Biology

Chemistry of Life

Structure of Atoms

Atoms are made up of protons (+), neutrons (0), and electrons (-).

Protons and neutrons are in the nucleus of the atom.

Electrons are in constant motion outside the nucleus (electron cloud).

ELEMENTS are pure substances consisting of one type of atom.

6

CCarbon12.011

Section 2-1 An Element in the Periodic Table

Go to Section:

ISOTOPES Isotopes are atoms of the same element

that have a different number of neutrons. This results in the isotopes having the same

atomic number, but different atomic masses.

Carbon-12, Carbon-13, and Carbon-14 are isotopes.

Radioactive isotopes can be used to determine the age of materials, treat cancer, and to trace the movement of substances in organisms.

Nonradioactive carbon-12 Nonradioactive carbon-13 Radioactive carbon-14

6 electrons6 protons6 neutrons

6 electrons6 protons8 neutrons

6 electrons6 protons7 neutrons

Section 2-1

Figure 2-2 Isotopes of Carbon

Go to Section:

Chemical Compounds A chemical compound is a substance

formed by the chemical combination of two or more elements in definite proportions.

The chemical formula for a compound tells the types of elements that are in it, and the ratio in which the atoms of those elements combine.

Ex) H2O means two hydrogen atoms always combine with one oxygen atom to form a water molecule.

CHEMICAL BONDS Ionic bonds form when two or more

electrons are transferred from one atom to another. Ex) NaCl

Covalent bonds form when electrons are shared between atoms. Ex) water

Van der Waals forces are slight attractions that occur between oppositely charged regions of nearby molecules. Not as strong as ionic or covalent bonds.

Sodium atom (Na) Chlorine atom (Cl) Sodium ion (Na+) Chloride ion (Cl-)

Transferof electron

Protons +11Electrons -11Charge 0

Protons +17Electrons -17Charge 0

Protons +11Electrons -10Charge +1

Protons +17Electrons -18Charge -1

Section 2-1

Figure 2-3 Ionic Bonding

Go to Section:

Water, Water Everywhere If you have ever seen

a photograph of Earth from space, you know that much of the planet is covered by water.

Water makes life on Earth possible. If life as we know it exists on some other planet, water must be present to support that life.

Go to Section:

Properties of Water

Water molecules are neutral, but polar. There is a slightly negative charge on oxygen, and slightly positive charge on the hydrogen atoms.

Water molecules are polar because there is an uneven distribution of electrons between the oxygen and hydrogen atoms.

Water is extremely cohesive because of its ability to form hydrogen bonds.

Cohesion vs. Adhesion Cohesion is the

attraction between molecules of the same substance. Ex) water molecules to each other

Adhesion is the attraction between molecules of different substances. Ex) water molecules cling to the inside of a plant stem

Mixtures

Mixtures are materials composed of two or more elements or compounds that are physically mixed together but not chemically combined.

Two types of mixtures made with water are homogenous mixtures and suspensions.

Homogenous mixtures Solution: Mixture of two or

more substances in which the molecules of the substance are evenly distributed.

Solvent- substance in which a solute is dissolved to form a solution. Ex) water

Solute- substance dissolved in a solvent to make a solution Ex) salt

Section 2-2

Figure 2-9 NaCI Solution

Go to Section:

Cl-

Water

Cl-

Na+

Water

Na+

Suspensions

Mixtures of water and undissolved materials that are so small they do not settle out.

Examples are blood and milk.

Acids, Bases, and pH

pH measures the concentration of hydrogen ions (H+) in solution. Ranges from 0 to 14.

ACIDIC solutions have high H+ concentrations, and a pH less than 7.

BASIC solutions have a low concentration of H+, and a pH greater than 7.

Solutions with pH of 7, such as pure water, are NEUTRAL.

BUFFERS are weak acids and bases that can react with strong acids or bases to prevent sudden changes in pH.

Oven cleaner

Bleach

Ammonia solution

Soap

Sea water

Human bloodPure waterMilkNormalrainfall

Acid rainTomatojuice

Lemon juice

Stomach acid

NeutralIn

crea

sing

ly B

asic

Incr

easi

ngly

Aci

dic

Section 2-2

pH Scale

Go to Section:

Carbon Compounds

Carbon forms strong covalent bonds. Carbon atoms can bond to other

carbon atoms to form long chains. Carbon-carbon bonds can be single,

double, or triple bonds. Carbon atoms can close upon

themselves to from rings.

Methane Acetylene Butadiene Benzene Isooctane

Section 2-3

Figure 2-11 Carbon Compounds

Go to Section:

Macromolecules Macromolecules are made from thousands

of smaller molecules. Monomers-small unit that can join with

other small units to form polymers. Polymers-large compound formed from

combinations of many monomers. Four groups of organic compounds found in

living things are carbohydrates, lipids, nucleic acids, and proteins.

Carbohydrates Carbohydrates are compounds made up of

carbon, hydrogen, and oxygen atoms, usually in a ratio of 1 : 2 : 1.

Living things use carbohydrates as their main source of energy. Stored as glycogen in animals and starch in plants.

