1. The Chemical Basis of Life
Chapter 2
REVIEW
The Chemical Basis of Life

2. Basic Chemistry-Review
Matter, Mass, and Weight
Matter: Anything that occupies space and has mass (liquid, solid or gas)
Mass: The amount of matter in an object
Weight: The gravitational force acting on an object of a given mass
Elements and Atoms
Elements: The simplest type of matter with unique chemical properties
Atoms: Smallest particle of an element that has chemical characteristics of that element

3. Atomic Structure Atoms: composed of subatomic particles Nucleus
Neutrons: no electrical charge
Protons: positive charge
Electrons: negative charge
Nucleus
Formed by protons and neutrons
Most of volume of atom occupied by electrons

4. Atomic Number and Mass Number
Atomic Number: Equal to number of protons in each atom which equals the number of electrons
Mass Number: Number of protons plus number of neutrons

6. Isotopes and Atomic Mass
Isotopes: Two or more forms of same element with same number of protons and electrons but different neutron number (important in medical imaging)
3 types of hydrogen
Denoted by using symbol of element preceded by mass number as 1H, 2H, 3H
Atomic Mass: Average mass of naturally occurring isotopes

7. Electrons and Chemical Bonding
Ion: When an atom loses or gains electrons and become charged
Cation: Positively charged ion
Anion: Negatively charged ion
Ionic Bonding
Cations and anions are attracted to each other

9. Covalent Bonding Atoms share one or more pairs of electrons
Single covalent: Share one pair of electrons
Double covalent: Share two pairs of electrons
Nonpolar covalent: Electrons shared equally
(Methane- CH4)
Polar covalent: Electrons shared unequally
(Water-H2O)

10. Molecules and Compounds
Molecules: Two or more atoms (same or different) chemically combined to form an independent unit
Examples: H2, H2O
Compounds: A substance composed of two or more different types of atoms chemically combined
Example: Glucose (C6H12O6)
Molecular Mass: Determined by summing atomic masses of its atoms or ions
Example: NaCl ( )

11. Intermolecular Forces
Result from weak electrostatic attractions between oppositely charged parts of molecules, or between ions and molecules
Weaker than forces producing chemical bonding

12. Intermolecular Forces
Hydrogen Bonds
Water: Positively charged hydrogen atoms bond with negatively charged oxygen atoms of other water molecules
Important role in determining shape of complex molecules

15. Intermolecular Forces
Solubility: Ability of one substance to dissolve in another
Example: Sugar dissolves in water
Dissociation or Separation
Ionic compounds in water
Cations are attracted to negative end and anions attracted to positive end of water molecules

16. Intermolecular Forces
Electrolytes: Cations (+) and anions (-) that dissociate in water
Capacity to conduct an electric current
Currents can be detected by electrodes
Nonelectrolytes: Molecules that do not dissociate form solutions that do not conduct electricity

17. Chemical Reactions & Energy
Chemical Reactions: Atoms, ions, molecules or compounds interact to form or break chemical bonds
Metabolism: An organism’s total chemical reactions.
Managing the material and energy resources of a cell
Examples:
Catabolism
Anabolism

18. Chem. Reactions & Energy (continued)
Catabolism: Decomposition reactions that break down molecules into smaller parts
Hydrolysis: Reactions that use water to decompose
Anabolism: Build complicated molecules from simpler ones for growth, maintenance, and repair of the body
Synthesis reactions: Produce molecules characteristic of life - ATP, proteins, carbohydrates, lipids, and nucleic acids

19. Synthesis and Decomposition Reactions
Synthesis Reactions
Two or more reactants chemically combine to form a larger product
Anabolism: All body’s synthesis reactions
Decomposition Reactions
Reverse of synthesis reactions
Catabolism: Reactions of decomposition in body

20. Oxidation-Reduction Reactions
Loss of an electron by an atom
Reduction
Gain of an electron by an atom
Oxidation-Reduction Reactions
The complete or partial loss of an electron by one atom is accompanied by the gain of that electron by another atom

21. Energy Energy: The capacity to do work Potential Energy: Stored energy
Kinetic Energy: Does work and moves matter
Mechanical Energy: Energy resulting from the position or movement of objects
Chemical Energy: Form of potential energy in the chemical bonds of a substance
Heat Energy: Energy that flows between objects of different temperatures

22. Energy and Chemical Reactions

23. Speed of Chemical Reactions
Activation Energy: Minimum energy reactants must have to start a chemical reaction
Catalysts: Substances that increase the rate of chemical reactions without being permanently changed or depleted
Enzymes: Biological catalysts – proteins that increase the rate of chemical reactions by lowering the activation energy necessary for reaction to begin

24. Activation Energy and Enzymes

25. Chemistry Inorganic Chemistry: Substances that do not contain carbon
Water
Oxygen
Organic Chemistry: Study of carbon-containing substances

26. Water (The most abundant substance in the human body)
Inorganic
Stabilizes body temperature
Protection
Necessary for many chemical reactions of life
Mixing Medium
Mixture: Substance physically but not chemically combined
Solution: Liquid, gas, or solid uniformly distributed
Solvent: What dissolves the solute
Solute: What is to be dissolved

