ECE 593-728ECE 593-728

Chapter TwoChapter Two

CHEMICAL COMPOSITION CHEMICAL COMPOSITION OF THE BODYOF THE BODY

• What is an atomWhat is an atom??

An atom is the smallest indivisible An atom is the smallest indivisible units of matter; each type of atom is units of matter; each type of atom is also called a chemical element. An also called a chemical element. An atom is made up of protons, atom is made up of protons, electrons and neutrons. These three electrons and neutrons. These three subatomic particles characterize the subatomic particles characterize the chemical properties of an atom. chemical properties of an atom.

Protons, Neutrons and Protons, Neutrons and ElectronsElectrons• The protons are positively charged, The protons are positively charged,

while the neutrons are negatively while the neutrons are negatively charged. Both the protons and charged. Both the protons and neutrons are confined to a very small neutrons are confined to a very small volume at the center of an atom called volume at the center of an atom called the atomic nucleus. On the other hand, the atomic nucleus. On the other hand, electrons are negatively charged and electrons are negatively charged and they can be found revolving around the they can be found revolving around the nucleus. nucleus.

Atomic numberAtomic number

• This is one characteristic that distinguish This is one characteristic that distinguish one chemical element from another. An one chemical element from another. An atomic number is the specific number of atomic number is the specific number of protons found in that chemical element. For protons found in that chemical element. For example hydrogen has one proton, thus its example hydrogen has one proton, thus its atomic number is one. Looking at the atomic number is one. Looking at the periodic table, one can also be able to periodic table, one can also be able to deduct the atomic number; elements in the deduct the atomic number; elements in the periodic tableperiodic table are usually numbered are usually numbered according to their atomic numbers. according to their atomic numbers.

Cont..Cont..

Hydrogen (H) has an atomic number of Hydrogen (H) has an atomic number of one; lithium (Li) has an atomic number of one; lithium (Li) has an atomic number of three and so on. three and so on.

• What is a moleculeWhat is a molecule??

A molecule is made up of two or more A molecule is made up of two or more atoms. A good example is water, a atoms. A good example is water, a molecule of water contains two hydrogen molecule of water contains two hydrogen atoms and one oxygen atom, thus water atoms and one oxygen atom, thus water can be represented as H2O. can be represented as H2O.

What is an IonWhat is an Ion??

• An atom is characterized as an ion when An atom is characterized as an ion when it loses or gains one or more electrons. it loses or gains one or more electrons. For example, when a sodium atom (Na), For example, when a sodium atom (Na), which has 11 electrons, loses one which has 11 electrons, loses one electron, it becomes a sodium ion with a electron, it becomes a sodium ion with a net positive charge; it still has 11 net positive charge; it still has 11 protons, but the loss of one electron protons, but the loss of one electron leaves it without only 10 electrons leaves it without only 10 electrons remaining. remaining.

Cont…Cont…

• On the other hand a chlorine atom On the other hand a chlorine atom which has 17 electrons can gain an which has 17 electrons can gain an electron and become a chloride ion electron and become a chloride ion with a net negative charge. This with a net negative charge. This chloride ion now has 18 electrons and chloride ion now has 18 electrons and 17 protons. Ions that have a net 17 protons. Ions that have a net positive charge are called cations, positive charge are called cations, while those that have a net negative while those that have a net negative charge are called anions.charge are called anions.

CLASSES OF ORGANIC CLASSES OF ORGANIC MOLECULESMOLECULES

• What are organic moleculesWhat are organic molecules??

These are molecules that have their These are molecules that have their basic skeleton made of carbons atoms, basic skeleton made of carbons atoms, hydrogen, oxygen and sometimes hydrogen, oxygen and sometimes nitrogen atoms. Generally organic nitrogen atoms. Generally organic molecules in the body can be classified molecules in the body can be classified into one of four groups: carbohydrates, into one of four groups: carbohydrates, lipids, proteins and nucleic acid.lipids, proteins and nucleic acid.

Carbohydrates Carbohydrates

• Carbohydrates are the abundant of the Carbohydrates are the abundant of the four main organic molecules. four main organic molecules. They fill They fill numerous roles in living things, such numerous roles in living things, such as the storage and transport of energy as the storage and transport of energy (starch, glycogen) and structural (starch, glycogen) and structural components (cellulose in plants, chitin components (cellulose in plants, chitin in animals). Most carbohydrates taste in animals). Most carbohydrates taste sweet, and the carbohydrates include sweet, and the carbohydrates include the substances known as sugars.the substances known as sugars.

Cont..Cont..

• The simplest sugars are known as The simplest sugars are known as monosaccharides, a good example of a monosaccharides, a good example of a monosaccharide is monosaccharide is glucoseglucose. Glucose is . Glucose is the major monosaccharide found in the the major monosaccharide found in the blood, when two monosaccharide are blood, when two monosaccharide are linked together they form a linked together they form a disaccharides. An example of a disaccharides. An example of a disaccharide is table sugar also known disaccharide is table sugar also known as sucrose. as sucrose.

