Biology Assignment: Protein Structure, Function, and Cell Membranes

This biology assignment delves into the intricacies of protein structure and function, covering key concepts such as protein domains, alpha helices, and beta sheets. It explores the role of hydrogen bonds in maintaining protein structures at both secondary and tertiary levels. Furthermore, the assignment examines the structure and function of cell membranes, including the properties of phospholipid bilayers, lipid solubility, and how molecules traverse membranes. The assignment provides an overview of the concepts and processes associated with protein structure and cellular membranes, offering insights into their importance in biological systems. The assignment includes references to relevant literature, such as Ezkurdia & Tress (2011) and Ingolfsson & Yona (2008), which provide further detail on protein structural domains and other related topics.

Running head: BIOLOGY 1
Biology
Student’s Name
Institutional Affiliation

BIOLOGY 2
Biology
Question one.
A protein domain is a particular unit of protein that can evolves and functions
independently. The domains are considered the building blocks of a protein. Each unit usually
forms a compact structure comprising of three dimensions that can similarly stand on their own
(Ingolfsson & Yona, 2008). Thus, a single domain can present itself in a variety of diverse
proteins.
Question two.
The alpha helix together with the beta sheet are found in the secondary level of the
protein structure. The two structures are similar in that their shapes are maintained by hydrogen
bonds. The development of the bonds of hydrogen occurs between the components of carbonyl O
and amino H of two different amino acids (Ezkurdia & Tress, 2011). The two structures differ in
that alpha helix involves the hydrogen bonding of a carbonyl of a particular amino acid to the
amino H of another amino acid while beta sheet involves at least two parts of a polypeptide chain
lying on adjacent to each other.
Question three
Hydrogen bonds are used to entirely determine the secondary protein structure whereas in
the tertiary protein structure, the hydrogen bonds need to interact with others such as the
disulphide bonds so as to form the structure (Ezkurdia & Tress, 2011). That is to say, the
hydrogen bonds found in the secondary protein structure are much stronger than those found in
the tertiary protein structure.
Question four

BIOLOGY 3
Naturally, the phospholid head is comprised of phosphate that is negatively charged.
Thus, the head is hydrophilic. On the contrary, the tail contains fatty acids that are uncharged and
nonpolar, thus making it hydrophobic (Ezkurdia & Tress, 2011). Since the head is hydrophilic it
will interact with water while the hydrophobic tail will not, thus, a bilayer is formed.
Question five
Molecules that are lipid-soluble are the ones able to easily pass through the phospholipid
bilayer. A semi-permeable membrane is one that selectively allows tiny molecules to pass
through it while disallowing bigger ones. Cells have multiple membranes with spanning regions
which create a passage via the lipid bilayer, hence permitting charged ions to cross through
(Ezkurdia & Tress, 2011). Such a process happens without the ions interacting with the fatty
acids.

BIOLOGY 4
References
Ezkurdia, I., & Tress, M. L. (2011). Protein structural domains: definition and
prediction. Current protocols in protein science, 66(1), 2-14.
Ingolfsson, H., & Yona, G. (2008). Protein domain prediction. In Structural Proteomics (pp.
117-143). Humana Press.