Chapter 2

The Chemistry of Life/ water

Section 1

The nature of matter

Objectives

What three subatomic particles make up atoms?

How are all the isotopes of an element similar?

What are the two types of chemical bonds?

The Big Idea Life Depends on chemistry Chemical reactions keep you

alive

Atom Basic unit of matter

Democrites

Subatomic particles Protons - Neutrons - Electrons -

Positively charged (+)Not charged (neutral)Negatively charged (-)

Bind together to form the nucleus

Electrons Protons

Neutrons

Nucleus

Element A pure substance that consists

of just one type of atom

6CCarbon12.011

Atomic number

An elements atomic number = number of protons

Isotope Atoms of the same element

that differ in the number of neutrons they contain

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

6 electrons6 protons6 neutrons

6 electrons6 protons8 neutrons

6 electrons6 protons7 neutrons

6CCarbon12.011 Mass number

The Sum of protons and neutrons in the nucleus of an atom is its mass number

The weighted average of the masses of an elements isotope is called its atomic mass

Radioactive isotopes Can be dangerous Can be used

practically forRadioactive datingTreat cancerKill bacteria

Compounds A substance formed by the

chemical combination of two or more elements in definite proportions

Ex) H2O, NaCl

Table Salt

Covalent Bond and Ionic Bond Ionic bond: electron transfer Covalent bond: electron sharing

Ionic Bonds Formed when one or more

electrons are transferred from one atom to another

Sodium Chloride: ionic bond formation

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

If an atom loses an electron it becomes positive

If an atom gains an electron it becomes negative

Ions Positively and negatively

charged atoms Positively charged ion is called

anode Negatively charged ion is

called cathode

Molecule The structure that results when

atoms are joined together by a covalent bond

Smallest unit of most compounds

Van der Waals Forces A slight attraction that

develops between the oppositely charged regions of nearby molecules due to unequal sharing of electrons

The Van der Waals forces

Homework

1. Describe the structure of an atom.Atoms are made up of protons and

neutrons in a nucleus. Electrons are

in constant motion in the space

around the nucleus.

2. Why do all isotopes of an element have the same chemical propertiesThey have the same number of

electrons

3. What is a covalent bond? A bond formed when electrons are shared between atoms

4. What is a compound? How are they related to moleculesA compound is a substance formed

by the chemical combination of two or

more elements in definite proportions.

A molecule is the smallest unit of

most compounds

5. How do Van der Waals forces hold molecules together?When the sharing of electrons

are unequal, a molecule has

regions that are charged. An

attraction can occur between

oppositely charged regions of

nearby molecules

6. How are ionic bonds and Van der Waals forces similar? How are they different?In both cases, particles are

held together by attractions

between opposite charges.

The difference is that ionic

charges are stronger

Section 2:

Chemistry of water

Objectives Why are water molecules polar? What are acidic solutions? What

are basic solutions? Correlation between water & life

The Big Idea

Much of our planet is covered in water

Water is necessary for life to exist If life exists on other planets,

there most likely is water present Water has many properties that

make life possible

Polarity(-)

(+)

The oxygen atom has a stronger attraction for electrons

Hydrogen Bonds Because of waters partial charges,

they can attract each other and create hydrogen bonds

Not as strong as covalent or ionic bonds

Waters ability to create multiple hydrogen bonds gives it many special properties

Cohesion Attraction between molecules of

the same substance

Adhesion Attraction between molecules of

different substances.

