Carbohydrates, lipids, proteins, and nucleic acids are the four main types of biological macromolecules. Each is a vital part of the cell and carries out a variety of tasks.
Biological macromolecules are massive molecules required for life and are constructed from smaller organic components. Carbohydrates, lipids, proteins, and nucleic acids are the four main types of biological macromolecules. Each is a vital part of the cell and carries out a variety of tasks.
These molecules make up most of a cell’s mass when they are all combined. Organic molecules, including carbon and hydrogen, make up biological macromolecules. They could also have tiny amounts of oxygen, nitrogen, phosphorus, sulphur, and other elements (Dryhurst, 2012).
Structure of the Water Molecule
Water, a biological molecule, differs from other molecules (hydrocarbons and hydrogenated sulphur molecules) due to its high boiling and melting temperatures, surface tension, density, and heat of vaporization. Only two properties—viscosity and diffusion with solute—are like those of other biological molecules of low molecular weight.
Water, a biological molecule, behaves uniquely by reaching its maximum density at 4 degrees Celsius. Due to the dipole moment’s contribution of an extra force to the preexisting van der Waals attraction, water has a high melting and boiling point.
These intermolecular interactions make the liquid almost crystalline and make it difficult for water to escape into the vapour phase. Water can hold a lot of heat. It implies that a significant amount of heat is required to increase its temperature.
Water has a higher relative permittivity than most liquids. Water is a suitable solvent for ionic substances because of this characteristic. These physical characteristics imply that intermolecular forces preserve the structure of water (Uchida et al., 2021).
The oxygen atom is in the centre of the tetrahedral structure of water, which also contains two hydrogen atoms at its corners. Water behaves like dipole molecules due to the shifting of electronic charge to a highly electronegative oxygen atom.
Based on this polarity property, one water molecule is coupled with four. Hydrogen bonding is responsible for these dipole-dipole attractions and is commonly found in water’s liquid and solid states (except gas).
The addition of solute molecules disturbs the current organization of water molecules. The perturbance depends on the nature of solute molecules, either hydrophobic or hydrophilic. The hydrophilic (water-loving) molecules tend to bind with water.
Hydrophilic compounds are electrolytes (ionic) that form ionic bonds with water, while non-electrolyte (neutral) compounds interact through hydrogen bonds. The ionic compounds, or hydrated ions, form anionic and cationic compounds.
The anionic compounds are known as structure formers due to their location outside of the tetrahedral structure and their readily available availability. So, the effect of anionic compounds on the molecular structure of water, a biological molecule, is limited compared to cations that disturb the water structure. The relative strength of anionic compounds in water is higher than that of cationic compounds and water dipoles.
Water, a biological molecule, can form hydrogen bonds on the same or separate biopolymers at two (or more) different locations. A “water bridge” is what is meant by this. A water molecule attached at multiple sites has a higher degree of unpredictability than a water molecule involved in a water bridge.
The energy required to break the bonds at two different places equals the point needed to release the molecule from its confinement. In protein systems, water bridging occurs frequently and has an impact on the structure of the proteins (Chaplin, 2019).
Due to their water attraction, hydrophobic groups disrupt the structure of the water molecules when they are introduced into a system. Although hydrophobic groups have relatively low polarity and little hydrogen bonding, it is thought that they can interact with water or other hydrophobic groups.
The latter interactions greatly aid the stability of the proteins’ shape. The water around hydrophobic groups of biological molecules in an aqueous solution has a more structured structure than the bulk water, according to research on thermodynamic parameters (entropy, enthalpy, etc.). The presence of hydrophobic groups lowers a substance’s solubility.
Additionally, there is less water besides a hydrophobic group that can participate in acid and base ionization. The reduced interfacial tension between water and hydrophobic groups is another effect. When hydrophobic groups stick together, the surrounding organised water is forced into the bulk, which takes on a less organized structure.
It frequently occurs in protein molecule chains and is crucial for the stability of the protein chain’s shape. Protein denaturation breaks the hydrophobic groups, exposing more previously water-impermeable sites to contact. As a result, it facilitates the development of a structured structure in the neighboring water. It could cause the solution’s pH and isoelectric point to increase (Chaplin, 2019).
Meat can have its water structure affected by the addition of electrolytes, and the electrolytes’ strong affinity may impact the meat’s mass transfer for water.
Water, a biological molecule, is removed from the meat during drying, and since the protein structure may alter due to the loss of water, the characteristics of the beef may vary throughout this process. Dry-cured ham has a higher pH than raw meat, consistent with the previously mentioned increase in pH brought on by the denaturation of proteins.
Structure of Proteins
Proteins, of all macromolecules, have the widest variety of roles and are among the most abundant organic molecules in biological systems. The functions of proteins are structural, regulatory, contractile, transport, storage, membranes, poisons, and enzymes.
Many thousands of proteins, each with a specific role in the body, can be found in every single cell of a live organism. Structures can differ widely, just as their purposes can. However, they are all linear polymers of amino acids (Ray & Fry, 2015).
There are 22 separate chemically unique amino acids that form long chains, and the amino acids can be in any order, resulting in a wide range of protein functions. Proteins, for instance, can have a role in the body as enzymes or hormones. Catalysts for biological reactions (such as digestion), enzymes are typically proteins produced by living cells.
When an enzyme is activated, it only reacts with its substrate. Enzymes can cut existing bonds, rearrange them, or create new ones. Salivary amylase is an enzyme responsible for the digestion of amylose, a type of starch.
