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Chapter 2
Chemical Basis of Life
Definition of Word Parts (p. 50)
bio–, life
di–, two
glyc–, sweet
iso–, equal
lip–, fat
-lyt, dissolvable
mono–, one
nucle–, kernel
poly–, many
sacchar–, sugar
syn–, together
-valent, having power
2.1 Introduction (p.51)
A. A biomarker is a substance in the body that is commonly used to identify a
disease process or exposure to a toxin. If the amount of a specific
biomarker changes, it can used to track the progression of a disease or in
tracking a response to treatment.
B. 1. A good test for a biomarker must have:
Sensitivity – the test is positive only when the object of the test is
present
Specificity – the test is negative when the object of the test is not
present.
Reproducibility – results mean the same thing across different
patients
Noninvasiveness – the test material or body fluid can be easily
obtained.
2. The chemicals in the human body that are commonly used for medical
testing are carbohydrates, lipids, proteins, and nucleic acids.
3. Genetic testing be useful if it can lead to an earlier diagnosis or if it can
predict a patient's response to a drug or drug class.
C. 1. Chemists study the composition of substances and how they change.
2. Biochemistry is the division of chemistry of interest to physiologists.
Study of the chemistry of living things is important to explain
physiological processes as well as to support the development of new
drugs and the mechanisms of disease.
2.2
Structure of Matter (p. 51)
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A. 1.
2.
3.
4.
Matter is anything that has weight and takes up space.
Basic substances are called elements.
Tiny, invisible particles that make up basic substances are call atoms.
Bulk elements are those elements that are required by the body in
large amounts, such as carbon, hydrogen, oxygen, nitrogen, sulfur,
and phosphorus.
5. Trace elements are those elements that are needed in small amounts.
6. Ultratrace elements are needed in very small amounts, frequently as
part of enzymes.
B. Elements and symbols
Element
Oxygen
Carbon
Hydrogen
Nitrogen
Calcium
Phosphorus
Potassium
Sulfur
Chlorine
Symbol
O
C
H
N
Ca
P
K
S
Cl
Element
Sodium
Magnesium
Cobalt
Copper
Fluorine
Iodine
Iron
Manganese
Zinc
Symbol
Na
Mg
Co
Cu
F
I
Fe
Mn
Zn
C. 1. Atomic number – 3
Atomic weight – 7
Eight electrons are needed to fill the outer shell.
This is an atom of lithium.
2. a. Neutron
b. Proton
c. Electron
d. Nucleus
D. Isotopes have a different number of neutrons and thus a different atomic
weight.
All isotopes participate in chemical reactions in the same way because
they all have the same number of electrons and it is electrons that
determine the way an atom behaves chemically.
A radioactive isotope has an unstable atomic nucleus that decomposes,
releasing energy until its atoms reach a stable state.
The three types of radiation are alpha, beta, and gamma radiation.
The half-life of an isotope is the time it takes for one half of the isotope to
decay to a nonradioactive form.
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Radioactive isotopes are useful in the treatment of diseases such as
hyperthyroidism and certain types of malignancies. They are also useful
as diagnostic tools. Thallium is commonly used to diagnose disorders of
the cardiac muscle.
E. In an ionic bond, anions and cations (+ and – ions) attract randomly and
form crystals. In a covalent bond, electrons are shared rather than gained
or lost.
F. 1. Alpha, beta, and gamma radiation is called ionizing radiation because
their energy adds or removes electrons from atoms.
2. Ionizing radiation has a negative impact on health because it disrupts
physiology at the cellular level. It can cause cancer, disrupt the lens of
the eye, and interferes with growth and development.
3. In the United States there are low levels of radiation emanating from
natural sources such as cosmic rays from space. Another source of
background radiation is from rocks and clay. It is possible to ingest
radioactive elements such as potassium-40 and carbon-14. Medical
and dental sources include imaging techniques such as X rays and
radioactive substances used to treat diseases. People who live near
sites of atomic weapon manufacture and nuclear power plants are
typically exposed to high levels of ionizing radiation from nuclear waste
products. Workers who mine and process radioactive materials are
exposed to ionizing radiation. And consumer products such as
luminescent watch dials, smoke detectors and color TV’s also give off
ionizing radiation. In short, the sources of this radiation are common in
our daily lives.
G. 1. Two or more atoms combine to form an element.
2. A formula that is a shorthand notation of the kinds and numbers of
atoms in a molecule is a molecular formula.
3. If atoms of different elements combine they form a molecule.
4. C
5. C
6. When atoms bond by sharing an electron a covalent bond is formed
H. 1. a. Decomposition
b. Synthesis
c. Reversible reaction
d. Exchange reaction
2. Catalysts influence the rates of chemical reactions but are unchanged
in the process.
I. HCl – acid
NaOH – base
H2SO4 – acid
Mg(OH)2 base
NaHCO3 –salt
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NaCl –salt
J. 1. The term pH refers to the hydrogen ion concentration of a substance.
2. Carrot – acid
Milk of magnesia – base
Human blood – neutral to slightly alkaline or base
Tomato – acid
Lemon – acid
Distilled water – neutral.
