Chapter 2The Chemical Level of

Organization

Lecture slides prepared by Curtis DeFriez, Weber State University

• Matter: Everything around you.

Atoms and compounds are all made of very small parts of matter.

• Matter exists in 3 forms:

Gas

Liquid

Solid

Matter

Introduction• Since chemicals compose your body (and all body activities are chemical in nature),

it is important to become familiar with the language and fundamental concepts of

chemistry.

Structure of Atoms• Units of matter of all chemical elements are called atoms.

• An element is a quantity of matter composed of atoms of the same type.

• There are 4 elements that compose most of the body’s mass:

Carbone – Hydrogen – Oxygen – Nitrogen

▪ Nucleus: The dense central core of an atom,

consists of protons (p+) & neutrons (no)

▪ Electrons (e-) surround the nucleus as a cloud

Atoms contain:

• Electrons are very small and light (mass about 1/1836th

that of proton or neutron), often represented as a “planet”

orbiting the “sun” (atomic nucleus).

• In reality, they are found in a “cloud” of probability.

• we can use the planets-orbiting-the-

sun model for this course!

Structure of Atoms

• Protons and neutrons form the nucleus of an atom; electrons

surround the nucleus.

• Protons are large, positively-charged particles

▪ The number of protons in the nucleus

(called the atomic number)

determines the element (gold vs. silver vs. lead).

Example:- Oxygen (symbol O) atomic number = 8 (has 8 protons)- Hydrogen (symbol H) atomic number = 1 (has 1 proton)- Carbon (symbol C) atomic number = 6 (has 6 protons)

Structure of Atoms

• Neutrons are the second large particle that make-up the nucleus of atoms.

▪ Unlike protons, neutrons have no charge.

▪ They do add mass

▪ And determine the variety, or “isotope” of a certain element.

Example:

carbon-12 vs. carbon-14, which has 2 extra neutrons in nucleus

(used in dating objects).

Structure of Atoms

• Mass is measured as a Dalton (atomic mass unit).

▪ Masses of subatomic particles:

• Neutron - mass of 1.008 Daltons

• Proton - mass of 1.007 Daltons

• Electron has mass of 0.0005 Dalton

Structure of Atoms

• Certain numbers are used to describe different properties of atoms (of elements).

▪ Atomic number is the number of protons in an atom.

▪ Mass number is the sum of protons and neutrons in an atom and indicates how

much the atoms “weighs”—this is always a whole number.

▪ Mass number = Number of protons [Atomic number ]+ Number of neutrons.

Structure of Atoms

Ions, Molecules, & Compounds• Ions are atoms that have given up or gained an electron in

their outer electron shell (also called the valence shell).

▪ Written with its chemical symbol and (+) or (–)

• Ionic bonds form when an atom loses or gains a valence electron.

Ions are formed.

▪ Positively and negatively charged ions are attracted to one another.

▪ Cations are positively charged ions that have given up one or more electrons

(they are electron donors.)

▪ Anions are negatively charged ions that have picked up one or more electrons

that another atom has lost (they are electron acceptors).

Chemical Bonds – Ionic

• Ionic Bond Formation

Chemical Bonds – Ionic

Chemical Reactions*

• Chemical reactions occur when electrons in the valence shell are shared

or transferred. New bonds form and/or old bonds are broken.

• Metabolism is the “sum of all the chemical reactions in the body”.

• Types of chemical reactions can be broadly classified as:

▪ Synthesis reactions – Anabolism

• A + B ➙AB

▪ Decomposition reactions – Catabolism

• AB ➙A + B

▪ Exchange reactions

• AB + CD ➙AD + CB

▪ Reversible reactions

• AC ↔ A + C

Chemical Reactions

Inorganic & Organic Compounds• Inorganic compounds are structurally simple molecules

that usually lack carbon - like the salt

potassium chloride (KCl).

• Organic compounds always contain carbon and

are usually large, complex molecules.

▪ Usually contain hydrogen

• Water is the most important and abundant inorganic compound in all living systems.

• Water as a solvent:

▪ In a solution, the solvent dissolves the solute.

▪ Substances which dissolve in water are hydrophilic.

▪ Substances which do not dissolve in water are hydrophobic.

▪ Water’s role as a solvent makes it essential for health and survival.

Inorganic Compounds

• A mixture is a combination of elements or compounds that are physically blended

together but are not bound by chemical bonds.

The three common mixtures:

1. Solution

2. Colloid

3. Suspension

Three Common Mixtures

1. Solution• In a solution:

- A substance called the solvent dissolves another substance called the solute.

- Usually there is more solvent than solute in a solution.

• In our bodies, the most common solvent is water:

We are 65-80% water (depending on age - babies are very “wet”).

Three Common Mixtures

2. Colloid

• A colloid differs from a solution mainly on the basis of the size of its particles,

with the particles in the colloid being large enough to scatter light (milk).

