Chapter 02: Chemistry of Life


- Matter: Anything that occupies space and has mass, Matter can be in liquid, gaseous, or solid form and is composed of elements, the smallest particles of which are atoms.- Elements Cannot be broken down further by natural forces- Oxygen, carbon, hydrogen, nitrogen, phosphorus, and sulfur are some of the elements most commonly found in living cells.- Atoms= Smallest particles of an element- Although chemical elements usually do not exist in free form, they do occur in combinations called Chemical Compounds, Elements in combination- Chemical formula= Shorthand expression for a chemical compound example NaCl or H2O

Atomic Model

-SUBATOMIC PARTICLES- Atomic nucleus Contains protons and neutrons- Protons (+)= Positively charged particles- Neutrons= Particles without charge- Electrons (-)= Negatively charged particles- Nucleus= (Protons +Neutrons)- Atomic Weight/Mass (P+N)= Equals the number of protons and neutrons- Atomic number(+)= Equals the number of protons- Orbitals/shells= Volume of space that contains electrons. -Electrons travel around the nucleus at high speed and occupy positions in a volume of space called an orbital or electron cloud. These orbitals form an energy level also referred to as shells, in which the electrons usually remain.

Atomic Structure

Models of Atomic Structure : It shows simplified diagrams of hydrogen and carbon atoms with the atomic nucleus containing protons and neutrons in the center of the atom, and the electrons in the surrounding shells.

Electron Shells/Orbitals

- Are energy levels around nucleus- Contain electrons- Number of shells depends on atomic number- First shell can hold only two electrons- Second shell can hold up to eight electrons- Electrons in more distant shells have higher energy- Shells always fill sequentially from the inside out, Two electrons in the first shell, Eight electrons in the next- When the outermost shell is filled with 8, the atom is stable

Valence Electrons

- Electrons in the outermost shell- Can participate in chemical reactions - Determine what kind of chemical bond, if any, the atom can form- If the outermost shell is filled, the atom is stable (inert) and cannot react with another atom, Example Helium is therefore called an inert gas.


-Atoms with the same number of protons but a different number of neutrons-Atomic number of isotopes is unchanged-Atomic weight is different-Radioisotopes are unstable because of their imbalance of energy in the nucleus.-When the nucleus loses a neutron, it gives off tremendous amount of energy- this is called "Radioactive".-Radioactivity is the release of energy and matter that results from the change of the an atom.


- Electrically charged atoms, molecules, particles- + or - due to electron loss or gain- Cations (+)- Anions (-) - Electrolytes: is a substance that freely dissociates into Free ions, when dissolved in water . - Solvent (e.g., water) & Salt (NaCl ) is solute- Several cations and anions are important components of higher life forms. All of these higher life forms require a complex electrolyte balance, called an osmotic gradient, between their intercellular and extracellular fluid compartments.

Chemical Bonds and Molecules

- Molecules are two or more atoms linked together by chemical bonding between valence electrons of atoms- Number of bonds possible between atoms is determined by the number of electrons needed to complete the outermost shell- Compounds are made from atoms of different elements

Covalent Bonds

- Result from sharing of electrons In bonds between identical atoms such as oxygen and hydrogen, the electrons are shared equally by each atom, this is called Nonpolar covalent bond, Equal sharing of electrons- Polar covalent bond= Unequal sharing of electrons, Electrons are pulled toward the larger atom, Result: One end of the molecule is more negative, the other more positive- Covalent bonds usually are the strongest chemical bonds.

Ionic Bonds

- Transfer of valence electrons from one atom to another- Forms charged atoms called ions - Loss of electron(s): Positive charge- Gain of electron(s): Negative charge

Hydrogen Bonds

- Weak chemical bonds- Attraction between charged atoms within a large molecule (e.g., DNA) or between adjacent molecules (e.g., H2O)- Always involve a hydrogen atom (+) attracted to an oxygen (-) or nitrogen (-) atom

van der Waals Forces

- Weakest of intermolecular forces- Dependent on interatomic distance- Determine final molecular arrangement- "Lock and key" concept, Example: Antibody and antigen complex

Chemical Reactions

- Synthesis (dehydration synthesis)= Formation of a larger molecule from smaller ones, Removal of H2O- Hydrolysis (decomposition)= Breakdown of large molecules, Requires H2O- Endergonic: Requires energy, Synthesis (it occurs in the dehydration synthesis of nutrient molecules during anabolism.)- Exergonic: Gives off energy, Hydrolysis (breakdown of large nutrient molecules e.g. carbohydrates)- Redox (reduction-oxidation), Reduction: Gain of electrons, Oxidation: Loss of electrons, Simultaneous electron transfer

Chemical Notations

- Also referred to as chemical shorthand, Shows chemical compounds and reactions- Rules:1. The abbreviation of an element represents one atom of that element and is its chemical symbol2. The number before the chemical symbol is the number of atoms; the number before the chemical formula is the number of molecules 2H2O3. The subscript after the chemical symbol of an element shows the number of that atom in the molecule H24. A superscript of plus or minus after the atomic symbol indicates an ion Na+5. Chemical reactions do not form or destroy atoms; they just rearrange them into new combinations

Inorganic Compounds

- These compounds consist of molecules that do not contain Carbon, with the exception of a few molecules that are classified as inorganic compounds although they contain carbon- Exceptions: CO2 (carbon dioxide) and CO (carbon monoxide)

