Chapter 2: Chemical Basis of Life

Transcription

1 Chapter 2: Chemical Basis of Life Chemistry is the scientific study of the composition of matter and how composition changes. In order to understand human physiological processes, it is important to understand how chemicals influence the human body. Energy is the ability to do work o Types of energy: Chemical energy energy produced during chemical reactions Electrical energy energy produced by electrically-charged substances Mechanical energy kinetic energy (energy in motion) Radiant energy energy produced by the sun Matter is anything that has weight (mass no gravitation pull) and takes up space. o States of matter: solids, liquids, and gases Elements are the fundamental composition of matter. Atoms are the building blocks of elements that retain the element s properties and characteristics. The anatomy of the atom o REFER TO FIGURES 2.1 & 2.2 o Subatomic structures Protons has a positive charge and is contained within the nucleus Neutrons has no charge and is contained within the nucleus Electrons has a negative charge and orbits within the energy shells ***We must assume an electrically neutral atom possess equal number of protons and electrons.**** On the period table (APPENDIX C-- p.566), the elements are organized in a particular pattern. Each element is assigned an abbreviation. A number is positioned superior to the abbreviation, and another number is positioned inferior to the abbreviation. REFER TO TABLE 2.2 The number on top is called the atomic number. This number represents the number of protons The number on the bottom is called the atomic weight. This number represents the total number of protons and neutrons. Notice that the atomic weight is not a whole number. We must round the number to the nearest whole number. If the first decimal point number is.5 or more, then round up to the next whole number. If the first decimal point number is.4 or less, then do not round the number up. The atomic weight is the average weight among the varieties of a given element. The varieties of an element are called isotopes. Isotopes possess the same number of protons but vary the number of neutrons. Radioactive isotopes are very unstable and only become more stable as they decompose. Radioactive isotopes are important in the medical field because they can be used to trace biological molecules, serve as tools for diagnosis and treatment. Examples are Iodine, Radium, and Cobalt. o Nucleus central portion of the atom that has a positive charge o Energy shells orbits surrounding the nucleus The outer shell or valence shell is important in determining how reactive an atom will be The first energy shell (closest to the nucleus) can only hold a maximum of two electrons. Holding two electrons signifies that the first energy shell is complete. If this first shell is the valence shell and it is not complete, then the atom will be reactive. 1

2 The other energy shells can hold multiples of eight electrons. Holding a multiple of eight electrons signifies that the energy shell is complete. An energy shell must hold the maximum electrons before forming another energy shell. If the valence shell does not have a multiple of eight electrons, then it is considered to be reactive. Molecules two or more similar atoms or components that chemically combine (Examples: hydrogen gas H 2 OR table sugar(sucrose) two glucose molecules chemically combine Compounds two or more different atoms that chemically combine Chemical Reactions o Inert elements- elements that are stable and will not react ( the valence or outer shell is complete) o Reactive element elements with unfilled valence shells. The atoms of these elements will react or chemically bond in order to fulfill the outer energy shell. o Patterns of chemical reactions Chemical equations: Reactants Products Reactants (what is being changed) are listed on the left of the arrow. The arrow represents yields or produces. The new products (the resulting formation) are to the right of the arrow. Catalyst can influence the rate of a particular reaction and leaves the reaction unaltered. Types of chemical reactions A + B AB (synthesis) **Chemical bond is formed.** AB A + B (decomposition) **Chemical bond is broken.** AB + CD AC +BD (exchange) **Chemical bonds are formed and broken.** A + B AB (reversible) **A catalyst often directs the reaction to go in one direction.** o Chemical bonds Types of chemical bonds Ionic bond when atoms bond and electrons are transferred during a reaction REFER TO FIGURE 2.3 & 2.4 o Once atoms lose or gain electrons, they become charged IONS o Anion is an atom that gains an electron(s) and becomes a negatively charged ion o Cation is an atom that loses an electron(s) and becomes a positively charged ion Covalent bond when atoms bond and electrons are shared among the atoms in the reaction o REFER TO FIGURE 2.5, 2.7, & 2.8 o Single bond when a pair of electrons are shared o Double bond when two pairs of electrons are shared o Triple bond when three pairs of electrons are shared o Nonpolar covalent bond when there is equal sharing of the electrons among the atoms o Polar covalent bond when there is an unequal sharing of the electrons among the atoms. One end is slightly more positive does not have a 2

