Key Concepts in Biochemistry

Running Head: KEY CONCEPTS IN BIOCHEMISTRY
Key Concepts in Biochemistry
Name of the student:
Name of the University:
Author Note:

KEY CONCEPTS IN BIOCHEMISTRY1
Part A
1. Pyrimidine is a class of heterocyclic nitrogenous bases that forms a six membered
diazine ring which has nitrogen placed in the 1st and the 3rd position.
Fig1: Pyrimidine (Cafferty & Hud, 2015)
Pyrimidine found in DNA are cytosine and thymine and in RNA uracil is replaced by
thymine. It plays an important function in human metabolism by formation of
ribonucleotide and deoxyribonucleotide bases (Cafferty & Hud, 2015).
2. Ethanol is an alcohol molecule which have a lone pair of electrons, the hydrogen atom
which have a partial positive charge binds to an oxygen molecule and forms hydrogen
bonds. Ethanal is an aldehyde molecule which has the partially positive carbon atom
that bonds with oxygen having a partially negative charge, C=O, to form a permanent
dipole-dipole bond. Hydrogen bonds are strong and requires more energy to break in
comparison to dipole-dipole bonds. Hence, ethanol has a higher boiling point.
3. Stearic acid and oleic acid are C18 long chain fatty acids but the difference between
them is that stearic acid is saturated and oleic acid is unsaturated. Melting point is
directly proportional to molecular weight and inversely proportional to level of
saturation (Yuan et al., 2014). Oleic acid has a carbon-carbon double bond, C=C
hence, it has a melting point lower than stearic acid.
4. Butyl ethanoate also known as n-Butyl acetate is an ester. Ester is an important
functional group. The hydroxyl (O-H) group of the acids is replaced by the alkoxy (O-
R) group. It is synthesized by Fischer Esterification Reaction (Eleuterio et al., 2015).
It is formed by condensation of the butanol with the acetic acid in the presence of

KEY CONCEPTS IN BIOCHEMISTRY2
sulphuric acid that acts as a catalyst. The reactants of the reaction are acetic acid and
butanol.
Fig 2: Butyl Ethanoate Synthesis (Eleuterio et al., 2015)
Part B
Human body requires nutritional energy from carbohydrates, proteins and lipids for
growth, maintenance and activity. The effective supply of energy from the different food
supplements vary, carbohydrates are the earliest in releasing energy and fats or lipids are
comparatively slow. Proteins are the building block of the body. These carbohydrates,
proteins and lipids are very essential for our body and are involved in all the vital activities of
the body but in this article the functions of these nutrients with respect to the cell membrane
structure is discussed.
Lipids are the main structural component of the cell membrane. The semipermeable nature
of the cell membrane is imparted by the lipid bilayer formed. The membrane consists of a
phospholipid bilayer which has a hydrophobic tail and a hydrophilic head (Rothfield, 2014).
A phospholipid is a triglyceride molecule in which the fatty acid chain in substituted by a
phosphate group (Holthuis & Menon, 2014). The lipid bilayer has the hydrophilic head on the
outer side facing the extracellular components and the hydrophobic tail is in the inner side
facing the intracellular components of the cell (Ingólfsson, et al., 2014). The hydrophobic
fatty acid tail permeates fat soluble molecules like oxygen whereas it prevents the entry of
larger water-soluble molecules like sugar molecules and some charged ions as well.
The essential contribution of proteins in the cell membrane include preventing the entry of
toxic substances inside the cell, they form specialised channels in the cell membrane that
allows selective entry of ions, nutrients and metabolic products and ensures exit of waste
products. They separate essential but incompatible metabolic processes that occur in
organelles. The proteins embedded in the membrane can be essentially classified into integral
membrane proteins and peripheral membrane proteins (Laganowsky et al, 2014). The