Module 2: The Chemical Level of Organization

Lesson 4: Inorganic Compounds Essential to Human Functioning

Các Hợp Chất Vô Cơ Cần Thiết Cho Hoạt Động Của Con Người

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Mỗi bài học (lesson) bao gồm 4 phần chính: Thuật ngữ, Luyện Đọc, Luyện Nghe, và Bàn Luận.
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Dưới đây là danh sách những thuật ngữ Y khoa của module The Chemical Level of Organization.
Khái quát được số lượng thuật ngữ sẽ xuất hiện trong bài đọc và nghe sẽ giúp bạn thoải mái tiêu thụ nội dung hơn. Sau khi hoàn thành nội dung đọc và nghe, bạn hãy quay lại đây và luyện tập (practice) để quen dần các thuật ngữ này. Đừng ép bản thân phải nhớ các thuật ngữ này vội vì bạn sẽ gặp và ôn lại danh sách này trong những bài học (lesson) khác của cùng một module.

Medical Terminology: The Chemical Level of Organization

compound that releases hydrogen ions (H+) in solution
activation energy
amount of energy greater than the energy contained in the reactants, which must be overcome for a reaction to proceed
adenosine triphosphate (ATP)
nucleotide containing ribose and an adenine base that is essential in energy transfer
amino acid
building block of proteins; characterized by an amino and carboxyl functional groups and a variable side-chain
atom with a negative charge
smallest unit of an element that retains the unique properties of that element
atomic number
number of protons in the nucleus of an atom
compound that accepts hydrogen ions (H+) in solution
electrical force linking atoms
solution containing a weak acid or a weak base that opposes wide fluctuations in the pH of body fluids
class of organic compounds built from sugars, molecules containing carbon, hydrogen, and oxygen in a 1-2-1 ratio
substance that increases the rate of a chemical reaction without itself being changed in the process
atom with a positive charge
chemical energy
form of energy that is absorbed as chemical bonds form, stored as they are maintained, and released as they are broken
liquid mixture in which the solute particles consist of clumps of molecules large enough to scatter light
substance composed of two or more different elements joined by chemical bonds
number of particles within a given space
covalent bond
chemical bond in which two atoms share electrons, thereby completing their valence shells
decomposition reaction
type of catabolic reaction in which one or more bonds within a larger molecule are broken, resulting in the release of smaller molecules or atoms
change in the structure of a molecule through physical or chemical means
deoxyribonucleic acid (DNA)
deoxyribose-containing nucleotide that stores genetic information
pair of carbohydrate monomers bonded by dehydration synthesis via a glycosidic bond
disulfide bond
covalent bond formed within a polypeptide between sulfide groups of sulfur-containing amino acids, for example, cysteine
subatomic particle having a negative charge and nearly no mass; found orbiting the atom’s nucleus
electron shell
area of space a given distance from an atom’s nucleus in which electrons are grouped
substance that cannot be created or broken down by ordinary chemical means
protein or RNA that catalyzes chemical reactions
exchange reaction
type of chemical reaction in which bonds are both formed and broken, resulting in the transfer of components
functional group
group of atoms linked by strong covalent bonds that tends to behave as a distinct unit in chemical reactions with other atoms
hydrogen bond
dipole-dipole bond in which a hydrogen atom covalently bonded to an electronegative atom is weakly attracted to a second electronegative atom
inorganic compound
substance that does not contain both carbon and hydrogen
atom with an overall positive or negative charge
ionic bond
attraction between an anion and a cation
one of the variations of an element in which the number of neutrons differ from each other
kinetic energy
energy that matter possesses because of its motion
class of nonpolar organic compounds built from hydrocarbons and distinguished by the fact that they are not soluble in water
large molecule formed by covalent bonding
mass number
sum of the number of protons and neutrons in the nucleus of an atom
physical substance; that which occupies space and has mass
two or more atoms covalently bonded together
monomer of carbohydrate; also known as a simple sugar
heavy subatomic particle having no electrical charge and found in the atom’s nucleus
class of organic compounds composed of one or more phosphate groups, a pentose sugar, and a base
organic compound
substance that contains both carbon and hydrogen
peptide bond
covalent bond formed by dehydration synthesis between two amino acids
periodic table of the elements
arrangement of the elements in a table according to their atomic number; elements having similar properties because of their electron arrangements compose columns in the table, while elements having the same number of valence shells compose rows in the table
negative logarithm of the hydrogen ion (H+) concentration of a solution
a lipid compound in which a phosphate group is combined with a diglyceride
addition of one or more phosphate groups to an organic compound
polar molecule
molecule with regions that have opposite charges resulting from uneven numbers of electrons in the nuclei of the atoms participating in the covalent bond
compound consisting of more than two carbohydrate monomers bonded by dehydration synthesis via glycosidic bonds
potential energy
stored energy matter possesses because of the positioning or structure of its components
one or more substances produced by a chemical reaction
lipid compound derived from fatty acid chains and important in regulating several body processes
class of organic compounds that are composed of many amino acids linked together by peptide bonds
heavy subatomic particle having a positive charge and found in the atom’s nucleus
nitrogen-containing base with a double ring structure; adenine and guanine
nitrogen-containing base with a single ring structure; cytosine, thiamine, and uracil
radioactive isotope
unstable, heavy isotope that gives off subatomic particles, or electromagnetic energy, as it decays; also called radioisotopes
one or more substances that enter into the reaction
ribonucleic acid (RNA)
ribose-containing nucleotide that helps manifest the genetic code as protein
homogeneous liquid mixture in which a solute is dissolved into molecules within a solvent
(also, sterol) lipid compound composed of four hydrocarbon rings bonded to a variety of other atoms and molecules
reactant in an enzymatic reaction
liquid mixture in which particles distributed in the liquid settle out over time
synthesis reaction
type of anabolic reaction in which two or more atoms or molecules bond, resulting in the formation of a larger molecule
lipid compound composed of a glycerol molecule bonded with three fatty acid chains
valence shell
outermost electron shell of an atom
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Dưới đây là các bài văn nằm ở bên trái. Ở bên phải là các bài luyện tập (practice) để đánh giá khả năng đọc hiểu của bạn. Sẽ khó khăn trong thời gian đầu nếu vốn từ vựng của bạn còn hạn chế, đặc biệt là từ vựng Y khoa. Hãy kiên nhẫn và đọc nhiều nhất có kể, lượng kiến thức tích tụ dần sẽ giúp bạn đọc thoải mái hơn.
The concepts you have learned so far in this chapter govern all forms of matter, and would work as a foundation for geology as well as biology. This section of the chapter narrows the focus to the chemistry of human life; that is, the compounds important for the body’s structure and function. In general, these compounds are either inorganic or organic.

