Inorganic Molecules by Doctor-dr

By Microbiology Doctor-dr (doctor_dr)(doctor-dr)

INORGANIC MOLECULES

There are two types of chemicals in living organisms: organic and inorganic. Organic compounds are described as molecules with carbon-carbon (C-C) or carbon-hydrogen (C-H) covalent bonds, or both types of bonds. Carbon atoms are rare in inorganic compounds, and none of them have C-C or C-H bonds. In comparison to inorganic molecules, organic molecules are often bigger and more complex. Both types of chemicals are found in the human body because they are equally vital to life's chemistry. The chemistry of inorganic compounds will be covered first, followed by some of the most significant forms of organic compounds.

Water

Because all living species require water to live, water has been dubbed the "cradle of life." Each bodily cell is submerged in fluid, and cells can only operate in this carefully regulated and homeostatically maintained environment. In addition to being surrounded by water, each cell's fundamental component, cytoplasm, is primarily made up of water. Water is by far the most prevalent and significant component in the human body. It accounts for almost 70% of body weight and performs a variety of essential functions. Understanding the fundamentals of water chemistry is critical due to its ubiquitous relevance in all living creatures. In a true sense, "water chemistry" is the foundation for life's chemistry.

Properties of water

Water is regarded as a simple substance by the chemist. It is made up of two covalent connections between a single oxygen atom and two hydrogen atoms, which gives it its atomic structure.

Remember that water molecules are polar, meaning that they contain a positively and negatively charged end. Water may function as a very effective solvent because of a basic chemical characteristic called polarity. A cell's efficient functioning necessitates the presence of several chemical compounds. Many of these compounds are extremely big, and in order for reactions to occur, they must be broken down into smaller, more reactive particles (ions). Water has a tendency to ionise things in solution due to its polar nature (Figure 2-1). The fact that so many chemicals dissolve in water is critical to the survival process.

Water's important role as a solvent allows numerous vital elements to be transported throughout the body. Water allows oxygen and food items to enter and exit the blood capillaries in the lungs and digestive organs, and eventually enter cells in every part of the body, by dissolving them in the blood. Waste products are then carried from the point of production to the excretory organs, where they are eliminated from the body.

The fact that water absorbs and releases heat slowly is another essential function of water. Water's characteristics allow it to keep a generally steady temperature. This permits the body's substantial water content to withstand abrupt temperature fluctuations. Water has a high specific heat, which means it can lose and acquire significant quantities of heat with little change in temperature, according to chemists. As a result, surplus body heat generated by muscular contractions during exercise, for example, may be carried to the body surface by the blood and dispersed into the environment with no change in core temperature.

Another essential physical property of water is its high heat of vaporisation, which is recognised by both chemists and biologists. To convert water from a liquid to a gas, this property necessitates the absorption of substantial quantities of heat. It takes a lot of energy to break the numerous hydrogen bonds that hold neighbouring water molecules together in the liquid form. As a result, if excess heat is created, the body can disperse it and maintain a normal temperature by evaporating water (sweat) from the skin surface.

It takes a lot of energy to break the numerous hydrogen bonds that hold neighbouring water molecules together in the liquid form. As a result, if excess heat is created, the body can disperse it and maintain a normal temperature by evaporating water (sweat) from the skin surface.

Each chapter of the book will emphasise the importance of the body's ability to maintain homeostasis. The importance of water in nearly every regulatory and control mechanism covered will be a constant that should not be overlooked as you go from system to system in the next chapters.

FIGURE 2-8 Water as a solvent. The polar nature of water favors ionization of substances in solution, Sodium (Na) ions (pen) and chloride (CI) ions (green) dissociate in the solution.

