The number of protons in all atoms of the same element is the same, but the number of neutrons is not always the same. An element's isotopes have the same number of protons but differ in the number of neutrons. Isotopes have the same fundamental chemical characteristics as every other atom of the same element, as well as the same atomic number, but their atomic weight differs due to the variable amount of neutrons.
Over 99 percent of all carbon atoms in nature contain six protons and six neutrons in their nuclei (atomic number, 6; atomic weight, 12). An significant carbon isotope has eight neutrons rather than six. It's known as carbon 14. Carbon 14 is an example of a radioactive isotope, or radioisotope, which is unstable and undergoes nuclear disintegration. (Tritium, by the way, is another radioisotope.) (Tritium, by the way, is another radioisotope.) Breakdown causes radioactive isotopes to produce nuclear particles and radiation, which is referred to as "decay."
A hydrogen atom usually contains one proton and no neutrons (atomic number, 1; atomic weight, 1). This most prevalent form of hydrogen and two of its isotopes are seen in Figure 2-3.
It's worth noting that deuterium is a hydrogen isotope with one proton and one neutron (atomic weight, 2). Tritium is a hydrogen isotope with one proton and two neutrons (atomic weight, 3).
Interaction Between Atoms
- Chemical Bonds
The activity of electrons in their outermost shell is primarily responsible for interactions between two or more atoms. Unpaired electrons are frequently involved in the end outcome, which is referred to as a chemical reaction.
In atoms with less or more than eight electrons in the outer shell, processes will eventually occur that result in the loss, gain, or sharing of unpaired electrons from one atom with those from another atom in order to meet the octet rule for both atoms. A molecule is formed as a result of such atom-to-atom interactions.
Two atoms of oxygen, for example, can unite with one atom of carbon to produce molecular carbon dioxide, or CO2. A compound is formed when atoms of more than one element unite, as previously stated. To put it another way, oxygen is a molecule (O2) and an element. Water is a chemical that occurs as a molecule (H2O). Chemical bonds are formed during reactions that hold atoms together. Ionic, or electrovalent, bonds and covalent bonds are the two types of chemical bonds that join atoms to form molecules.
Bonds that are ionic or electrovalent
An ionic, or electrovalent, bond is a chemical connection produced by the transfer of electrons from one atom to another. The attraction between atoms that have been electrically charged as a result of electron loss or gain causes such a bond to form. Ions are atoms like this (see Figure 2-4). Ions can be positively or negatively charged, and ions with opposing charges are attracted to each other.
In Figure 2-4 A, you can see that the sodium atom has a single unpaired electron in its outer shell. The outer ring would be stable if this electron were "lost" since it would have a full outer octet (four pairs of electrone). The loss of one electron results in the creation of a positively charged sodium ion (Na). This is due to the fact that there is now one more proton (+) than there are electrons (-). The chlorine atom, on the other hand, contains one unpaired electron plus three paired electrons in its outer shell, for a total of seven electrons. Chlorine would meet the octet rule by adding another electron, giving it a full complement of four paired electrons in its outer energy shell. The creation of a negatively charged chloride ion would occur from the addition of another electron (CI). A chemical reaction is about to take place. Sodium gives up one of its unpaired electrons to chlorine, resulting in the positively charged sodium ion (Na+). Chlorine takes the electron from sodium and pairs it with one of its own unpaired electrons, resulting in a negatively charged chlorine (CI) ion with a maximum of four electron pairs in its outer shell. The negatively charged chloride ion (CI) is attracted to the positively charged sodium ion (Na+), resulting in the production of NaCl, common table salt. Ionic or electrovalent bonding is seen in this chemical process.
The electron transfer transformed the two sodium and chlorine atoms into ions. The strong electrostatic force that binds positively and negatively charged ions together is known as the ionic bond.
Figure 2 - 4 Example of an ionic bond. A, Steps involved in forming an ionic bond between atoms of sodium and chlorine B, Molecules of sodium chloride (table salt) in typical cube shape formation.
Covalent Bonds
Atoms can be connected together by sharing electrons, just as they can be kept together by ionic bonds created when atoms gain or lose electrons. A covalent bond is a chemical connection produced by the sharing of one or more pairs of electrons between the outer shells of two atoms. In physiology, this sort of chemical bonding is extremely important. Covalent bonds are formed nearly usually when the body's main elements (carbon, oxygen, hydrogen, and nitrogen) share electrons.