  • An inorganic compound is a substance that does not contain both carbon and hydrogen. A great many inorganic compounds do contain hydrogen atoms, such as water (H2O) and the hydrochloric acid (HCl) produced by your stomach. In contrast, only a handful of inorganic compounds contain carbon atoms. Carbon dioxide (CO2) is one of the few examples.
  • An organic compound, then, is a substance that contains both carbon and hydrogen. Organic compounds are synthesized via covalent bonds within living organisms, including the human body. Recall that carbon and hydrogen are the second and third most abundant elements in your body. You will soon discover how these two elements combine in the foods you eat, in the compounds that make up your body structure, and in the chemicals that fuel your functioning.

The following section examines the three groups of inorganic compounds essential to life: water, salts, acids, and bases. Organic compounds are covered later in the article.
As much as 70 percent of an adult’s body weight is water. This water is contained both within the cells and between the cells that make up tissues and organs. Its several roles make water indispensable to human functioning.

A. Water as a Lubricant and Cushion

Water is a major component of many of the body’s lubricating fluids. Just as oil lubricates the hinge on a door, water in synovial fluid lubricates the actions of body joints, and water in pleural fluid helps the lungs expand and recoil with breathing. Watery fluids help keep food flowing through the digestive tract, and ensure that the movement of adjacent abdominal organs is friction free.

Water also protects cells and organs from physical trauma, cushioning the brain within the skull, for example, and protecting the delicate nerve tissue of the eyes. Water cushions a developing fetus in the mother’s womb as well.

