC.  Key Concepts Atoms bond together, forming molecules—enzymes catalyze reactions of molecule synthesis, degradation, and exchange Some atoms and molecules are charged (ions), with acids and bases being special compounds that ionize Biomolecules can be hydrophobic and nonpolar, others are hydrophilic and are either charged (ions) or polar (contain partial charges) Cell membranes have a lipid hydrophobic core that forms a barrier between two aqueous solutions—intracellular fluid and extracellular fluid Small biomolecules build to macromolecules 2 © Springer Publishing Company, LLC. Atoms Found in the Body The Big Four: Oxygen (O), Carbon (C), Hydrogen (H), Nitrogen (N) Also found in lesser amounts: Calcium (Ca), Phosphorus (P), Potassium (K), Sulfur (S), Sodium (Na), Chlorine (Cl), Magnesium (Mg), Iron (Fe), Copper (Cu), Zinc (Zn), Iodine (I), and a few others 3 © Springer Publishing Company, LLC. Atomic Structure Nucleus Protons (positive charge)s—determine atomic number Neutrons Electrons—negatively charged, move in a cloud around the nucleus 4 © Springer Publishing Company, LLC.  Periodic Table of Elements Elements fall into groups Within groups, elements share similar properties Note the following groups of atoms found in the body: Group 1—Na, K Group 2—Mg, Ca Group 15—N, P Group 16—O, S Group 17—Cl, I 5 © Springer Publishing Company, LLC.  Electron Shells Electrons are organized into shells, with the innermost shell able to hold two electrons, and the remaining shells able to hold eight electrons Incomplete filling of the outermost shell makes an element chemically reactive Hydrogen (element 1)—one electron, good chemical reactivity Helium (element 2)—two electrons fill outer shell—chemically inert Lithium (element 3)—can lose one electron and become Li+, good chemical reactivity, same group as sodium Beyond these three elements, the outer shell has eight places. When all are not filled, the octet rule is not satisfied, and the element is reactive (C, K) 6 © Springer Publishing Company, LLC.  Gaining or Losing Electrons Creates Charged IONS The outer valence shell of sodium contains one electron—stability is improved by giving up that electron and developing a positive charge (Na+) The outer valence shell of chlorine has seven electrons—stability is improved by gaining one electron and becoming a negatively charged chloride ion (Cl−) Sodium chloride is formed by an ionic bond between Na+ and Cl− 7 © Springer Publishing Company, LLC.  Water Molecules Surround Ions In Solution Water molecules have partial positive and negative charges When NaCl dissolves in water, the ionic bond is broken and hydrogen atoms of water are attracted to Cl−, while oxygen atoms of water are attracted to Na+ The ions of the body are all stable when surrounded by water molecules 8 © Springer Publishing Company, LLC.  Acids and Bases Dissociate In Solution Acids are proton (H+) donors, bases are proton acceptors When HCl (strong acid) dissolves in water, the ionic bond is broken and hydrogen atoms of water are attracted to Cl−, while oxygen atoms of water add the H+ and become hydronium ions When NaOH (strong base) dissolves in water, Na+ is surrounded by water molecules, and hydroxide ion is stable. 9 © Springer Publishing Company, LLC.  Body Fluids Differ in Composition by Location Extracellular fluid is rich in Plasma Interstitial Intracellular Na+, Cl− Fluid Fluid Plasma has protein anions Interstitial fluid has few proteins Intracellular fluid is rich in K+, PO43− (phosphate) and proteins 10 © Springer Publishing Company, LLC.  Body Buffer Systems Maintain pH between 7.35-7.45 Carbonic acid buffer system is centered on carbonic acid that can dissociate into water + CO2 (which can be removed by lungs), or into bicarbonate + H+—either can be secreted or reabsorbed by kidneys to maintain balance Amino acids have acidic carboxyl groups and basic amine groups that buffer pH changes. 11 © Springer Publishing Company, LLC. Covalent Bonding involves Atom Electron Sharing Sharing with one electron contributed from each atom forms a single covalent bond Sharing with two electrons contributed from each atom forms a double covalent bond Sharing with three electrons contributed from each atom forms a triple covalent bond 12 © Springer Publishing Company, LLC.  