Chemical Basis of Life Chapter 2 Chemistry - study of matter Biochemistry-chemistry of organisms

2.1: Introduction Why study chemistry in an Anatomy and Physiology class? - Body functions depend on cellular functions - Cellular functions result from chemical changes - Biochemistry helps to explain physiological processes

2.2: Structure of Matter Matter – anything that takes up space and has mass (weight). It is composed of elements. Elements – composed of chemically identical atoms: Bulk elements – required by the body in large amounts Trace elements - required by the body in small amounts Ultratrace elements – required by the body in very minute amounts Atoms – smallest particle of an element

Structure of Matter A. Atoms-basic unit 1. Nucleus a. proton- “+”, 1 amu b. neutron- no charge, 1 amu 2. Energy Levels/Shells a. electron- “-”, 0 amu 2,8,8

All atoms are electrically neutral because the # of p+ = # of e-. Atomic number = # of protons. Atomic weight = # of protons + neutrons. Isotopes-atoms of the same element having different atomic masses. Radioactive isotopes-an isotope which easily loses subatomic particles.

Molecules and Compounds Molecule – particle formed when two or more atoms chemically combine Compound – particle formed when two or more atoms of different elements chemically combine Molecular formulas – depict the elements present and the number of each atom present in the molecule H2 C6H12O6 H2O

Bonding of Atoms: Ions Ion An atom that gains or loses electrons to become stable An electrically charged atom Cation A positively charged ion Formed when an atom loses electrons 11p+ 17p+ 12n0 18n0 Anion A negatively charged ion Formed when an atom gains electrons Sodium atom (Na) Chlorine atom (Cl) (a) Separate atoms If a sodium atom loses an electron to a chlorine atom, the sodium atom becomes a sodium ion (Na+), and the chlorine atom becomes a chloride ion (Cl–).

Covalent Bonding occurs when the atoms forming the bond SHARE one or more pairs of electrons this results in MOLECULES Each “dash” represents a pair of shared electrons (single covalent bond)

Bonding of Atoms: Structural Formula Structural formulas show how atoms bond and are arranged in various molecules Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H H H H O O O O C O H2 O2 H2O CO2

Bonding of Atoms: Polar Molecules Molecule with a slightly negative end and a slightly positive end Results when electrons are not shared equally in covalent bonds Water is an important polar molecule Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. Slightly negative end (a) Slightly positive ends

Hydrogen Bonds Hydrogen Bonds A weak attraction between the positive end of one polar molecule and the negative end of another polar molecule Formed between water molecules Important for protein and nucleic acid structure Copyright © The McGraw-Hill Companies, Inc. Permission required for reproduction or display. H H O H Hydrogen bonds O H H O H H O H H O H (b)

Chemical Reactions Chemical reactions occur when chemical bonds form or break among atoms, ions, or molecules Reactants are the starting materials of the reaction - the atoms, ions, or molecules Products are substances formed at the end of the chemical reaction NaCl ’ Na+ + Cl- Reactant Products

Chemical Reactions SYNTHESIS - “A + B---> AB” Ex: H2 + O2---> H2O DECOMPOSITION - “AB ---> A + B” Ex: 2H2O ---> 2H2 + O2 EXCHANGE - “AB + CD ---> AD + CB” Ex: HCl + NaOH ---> NaCl + H2O Many reactions are reversible Ex: A + B <---> AB

Acids, Bases, and Salts NaCl  Na+ + Cl- HCl  H+ + Cl- Electrolytes – substances that release ions in water NaCl  Na+ + Cl- Acids – electrolytes that dissociate to release hydrogen ions in water HCl  H+ + Cl- Bases – substances that release ions that can combine with hydrogen ions NaOH  Na+ + OH- Salts – electrolytes formed by the reaction between an acid and a base HCl + NaOH  H2O + NaCl

pH-measurement of the H+ concentration of a solution 0<---------7---------->14 acidic alkaline (basic) distilled water is neutral, having a pH of 7.0 blood pH = 7.4 if below--->acidosis if above--->alkalosis pH scale ranges from 0 - 14

Figure 02.10

Organic -contain C & H Inorganic-don’t contain both C & H Chemistry of Cells Organic -contain C & H Inorganic-don’t contain both C & H

2.3: Chemical Constituents of Cells Organic v. Inorganic Molecules Organic molecules Contain C and H Usually larger than inorganic molecules Dissolve in water and organic liquids Carbohydrates, proteins, lipids, and nucleic acids Inorganic molecules Generally do not contain C Usually smaller than organic molecules Usually dissociate in water, forming ions Water, oxygen, carbon dioxide, and inorganic salts

Organic Compounds Organic compounds almost always have covalent bonds. The four types we will discuss are:

1. Carbohydrates contain C, H, O---H:O ratio is 2:1 Ex: C6H12O6 C12H22O11 provide immediate energy source short-term energy storage carbon is in short chains or RINGS Monosaccharides (simple sugars) examples are: glucose, fructose, galactose, ribose, deoxyribose

Disaccharides (double sugars): examples are sucrose, lactose, maltose Disaccharides (double sugars): examples are sucrose, lactose, maltose. These are each made of 2 rings of carbons (2 simple sugars joined together. Polysaccharides: examples are starch, glycogen (animal starch), and cellulose. These are made of many rings of carbon (many simple sugars joined together).

Figure 02.12

2. Lipids provide long-term energy storage water insoluble (either the entire molecule or part of the molecule) cell structure, vitamins, hormones types: fats, phospholipids, cholesterol

Fats (animal fats, oils) made of C,H,&O, but H:O ratio is MUCH greater than 2:1 (C57H110O6) Each molecule is called a triglyceride, and is made of 1 glycerol and 3 fatty acids. An unsaturated fat has at least one carbon to carbon double or triple bond in its fatty acids, and it is usually liquid--good. A saturated fat has no C=C or triple, usually solid--bad.

Phospholipids major component of cell membranes Each molecule is made of 1 glycerol, 2 fatty acids, and 1 phosphoric acid partially water insoluble

Cholesterol important in cell membranes and as source of steroid hormones partially water insoluble

3. Proteins structural component of cells, some hormones, transporters, enzymes Each molecule is made of a LONG chain of amino acids. This chain takes on a 3-dimensional shape due to hydrogen bonding between the amino acids. Denaturization-results from the breaking of H-bonds---alters shape--destroys function

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4. Nucleic Acids DNA, RNA made of chains of nucleotides--each nucleotide is made of: 5-C sugar, phosphate, and nitrogenous base DNA-found in chromosomes-provides code for protein production (genes) RNA-helps in protein production

Figure 02.21