B. Water as a Heat Sink

A heat sink is a substance or object that absorbs and dissipates heat but does not experience a corresponding increase in temperature. In the body, water absorbs the heat generated by chemical reactions without greatly increasing in temperature. Moreover, when the environmental temperature soars, the water stored in the body helps keep the body cool. This cooling effect happens as warm blood from the body’s core flows to the blood vessels just under the skin and is transferred to the environment. At the same time, sweat glands release warm water in sweat. As the water evaporates into the air, it carries away heat, and then the cooler blood from the periphery circulates back to the body core.

C. Water as a Component of Liquid Mixtures

A mixture is a combination of two or more substances, each of which maintains its own chemical identity. In other words, the constituent substances are not chemically bonded into a new, larger chemical compound. The concept is easy to imagine if you think of powdery substances such as flour and sugar; when you stir them together in a bowl, they obviously do not bond to form a new compound. The room air you breathe is a gaseous mixture, containing three discrete elements—nitrogen, oxygen, and argon—and one compound, carbon dioxide. There are three types of liquid mixtures, all of which contain water as a key component. These are solutions, colloids, and suspensions.

For cells in the body to survive, they must be kept moist in a water-based liquid called a solution. In chemistry, a liquid solution consists of a solvent that dissolves a substance called a solute. An important characteristic of solutions is that they are homogeneous; that is, the solute molecules are distributed evenly throughout the solution. If you were to stir a teaspoon of sugar into a glass of water, the sugar would dissolve into sugar molecules separated by water molecules. The ratio of sugar to water in the left side of the glass would be the same as the ratio of sugar to water in the right side of the glass. If you were to add more sugar, the ratio of sugar to water would change, but the distribution—provided you had stirred well—would still be even.

Water is considered the “universal solvent” and it is believed that life cannot exist without water because of this. Water is certainly the most abundant solvent in the body; essentially all of the body’s chemical reactions occur among compounds dissolved in water. Because water molecules are polar, with regions of positive and negative electrical charge, water readily dissolves ionic compounds and polar covalent compounds. Such compounds are referred to as hydrophilic, or “water-loving.” As mentioned above, sugar dissolves well in water. This is because sugar molecules contain regions of hydrogen-oxygen polar bonds, making it hydrophilic. Nonpolar molecules, which do not readily dissolve in water, are called hydrophobic, or “water-fearing.”

D. Concentrations of Solutes

Various mixtures of solutes and water are described in chemistry. The concentration of a given solute is the number of particles of that solute in a given space (oxygen makes up about 21 percent of atmospheric air). In the bloodstream of humans, glucose concentration is usually measured in milligram (mg) per deciliter (dL), and in a healthy adult averages about 100 mg/dL. Another method of measuring the concentration of a solute is by its molarity—which is moles (M) of the molecules per liter (L). The mole of an element is its atomic weight, while a mole of a compound is the sum of the atomic weights of its components, called the molecular weight. An often-used example is calculating a mole of glucose, with the chemical formula C6H12O6. Using the periodic table, the atomic weight of carbon (C) is 12.011 grams (g), and there are six carbons in glucose, for a total atomic weight of 72.066 g. Doing the same calculations for hydrogen (H) and oxygen (O), the molecular weight equals 180.156g (the “gram molecular weight” of glucose). When water is added to make one liter of solution, you have one mole (1M) of glucose. This is particularly useful in chemistry because of the relationship of moles to “Avogadro’s number.” A mole of any solution has the same number of particles in it: 6.02 × 1023. Many substances in the bloodstream and other tissue of the body are measured in thousandths of a mole, or millimoles (mM).

A colloid is a mixture that is somewhat like a heavy solution. The solute particles consist of tiny clumps of molecules large enough to make the liquid mixture opaque (because the particles are large enough to scatter light). Familiar examples of colloids are milk and cream. In the thyroid glands, the thyroid hormone is stored as a thick protein mixture also called a colloid.

A suspension is a liquid mixture in which a heavier substance is suspended temporarily in a liquid, but over time, settles out. This separation of particles from a suspension is called sedimentation. An example of sedimentation occurs in the blood test that establishes sedimentation rate, or sed rate. The test measures how quickly red blood cells in a test tube settle out of the watery portion of blood (known as plasma) over a set period of time. Rapid sedimentation of blood cells does not normally happen in the healthy body, but aspects of certain diseases can cause blood cells to clump together, and these heavy clumps of blood cells settle to the bottom of the test tube more quickly than do normal blood cells.