3. Alkalosis is blood pH of 7.5 – 7.8. The symptoms are a sense of
agitation or anxiety and dizziness. It can be caused by breathing
rapidly, overdosing on antacids, fever, anxiety, or the loss of stomach
acid as occurs with mild vomiting.
4. Acidosis is a blood pH of 7.0 – 7.3. Symptoms are disorientation,
fatigue, and difficulty breathing. Acidosis can result from severe
vomiting that empties the alkaline small intestine; diabetes; brain
damage; breathing impairment such as pneumonia or other diseases
of the lung; and kidney disease.
2.3
Chemical Constituents of Cells (p. 61)
A. Water is the most abundant substance in the human body and may be
the most important. One role of water in the cell is to dissolve molecules,
forming ions. Ions are most likely to take part in chemical reactions. Water
is an important component of blood and forms a large part of the
intercellular matrix of blood. Blood transports oxygen, carbon dioxide and
nutrients and electrolytes to cells. Water also has an important role in
absorbing heat from metabolism of cells and transporting it to the body
surface where it can be released to the environment.
Oxygen enters the body via the lungs and is carried to all cells by the
blood. It is essential to reactions that release energy for chemical
reactions within cells.
Carbon dioxide is the waste product of cellular reactions. It moves from
cells to the blood where it reacts with water to form carbonic acid, a weak
acid. It is in this form that most carbon dioxide is returned to the lungs and
excreted as the carbon dioxide is released from the carbonic acid
molecule.
Inorganic salts (sodium, potassium, bicarbonate, and phosphate being the
most plentiful) are the sources of ions that have essential roles in many
metabolic processes. These processes help maintain normal water
concentrations and pH in body fluids, are a part of the blood-clotting
cascade, are essential to bone development, and play important roles in
muscle and nerve function.
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B. Nitric acid (NO) and carbon monoxide (CO) in large quantities are toxic
substances and can lead to death. However, in small quantities they play
important roles in normal physiology. NO is found in smog, cigarettes, and
acid rain. Carbon monoxide is a colorless, odorless gas produced as
waste in home heating systems and in the exhaust of gasoline powered
engines.
As a part of normal physiology, NO is involved in digestion, memory,
respiration, and circulation. CO has a role in the recycling of old red blood
cells.
C. 1. Carbohydrates are an important source of energy for cells, and
reserves of them are stored to assure a continuing supply.
2. The elements found in carbohydrates are carbon, oxygen, and
hydrogen.
3. Carbohydrate molecules are water-soluble and contain atoms of
carbon, hydrogen and oxygen. Simple carbohydrates such are sugars
are small molecules that are rapidly available sources of energy.
Complex carbohydrates are very large molecules built from many
molecules of simple carbohydrates. They are found in such foods as
potatoes and pasta. They require more complex digestive processes
to release their energy
D. 1. C6H12O6
2. This is a molecule of glucose.
E. 1. Lipids contain carbon, oxygen, and hydrogen but in different
proportions than found in carbohydrates.
2. Lipids contain a number of compounds such as fats, phospholipids,
and steroids. Phospholipids are an important component of the cell
wall. The most common lipids are fats, which are rich sources of
energy.
3. Fatty acids and glycerol
4. Monounsaturated
5. Polyunsaturated
6. A phospholipid molecule contains two fatty acids rather than the three
found in fats. They have a phosphate group in place of the third
molecule of fatty acid. The phosphate-containing end of the
phospholipid is water-soluble and is called the head of the molecule,
and the fatty acid portion is known as the tail and is insoluble in water.
7. Cholesterol, which is used to synthesize other steroids, sex hormones
(estrogen and progesterone and testosterone), as well as some
adrenal hormones.
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F. 1. The role of protein in maintaining the cell is to serve as structural
material, energy sources, and chemical messengers (hormones).
2. The elements found in protein are carbon, hydrogen, oxygen, and
nitrogen.
3. The building materials of proteins are amino acids.
4. Denatured
5. a. Amino acid sequence
b. Coil or a pleated sheet
c. Hydrogen bonding and covalent bonding
G. DNA molecules store information in a molecular code that cells use to
construct specific protein molecules. RNA molecules help to synthesize
proteins.
H. PET stands for positron emission tomography. It uses radioactive isotopes
to detect biochemical activity in a specific body part.
I. A CT scan produces a three-dimensional image rather than the twodimensional image produced by traditional X rays. A CT scan can image
minute “slices” of a body part and then combine them mathematically,
using a computer to produce the three-dimensional image. A CT scan can
differentiate between different densities of tissue, allowing for more
precise information about the type of pathology.
Clinical Focus Question
In order to answer this question, you must have an understanding of the role of
water and various electrolytes carried in water in human physiology. The most
important part of the answer to this question is how to conserve or replace water
lost in vomiting and diarrhea. Conservation can be accomplished by halting the
vomiting and diarrhea. Sometimes this can be accomplished by dietary
interventions; sometimes it is necessary to use medications.
In most cases, water can be replaced orally by taking it in small, frequent
amounts. Sometimes, however, intravenous replacement is necessary. If the
vomiting and diarrhea persist long enough or are severe enough, fluid
replacement containing electrolytes may be needed in order to maintain
electrolyte balance.
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