27. Acids and Bases; Salts and Buffers
Acid: A proton donor or any substance that releases hydrogen ions (H+) (HCL- H+ + Cl-)
Bases: A proton acceptor or any substance that binds to or accepts hydrogen ions (OH-) (NaOH- Na+ + OH- )
Salts: An ionic compound consisting of a cation other than a hydrogen ion and an anion other than a hydroxide ion (NaCl)
Buffers: A solution of a conjugate acid-base pair in which the acid and base components occur in similar concentrations
(maintain body pH at ~ 7.4)

28. Buffer systems in the body-
Homeostasis -near neutral pH (~7.4) in the body prevent large changes in acidity or alkalinity in the human body
weak acids
Ex. carbonic acid (H2CO3)
H2CO H+ + HCO3+
weak bases
Ex. bicarbonate ion (HCO3-)
NaHCO3
HCL + NaHCO NaCl + H2CO3
(strong acid) (weak acid)
NaOH + H2CO3 NaHCO3 + H2O
(strong base) (weak base)
Other buffers: phosphates, amino acids, proteins (most abundant)

29. The pH Scale Refers to the Hydrogen ion concentration in a solution
Neutral: pH of 7 or equal hydrogen and hydroxide ions
Acidic: a greater concentration of hydrogen ions
Alkaline or basic: a greater concentration of hydroxide ions

30. Organic Chemistry Carbohydrates Lipids Proteins
Composed of carbon, hydrogen, oxygen
Lipids
Composed mostly of carbon, hydrogen, oxygen, phosphorus, nitrogen
Proteins
Composed of carbon, hydrogen, oxygen, nitrogen, and sulfur
Nucleic Acids: DNA and RNA
Composed of carbon, hydrogen, oxygen, nitrogen, phosphorus
Adenosine Triphosphate (ATP)
Composed of adenosine and three phosphate groups

31. Carbohydrates Monosaccharides Disaccharides Polysaccharides
Simple sugars: glucose, fructose, galactose
Trioses, tetroses, pentoses, or hexoses
Disaccharides
Two simple sugars bound together by dehydration: sucrose, lactose, maltose
Polysaccharides
Long chains of many monosaccharides: glycogen in animals; starch and cellulose in plants

33. Monosaccharides

34. Disaccharide and Polysaccharide

35. Lipids
Lipids: Can be dissolved in nonpolar organic solvents such as alcohol but relatively insoluble in water
Fats: Ingested and broken down by hydrolysis
Triglycerides: 95% of fats in the human body - composed of glycerol and fatty acids
Phospholipids: Important structural component of cell membranes
Eicosanoids: Importatnt regulatory molecules derived from fatty acids
Steroids: Cholesterol, bile salts, estrogen, testosterone
Fat-soluble Vitamins: Vitamin E

37. Fats (triglycerides/neutral fats)
1 glycerol + 3 fatty acids
Differ- length and saturation of of carbon chains
( usually carbon chains)
Saturated fats- no double bonds between carbon atoms; animal foods - unhealthy
Unsaturated fats- one or more double bonds between carbon atoms (mono/poly) – do not contribute to development of cardiovascular disease. Vegetable oils, fish oils, and olive (monounsaturated) oil.
Functions
Source of long-term energy; not metabolized efficiently
Protection by surrounding and padding organs
Insulation to prevent heat loss

38. Phospholipids-Cell membranes)

39. Steroids

40. Proteins Amino acids: The building blocks of protein
Peptide bonds: Covalent bonds formed between amino acids during protein synthesis
Structure
Primary, secondary, tertiary, quaternary
Enzymes: Protein catalysts
Lock-and-key model
Active site
Cofactors – Non-protein substances necessary for some enzymes. Can be an ion or an organic molecule.
Coenzymes – Organic cofactors such as certain vitamins

42. Peptide Bonds

43. Proteins Most complex and varied physiological molecules Diversity-
Amino acids
A+B+C+D = polypeptide A
A+B+E+D = polypeptide B
Denaturation-
Proteins influenced by changes in temperature, pH, salt concentrations. Such changes result in nonfunctional protein.

44. Protein Structure and Enzyme Action

45. Nucleic Acids: DNA and RNA
Two Types of Nucleic Acids
DNA (Deoxyribonucleic Acid) and RNA (Ribonucleic Acid)
Both DNA and RNA consist of basic building blocks called nucleotides
Each nucleotide is a pentose sugar, phosphate group, and a nitrogenous base
Two groups of nitrogenous bases: pyrimidines and purines
Pyrimidines are cytosine (DNA & RNA), thymine (DNA only), and uracil (RNA only).
Purines are guanine and adenine (both in DNA and RNA)

46. Nucleic Acids: DNA and RNA
DNA: Deoxyribonucleic acid
Genetic material of cells copied from one generation to next
Contains the information that determines the structure of proteins
Composed of 2 strands of nucleotides called the double helix
Each nucleotide contains deoxyribose as the pentose sugar and one of the organic bases: adenine, guanine, thymine, or cystosine.

47. Nucleic Acids: DNA and RNA
RNA: Ribonucleic acid
Functions in protein synthesis
Three types of RNA: mRNA, tRNA, and rRNA
Similar to a single strand of DNA
Pentose sugar is ribose
Same nitrogenous bases as DNA except thymine is replaced with uracil

48. DNA Structure

49. Nucleotides and Nitrogenous Bases

50. Adenosine Triphosphate (ATP)
Energy currency of the body
Provides energy for chemical reactions such as anabolism or to drive cellular processes such as muscle contraction
All energy-requiring chemical reactions stop when there is inadequate ATP