Plants and some animals use carbohyrates for structural purposes. Plants have cellulose, animals have chitin.

Carbohydrate storage

Starch in a plant cell

Glycogen in an animal cell

Carbohydrates for structure

Cellulose in plant cells

(we don’t have enzymes to digest it)

Chitin in animal cells—arthropod shells and insects. Also found incells walls of fungi

Monosaccharides are single sugar molecules, such as glucose.

Polysaccharides are large macromolecules formed from monosaccharides, such as starch.

Starch

Glucose

Section 2-3

Figure 2-13 A Starch

Go to Section:

Lipids Lipids are a group of organic

molecules made mostly of carbon and hydrogen atoms.

Generally not soluble in water. Grouped as fats, oils, and waxes. Used to store energy, form parts of

biological membranes, and form waterproof coverings.

Examples: steroids, triglycerides

Saturated fats have the maximum number of possible hydrogen bonds. Tend to be solid at room temperature. Examples: meat fat, Crisco, butter, lard, etc.

Unsaturated fats have at least one carbon-carbon double bond C=C.

Polyunsaturated fats contain C=C double bonds, and are liquid at room temperature, Examples: olive oil, vegetable oils

Saturated vs. Unsaturated Fats

Nucleic acids Nucleic acids are macromolecules

containing hydrogen, oxygen, nitrogen, carbon, and phosphorus

Nucleotides have three parts: 5-carbon sugar, phosphate group, and a nitrogenous base.

Nucleic acids store and transmit hereditary or genetic information

Examples: DNA (deoxyribonucleic acid) and RNA (ribonucleic acid)

The Double Helix

Hydrogen bonds

Nucleotide

Sugar-phosphate backbone

Key

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

Nucleotide is a sugar, phosphate, & nitrogen base

Proteins Proteins are macromolecules that

contain nitrogen, carbon, hydrogen, and oxygen.

Proteins are polymers of amino acids. Have an amino group (--NH2) and a carboxyl group (--COOH) at the other.

The amino acids form chains that fold into complex structures.

General structure Alanine Serine

Section 2-3

Figure 2-16 Amino Acids

Go to Section:

Amino group Carboxyl group

Proteins control the rate of reactions and regulate cell processes.

Proteins help form muscle and bone tissue.

Proteins help transport substances into and out of cells.

Help fight diseases.

Aminoacids

Section 2-3

Figure 2-17 A Protein

Go to Section:

CarbonCompounds

include

that consist of

which contain

that consist of that consist of that consist of

which contain which contain which contain

Section 2-3

Concept Map

Carbohydrates Lipids Nucleic acids Proteins

Sugars and starches

Fats and oils Nucleotides Amino Acids

Carbon,hydrogen,

oxygen

Carbon,hydrogen,

oxygen

Carbon,hydrogen,oxygen, nitrogen,

phosphorus

Carbon,hydrogen,oxygen,

nitrogen,

Go to Section:

Chemical reactions and enzymes

A chemical reaction is a process that changes one set of chemicals into another set of chemicals.

Chemical reactions always involve the breaking of bonds in the reactants (starting materials) and the formation of new bonds in the products (results of the reaction)

When this occurs, energy is either released or absorbed.

Evidence that a chemical reaction has occurred includes heat, light, or gas being given off. Products are different from the reactants.

Energy in Reactions Since chemical reactions involve changes in

chemical bonds, they also involve changes in energy.

Exothermic- reactions that release energy. Often occur spontaneously.

Endothermic- reactions that must absorb energy to take place.

The energy needed to get a reaction started is called the activation energy.

Energy-Absorbing Reaction Energy-Releasing Reaction

Products

Products

Activation energy

Activation energy

Reactants

Reactants

Section 2-4

Figure 2-19 Chemical Reactions

Go to Section:

Enzymes Enzymes are catalysts that speed up

chemical reactions that take place in cells. Enzymes lower the activation energy of the

reaction. Enzymes provide a site where substrates

(reactants) are brought together so that the reaction can occur.

This is often described as a “lock and key” mechanism. Products are released. The enzyme is not used up in the reaction.

Reaction pathwaywithout enzyme Activation energy

without enzyme

Activationenergywith enzymeReaction pathway

with enzyme

Reactants

Products

Section 2-4

Effect of Enzymes

Go to Section:

Glucose

Substrates

ATP

Substratesbind toenzyme

Substratesare convertedinto products

Enzyme-substratecomplex

Enzyme(hexokinase)

ADPProducts

Glucose-6-phosphate

Productsare released

Section 2-4

Figure 2-21 Enzyme Action

Go to Section:

Active site

Enzymes, cont.

Optimal temperature and pH are needed for most enzymes to be effective.

Enzymes in the human body function best near normal body temperature: 35-400 C.

Below the optimum temperature, the reaction is slower or may not occur at all.

Enzymes, cont.

High temperatures disrupt the chemical bonds in the enzyme and changes it shape (denaturation).

This occurs when the body has a very high fever. Since denaturation is not reversible, a temperature higher than 440 C usually causes death.

Proteins begin to denature at 107 F.