3 strong hold on the shared electrons, and the other end is slightly more negative has a stronger attraction or hold on the shared electrons. Hydrogen bond weak chemical bond between the positive hydrogen end of a polar molecule to the negative end (usually nitrogen or oxygen) of another polar molecule. Hydrogen bonds are easy to break. REFER TO FIGURE 2.6 & 2.7; SUMMARY OF PARTICLES OF MATTER TABLE 2.3 Biochemistry o Inorganic compounds- compounds that do not possess both carbon and hydrogen or either Water Most abundant inorganic compound in the human body Universal solvent can dissolve many substances due to its polarity Transports chemicals, nutrients, wastes throughout the body Absorbs and transport heat Induces chemical reactions or metabolism Inorganic salts compounds that are composed of oppositely charged ions. Inorganic salts are important metabolic functions such as muscle contraction and nerve impulse conduction. Electrolytes are inorganic salts that release ions in water. Acids electrolyte that releases hydrogen ions in water Bases electrolyte that release hydroxide ions in water When adding an acid to a base, the resulting products are water and an inorganic salt. o ph scale: measurement of hydrogen ion concentration released in water. The scale ranges from zero to fourteen. Each whole number on the ph scale represents a tenfold difference in the hydrogen ion concentration. The smaller the ph value, the greater the concentration of hydrogen ion. o ph of seven or less is considered to be acidic (contains more hydrogen ions than hydroxide ions) o ph of seven is considered neutral (equal number of hydrogen and hydroxide ions) o ph of seven or more is considered to be basic (contains more hydroxide ion than hydrogen ions) o Buffers chemical that resist fluctuations in ph. Buffers are important in maintaining the ph value of our bodily fluids such as blood when chemicals are being transported. Buffers will either hold hydrogens ions so that the ions are not released. o REFER TO FIGURE 2.11 Oxygen releases energy from nutrients to drive metabolism Carbon dioxide waste product from metabolism that will be released into the air during exhalation o Organic compounds compounds that possess both carbon and hydrogen REFER TO TABLE 2.6 Carbohydrates water-soluble REFER TO FIGURE 2.12 & 2.13 Elements: Carbon, Hydrogen, Oxygen Building Blocks: Monosaccharide Complex Carbohydrates: Dissacharides, Polysaccharides Functions: Main source of energy Examples: Fructose, Glycogen Lipids water-insoluble 3

4 REFER TO FIGURE 2.14, 2.15, 2.16, & TABLE 2.5 Elements: Carbon, Hydrogen (abundant element), Oxygen (least abundant element) Building Components: Glycerol backbone, fatty acids, and phospholids Types of lipids: o Natural fat or triglyceride: Glycerol with 3 fatty acids o Phospholipid: Glycerol with 3 fatty acids and 1 phosphate group fatty acid end is considered to be hydrophobic while the phosphate end is hydrophillic o Steroid: complex ring structure Functions: Building living matter such as cell membrane, insulation Examples: Cholesterol, omega-3 Proteins water-soluble; most abundant organic substance in the body REFER TO FIGURE 2.17& 2.18 Elements: Carbon, Hydrogen, Oxygen, Nitrogen, and sometimes Sulfur Building Blocks: Amino acids carboxyl group, amino group, and R group (the R group varies from amino acid type to another amino acid Proteins are sensitive to denaturing. Denature results in alteration of the physical properties and characteristics but does not affect the functional properties. o Factors that can denature proteins Temperature Radiation Chemicals Structural Levels of proteins o Primary specific sequence of amino acids o Secondary 2D folding of the protein helix or pleated pattern o Tertiary specific way that the protein bends and folds on itself o Quaternary specific way and location one protein bonds to another protein. Hydrogen bond holds proteins together. Remember - hydrogen bonds are weak bonds and thus, proteins are subject to denaturing. Functions: structure, contractile properties, catalytic properties, regulatory, transport, and immunological properties Examples: keratin, actin, myosin, enzymes, hemoglobin, transferrin Nucleic Acids water-soluble REFER TO FIGURE 2.20, 2.21, 2.22 Elements; Carbon, Hydrogen, Oxygen, Nitrogen, and Phosphorus Building Blocks: Nucleotides 5-carbon sugar, phosphate group, and one organic base o Nucleotide organic base: Adenine, Thymine, Cytosine, Guanine, and Uracil o Organic bases are base-pair specific Functions: Blueprint of life (genetic information) and coding for protein synthesis Examples: Deoxyribonucleic acid (DNA) and Ribonucleic acid (RNA) o DNA is double-stranded contains genetic material The strands are held together by hydrogen bond at the organic bases Adenine pairs with Thymine Guanine pairs with Cytosine o RNA is single-stranded contains the instruction for proteins 4

5 RNA is formed by base pairing to DNA Adenine pairs with Uracil Guanine pairs with Cytosine Adenosine Triphosphate (ATP) the chemical energy for cells to do work REFER TO FIGURE 4.6 & 4.7 p. 81 Chemical energy is released from ATP by breaking the last phosphate in the chain of the ATP structure. Metabolism is a series of reactions in our bodies that converts potential energy from the nutrients consumed into the chemical energy, ATP. 5