3. Suspension

• In a suspension, the suspended material may mix with the liquid or suspending

medium for some time, but it will eventually settle out (blood is a suspension.)

Three Common Mixtures

• pH = (concentration of H+ in moles/l)

• It is a scale that runs from 0 to 14

Acids and Bases

• The pH scale is a logarithmic scale, not a linear scale.

• Because of the “negative” in the formula:

The lower the number, the higher the H+ concentration ([H+]).

• Because it is logarithmic, a change of two or three pH units represents a change

in the [H+] of 100 or 1000.

▪ A solution with pH=1 is 100 times more concentrated in H+ ions than a solution with a pH=3.

▪ A solution with pH=11 contains 1000 times less H+ ions than a solution with a pH=8.

Acids and Bases*

Acids and Bases• pH < 7 is acidic ([H+] > [OH-])

• pH > 7 is alkaline ([H+] < [OH-])

• A salt (like KCl) is neutral

Buffers: Substances that neutralize pH in body fluids

• Human blood has a normal pH between 7.35 and 7.45 and is considered slightly alkaline.

Main organic compounds:Carbohydrates: Monosaccharides, Disaccharides, and Polysaccharides .

Lipids: Like; Triglycerides

Proteins: Like; Enzymes

Nucleic acids: Like DNA and ATP

Organic Compounds

• Carbohydrates provide most of the energy needed for life and include sugars,

starches, glycogen, and cellulose.

• Some carbohydrates are converted to other substances which are used to build structures

and to generate ATP.

• Other carbohydrates function as food reserves.

• Carbohydrates are divided into three major groups based on their size: monosaccharides,

disaccharides, and polysaccharides .

Organic Compounds

• Lipids are another major group of organic molecules.

▪ Like carbohydrates, they contain carbon, hydrogen, and oxygen;

▪ Unlike carbohydrates, they do not have a 2:1 ratio of hydrogen to oxygen.

• They are hydrophobic and mostly insoluble in water.

• They combine with

proteins (lipoproteins)

for transport in blood.

Organic Compounds

• Triglycerides are the most plentiful lipids in the body and provide protection,

insulation, and energy (both immediate and stored).

▪ At room temperature, triglycerides may be either solid (fats) or liquid (oils).

▪ Triglyceride storage is virtually unlimited.

▪ Excess dietary carbohydrates, proteins, fats, and oils are deposited in adipose

tissue as triglycerides.

Organic Compounds

• Proteins are large molecules that contain carbon, hydrogen, oxygen, and nitrogen.

• They are the most “human” of all organic compounds.

• We can rightly say that humans are protein creatures, using:

carbohydrates to burn as fuels, and

lipids for structural support, energy storage, and hormones.

• This graphic is a model of an enzyme protein.

Organic Compounds

▪ Denaturation (loss of protein structure) by a hostile environment causes loss of

its characteristic shape and function.

▪ An egg white turning solid white when exposed

to high temperatures is an example of protein

denaturation.

Proteins

• Enzymes are special proteins that catalyze (speed up) metabolic reaction in all

living cells.

• The substrate is the substance upon which an enzyme has its effect.

In this regard, enzymes are highly specific.

Proteins

• Nucleic acids are universal in living things.

• These molecules carry genetic information as deoxyribonucleic acid (DNA) and

ribonucleic acid (RNA).

▪ By controlling the formation of

proteins, the genetic code

regulates most of the activities

that take place in our cells

throughout a lifetime.

Organic Compounds

• The nucleotides of DNA and RNA are joined to a “sugar-phosphate”

backbone to make a long chain.

• There are 2 sugar-phosphate strands of DNA, joined in the middle by

hydrogen bonds from one nucleotide to another.

DNA Nucleotide:1. The Sugar: Deoxyribose

2. The Nitrogenous Base: Thymine, Cytosine, Adenine, Guanine

3. The Phosphate

Nucleic Acids*

• RNA structure differs from DNA in that it is single stranded (instead of double stranded),

ribose replaces the sugar deoxyribose, and uracil is the nitrogenous base that replaces thymine.

RNA Nucleotide:1. The Sugar: Ribose

2. The Nitrogenous Base: Uracil, Cytosine, Adenine, Guanine

3. The Phosphate

• There are 3 types of RNA within the cell, each with a specific function:

▪ Messenger RNA

▪ Ribosomal RNA

▪ Transfer RNA

Nucleic Acids*

DNA Nucleotide:

1. The Sugar: Deoxyribose

2. The Nitrogenous Base: Thymine, Cytosine, Adenine, Guanine

3. The Phosphate

RNA Nucleotide:

1. The Sugar: Ribose

2. The Nitrogenous Base: Uracil, Cytosine, Adenine, Guanine

3. The Phosphate

Nucleic Acids

• Other example of nucleic acid:

• Nucleic acids are also used in making a very important energy-carrying molecule

in the body called Adenosine Triphosphate (ATP).

• ATP is used as a temporary storage of energy

Nucleic Acids*

The End