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.

  1. The chemicals in the human body that are commonly used for medical testing are carbohydrates, lipids, proteins, and nucleic acids.
  2. 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.
  1. 1.Chemists study the composition of substances and how they change.
  1. 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.

2.2Structure of Matter (p. 51)

  1. 1. Matter is anything that has weight and takes up space.
  1. Basic substances are called elements.
  2. Tiny, invisible particles that make up basic substances are call atoms.
  3. Bulk elements are those elements that are required by the body in

large amounts, such as carbon, hydrogen, oxygen, nitrogen, sulfur,

and phosphorus.

  1. Trace elements are those elements that are needed in small amounts.
  2. Ultratrace elements are needed in very small amounts, frequently as

part of enzymes.

  1. Elements and symbols

Element / Symbol / Element / Symbol
Oxygen / O / Sodium / Na
Carbon / C / Magnesium / Mg
Hydrogen / H / Cobalt / Co
Nitrogen / N / Copper / Cu
Calcium / Ca / Fluorine / F
Phosphorus / P / Iodine / I
Potassium / K / Iron / Fe
Sulfur / S / Manganese / Mn
Chlorine / Cl / Zinc / Zn
  1. 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.

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.

  1. 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.
  2. 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

  1. Reversible reaction
  2. Exchange reaction
  1. Catalysts influence the rates of chemical reactions but are unchanged in the process.
  1. HCl – acid

NaOH – base

H2SO4 – acid

Mg(OH)2 base

NaHCO3 –salt

NaCl –salt

  1. 1.The term pH refers to the hydrogen ion concentration of a substance.
  1. Carrot – acid

Milk of magnesia – base

Human blood – neutral to slightly alkaline or base

Tomato – acid

Lemon – acid

Distilled water – neutral.

  1. 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.
  2. 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.

2.3Chemical Constituents of Cells (p. 61)

  1. 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.

  1. 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.

  1. 1. Carbohydrates are an important source of energy for cells, and reserves of them are stored to assure a continuing supply.
  1. The elements found in carbohydrates are carbon, oxygen, and hydrogen.
  2. 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
  1. 1. C6H12O6
  1. This is a molecule of glucose.
  1. 1.Lipids contain carbon, oxygen, and hydrogen but in different proportions than found in carbohydrates.
  1. 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.
  2. Fatty acids and glycerol
  3. Monounsaturated
  4. Polyunsaturated
  5. 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.
  6. Cholesterol, which is used to synthesize other steroids, sex hormones (estrogen and progesterone and testosterone), as well as some adrenal hormones.
  1. 1.The role of protein in maintaining the cell is to serve as structural material, energy sources, and chemical messengers (hormones).
  1. The elements found in protein are carbon, hydrogen, oxygen, and nitrogen.
  2. The building materials of proteins are amino acids.
  3. Denatured
  4. a.Amino acid sequence
  1. Coil or a pleated sheet
  2. Hydrogen bonding and covalent bonding
  1. DNA molecules store information in a molecular code that cells use to construct specific protein molecules. RNA molecules help to synthesize proteins.
  1. PET stands for positron emission tomography. It uses radioactive isotopes to detect biochemical activity in a specific body part.
  1. A CT scan produces a three-dimensional image rather than the two- dimensional 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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