University Essay: Human Structure and Function, SCH1134D

This essay delves into the intricacies of human structure and function, concentrating on the macromolecule protein. It begins by describing the general structure of proteins, followed by detailed examinations of two specific examples: hemoglobin and actin. The essay highlights their structural differences and diverse functions within the human body. Hemoglobin, a metalloprotein, is presented as the oxygen carrier in red blood cells, while actin, a multifunctional globular protein, plays a crucial role in cellular processes. The essay further explores the role of these macromolecules in cellular respiration, clarifying how hemoglobin facilitates oxygen transport and how actin utilizes ATP to drive motor functions. Additionally, the essay touches upon cytoanatomy, discussing the cytoskeleton's components, including microtubules, microfilaments, and ribosomes, and their respective functions. The essay concludes by referencing key scientific publications that support the presented information.

Running head: HUMAN STRUCTURE AND FUNCTION
Human structure and function
Name of the student:
Name of the University:
Author note:

1HUMAN STRUCTURE AND FUNCTION
Table of Contents
Macromolecule:..........................................................................................................................2
Examples of macromolecule:.....................................................................................................2
Structure:....................................................................................................................................2
Cellular respiration:....................................................................................................................2
Cytoanatomy:.............................................................................................................................3
References:.................................................................................................................................4

2HUMAN STRUCTURE AND FUNCTION
Macromolecule:
The chosen macromolecule is protein.
Examples of macromolecule:
Proteins are macromolecules made up of amino acid residues connected with peptide
bonds. Chosen proteins for this essay are Haemoglobin and Actin. Haemoglobin is a
metalloprotein and actin is a multifunctional globular protein (Blanchoin et al., 2014).
Structure:
Haemoglobin is the oxygen carrier protein pigment present in Red Blood Cells.
Haemoglobin has a tertiary structure and it is a multi-subunit protein (Gleixner et al., 2016).
Each subunit has a protein part and a metal ion or heme group as a prosthetic group. The
heme group is held by porphyrin ring. It mostly has alpha helices and they are stabilized by
hydrogen bonding. It has two alpha and two beta chains each consisting of approximately 150
amino acid residues (Gleixner, 2016). The molecular formula of haemoglobin is
C2932H4724N828O840S8Fe4, from which the CHO ratio can be defined as 733:1181:210.
Actin is a globular (G-actin) as well as filamentous (F-actin) and multi-domain
protein. It has ATP hydrolysing activity. It has been found that actin possesses tertiary and
super secondary structures (Blanchoin et al., 2014). The molecular formula of F-actin
consists of C, H and O in the ratio of 25:34:6.
Cellular respiration:
The chosen macromolecule is protein. Haemoglobin in blood carries oxygen from
lungs to cells, enabling the tissues to continue with the cellular aerobic respiration cycles.
Thus, haemoglobin is not directly associated with the cellular respiratory processes, but
simply works as a transport medium of respiratory gases. The globular protein molecule

3HUMAN STRUCTURE AND FUNCTION
actin, on the other hand, utilizes the chemical energy stored in ATP molecules to drive motor
functions, in conjunction with myosin (Blanchoin et al., 2014).
Proteins are not directly broken down in the catabolic pathways involved in cellular
respiration. The pathways of respiration which are glycolysis and TCA cycle break only
glucose. Proteins need to be broken down into simpler forms like peptone or peptides by the
action of digestive enzymes like trypsin and chymotrypsin. Again the peptone is broken down
to amino acids. Several amino acids like glutamic acid and aspartic acid produce
intermediates for the TCA cycle in the form of alpha keto glutarate by deamination or
transamination. Thus amino acid metabolism by products enter into the cellular respiratory
pathway (Gleixner, 2016).
Cytoanatomy:
Cytoskeleton is made up of microtubules, microfilaments and intermediate filaments.
Microtubule is the largest type of filament, made up of tubulin units. Microfilaments are the
smallest type of filaments, made up of polymers of F-actin filament (Blanchoin et al., 2014).
Septins, spectrins are also cytoskeleton proteins present in eukaryotes. Microfilaments have
spiral filamentous structure, made up of globular actin protein molecules, which together with
myosin protein, play a major role in muscle contraction. These filaments help with the
cellular movement by providing support and strength to the plasma membrane.
Ribosome is another cell organelle made up of ribosomal RNAs (rRNA) and different
proteins. Both rRNA and ribosomal proteins play significant roles in the structural assembly
of the organelle. Eukaryotic ribosome has more than 80 proteins present on the surface and
stabilizes the structure (Bai et al., 2013). Although some of these proteins do not have any
role in the mature ribosome. These proteins, along with the rRNAs make up the ribosomal
subunits that are responsible for the essential process of translation.

4HUMAN STRUCTURE AND FUNCTION
References:
Bai, X. C., Fernandez, I. S., McMullan, G., & Scheres, S. H. (2013). Ribosome structures to
near-atomic resolution from thirty thousand cryo-EM particles. elife, 2, e00461, 1-12.
Blanchoin, L., Boujemaa-Paterski, R., Sykes, C., & Plastino, J. (2014). Actin dynamics,
architecture, and mechanics in cell motility. Physiological reviews, 94(1), 235-263.
Gleixner, E., Ripp, F., Gorr, T. A., Schuh, R., Wolf, C., Burmester, T., & Hankeln, T. (2016).
Knockdown of Drosophila hemoglobin suggests a role in O2 homeostasis. Insect
biochemistry and molecular biology, 72, 20-30.