E. The Role of Water in Chemical Reactions

Two types of chemical reactions involve the creation or the consumption of water: dehydration synthesis and hydrolysis.

  • In dehydration synthesis, one reactant gives up an atom of hydrogen and another reactant gives up a hydroxyl group (OH) in the synthesis of a new product. In the formation of their covalent bond, a molecule of water is released as a byproduct (Figure 1). This is also sometimes referred to as a condensation reaction.
  • In hydrolysis, a molecule of water disrupts a compound, breaking its bonds. The water is itself split into H and OH. One portion of the severed compound then bonds with the hydrogen atom, and the other portion bonds with the hydroxyl group.

These reactions are reversible, and play an important role in the chemistry of organic compounds (which will be discussed shortly).
Recall that salts are formed when ions form ionic bonds. In these reactions, one atom gives up one or more electrons, and thus becomes positively charged, whereas the other accepts one or more electrons and becomes negatively charged. You can now define a salt as a substance that, when dissolved in water, dissociates into ions other than H+ or OH–. This fact is important in distinguishing salts from acids and bases, discussed next.

A typical salt, NaCl, dissociates completely in water (Figure 2). The positive and negative regions on the water molecule (the hydrogen and oxygen ends respectively) attract the negative chloride and positive sodium ions, pulling them away from each other. Again, whereas nonpolar and polar covalently bonded compounds break apart into molecules in solution, salts dissociate into ions. These ions are electrolytes; they are capable of conducting an electrical current in solution. This property is critical to the function of ions in transmitting nerve impulses and prompting muscle contraction.

Many other salts are important in the body. For example, bile salts produced by the liver help break apart dietary fats, and calcium phosphate salts form the mineral portion of teeth and bones.
Acids and bases, like salts, dissociate in water into electrolytes. Acids and bases can very much change the properties of the solutions in which they are dissolved.

A. Acids

An acid is a substance that releases hydrogen ions (H+) in solution (Figure 3a). Because an atom of hydrogen has just one proton and one electron, a positively charged hydrogen ion is simply a proton. This solitary proton is highly likely to participate in chemical reactions. Strong acids are compounds that release all of their H+ in solution; that is, they ionize completely. Hydrochloric acid (HCl), which is released from cells in the lining of the stomach, is a strong acid because it releases all of its H+ in the stomach’s watery environment. This strong acid aids in digestion and kills ingested microbes. Weak acids do not ionize completely; that is, some of their hydrogen ions remain bonded within a compound in solution. An example of a weak acid is vinegar, or acetic acid; it is called acetate after it gives up a proton.

B. Bases

A base is a substance that releases hydroxyl ions (OH–) in solution, or one that accepts H+ already present in solution (see Figure 3b). The hydroxyl ions (also known as hydroxide ions) or other basic substances combine with H+ present to form a water molecule, thereby removing H+ and reducing the solution’s acidity. Strong bases release most or all of their hydroxyl ions; weak bases release only some hydroxyl ions or absorb only a few H+. Food mixed with hydrochloric acid from the stomach would burn the small intestine, the next portion of the digestive tract after the stomach, if it were not for the release of bicarbonate (HCO3–), a weak base that attracts H+. Bicarbonate accepts some of the H+ protons, thereby reducing the acidity of the solution.

C. The Concept of pH

The relative acidity or alkalinity of a solution can be indicated by its pH. A solution’s pH is the negative, base-10 logarithm of the hydrogen ion (H+) concentration of the solution. As an example, a pH 4 solution has an H+ concentration that is ten times greater than that of a pH 5 solution. That is, a solution with a pH of 4 is ten times more acidic than a solution with a pH of 5. The concept of pH will begin to make more sense when you study the pH scale, like that shown in Figure 4. The scale consists of a series of increments ranging from 0 to 14. A solution with a pH of 7 is considered neutral—neither acidic nor basic. Pure water has a pH of 7. The lower the number below 7, the more acidic the solution, or the greater the concentration of H+. The concentration of hydrogen ions at each pH value is 10 times different than the next pH. For instance, a pH value of 4 corresponds to a proton concentration of 10–4 M, or 0.0001M, while a pH value of 5 corresponds to a proton concentration of 10–5 M, or 0.00001M. The higher the number above 7, the more basic (alkaline) the solution, or the lower the concentration of H+. Human urine, for example, is ten times more acidic than pure water, and HCl is 10,000,000 times more acidic than water.