Cont…Cont…

• When many monosaccharide are linked When many monosaccharide are linked together they form a molecule known together they form a molecule known as a polysaccharide. An example of a as a polysaccharide. An example of a polysaccharide is polysaccharide is glycogenglycogen. Glycogen . Glycogen is found in animal cells and it serves as is found in animal cells and it serves as primary short term energy storage in primary short term energy storage in animal cells. It is made primarily by the animal cells. It is made primarily by the liver and the muscles.liver and the muscles.

LipidsLipids

• Lipids are fat-soluble, naturally occurring Lipids are fat-soluble, naturally occurring molecules; unlike carbohydrates lipids are molecules; unlike carbohydrates lipids are insoluble in water. The main biological insoluble in water. The main biological functions of lipids include energy storage, functions of lipids include energy storage, acting as structural components of acting as structural components of cell membranescell membranes, and participating as , and participating as important important signaling moleculessignaling molecules. Lipids can be . Lipids can be divided into four subclasses namely: divided into four subclasses namely: fatty acidsfatty acids, triglycerides, phospholipids, and , triglycerides, phospholipids, and steroidssteroids. .

ProteinsProteins

• Proteins are large organic compounds Proteins are large organic compounds made up of amino acids (amino acids are made up of amino acids (amino acids are organic molecules that are made of organic molecules that are made of carbon, nitrogen and hydrogen atoms). carbon, nitrogen and hydrogen atoms). These amino acids are arranged in a These amino acids are arranged in a linear chain and joined together by linear chain and joined together by peptide bonds between the carboxyl and peptide bonds between the carboxyl and amino groups of adjacent amino acid amino groups of adjacent amino acid residues. residues.

Example illustrating the Example illustrating the formation of a peptide bondformation of a peptide bond

Cont…Cont…

• Peptide bonds are formed between Peptide bonds are formed between the amino and carboxyl group. These the amino and carboxyl group. These bonds can be broken by hydrolysis to bonds can be broken by hydrolysis to yield individual amino acids. The yield individual amino acids. The figure on the previous slide figure on the previous slide illustrates the hydrolysis of a protein.illustrates the hydrolysis of a protein.

PROTEIN STRUCTUREPROTEIN STRUCTURE

Proteins are characterized of three types Proteins are characterized of three types of structures namely: primary, secondary, of structures namely: primary, secondary, tertiary and quaternary structure.tertiary and quaternary structure.

• Primary Protein Structure Primary Protein Structure

The primary structure of a protein The primary structure of a protein refers to the number and sequence of refers to the number and sequence of amino acids in the protein. The primary amino acids in the protein. The primary structure of a protein is very important in structure of a protein is very important in the identification of a protein. the identification of a protein.

Diagram showing the primary Diagram showing the primary structure of a proteinstructure of a protein

Cont..Cont..

• Secondary Protein StructureSecondary Protein Structure

The secondary protein structure The secondary protein structure is the specific geometric shape is the specific geometric shape caused by intramolecular and caused by intramolecular and intermolecular hydrogen bonding of intermolecular hydrogen bonding of amide groups. The most common amide groups. The most common secondary structures of proteins are secondary structures of proteins are the alpha helices and beta sheet.the alpha helices and beta sheet.

Diagram showing the Diagram showing the secondary structure of a secondary structure of a

proteinprotein

Cont…Cont…

• Tertiary Protein StructureTertiary Protein Structure

The third type of structure found in The third type of structure found in proteins is called tertiary protein proteins is called tertiary protein structure. The tertiary structure is the structure. The tertiary structure is the final specific geometric shape that a final specific geometric shape that a protein assumes. This final shape is protein assumes. This final shape is determined by a variety of bonding determined by a variety of bonding interactions between the "side chains" interactions between the "side chains" on the amino acids. on the amino acids.

These bonding interactions may be These bonding interactions may be stronger than the hydrogen bonds stronger than the hydrogen bonds between amide groups holding the between amide groups holding the helical structure. As a result, bonding helical structure. As a result, bonding interactions between "side chains" may interactions between "side chains" may cause a number of folds, bends, and cause a number of folds, bends, and loops in the protein chain. Different loops in the protein chain. Different fragments of the same chain may fragments of the same chain may become bonded together.become bonded together.

• The figure on the next slide, shows the The figure on the next slide, shows the difference between primary, secondary difference between primary, secondary and tertiary protein structures:and tertiary protein structures:

Different protein structuresDifferent protein structures

Quaternary Protein Quaternary Protein StructureStructure

• The quaternary protein structure The quaternary protein structure involves the clustering of several involves the clustering of several individual peptide or protein chains individual peptide or protein chains into a final specific shape. A variety into a final specific shape. A variety of bonding interactions including of bonding interactions including hydrogen bonding, salt bridges, and hydrogen bonding, salt bridges, and disulfide bonds hold the various disulfide bonds hold the various chains into a particular geometry. chains into a particular geometry.

Figure showing quaternary Figure showing quaternary protein structureprotein structure

Nucleic AcidsNucleic Acids

• These organic molecules are responsible These organic molecules are responsible for the storage, expression, and for the storage, expression, and transmission of genetic information. It is transmission of genetic information. It is the expression of genetic information the expression of genetic information that determines whether a cell is a that determines whether a cell is a muscle cell or a nerve cell. There are muscle cell or a nerve cell. There are basically two classes of nucleic acids, basically two classes of nucleic acids, deoxyribonucleic acid (DNA) and deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).ribonucleic acid (RNA).