Biology 1 Assignment: Macromolecules and Key Biological Processes

This biology essay delves into the structure and function of macromolecules within prokaryotic and eukaryotic organisms. Part A focuses on sickle cell anemia, discussing its genetic and molecular origins, inheritance patterns, and the impact of mutations on hemoglobin. Part B explores the structure and functions of cell membrane components, including phospholipids, integral and peripheral proteins, and carbohydrates, highlighting their roles in cell protection, transport, and recognition. Part C examines aerobic respiration, emphasizing the role of enzymes, their structure-function relationship, and their catalytic mechanisms in cellular energy production. The essay comprehensively covers the key biological processes associated with these macromolecules and their importance.

Running head: BIOLOGY
MACROMOLECULES AND IMPORTANCE IN KEY BIOLOGICAL PROCESSES
Name of the Student
Name of the University
Author Note

1BIOLOGY
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.

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Phospholipids can be stated to consist of a glycerol backbone with two fatty acids and
a phosphate group which has been modified by alcohol. The phosphate group has been
observed to contain a hydrophilic (water-loving) polar head. The chains of fatty acids have
been observed as uncharged, hydrophobic and to consist of hydrophobic polar tails.
Phospholipids have been observed to perform a significantly important function by protecting
the internal cellular components (Lin et al. 2019). Phospholipid forms a bilayer in most of the
prokaryotic organism cell membranes.
Fig 2: Membrane phospholipids
Source: Lin et al. (2019)
Membrane proteins are of two types such as integral and peripheral proteins. Integral
protein has been defined as the membrane proteins which are intrinsic in nature with one or
more of their segments inserted in the bilayer of phospholipid in the cell membrane

5BIOLOGY
(Cockcroft and Raghu 2018). Proteins are synthesized by amino acid sequences being linked
by various hydrophobic and many linkages with bindings. Most of the integral proteins
consist of residues associated with the hydrophobic side chains which interact with the fatty
acyl membrane groups of phospholipids which anchor the protein with the membrane.
Carbohydrates have been found to covalently linked to the membrane proteins
(glycoproteins) or glycolipids which are also essential for cell membranes. These compounds
are known as sugars for the protein and lipid attachment outside the cell membrane. The
empirical structure of carbohydrate is (CH2O)n. Most of the membrane contains
polysaccharides as the carbohydrate linkage.
All three components have essential importance in cell membrane functions.
Phospholipids have been observed to provide cell membrane barriers to protect the cells and
make organelle barriers for cells. Phospholipids have been found to provide the pathways for
the movement of various substances across the cell membrane. Phospholipids have been
found to provide a basic cell membrane structure in a form known as the lipid bilayer. Lipid
bilayers are scattered as cholesterol molecules in order to keep the membrane fluid consistent.
Lipid bilayers have been found to be amphipathic in their character consisting of two
hydrophilic heads and fatty acid tails. The components of the whole structure have been
found to coordinate with each other in order to perform the membrane functions as discussed
in the previous sections (Cockcroft and Raghu 2018).
Membrane proteins have been found to perform various functions that are essential
for the survival of organisms. The receptor proteins associated with membrane receptors have

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been found to relay the signals between the internal and external environments of the cell.
Protein transport has been found to move ions and molecules across the cellular membrane.
Five major functions have been found to be associated with membrane proteins associated
with transport, signal transduction, intercellular joining, cell to cell recognition and enzymatic
activity associated with the cytoskeleton and extracellular matrix (ECM) attachment.
Membrane protein transport functions are very much necessary in order to perform various
functions associated with the biological transport of ions inside and outside the cell in order
to maintain an osmotic balance in the cell (Phan et al. 2019). When the proteins of a cell fail
to function, osmotic imbalance occurs which results in the death of the cell by either lysis or
shrinkage. These are the overall functions of membrane proteins associated with both
prokaryotic and eukaryotic organisms.
Membrane carbohydrates have been observed to perform two significant functions
that participate in cellular adhesion and recognition. Cell signaling or pathogen cell
interactions have been found to be associated with the functions of membrane carbohydrates
(Kozlova et al. 2019). Cell membrane carbohydrates have also been found to act as physical
barriers against external compounds that come near the cell membrane. Carbohydrates form
the major component of the bacterial cell wall (peptidoglycan) along with proteins that
protect the organisms from the external environment.
Thus, it can be stated that phospholipids, proteins, and carbohydrates are combined
with each other during their functioning in the protection of the associated organism. All the
three macromolecules coordinate with each other in order to maintain the cell membrane in
performing all the associated biological functions, transport and maintain the overall structure
and function of cells.

