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 ElementsElement 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

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.

CH3COCHCHOCHClCHNH

-C-C-C=C-O-C-C=N-

H O H Cl

H H H HHH

Chemical Formula

Lewis Dot Structure (no lone pairs drawn)

.

Formula Examples

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.Many coenzymes are vitamins.If a vitamin is missing from the human body, a certain enzyme cannot functionIf 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.

B12

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

The lower the pH number, the stronger the acid solution is.

A pH above 7 indicates that the solution is basic.

The higher the pH, the more strongly basic is the solution.