Covalent Bond Examples Each of these molecules allows roughly equal sharing of electrons between atoms: characterizing nonpolar bonding 13 © Springer Publishing Company, LLC. Bond Properties Depend on Atom Electronegativity Polar covalent bonds have unequal electron sharing (one atom has stronger “pull” on bonding electrons) This results in molecules with partial charges, shown as d+ or d− Bond Type Electronegativity Example Difference Nonpolar 0-0.4 O2 Polar covalent 0.4-2.0 H2 O Ionic > 2.0 NaCl 14 © Springer Publishing Company, LLC.  Water is the Polar Solvent of the Body Fluids Hydrogen bonds (dashed lines) are weak bonds formed by the attraction between partially charged molecules. Water has high surface tension because of hydrogen bonding Water makes hydrogen bonds with itself and with other polar molecules (like urea, shown on right) 15 © Springer Publishing Company, LLC. Examples of Polar Biomolecules Biomolecules that have bonds between hydrogen and electronegative oxygen or nitrogen generally have polar qualities Carbohydrates, amino acids, nucleic acids, are all polar compounds, and are therefore hydrophilic (water-loving) As noted earlier, ions are charged compounds, and they are also hydrophilic, easily soluble in water and aqueous solutions Lipids have many C-H bonds with equal electron sharing, they are nonpolar and hydrophobic (water-hating) 16 © Springer Publishing Company, LLC.  Organic Molecules and Terminology Core structures are based on carbon’s ability to make up to four bonds, allowing complex chains and branching molecules Organic groups that include oxygen and nitrogen can modify carbon chains and rings, creating molecules with unique functional properties Many organic groups are polar or have characteristics of acids or bases The addition of an organic group to an existing molecule is described with the suffix “-ation” (methylation, phosphorylation, hydroxylation) The removal of an organic group from an existing molecule is described with the prefix “de-” and suffix “-ation” (demethylation, deamination, decarboxylation) Many reactions are carried out by enzymes with the suffix “-ase” (carboxylase, hydroxylase) 17 © Springer Publishing Company, LLC. Organic Compounds and Functional Groups Amine Aldehyde Hydroxyl Ketone Methyl Carboxyl Amino Acid Sugar Sugar Alanine Ribose Ribulose 18 © Springer Publishing Company, LLC. Sulfur-containing Functional Groups Disulfide bond Thiol Amino Acid Amino Acid Cysteine Cystine 19 © Springer Publishing Company, LLC. Disulfide Bonds Shape Cysteine-containing Proteins Insulin 20 © Springer Publishing Company, LLC. Reactions Synthesize, Decompose, and Change Molecules Glycogen synthesis describes the serial addition of glucose molecules by glycogen synthase Chemical reactions involving glucose require that it be Glycogen decomposition phosphorylated by a kinase describes the progressive enzyme removal of glucose molecules by glycogen This is an exchange reaction with phosphorylase ATP giving up one phosphate that is transferred to glucose by hexokinase or glucokinase 21 © Springer Publishing Company, LLC.  Carbohydrates Hexoses (six carbon) and other monosaccharide sugars Chiral compounds, based on arrangement of four attachments to a central carbon D- and L- forms, D-sugars are most common in nature Ribose (five carbon) and deoxyribose sugars are contained in nucleotides and nucleic acids Disaccharides consist of two monosaccharides bonded together Sucrose (table sugar) = glucose + fructose Lactose (milk sugar) = glucose + galactose (absence of enzyme lactase leads to lactose intolerance) Maltose = glucose + glucose – breakdown product of many starches Hydroxyl groups on sugars make them very hydrophilic, easily soluble in water, cannot diffuse across cell membrane lipid barrier, so they require carrier proteins 22 © Springer Publishing Company, LLC.  D-glucose Principal energy source Sole energy source for the brain under most conditions Liver regulates blood glucose by synthesis of glycogen after meals, release of glucose from glycogen while fasting Optimal levels: 70–110 mg/dL Hyperglycemia occurs in diabetes mellitus, leads to chronic complications Chain Form Ring Form Hypoglycemia can cause brain dysfunction and coma 23 © Springer Publishing Company, LLC.  Carbohydrates are Attached to Cell Surface Membrane surface markers when attached to proteins (forming glycoproteins) and lipids (forming glycolipids) Blood groups are distinguished by A, B, and O antigens attached to membrane sphingolipids O antigen A antigen B antigen 24 © Springer Publishing Company, LLC.