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Part C will discuss aerobic respiration which is described as the process by which the
cell obtains energy. 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 amino 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 functioning units of proteins,
synthesized by the specific sequence of codons in the mRNA. Enzymes require substrates for
the catalysis of a reaction. Most of the enzymes follow an induced fit hypothesis in order to
enhance the rate of a reaction. Enzymes do not participate directly in the reaction. They
enhance the rate of the reaction by decreasing the activation energy of the reaction. Aerobic
respiration has been defined as the [process of cellular energy production which involves
oxygen in their pathway (Orang et al. 2019). Most of the discovered enzymes are the proteins
with their functions specific to their structure. Enzymes have been found to bind with the
appropriate substrate only in the orientation and correct alignment of the molecules. The
shape of an enzyme is the most important criterion having a direct effect on the catalyzation
of a reaction. According to various research studies, the enzyme's shape has been found to be
determined by the amino acid sequence of the amino acids in the enzyme structure. The
structure of an enzyme is determined by the chemical bonds and their orientations present
within the atoms in that molecule (Tyzack et al. 2017). The shape of an enzyme has been
observed to consist of an active site for the binding of a substrate. The active site of an
enzyme is complementary to the substrate in order to ensure a proper fit for the reaction to
progress. When the shape of an enzyme is changed, the enzyme active site gets changed and
the substrates cannot bind with the enzyme and t erection stops. The tertiary structure of an
enzyme is the most significant structure of an enzyme related to its function. This is because
of the fact that it spatially connects the functional protein pieces together in order to perform

8BIOLOGY
the reaction. Thus, the task can be stated to be connected to the structure level of an enzyme.
Since enzymes are proteins, the level of the structure plays a major role in the functioning of
that enzyme.
Aerobic respiration is a metabolic procedure which is responsible for the production
of ATP. Aerobic respiration of cells has been divided into three stages known as Glycolysis,
Krebs Cycle, and Electron Transport System. The steps of aerobic cellular respiration are:
 Glycolysis (the break down of glucose)
 Link reaction.
 Krebs cycle.
 Electron transport chain, or ETC.
The steps of glycolysis include the enzymes provided below according to their functioning
orientation:
1. Step 1: Hexokinase.
2. Step 2: Phosphoglucose Isomerase.
3. Step 3: Phosphofructokinase. ...
4. Step 4: Aldolase.
5. Step 5: Triosephosphate isomerase.
6. Step 6: Glyceraldehyde-3-phosphate Dehydrogenase.
7. Step 7: Phosphoglycerate Kinase.
8. Step 8: Phosphoglycerate Mutase.

9BIOLOGY
The enzymes involved in Kreb’s cycle or tricarboxylic acid cycle has been provided below:
 Citrate synthase
 Aconitase
 Isocitrate dehydrogenase
 α-ketoglutarate dehydrogenase
 Succinyl coenzyme A synthetase
 Succinate dehydrogenase
 Fumarase
 Malate dehydrogenase
The enzymes involved in the electron transport chain are:
1. Complex I enzyme is known as the NADH reductase (enzyme)
2. Complex II enzyme is known as the succinate dehydrogenase system
3. Complex III cytochrome Bc1 complex
4. Complex IV or the cytochrome oxidase system.

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Fig 3: Aerobic respiration
Source: Soo et al. (2017)

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of cerebral steno-occlusive arteriopathy and stroke in sickle cell anemia. Journal of Stroke
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Bai, H., Cai, L., Machairaki, V., Gao, Y., Ye, Z. and Cheng, L., 2017. A Universal Approach
to Correct Various HBB Gene Mutations in Human Stem Cells for Gene Therapy of Beta-
Thalassemia and Sickle Cell Disease. Blood, 130(Supplement 1), pp.5564-5564.
Cockcroft, S. and Raghu, P., 2018. Phospholipid transport protein function at organelle
contact sites. Current opinion in cell biology, 53, pp.52-60.
Eaton, W.A., 2020. Hemoglobin S polymerization and sickle cell disease: A retrospective on
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