Biology: Elements and Functional Groups

Important elements in Biology

• Six important elements in biology are Carbon (C), Hydrogen (H), Nitrogen (N), Phosphorus (P), Oxygen (O) and Sulfur (S).

Valency of elements found in biomolecules

• Carbon (C) can form 4 bonds.
• Hydrogen (H) can form 1 bond.
• Nitrogen (N) can form 3 bonds.
• Phosphorus (P) can form 5 bonds (sometimes 3).
• Oxygen (O) can form 2 bonds.
• Sulfur (S) can form 2 bonds (sometimes 6 or 4).

Functional groups in biomolecules (1)

• Carboxylic acids contain a -COOH functional group.
• Aldehydes contain a -CHO functional group.
• Ketones contain a -CO- functional group.
• Esters contain a -COOR functional group.
• Biomolecules with a (C=O) group are called carbonyls.

Functional groups in biomolecules (2)

• Acid anhydrides contain a -COOCO- functional group.
• Amides contain a -CONH2 functional group.
• Thioesters contain a -COSR functional group.

Functional groups in biomolecules (3)

• Acid chlorides contain a -COCl functional group.
• Haloalkanes contain a C-X functional group (where X is a halogen, such as F, Cl, Br, or I).
• Haloarenes contain a C-X bond attached to an aromatic ring (where X is a halogen, such as F, Cl, Br, or I).

Functional groups in biomolecules (4)

• Primary alcohols.
• Secondary alcohols.
• Tertiary alcohols.

Functional groups in biomolecules (5)

• Primary amines contain an -NH2 functional group.
• Secondary amines contain an -NHR functional group.
• Tertiary amines contain an -NRR' functional group.

Functional groups in biomolecules (6)

• Phenol contains a -OH group directly bonded to a benzene ring.
• Thiols contain an -SH functional group.
• Phosphodiester linkages are found in DNA and RNA.

Tetrahedral geometry

• When neutral carbon has only single bonds (sp³ C) the arrangement is tetrahedral.
• The bond angle in a tetrahedral arrangement is 109.5°.
• A diagram of a tetrahedron shape. The bond angles between the bonds should be specified as 109.5°.
• The arrangement of bonds at saturated C (only single bonds) is tetrahedral.

Optical Isomers

• If 4 atoms or groups around carbon are the same, the mirror image is the same.
• If 3 atoms or groups around carbon are the same, the mirror image is the same.
• If 2 atoms or groups around carbon are the same, the mirror image is the same.
• If all 4 atoms or groups around carbon are different, the mirror image is not the same.
• When there are 4 different atoms or groups around C, it is necessary to use 1 dash and 1 wedge bond.
• The wedge bond is a bond in front of the plane and the dash bond is behind the plane.
• One mirror image is called the (R) form, the other is called (S) form.

Cahn-Ingold-Prelog Rules

• Assign a priority to each of the 4 groups surrounding carbon.
• First look at each atom around the central C. The atom with the highest atomic number is '1'.
• Hydrogen has the lowest atomic number.
• If the two remaining atoms are the same element, look at the next atom out from C.
• Join the numbers 1 & 2 with an arrow. If the arrow goes clockwise, then the configuration is (R). If the arrow goes anticlockwise, then the configuration is (S).

Alkanes

• A chain of single carbon–carbon bonds and C–H bonds is called an alkane.
• In the skeletal structure of an alkane, hydrogens are not drawn but are assumed to be present (only the carbon chain is drawn).

Alkenes

• If a carbon–carbon double bond is present, the molecule is called an alkene.
• Alkanes have the maximum number of hydrogens and are therefore said to be ‘saturated’. Alkenes have fewer H atoms and are therefore ‘unsaturated’.
• Oleic acid is a monounsaturated fatty acid because it has 1 C=C double bond.
• To identify omega-3 fatty acids, count the positions from the last carbon atom in the carboxyl group (CO2H) to the first double bond.
• Oleic acid is an omega-9 monounsaturated (healthy) fatty acid.
• Note:* The text provided describes the structure and properties of fatty acids which are covered in greater detail in organic chemistry courses. This note contains only a brief introduction to this complex topic.

Test your knowledge on the six important elements in biology and their valencies. Explore the different functional groups present in biomolecules, including carboxylic acids, aldehydes, and amides. This quiz will help deepen your understanding of the building blocks of life.