Macromolecules and Importance in Key Biological Processes

Running head: BIOLOGY
MACROMOLECULES AND IMPORTANCE IN KEY BIOLOGICAL PROCESSES
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This essay will discuss the structure and functions of various macromolecules
associated with the building up of cell membranes of prokaryotic and eukaryotic organisms.
In part A, an inherited disease (sickle cell anemia) will be discussed from a genetic
and molecular point of view. Sickle cell disease has been found to originate from the
mutations which were primarily found in Africa, Saudi Arabia, and Central India. These
events have been found to occur between 4000 to 6000 generations ago that is approximately
70 to 150,000 years ago (Paramore et al. 2018). RBCs are responsible for the transferring of
oxygen to the through the blood to all the parts of the human body. The human heart has bee
stated to be responsible for the pumping of blood. RBCs are the major oxygen carriers of
oxygen due to the presence of oxygen-carrying heme protein in hemoglobin. Sickle cell
anemia is a disease that produces abnormal red blood cells (RBCs) which have a sickle or
crescent shape. This condition has been found to be caused by the modification in the HBB
gene and gets inherited in a recessive and autosomal pattern (Bai et al. 2017). The specific
gene responsible for sickle cell anemia is the hemoglobin Beta gene located in chromosome
11. The protein known as hemoglobin has been found to transport oxygen from the lungs to
every part of the body (Steinberg 2016). According to the central dogma, protein is
synthesized from the combination of ribosome, mRNA, and tRNA. This condition states that
nucleotide bases are responsible for the synthesis of proteins. Every protein has its specific
set of codons responsible for the synthesis of the associated protein. Deletion or substitution
of a particular nucleotide base in the gene sequence associated with the synthesis of protein
leads to the non-functioning of the synthesized protein. Enzymes have been observed to make
up amino acids that can be linked together to form the peptide bonds present in linear chains.
This is known as the primary structure of an enzyme and the resulting ami8no acid chain is
known as a polypeptide chain. Aerobic respiration has been found to be catalyzed by various
enzymatic reaction pathways essential for the undergoing of the process. Enzymes are

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functioning units of proteins, synthesized by a specific sequence of codons in the mRNA.
Thus, it can be stated that gene sequence (appropriate) is necessary for the synthesis of a
proper and functioning protein. Any type of change in the gene sequence is termed as a
mutation although it can be silent or missense sometimes. The normal gene sequence
responsible for the synthesis of RBC proteins produces smooth and round cells with normal
hemoglobin A which can glide through the blood vessels. Sickle cells get stuck inside the
blood vessels and block the blood flow. Normally, hemoglobin A consists of two alpha
chains and two beta chains. However, in sickle cell disease, one of the beta chains is replaced
by hemoglobin S. A single gene defect has been observed in the form of single nucleotide
mutation where the start codon GAG changes to GTG in the beta chain gene. This condition
is associated with the substitution of glutamic acid by valine at position 6 of the protein
sequence (Vichinsky and Mahoney Jr 2019). However, secondary, tertiary and quaternary
structures of hemoglobin are not affected by the mutation and oxygen concentrations in them
are also normal. The problem arises with the low oxygen concentration when the HbS
precipitates in the form of fibrous structures since the deoxyhemoglobin form cannot
maintain its structure due to the amino acid substitution (Eaton 2020).
This section will discuss the inheritance pattern of sickle cell anemia in the human
community. Sickle cell disease has been observed to follow an autosomal recessive pattern of
inheritance (Wheeler et al. 2019). This statement means that the host needs to have both the
copies of the gene in order to have mutations in each of the RBCs which are produced by
their body. People who carry only a single copy of the gene (mutated), are not found to
express the symptoms of sickle cell anemia throughout their life. These hosts having half
mutated sickle cell disease are termed as the carriers for the disease. As an example, it can be
stated that when two carriers are considered as the parents, there is a 25% chance of their
child to express the disease according to pedigree analysis (Amlie-Lefond et al. 2018). Thus,

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it can be said that the disease only gets 100% transferred to the next generation only when
both the parents are dominant for the disease. Therefore, the inheritance pattern has been
termed as an autosomal recessive pattern. This disease is not associated or varies with the sex
of the associated individual. Therefore it has been called an autosomal disorder. One of the
most significant advantages of sickle cell carriers is that they are resistant to the malarial
parasites.
Fig 1: Point mutation in sickle cell anemia
Source: Vichinsky and Mahoney Jr (2019)
In part B, membranes of the cells having various types of molecules such as proteins,
phospholipids, and carbohydrates will be discussed on the basis of their structures and
function.