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Chapter 2: Chemistry of Living Things
Theory Lecture Outline
Objectives
1. Relate the importance of chemistry and biochemistry to health care
2. Define matter and energy
3. Explain the structure of an atom, an element and a compound
4. Explain the importance of water to our body
5. Describe the four main groups of organic compounds: carbohydrates, fats, proteins and nucleic
acids
6. Explain the difference between the DNA molecule and the RNA molecule
7. Explain the difference between an acid, base and salt
8. Describe why homeostasis is necessary for good health
9. Define the key words that relate to this chapter
Introduction
The study of the human body is essential for those planning a career in health sciences
Terms
• Chemistry – the study of the structure of matter and the composition of substances, their
properties and their chemical reactions
• Matter – anything that has weight (mass) and occupies space
o Matter exists in the forms of solid, liquid and gas
• Energy – the ability to do work or to put matter into motion
a. Types
1. Potential energy is energy stored in cells waiting to be released
2. Kinetic energy is work resulting in motion
b. Example: Lying in bed is an example of potential energy and getting out of bed is an
example of kinetic energy
Atoms
• Atom
a. Smallest piece of an element
• Subatomic particles
a. Proton
b. Neutron
c. Electron
The number of protons of an atom is equal to the number of electrons; atoms are electrically neutral –
neither negative nor positive
Terms
• Elements – made up of like atoms; substance that can neither be created nor destroyed
o Represented by symbols (i.e. hydrogen – H or carbon – C)
• Compounds – elements combined in definite proportion by weight to form new substance
a. Represented by a formula
b. Common formulas
1. H2O = water
2. NaCl = sodium chloride or table salt
3. HCl = hydrochloric acid
4. NaHCO3 = sodium bicarbonate or baking powder
c. The elements carbon, hydrogen and oxygen are united to form organic compounds in
many living organisms
An organic compound is any compound that contains the element carbon
• Molecules – smallest unit of the compound that still has the properties of the compound and the
capability to lead its own stable and independent existence
Ann Senisi Scott & Elizabeth Fong: Body Structures & Functions 11th Edition
Elements
o
There are 92 elements found naturally in our world; additional elements have been manmade by scientists.
Table 2-1 pg. 17 Sample elements and their symbols
Ions and Electrolytes
• Ion
Ion is an electrically charged atom
o Can be either Positive or negative charges
• Electrolytes
o Electrically charged particles that help determine fluid and acid-base balance
In the cells and tissue fluids of the body, ions make it possible for materials to be altered, broken down
and recombined to form new substances or compounds
Types of Compounds
The various elements can combine to form a great number of compounds. All known compounds,
whether natural or synthetic, can be classified into two groups: inorganic compounds and organic
compounds
• Inorganic compounds
a. Normally do not contain carbon (exceptions include carbon dioxide CO2 and calcium
carbonate CaCO3)
b. Water (most important inorganic compound to living organisms) is 55-65% of the body
weight
Functions of water include:
1. Regulates body temperature
2. Takes nutrients to cells and takes away the waste products
3. Necessary for homeostasis
4. Essential to life
• Organic compounds
a. Found in living things
b. Always have carbon
Carbons have the ability to combine with other elements to form a large number of organic compounds.
Their molecules are comparatively large and complex.
Organic Compounds
• Four Main Groups
a. Carbohydrates
b. Lipids
c. Proteins
d. Nucleic acids
Carbohydrates
• Elements
o Carbon, hydrogen, and oxygen
• Three Groups
a. Monosaccharides
b. Disaccharides
c. Polysaccharides
Ann Senisi Scott & Elizabeth Fong: Body Structures & Functions 11th Edition
Lipids
• Elements
o Carbon, hydrogen, and oxygen
• Characteristics
a. Lipids are an important source of stored energy
b. Lipids make up essential steroid hormones
c. Lipids help to insulate the body
• Types
a. Fats (aka triglycerides) - most abundant in the body
b. Phospholipids – contains phosphorus in addition to carbon, hydrogen and oxygen
c. Steroids - contains cholesterol
1. Liver can manufacture cholesterol without a food source
2. Functions of Cholesterol
o Essential in the structure of the semipermeable membrane of the cell
o Necessary to manufacture vitamin D
o Necessary in the production of male and female hormones
o Needed to make adrenal hormone cortisol
Proteins
• Elements
o Carbon, hydrogen, oxygen, and nitrogen and often, phosphorus
and sulfur
• Most diverse and essential organic compound
• Found in every living part of a living cell
• Amino acids – are the small molecular units that make up the very large protein molecules
a. 22 different amino acids
b. 9 essential amino acids – must be ingested because they cannot be made by the body
Enzymes
• Specialized protein molecules found in all living cells
• Help control chemical reactions
a. Help provide energy for cells
b. Assist in making new cell parts
c. Control almost every process in a cell
• Organic catalysts – affects the rate or speed of a chemical reaction without itself being changed
• Highly specific in its action and can be used over and over again
Nucleic Acids
• Organic compound containing carbon, oxygen, hydrogen, nitrogen, and phosphorus
• Structure of nucleic acids (Types)
a. DNA (Deoxyribonucleic acid)
Double-stranded molecule or double helix
1. DNA is involved in the process of heredity
2. The nucleus of every human cell contains 46 (23 pairs) of chromosomes
3. The DNA molecule passes on the genetic information from one generation to the
next
4. DNA structures are unique for each person and are used as a means of
identification
b. RNA (Ribonucleic Acid)
Single stranded molecule
o Play key role in protein synthesis
Ann Senisi Scott & Elizabeth Fong: Body Structures & Functions 11th Edition
Acids, Bases and Salts
• Many inorganic and organic compounds found in living organisms are ones that we use in our
daily lives. They can be classified into one of three groups – acids, bases and salts
Acids
• Sour taste (i.e. grapefruit, lemons, limes and vinegar)
• When dissolved in water, will ionize into positively charged hydrogen ions (H+) and negatively
charged ions of some other element or more simply
o Yields hydrogen ions (H+) in solution
• Litmus paper testing (blue litmus paper turns red if substance is acidic)
Bases
• Bitter taste (also feels slippery between the fingers)
• Also called alkali
• When dissolved in water, ionizes into negatively charged hydroxide (OH-) and positively charged
ions of a metal
• Litmus paper testing (red litmus paper turns blue if substance is basic)
Neutralization and Salts
• Neutralization
o Exchange reaction occurs when an acid and a base are combined to form a salt and water
• Acid + base = salt + water
• HCL + NaOH = NaCL + H2O
pH Scale
• Measure of acidity or alkalinity
• Ranges from 0 to 14
• pH of 7 = neutral (solution has the same number of hydrogen ions as hydroxide ions)
• pH 0-6.9 = acid
• pH 7.1-14 = alkaline (basic)
• Examples of pH levels
a. Tears – 7.4
b. Blood – 7.35-7.45
Homeostasis
• Homeostasis is essential for living cells to function optimally
• Maintenance of balanced pH
o Through compound called a buffer (NaHCO3)
Buffers help a living organism to maintain a constant pH value
• Optimum cell functioning requires a stable cellular fluid environment
• Intracellular and extracellular fluids
Ann Senisi Scott & Elizabeth Fong: Body Structures & Functions 11th Edition