D. Buffers

The pH of human blood normally ranges from 7.35 to 7.45, although it is typically identified as pH 7.4. At this slightly basic pH, blood can reduce the acidity resulting from the carbon dioxide (CO2) constantly being released into the bloodstream by the trillions of cells in the body. Homeostatic mechanisms (along with exhaling CO2 while breathing) normally keep the pH of blood within this narrow range. This is critical, because fluctuations—either too acidic or too alkaline—can lead to life-threatening disorders.

All cells of the body depend on homeostatic regulation of acid–base balance at a pH of approximately 7.4. The body therefore has several mechanisms for this regulation, involving breathing, the excretion of chemicals in urine, and the internal release of chemicals collectively called buffers into body fluids. A buffer is a solution of a weak acid and its conjugate base. A buffer can neutralize small amounts of acids or bases in body fluids. For example, if there is even a slight decrease below 7.35 in the pH of a bodily fluid, the buffer in the fluid—in this case, acting as a weak base—will bind the excess hydrogen ions. In contrast, if pH rises above 7.45, the buffer will act as a weak acid and contribute hydrogen ions.

OpenStax. (2022). Anatomy and Physiology 2e. Rice University. Retrieved June 15, 2023. ISBN-13: 978-1-711494-06-7 (Hardcover) ISBN-13: 978-1-711494-05-0 (Paperback) ISBN-13: 978-1-951693-42-8 (Digital). License: Attribution 4.0 International (CC BY 4.0). Access for free at

Monomers, the basic units for building larger molecules, form polymers (two or more chemically-bonded monomers). (a) In dehydration synthesis, two monomers are covalently bonded in a reaction in which one gives up a hydroxyl group and the other a hydrogen atom. A molecule of water is released as a byproduct during dehydration reactions. (b) In hydrolysis, the covalent bond between two monomers is split by the addition of a hydrogen atom to one and a hydroxyl group to the other, which requires the contribution of one molecule of water.

Notice that the crystals of sodium chloride dissociate not into molecules of NaCl, but into Na+ cations and Cl anions, each completely surrounded by water molecules.

(a) In aqueous solution, an acid dissociates into hydrogen ions (H+) and anions. Nearly every molecule of a strong acid dissociates, producing a high concentration of H+. (b) In aqueous solution, a base dissociates into hydroxyl ions (OH) and cations. Nearly every molecule of a strong base dissociates, producing a high concentration of OH.

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  1. Inorganic compounds essential to human functioning include water, salts, acids, and bases.
  2. These compounds are inorganic; that is, they do not contain both hydrogen and carbon.
  3. Water is a lubricant and cushion, a heat sink, a component of liquid mixtures, a byproduct of dehydration synthesis reactions, and a reactant in hydrolysis reactions.
  4. Salts are compounds that, when dissolved in water, dissociate into ions other than hydrogen ion or hydroxide.
  5. In contrast, acids release hydrogen ion in solution, making it more acidic.
  6. Bases accept hydrogen ion, thereby making the solution more alkaline.
  7. The pH of any solution is its relative concentration of hydrogen ion.
  8. A solution with pH 7 is neutral.
  9. Solutions with pH below 7 are acids, and solutions with pH above 7 are bases.
  10. A change in a single digit on the pH scale (for example, from 7 to 8) represents a ten-fold increase or decrease in the concentration of hydrogen ion.
  11. In a healthy adult, the pH of blood ranges from 7.35 to 7.45.
  12. Homeostatic control mechanisms important for keeping blood in a healthy pH range include chemicals called buffers.
  13. Weak acids and weak bases released when the pH of blood or other body fluids fluctuates in either direction outside of this normal range.
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