Chemistry of Living Things © Lisa Michalek

Basics of Chemistry The cell is a complex “chemical factory”. It is made up of atoms, elements, compounds, and molecules. The chemical processes of the organism takes place inside the organism’s cells.

The Atom Living and nonliving things are made up of tiny units called atoms. The center core is called the nucleus.

The Atom The nucleus is made up of particles called protons and neutrons Protons have a positive charge (+1) and neutrons have no electrical charge (0). Negatively charged particles, called electrons (-1) revolve around the nucleus at different distances from the nucleus.

The Atom The electrons move in paths called shells or energy levels. Atoms have the same number of electrons and protons. Therefore, they are electrically neutral (have no electrical charge).

Elements There are about 100 different kinds of atoms known to scientists today. A substance made up entirely of one kind of atom is called an element. Ninety-two elements occur naturally and the others were made up in a laboratory. Elements differ from one another in their proton, neutron, and electron number.

The Periodic Table of Elements

Most Common Elements Element Symbol Carbon C Hydrogen H Oxygen O Nitrogen N Sulfur S Phosphorus P Magnesium Mg Iodine I Iron Fe Calcium Ca Sodium Na Chlorine Cl Potassium K Zinc Zn Most Common Elements

Elements An element cannot be broken down into any other substance or matter. Pure silver is an element. It is made up only of silver atoms. When you break down a silver atom, you get electrons, protons, and neutrons.

Element Symbols Each element is represented by a symbol made up of one or two letters.

Compounds A compound is formed when two or more elements combine chemically.

Compound Properties The properties (characteristics) of compounds are quite different from the properties of the elements of which they are composed. For example, table sugar is made up of the elements carbon, hydrogen, and oxygen. Carbon is a black solid, and hydrogen and oxygen are colorless gases. However, when they combine chemically they form a white granular substance.

Compounds Elements combine to form compounds by a process called chemical bonding. The formation of a chemical bond involves either the transfer of electrons from one atom to another, or the sharing of electrons between atoms.

Chemical Bonding

Molecules A molecule of a particular compound is made up of definite numbers and kinds of atoms bonded (joined) together. A molecule of water contains two hydrogen atoms and one oxygen atom bonded together. Two atoms of hydrogen bond together form a molecule of hydrogen.

Ions An ion is an atom that has gained or lost an electron. Ions are formed during chemical bonding that involves the transfer of electrons. When electrons are transferred from one atom to another, both atoms become electrically charged. The atom that loses electrons becomes positively charged. The atom that gains electrons becomes negatively charged. The ions with opposite electrical charges are attracted to one another.

Ionic Bonds A chemical bond formed when atoms lose or gain electrons is called an ionic bond.

Covalent Bonds Covalent bonds are formed when atoms produce compounds by sharing electrons. When making hydrogen gas, one molecule of hydrogen gas is formed when two hydrogen atoms join by sharing electrons.

. Chemical Formulas A chemical formula represents the chemical makeup of a compound. It shows the numbers and kinds of atoms present in a compound. It is a kind of “shorthand” that scientists use.

Formula Examples H2O (water) SO2 (sulfur dioxide) CO2 (carbon dioxide) The chemical formula for sugar is C6H12O6 This means that in one molecule of sugar there are six carbon atoms, twelve hydrogen atoms and six oxygen atoms. H2O (water) SO2 (sulfur dioxide) CO2 (carbon dioxide)

Structural Formulas A formula can also show the kinds, numbers, and arrangement of atoms. This is called a structural formula. Here is the structural formula of Hydrogen.

Equations Equations are used to describe chemical reactions. The substances that start the reaction are called the reactants. The reactants are placed on the left side of the equation. The substances formed by the reaction are called the products. The products are placed on the right side of the equation. The arrow means “to make” or “to form”.

Equations Reactions may be represented either by words or formulas. The word equation for aerobic respiration is: (enzymes) SUGAR + OXYGEN  ENERGY + CARBON DIOXIDE + WATER An equation using formulas instead of words is called a chemical equation. The chemical equation for aerobic respiration is: C6H12O6 + O2  6H2O + 6CO2

Organic and Inorganic Compounds Living things are made up of inorganic and organic compounds. Compounds that do not contain both carbon and hydrogen are called inorganic compounds. The principal inorganic compounds found in living things are: water salts inorganic acids Inorganic bases

Organic and Inorganic Compounds Organic compounds are compounds that contain both carbon and hydrogen. The classes of organic compounds found in living things are: Carbohydrates Proteins Lipids Nucleic acids

Carbohydrates Carbohydrates are the main source of energy for cell activities. starch and sugar Carbohydrates are made up of the elements carbon, oxygen, and hydrogen. Generally, there are twice as many hydrogen atoms as oxygen atoms in carbohydrates (2:1 ratio).