Acids and Bases

- The strength of acids and bases is determined by the hydrogen ion concentration of the water in which they dissociate. - The higher the hydrogen ion concentration in the solution, the more acidic the solution. -A low hydrogen ion concentration of a solution indicates a basic solution.- Substances that dissociate in water can form acids, bases, or salts- Acids= Substances that release hydrogen ions (H+)- Bases= Substances that release hydroxyl ions (OH− )

pH Scale (Potential of Hydrogen)

- Measures the alkalinity or acidity of a solution- Based on the hydrogen ion concentration- pH scale runs from 0 to 14- Pure H2O is neutral: pH of 7- Acids: pH <7 - Bases: pH >7- A change of 1 unit on the pH scale (the negative logarithm scale) represents a ten-fold change in the hydrogen ion concentration.


- Chemicals that can absorb hydrogen or hydroxyl ions- Can resist pH changes of a solution- Buffers are essential for maintaining the pH necessary for the survival of living cells- All biological fluids, both intracellular and extracellular, are heavily buffered. ( Sodium bicarbonate HCO3(−)synthesized by Pancreas and Kidneys)


- Substances that dissociate in water and do not release hydrogen or hydroxyl ions- Formed by acid-base reaction or metal-acid reaction- Naming: Specific= Starts with name of cation, Followed by name of anion, E.g. NaCl - Different salts can stimulate sensations of all five basic tastes: Salty (sodium chloride), sweet (lead diacetate), sour (potassium bitartrate), bitter (magnesium sulfate), and umami (monosodium glutamate).


- Water is the most abundant molecule in the human body & in microorganisms, which is at least 70%, and the earth's surface is 71% covered by it as well.- Necessary for all life forms on earth- Exists in three different temperature-dependent states- Important solvent- Held together by hydrogen bonds- Consists of hydrogen and oxygen in a ratio of two to one- Polar molecule (polar covalent bond)- Hydration spheres= Ions attract polar water molecules- Hydrophilic= Water-soluble (water-loving) compounds- Hydrophobic= Insoluble in water (water-repelling)

Water: Universal Solvent

- Water acts as the solvent, sodium and chloride ions are the solutes, and when solutes are dissolved (dissociated) in a solvent, a solution is formed.

Water: Solutions

1. Isotonic= Solute concentration equal on inside and outside of cell2. Hypertonic= Solute concentration in cell less than outside of cell3. Hypotonic= Solute concentration in cell higher than outside of cell

Organic Molecules

- All Organic molecules contain atoms of carbon and hydrogen.- The major organic molecules in living organisms are carbohydrates, proteins, lipids, and nucleic acids- Carbon (hydrocarbon) backbone= Chain, Ring- Monomer= Building block, unit molecule- Polymer= Consists of monomers


- Contain carbon, hydrogen, oxygen in a ratio of 2:1:2- Monomers: Monosaccharides (simple sugars) like Glucose, Fructose, Galactose, Ribose, Deoxyribose-Disaccharides: Are 2 Monosaccharides joined covalently- Sucrose= Glucose + fructose- Lactose= Glucose + galactose- Maltose= Glucose + glucose- Polysaccharides: Many monosaccharides linked together- Starch= Storage form of glucose in plants- Glycogen= Storage form of glucose in animals- Cellulose= Component of the cell walls of plants, fungi, and most algae


-Monomers: Amino acids- 20 naturally occurring amino acids- All consist of an amino group, carboxyl group, and variable side chain (R group)- Dipeptide: Two amino acids joined by a peptide bond- Polypeptide: 10 or more amino acids- Proteins: They are the monomers of proteins.

Proteins: Structural Arrangements

- Primary structure= Single chain of amino acids- Secondary structure= α Helix or β sheet- Tertiary structure= Globular shape: Three-dimensional- Quaternary structure= More than one tertiary protein


-Triglycerides: Fats and oils saturated and unsaturated -Consist of glycerol and fatty acid chains (neutral fats)-Insoluble in water-Room temperature• Fats: Solid• Oils: Liquid-Phospholipids: Glycerol, two fatty acid chains, phosphate group on one end, Polar heads, nonpolar tails, Main component of the plasma (cell) membrane, Basis of biological barrier properties

Lipids : Different types of Steroids

- Anabolic steroids (it resembles testosterone in promoting the growth of muscle& bone mass.)- Sex steroids ( secondary sex characteristic)- Mineralocorticoids (maintain blood volume & salt balance in the body)- Glucocorticoids= Metabolism and immune function (prescribed to reduce inflammatory conditions) -Phytosterols= Steroid alcohols: Naturally occur in plants such as yeast and fungi- Cholesterol= Precursor of steroids and vitamin D- Prostaglandins= Local hormones, In a variety of tissues, Involved in Defense mechanisms - Blood clotting and inflammation

Nucleic Acids

- Monomers: Nucleotides- Functions:1. DNA: Deoxyribonucleic acid= Storage of genetic information2. RNA: Ribonucleic acid= Directing protein synthesis3. ATP: Adenosine triphosphate= is the energy molecule of cells-The bases in a nucleic acid polymer can form hydrogen bonds with the neighboring bases by a process called complementary base pairing-Nucleotides1. Pentose sugar2. Phosphate 3. Nitrogen base= Purines Adenine (A) and guanine (G) and Pyrimidines Cytosine (C), thymine (T), and uracil (U)