Chapter 2

THE CHEMISTRY OF LIVING THINGS

2A MATTER, ENERGY, AND LIFE

What are living things made of?

MATTER

What is matter?

The physical stuff that makes up the universe.

Anything that occupies space and has mass.

Chemistry is the study of matter and the changes it experiences.

Atoms are the basic building blocks of matter. They are the smallest individual particles of which matter is made.

Nucleus

Protons (positive)

Neutrons (neutral)

Electrons (negative)

Same # protons and electrons means electrically neutral

Different # protons and electrons produce ions

Anion (negative)

Cation (positive)

Elements are classified by the number of protons in their nuclei.

Elements are pure substances made of only one kind of atom.

ENERGY

What is energy?

The immaterial stuff that gets things done.

The ability to do work.

Without energy, nothing happens.

Different kinds of energy

Mechanical

Acoustic

Light

Chemical

Thermal

The measure of the speed at which particles move is

the temperature of a substance or organism.

Energy can be changed from one form to another.

Energy

Where do living things get energy?

Consumers get energy from food.

Producers get energy from the sun.

Energy tends to spread out.

The tendency of energy to disperse is

called entropy.

CHANGES IN MATTER

The amount of matter and energy in the universe never

changes.

The conservation of energy is called the first law of

thermodynamics.

Living things do not create new energy or matter; they

can only change the form of matter that is already out

there.

Changes that do not change a matter’s identity are called physical

changes.

When matter changes in a way that completely transforms its

identity, it is called a chemical change.

Physical Changes Chemical Changes

Definition Identity of matter not

changed

Identity of matter

changed

Observations Change in state or

shape

Generation of light,

heat, sound, or gas;

change in color

Examples Ice melting, wheat

being ground to flour,

salt dissolving in water

Metal rusting, wood

burning or rotting, food

being digested

COMPOUNDS AND MOLECULES

When substances made of only one kind of element

undergo a chemical change, their atoms react with the

valence electrons from other atoms in a way that stores

energy.

Stored chemical energy that holds two atoms together is

called a bond.

A compound is a pure substance made of two or more

elements chemically combined.

Example: Rust

IONIC COMPOUNDS

When atoms in the process of bonding give away their valence electrons, they transform into ions.

One becomes a cation and the other becomes an anion.

Oppositely charged ions attract to form ionic compounds.

The smallest part of an ionic compound is called a formula unit.

Formula units build on each other to form crystals.

IONIC COMPOUNDS: SODIUM CHLORIDE

Sodium donates a valence electron to chlorine to form a

sodium chloride (NaCl) formula unit that combines with other

formula units to form a crystal.

COVALENT COMPOUNDS

When atoms in the process of bonding share their

electrons instead of donating them, they form a

covalent compound.

The smallest part of a covalent compound is

called a molecule.

COVALENT COMPOUNDS: WATER

MATTER

PURE SUBSTANCES

ELEMENTS IONIC COMPOUNDS COVALENT COMPOUNDS

ATOMS FORMULA UNITS MOLECULES

EX: CARBON EX: SODIUM CHLORIDE EX: WATER

2B: THE CHEMICAL PROCESSES OF LIFE

How do chemical processes keep life going?

PHYSICAL CHANGES

Alter matter in ways that don’t change its

identity.

PHYSICAL CHANGES: SOLUTIONS

Mixture: a combination of two or more substances

in which each substance retains its individual

characteristics and properties.

Solution: A uniform (homogeneous) mixture

formed when a substance (the solute) is dissolved

in another substance (the solvent).

The amount of solute packed into a solvent is

called the concentration of a solution.

SOLUTIONS: Acids and Bases

An acid is a substance that dissolves in water to

form hydrogen ions (H+)

A base is a substance that dissolves in water to

form hydroxide ions (OH-) or other ions that can

accept hydrogen ions.

When a strong acid and base react with each

other, the hydrogen (H+) and hydroxide (OH-) ions

combine to form water.

DIFFUSION

The process by which particles in solution are

evenly distributed throughout the solvent by

Brownian motion:

Particles are in constant random motion.

Temperature is related to the average speed that

particles in a substance move.

This motion is caused by collisions between particles.

Brownian motion affects the motion of especially small

particles.

Matter, like energy, tends to spread out.

CHEMICAL CHANGES

CHEMICAL EQUATIONS

Example: The combustion of glucose

Chemical reactions that produce energy are called exothermic reactions.

The energy of the products is lower than the energy of the reactants.

Some of the chemical energy stored in the glucose is not stored in the water vapor and carbon dioxide. Instead, it escapes as heat and light.

reactants products

Photosynthesis

Plants need energy to form glucose, which they get from the

sun.

This is how a plant stores energy and makes its own food.

An endothermic reaction is a chemical change in which the

reactants have less energy than the products.

CATALYSTS AND ENZYMESHow to overcome the activation energy (Ea)

required for a chemical reaction?

A catalyst is a substance that lowers the activation energy of a

reaction without changing the amount of energy that is stored or

released during the reaction.

Enzymes are a special class of catalysts that naturally occur in

living things. Ex: RuBisCO

Enzymes are usually proteins.

Enzymes make a chemical reaction happen faster.

Enzymes lower the activation energy.

Enzymes allow a reaction to proceed at a lower temperature.

How do enzymes work?

An inhibitor can decrease the activity of an enzyme by binding to the enzyme’s active site.

BIOCHEMISTRYWhat chemical compounds are important to life?

WATER

A polar molecule in which areas of

charge are asymmetrical.

Good at dissolving things; the

universal solvent.

Intermolecular attractions

between water molecules are

called hydrogen bonding.

PROPERTIES OF WATER

The attraction of water molecules for each other is called cohesion.

The attraction of water molecules for other substances is called adhesion.

ORGANIC COMPOUNDS

Molecules that contain carbon covalently

bonded to other elements, typically

oxygen, nitrogen, hydrogen etc.

The compounds associated with life.

Why is carbon so important to life?

It can form up to four bonds

It can bond with itself

It can form long chains or rings

It has an amazing chemical flexibility-

scientists know about 50 million carbon

compounds!

ORGANIC COMPOUNDS

Carbohydrates

Lipids

Proteins

Nucleotides

These are all polymers, large molecules

consisting of repeating subunits.

CARBOHYDRATES

Organic compounds made of carbons,

hydrogens, and oxygens.

The most abundant biological compounds.

Provide fuel for living things.

CARBOHYDRATES

Simple carbohydrates are called sugars.

Glucose is the most important sugar for living

things.

LIPIDS

Nonpolar molecules.

Do not mix with water.

Living things use lipids to store energy.

Lipids include substances like fats and oils.

LIPIDS

PROTEINS

Proteins are used to make our muscles, blood, and body coverings (hair, nails and skin).

Proteins are polymers of small organic compounds called aminoacids.

Polypeptides form when amino acids combine

to release water through the formation of a

peptide bond.

NUCLEOTIDES/NUCLEIC ACIDS

Nucleic acids are polymers

of nucleotides (DNA, RNA).

The main purpose of nucleic

acids is to carry

information.