Carbohydrates The simplest carbohydrates are called monosaccharides or simple sugars. They are called the “building blocks” of carbohydrates. A common monosaccharide is glucose (C6H12O6). Glucose is formed during photosynthesis.

Carbohydrates When two simple sugars combine, they form a disaccharide or double sugar. Maltose (C12H22O11) is an example of a common disaccharide. Maltose is formed when two glucose molecules chemically combine.

Carbohydrates Long chains of monosaccharides (sugar molecules) bonded together form polysaccharides. Important polysaccharides found in living things are starch and cellulose.

Lipids Lipids include fats and oils. Fats are solid at room temperature. Oils are liquids at room temperature. In living organisms, lipids form part of the structure of cell membranes. Extra food that is not immediately needed as a source of energy is changed to fat and stored. Lipids are a source of stored energy in living organisms.

Lipids Lipids, like carbohydrates, contain the elements carbon, hydrogen, and oxygen. The building blocks of lipids are fatty acids and glycerol.

Proteins Proteins form important cell products such as enzymes, hormones, antibodies, and hemoglobin. Proteins also play an Important role in cell repair and growth. Proteins are made up of carbon, hydrogen, oxygen, and nitrogen. Some proteins also contain sulfur.

Proteins Proteins are composed of simpler units (building blocks) called amino acids. There are twenty amino acids found in living things. Amino acids can be joined together in any sequence and combination. Because of this, there are a very large number of different proteins.

Proteins Two amino acids bonded together form a dipeptide. Many amino acids bonded together form polypeptides. Proteins are made up of long polypeptide chains.

Enzymes Each chemical reaction that occurs in a living thing is controlled by an enzyme. Enzymes are large, complex protein molecules that control the rate of chemical reactions. Enzymes are the organic catalysts in cellular chemical reactions. In chemistry, a catalyst is something that speeds up or slows down a chemical reaction. Catalysts are neither permanently changed nor used up by the reaction they catalyze.

Enzymes In organisms, enzymes allow the chemical reactions of metabolism to take place more efficiently than they otherwise would at body temperature. For example, amino acids are produced from protein digestion. The enzymes needed for this reaction are not changed but must be present for the reaction to occur.

Enzymes Some enzymes have a nonprotein part called a coenzyme. B12 Some enzymes have a nonprotein part called a coenzyme. Many coenzymes are vitamins. If a vitamin is missing from the human body, a certain enzyme cannot function If an enzyme doesn’t function, one or more metabolic reactions cannot occur. This is one of the reasons why it is important that you eat a well-balanced diet every day. Without coenzymes (vitamins) needed by the body, the chemical processes necessary for proper metabolism cannot take place.

Enzymes The rate of enzyme action is influenced by several factors: Temperature Relative concentrations of enzyme and substrate pH Each enzyme has an optimum temperature and pH, a temperature or pH at which it functions most efficiently and its rate of activity (action) is the greatest.

Enzymes and Temperature At temperatures below the optimum, the rate of enzyme activity (action) is low. Enzyme activity increases with increasing temperature up to the optimum temperature. Above the optimum temperature, the rate of enzyme activity decreases.

Enzymes and pH At pH levels below the optimum, the rate of enzyme activity (action) is low. Enzyme activity increases with increasing pH up to the optimum pH. Above the optimum pH, the rate of enzyme activity decreases.

Nucleic Acids Nucleic acids are very large molecules made up of carbon, oxygen, nitrogen and phosphorus. The simplest unit or building block of nucleic acids is the nucleotide. Nucleotides are composed of a sugar molecule, a nitrogen base, and a phosphate group.

Nucleic Acids DNA and RNA are two kinds of nucleic acids. DNA makes up genes and is involved in heredity. RNA is involved in the making of proteins.

The pH Scale The pH scale measures whether a solution is acid, basic or neutral. The scale runs from 0 to 14. A pH of 7 indicates that the solution is neutral. This means that the solution is neither an acid nor a base.

The pH Scale A pH above 7 indicates that the solution is basic. The higher the pH, the more strongly basic is the solution. The lower the pH number, the stronger the acid solution is.