Figure 2 - 5 Types of covalent bonds. A single covalent link is said to exist when two hydrogen atoms share one electron pair, resulting in a molecule of hydrogen gas (Figure 2-5, A). Double covalent bonds, or simply double bonds, are covalent bonds that link atoms together by sharing two pairs of electrons (Figure 2-5, B). Two oxygen atoms share two electrons with a carbon atom in the case depicted to obtain a full outer shell of eight electrons and therefore meet the octet rule. The end outcome is a carbon dioxide molecule.
Hydrogen Bonds
A third sort of chemical connection, called a hydrogen bond, can exist within or between physiologically relevant molecules in addition to ionic and covalent bonds, which actually create molecules. Because hydrogen bonds take less energy to break than ionic or covalent connections, they are significantly weaker. Hydrogen bonds occur as a result of uneven charge distribution on a molecule, rather than as a result of electron transfer or sharing. Polar molecules, such as water, are described as such.
Although an atom of water is electrically neutral (number of negative charges equals number of positive charges), it contains a partial positive charge (the hydrogen side) and a partial negative charge (the oxygen side) as seen in Figure 2-6. (the oxygen side). The negative (oxygen) side of one water molecule is weakly attached to the positive (hydrogen) side of a neighbouring water molecule via hydrogen bonds.
Figure 2 - 6 Water is a polar molecule.
Figure 2 - 7 Hydrogen bonds between water. Hydrogen bonding between water molecules is seen in Figure 2-7. Many of the unique characteristics of water, which make it an excellent medium for life chemistry, are due to the capacity of water molecules to establish hydrogen bonds with one another. Hydrogen bonds are also necessary for the three-dimensional structure of proteins and nucleic acids, which will be discussed later in the chapter.
Chemical Reactions
Chemical reactions involve interactions between atoms and molecules that, in turn, involve the formation or breaking of chemical bonds. Three basic types of chemical reactions that you will learn to recognize as you study physiology are:
1. Synthesis reactions
2. Decomposition reactions
3. Exchange reactions
Chemical reactions are represented by variations on a simple formula. In synthesis processes, two or more reactants combine to produce a more complex chemical termed a product (from the Greek syn, "together," and thesis, "placing"). The following formula can be used to describe the procedure:
A+B (Reactants) ------Energy-------> AB (Product)
Synthesis reactions result in the creation of new bonds, both the reaction and the new product require energy to occur. In the human body, several of these responses take place. For example, every cell uses amino acid molecules as reactants to create complex protein complexes as products. This sort of response may be seen in the body's capacity to create new tissue during wound healing. Decomposition reactions occur when a complex material is broken down into two or more simpler ones. Chemical bonds are destroyed and energy is released in this process. Energy can be discharged in the form of heat or collected and stored for later use. The following formula can be used to summarise decomposition reactions:
AB → A + B + Energy
When a complex nutrient is broken down in a cell to liberate energy for other cellular activities, decomposition reactions occur. Ultimately, the waste products of such a reaction are waste products. Synthesis and decomposition are diametrically opposed. Decomposition breaks down while synthesis builds up. Chemical bonds are formed during synthesis; chemical bonds are broken during breakdown. Decomposition and synthesis processes are frequently linked such that the energy generated during a decomposition event may be utilised to power a synthesis reaction.
The nature of exchange reactions allows two separate reactants to swap components and create two new products as a consequence. The following is a common symbol for an exchange reaction:
AB+CD----->AD + CB
In exchange reactions, two molecules are broken down or decomposed, and two new compounds are synthesised in their place. In the blood, some exchange processes take happen. The interaction of lactic acid with sodium bicarbonate is one example. The production of sodium lactate and carbonic acid is swapped for the breakdown of both compounds. In an equation, these changes are easier to notice.
H.Lactate + NaHCO3 ---> Na.Lactate + H.HCO3
Lactate + H. "H lactate" stands for lactic acid; "NaHCO" stands for sodium bicarbonate; "Na lactate" stands for sodium lactate; and "H-HCO" stands for carbonic acid.
Reversible reactions, as their name implies, can go both ways. Many synthesis, breakdown, and exchange processes are reversible, and some of them are discussed in the book's later chapters. A reversible reaction is indicated by an arrow pointing in both directions:
A + B - AB
QUICK INSPECTION
1. Describe the three different types of chemical bonds and how they are created.
2. Draw a diagram of the three most common chemical processes.