Oxygen and Carbon Dioxide

Carbon dioxide (CO2) and oxygen (O2) are essential inorganic compounds that are strongly linked to biological respiration. In the organism, molecular oxygen is made up of two oxygen atoms linked by a double covalent bond. The breakdown processes necessary for the release of energy from nutrients burnt by the cell require oxygen. Carbon dioxide is one of a series of inorganic carbon-containing chemicals that are relatively simple. Inorganic compounds do not contain carbon, which is a significant exception to the "rule of thumb." CO2 is involved in cellular respiration, much like oxygen. It is generated as a waste product during the breakdown of complex nutrients, and it also plays a crucial function in regulating the body's acid-base balance.

Table 1-1 Properties of water
Property	Description	Example of Benefit to the Body
Strong Polarity	Polar water molecules attract ions and other polar compounds, causing them to dissociate	Many kinds of molecules can dissolve in cells, permitting a variety of chemical reactions and allowing many substances to be transported
High Specific Heat	Hydrogen bonds absorb heat when they break and release heat when they form, minimizing temperature changes	Body temperature stays relatively constant
High Heat of Vaporization	Many hydrogen bonds must be broken for water to evaporate	Evaporation of water in perspiration cools the body
Cohesion	Hydrogen bonds hold molecules of water together	Water works as lubricant or cushion to protect against damage from friction or trauma

Electrolytes

Acids, bases, and salts are examples of inorganic substances. Electrolytes are a broad category of compounds that include these chemicals (e-LEK-tro-lites). Electrolytes are chemicals that break up in solution, or dissociate, into charged particles called ions. Positively charged ions are referred to as cations, whereas negatively charged ions are referred to as anions. Figure depicts how water molecules breakdown sodium chloride (NaCl) into Na cations and Cl anions in a typical electrolyte.

Acids and bases

Acids and bases are ubiquitous and vital chemical compounds in the human body. Taste and the capacity to modify the colour of particular dyes were used by early chemists to classify acids and bases. Acids, for example, have a sour flavour, whereas bases have a bitter flavour. When exposed to bases, the dye litmus turns blue, and when exposed to acids, it turns red. These and other observations highlight a key point: acids and bases are chemical polar opposites. Despite the fact that acids and bases both dissociate in solution, they produce distinct kinds of ions. The best method to distinguish acids and bases while they're in solution is to look at their chemical characteristics.

Acids. An acid is defined as any chemical that, when in solution, releases a hydrogen ion (H*). A hydrogen ion is nothing more than a proton, which is the nucleus of a hydrogen atom. Be a result, acids are usually referred to as "proton do nors." The chemical characteristics of acids are determined by the quantity of hydrogen ions. The quantity of hydrogen ions released by a certain acid determines the "acidity" of a solution.

There is one aspect regarding water that has to be understood. Water molecules breakdown continuously to create hydrogen ions (H+) and hydroxide ions (OH) in a reversible reaction:

H₂O=H + OH-

Remember from our study of ionic bonding (pp. 40–41) that an atom with a single unpaired electron in the outer shell is unstable, and that removing that electron makes the structure more stable. Dissociation of water happens for just this reason. The equilibrium between these two ions is equal in pure water. When an acid, such as hydrochloric acid (HCI), dissociates into H* and Cl, the H/OH balance is shifted in favour of surplus H ions, raising the acidity level.

A strong acid is one that dissociates entirely or almost completely to produce H+ ions. A weak acid, on the other hand, dissociates extremely slowly and so creates a little amount of excess H+ ions in solution. The body has a variety of essential acids that serve a variety of purposes. For example, hydrochloric acid is an acid generated in the stomach to assist digestion.

Bases. Bases, also known as alkaline substances, are electrolytes that alter the H*/OH balance in favour of OH when dissociated in solution. This can be done by increasing the amount of hydroxide (OH) ions in the solution or lowering the number of H* ions in the solution. The phrase "proton acceptor" refers to the ability of bases to interact with or receive hydrogen ions (protons). The cation Na+ and the OH anion are produced when a common base, sodium hydroxide, is dissociated. 