Correlation between water & life

Mixture Material composed of two or more

elements or compounds that are physically mixed but not chemically combined

Ex.) salt & pepper, earths atmosphere

Solutions Mixture of two or more

substances in which the molecules are evenly distributed

Ex.) salt water Settles out over time

Solutions

Cl-

Water

Cl-

Na+

Water

Na+

Solute Substance that is dissolved Ex.) salt

Solvent The substance that does the

dissolving Ex.) Water

Suspensions Mixture of water and non-

dissolved materials Ex.) sugar solution, blood Separate into pieces so small,

they never settle out

The pH scale Indicated the concentration of

hydrogen ions in a solution

Neutral

Acid

Base

Acids Any compound that forms H+

(hydrogen) ions in solution

Base A compound that produces OH-

(hydroxide) ions in solution

Buffers Weak acids or bases that can

react with strong acids or bases to prevent sharp, sudden pH changes

Homework

1. Use the structure of a water molecule to explain why its polarOxygen atom has greater

attraction for electrons, therefore

the oxygen atom is negative and

the hydrogen end is positive

2. Compare acidic and basic solutions in terms of their H+ ion and OH- ion concentrationsAcid have more H

+

ions than OH

-

ions, and bases have more OH

-

ions than H

+

ions

3. What is the difference between a solution and a suspension?In a solution, all components are

evenly distributed. In a

suspension, un-dissolved

particles are suspended

4. What does pH measure?The concentration of H

+

ions in a

solution

5. The strong acid hydrogen floride (HF) can be dissolved in pure water. Will the pH of the solution be greater or less than 7? less than 7

The Big Idea Living things are made up of

chemical compounds Everything that happens to an

organism is based on chemical reactions

Chemical Reactions A process that changes or

transforms one set of chemicals into another

Reactants Elements or compounds that

enter into a reaction

Products Elements or compounds

produced by a chemical reaction

Example Reaction: Getting rid of carbon dioxide

In the blood

In the lungs

CO2 + H20 H2CO3 (carbonic acid)

H2CO3 CO2 + H2OReleased as you breathe

Energy in reactions Energy-Absorbing Reaction Energy-Releasing Reaction

Products

Products

Activation energy

Activation energy

Reactants

Reactants

Activation Energy The energy that is needed to get

a reaction started

Enzymes Some chemical reactions are too

slow or have activation energies that are too high to make them practical for living tissue

These chemical reactions are made possible by catalysts

Catalyst Substance that speeds up the

rate of chemical reactions Work by lowering a reactions

activation energy

Enzyme Biological catalysts Speed up reactions in cells Very specific Named for the reaction is catylzes Enzyme names always end in -

ase

Reaction pathwaywithout enzyme Activation energy

without enzyme

Activationenergywith enzyme

Reaction pathwaywith enzyme

Reactants

Products

Substrates The reactants of enzyme

catalyzed reactions The active site of the enzyme and

the substrate have complementary shapes

Fit like a lock and key

Enzyme Action

Enzyme substrate complex

Glucose

Substrates

ATP

Substratesbind toenzyme

Substratesare convertedinto products

Enzyme-substratecomplex

Enzyme(hexokinase)ADP

Products

Glucose-6-phosphate

Productsare released

Active site

Regulation of Enzyme Activity

Enzymes are affected by any variable that affects chemical reactions

1. pH2. Temperature3. Concentration

of enzyme

Homework

1. What happens to chemical bonds during chemical reactionsBonds are broken in reactants and

new bonds are formed in products

2. Describe the role of energy in chemical reactionssome chemical reactions release

energy, and other chemical

reactions absorb energy. Energy

changes determine how easily a

chemical reaction will occur

3. What are enzymes, and how are they important to living things?Enzymes are biological catylasts.

Cells use enzymes to speed up

virtually every important chemical

reaction that takes place in cells

4. Describe how enzymes work, including the role of the enzyme substrate complexSubstrates, the reactants of an

enzyme-catylzed reaction, attach

to the enzyme at an active site

and form an enzyme substrate

complex. Once the complex is

formed, the enzyme helps convert

substrate into product

5. A change in pH can change the protein. How might a change in pH affect the function of an enzyme such as hexokinase (hint: think about the analogy of the lock and key)A change in pH could change the

shape of hexokinase. This change

would diminish the ability of glucose

and ATP to bind to the active site of

the enzyme.