By Frank H. Osborne, Ph. D. Chemistry of Life Principles of Biology By Frank H. Osborne, Ph. D. Chemistry of Life

The Scientific Method The Scientific Method has several steps: A natural phenomenon is observed A hypothesis (proposed explanation) is made An experiment is performed Results are obtained The hypothesis is supported or disproved Any scientific explanation is called a theory

The Scientific Method How science works: We learn not by proving something but by disproving something else. Inquiry is used to make observations, formulate hypotheses and test them. Science works by asking questions and answering them.

The Metric System The Metric System is used for measurement. Length is measured in units of the meter. Volume is measured in units of the liter. Mass is measured in units of kilograms. Time is measured in units of seconds.

Prefixes used in the Metric System

.00055 = 5.5 x 10-4 Scientific Notation Numbers are represented as a number between 1 and 10 x 10 raised to an appropriate power. Examples: 2800 = 2.8 x 103 .00055 = 5.5 x 10-4

Simple Chemistry Biology involves understanding some simple concepts of chemistry. Atoms pH scale Chemical bonding

ATOMS Atoms are composed of protons, neutrons and electrons. The nucleus is made of protons and neutrons. The electrons travel in orbits around the nucleus. Atomic number is the number of protons. Atomic mass is the number of protons and neutrons. Find the number of neutrons by subtraction.

Atomic Structure Structure of the Atom Each atom (element) has its own symbol. Example: Helium

Examples of Atoms

Examples of Atoms

Examples of Atoms

Examples of Atoms

Examples of Atoms

Dot Structures The outer electrons of the atom are all that matter in chemical bonding. It is customary to represent them using dots.

Principal Elements in Protoplasm Water is most CHON are most abundant abundant elements compound Element Symbol Percentage Hydrogen H 63 Oxygen O 25.5 Carbon C 9.1 Nitrogen N 1.4 Phosphorus P < 1 Sulfur S

Molecules Molecules are electrically neutral aggregates of atoms bonded together. "Electrically neutral" means that the number of protons equals the number of electrons.

Compounds and Molecules A compound is a substance with a definite composition that can be decomposed into two or more substances (examples are salt (NaCl) and water H2O)). A molecule is the smallest unit of a substance that has the chemical properties of the substance.

Bonding An ionic bond is formed by complete transfer of one or more electrons from one atom to another. Example: NaCl A covalent bond is formed by sharing of electrons between atoms. Example: H2O

Ionic Bonding

Covalent Bonding

Some Important Compounds

Counting Atoms

The pH Scale The pH scale shows the strength of an acid or a base. It ranges from 0 to 14. A pH of 7 is neutral. A pH less than 7 is acidic. A pH greater than 7 is alkaline (basic).

The pH Scale

ORGANIC CHEMISTRY Organic chemicals contain carbon. The more important ones are: carbohydrates lipids proteins nucleic acids

CARBOHYDRATES Carbohydrates contain carbon (C), hydrogen (H), and oxygen (O). The ratio of hydrogen to oxygen is 2:1 in carbohydrates. This means that there is twice as much hydrogen as there is oxygen.

Simple Sugars (Monosaccharides) Simple sugars contain from three to seven carbon atoms. Some of the larger ones can form rings.

Glucose makes a hexagonal ring form Glucose Can Form Rings Glucose makes a hexagonal ring form

Condensation Reactions A condensation reaction occurs between two molecules when an enzyme removes water from them and joins them together with a single bond. This process is known as dehydration synthesis. The water is always removed in the form of H from one molecule and OH from the other.

Disaccharides Disaccharides consist of two monosaccharides connected by a condensation reaction. An example is maltose which is formed by reaction between two glucose molecules.

Formation of Maltose

Polysaccharides Polysaccharides contain many monosaccharides linked together by condensation reactions. These consist of long chains called polymers. The three polymers of glucose are starch, cellulose and glycogen.

The Hydrolysis-Synthesis Cycle

The Carbohydrate Pyramid Many sugars (many glucose) Two glucose (maltose) One glucose

LIPIDS Lipids contain carbon, hydrogen and oxygen. There is much less oxygen in a lipid than there is in a carbohydrate. The types of lipids are: triglycerides waxes phospholipids steroids

Fats and Oils Fats and oils are examples of triglycerides. Fat is solid at room temperature, oil is liquid. The building blocks of triglycerides are fatty acids and glycerol. Molecules of triglycerides contain one glycerol and three fatty acids.

Forming a Triglyceride (1)

Forming a Triglyceride (2)

Saturated/Unsaturated Fats Saturated fats do not have double bonds between the carbon atoms. Unsaturated Fats have double bonds between the carbon atoms.

Types of Fatty Acids

Waxes Waxes are formed by condensation reactions between long-chain fatty acids and long-chain alcohols. They are found in various places, such as the surfaces of leaves.

Phospholipids Phospholipids contain glycerol, two fatty acids, phosphorus and sometimes nitrogen. They have polar heads and non-polar tails. The polar end is hydrophilic. The non-polar end is hydrophobic. These molecules are the major component of all biological membranes

Diagram of a phospholipid molecule. Phospholipids Diagram of a phospholipid molecule.

Steroids Steroid molecules have a complicated structure of interlocking carbon rings. This is an important type of lipid. It includes the sex hormones, cortisone, cholesterol, and related molecules.

PROTEINS Proteins are long-chain polymers of amino acids which are linked together by condensation reactions (dehydration synthesis). They are the fundamental structural molecules in biology. The structural properties of proteins are due to the presence of nitrogen.

Amino Acids There are 20 different types of amino acids. They can combine in a variety of ways. Amino acids are required for synthesis of proteins.

Formation of Proteins Proteins are formed by condensation reactions (dehydration synthesis). When two amino acids are joined together, the result is a dipeptide (two amino acids) joined by a peptide bond, and the water molecule which was removed.

Formation of Proteins Peptide Bond

The Protein Pyramid

Functions of Proteins Structural proteins. Structural proteins hold biological structures together or form body structures. An example is keratin. Keratin is found in hair, skin, nails, and the corresponding parts of other animals such as fur, hooves, claws, as well as fish and reptile scales.

Functions of Proteins Enzymes. An enzyme is a catalyst that allows the occurrence of a chemical reaction at body temperature. All enzymes are proteins. Condensation reactions are examples of biological reactions that are catalyzed by enzymes. There is also an enzyme called catalase. Catalase is another example of an enzyme.

NUCLEIC ACIDS There are two types of nucleic acids. These are known as: Deoxyribonucleic acid (DNA) Ribonucleic acid (RNA)

Nucleotides Nucleotides are the building blocks of nucleic acids. They have three components: a base, a sugar and a phosphate. The bases are rings of carbon and nitrogen atoms and are sometimes called nitrogenous bases. Phosphate is derived from phosphoric acid. The sugar found in DNA is called deoxyribose while the sugar found in RNA is called ribose.

Formation of Nucleic Acids The phosphate from one nucleotide becomes joined to the sugar of another nucleotide by a condensation reaction. This process builds very long chains of nucleotides.

The Nucleic Acid Pyramid

Functions of the Nucleic Acids Deoxyribonucleic acid (DNA). DNA is found in the chromosomes of the nucleus of the cell. It directs all aspects of cell function. It is organized into genes which determine the properties of the organism.

Functions of the Nucleic Acids Ribonucleic acid (RNA). There are three types of RNA. Each is associated in some way with protein synthesis. The structure of proteins (the sequence of the amino acids in the protein) is ultimately determined by the DNA of the cell.

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