Bases are categorised as strong or weak based on how easily and thoroughly they breakdown into ions, similar to acids. The bicarbonate ion (HCO3), for example, plays a crucial function in the transport of respiratory gases and the removal of many products from the body.

Acidity and alkalinity are measured using the pH scale. The word pH refers to the concentration of hydrogen ions (H*) in a solution (Figure 2-2). The negative logarithm of the hydrogen ion concentration is what pH stands for. The pH of a solution reflects its acidity or alkalinity. When the concentration of hydrogen ions rises, the pH drops and the solution becomes more acidic; when the concentration of hydrogen ions falls, the pH rises and the solution becomes more alkaline. A pH of 7 implies neutrality (equal quantities of Hand OH), a pH below 7 suggests acidity (more H* than OH), and a pH over 7 indicates alkalinity (more H* than OH) (more OH than H). On a logarithmic scale of 1 to 14, the total pH range is frequently represented quantitatively. Keep in mind that a change of one pH unit on this scale corresponds to a tenfold variation in real hydrogen ion concentration.

Figure 2-2 The pH range. Note that as concentration of H+ increases, the solution becomes increasely acidic and the pH value decreases. As OH- concentration increases, the pH value also increases, and the solution becomes more and more basic, or alkaline.

Buffers

Blood and other bodily fluids have a very limited pH range. Venous blood, for example, is just slightly more acidic than arterial blood (pH 7.36) (pH 7.41). Carbon dioxide, a waste product of cellular metabolism, enters venous blood and causes the difference. Because carbon dioxide is transported as carbonic acid (H2CO3), the pH of venous blood is lowered. Every day, around 30 litres of carbonic acid are carried in the venous blood and exhaled by the lungs as CO2.

Salts

Any substance formed by the chemical reaction of an acid and a base is referred to as a salt. Salts are electrolyte compounds that dissociate in solution to create positively and negatively charged ions, similar to acids and bases. In a normal exchange reaction, the positive ion (cation) of a base and the negative ion (anion) of an acid will combine to create a salt and water when combined and allowed to react. A neutralisation reaction occurs when an acid and a base combine to create a salt and water:

( A B + C D    ------> C B  + A D) 

HCI + NaOH ------> NaCl + H₂O

Acid + Base ------> Salt + Water

(hydrochloric acid) + (sodium hydroxide) ------> (sodium chloride)

For nerve activity and muscular contraction, the correct amount and concentration of mineral salt electrolytes such as potassium (K), calcium (Ca), and sodium (Na) are necessary. Specific homeostatic control mechanisms that govern electrolyte balance in blood and other bodily fluids are discussed in Chapter 28. Table 2-3 includes a number of inorganic salts that, when dissociated in physiological fluids, provide essential electrolytes for a variety of bodily processes. For nerve activity and muscular contraction, the correct amount and concentration of mineral salt electrolytes such as potassium (K), calcium (Ca), and sodium (Na) are necessary. Specific homeostatic control mechanisms that govern electrolyte balance in blood and other bodily fluids are discussed in Chapter 28. Table 2-3 includes a number of inorganic salts that, when dissociated in physiological fluids, provide essential electrolytes for a variety of bodily processes.

Table 2-2  Inorganic salts important in body functions
Inorganic Salt	Chemical Formula	Electrolytes
Sodium chloride	NaCl	Na+ + CI-
Calcium chloride	CaCl₂	Ca+ +2Cl-
Magnesium chloride	MgCl₂	Mg+ + + 2Cl-
Sodium bicarbonate	NaHCO3	Na* + HCO3-
Potassium chloride	KCl	K+ + Cl-
Sodium sulfate	Na2SO4	2Na+ SO4=
Calcium Carbonate	CaCO3	Ca++ + CO3=
Calcium phosphate	Ca3(PO4)2	3Ca++ +2PO4=

QUICK CHECK

1. Discuss the properties of water that make it so important in living organisms.

2. What is an electrolyte? 

3. How do acids and bases react with each other when in solution?

4. What is pH?