Growth, development, metabolism, and reproduction are only some of the physiological activities that hormones influence or regulate. Hormones are chemical signaling molecules released by an endocrine gland or collection of endocrine cells. Insulin is a protein hormone that regulates blood sugar levels.
Some proteins are spherical, while others are fibrous, and molecular weights can range from very small to very large. Haemoglobin is an example of a globular protein, while collagen is an example of a fibrous protein found in the skin.
The three-dimensional structure of proteins is essential to their biological roles. Denaturation or loss of protein function can occur when the protein is exposed to extremes of temperature, pH, or chemicals. The 22 different amino acids are arranged in various ways to form proteins.
Proteins are polymers composed of amino acids. All amino acids have the same basic structure, with a core carbon atom connected to an amino group (-NH2), a carboxyl group (-COOH), and a hydrogen atom.
One more atom or group of atoms, called the R group, is attached to the core carbon atom in every amino acid. All 22 amino acids have the same structure besides the R group. Amino acids inside a protein have a certain chemical composition depending on the type of the R group (that is, whether it is acidic, basic, polar, or nonpolar) (Branden & Tooze, 2012).
A protein’s size, shape, and function are determined by the order and number of its amino acids. Peptide bonds, or covalent bonds between amino acids, are generated through a dehydration reaction. Whenever two amino acids bond, the carboxyl group from the first acid and the amino group from the second acid combine to form a water molecule, a biological molecule.
The peptide bond is the consequent chemical link. Polypeptides are proteins that have been joined together in this way. Although the phrases are often used interchangeably, a polypeptide is simply a chain of amino acids. In contrast, a protein is a chain of polypeptides that have been folded into a certain structure and serve a specific purpose.
Structure of hydrophobic surfaces
The ability to deflect water droplets from the surface makes it hydrophobic. From the Greek words for “water” (hydro) and “fear” (phobos), we get the word “hydrophobicity,” which describes surfaces that are resistant to water.
The contact angle of water droplets with a surface is a standard method for determining their hydrophobicity. Water droplets on a hydrophobic surface have a contact angle greater than 90 degrees, allowing them to flow easily while maintaining their spherical shape.
On the other hand, super-hydrophobic materials have contact angles greater than 150 degrees, making them difficult to wet. In contrast, hydrophilic surfaces have a narrow contact angle (less than 90 degrees), so water droplets spread over a larger area. Drops of water do not roll but rather glide across these surfaces (Feng et al., 2002).
Surface energies and wettability explain why some surfaces are more prone to water droplets than others. Typically, a reduced contact angle results from a hydrophilic surface, which occurs when a substance has a higher energy state at its surface.
For materials with lower surface energy, water droplets are more attracted to each other than the surface, leading to a larger hydrophobic contact angle. In addition, wettability, or how liquids act when they come into contact with a solid surface, was a crucial phenomenon for many technological uses of hydrophobic characteristics
The contact angle between a liquid droplet and a solid interface is commonly used to describe wettability (Bresme et al., 2008).
For example, lotus leaves (Nelumbo nucifera) have a hydrophobic surface that helps them resist water. A symbol of super-hydrophobicity and self-cleaning abilities, the lotus leaf was first introduced in 1992 as the “lotus effect.” N. nucifera, more often known as lotus, is a semiaquatic plant with enormous, water-repellent petals that can reach a diameter of up to 30 centimeters.
The hydrophobic qualities of the leaf surfaces are on full display as water beads up and rolls off the surface rather than sliding. As can be seen in Fig. 8.2A-D, the surface of lotus leaves is rough due to the wax that coats them and the number of microscopic papillae.
These two surface characteristics work together to make the lotus leaf hydrophobic, allowing water droplets to roll over it and pick up pollutants.
Numerous studies have demonstrated that surfaces with a mix of roughness and low surface energy have a higher hydrophobicity, which is useful for self-cleaning. Various architectures can create surfaces with a large contact angle. so long as the introduced roughness is combined with low surface energy.
Coating materials have been prepared using a wide range of organic and inorganic ingredients to achieve the desired effect of lotus behavior. Fabricating surface roughness is the main concern for polymeric materials, as they are typically inherently hydrophobic.
Since organic materials are naturally hydrophilic, they require a hydrophobic surface treatment following the fabrication of surface structures. Compounds based on carbon are of commercial interest among organic materials.
As a distinct field within the ever-expanding field of modern materials science, the design of hydrophobic materials and coatings has been making significant strides in recent years. Moreover, the business and academic communities have shown considerable interest in hydrophobic materials.
The number of studies published on the design, preparation, and wettability qualities of textured surfaces, surface conditions, and surface compositions that can be used to alter their hydrophobicity is evidence of this trend.
Many industries and fields find great value in hydrophobic materials. For instance, hydrophobic materials have applications such as roof tiles and windows. Another good use for hydrophobic materials is in the field of textile waterproofing.
One reason for this is that the substrate may be kept absorbent and comfortable to wear without compromising the textile’s fibre structure. It’s not cheap to run and maintain a marine vehicle, and a ship’s hull is particularly at risk of the costly biofouling problem.
Using hydrophobic material for the ship’s hull can help alleviate this issue by reducing the amount of water on the hull and reducing the likelihood of biological organisms settling on the surface.
Technological hurdles remain despite the enormous successes in using hydrophobic materials. For hydrophobic materials to be used in a commercial product, it is important to consider not only the scale of manufacturing but also the availability and cost of raw materials.
It has led to many active research projects that aim to discover future uses for hydrophobic substances, such as in manufacturing specialty materials (Cao et al., 2011).
Structure of the Cell Membrane
The cell membrane, also known as the plasma membrane, is a very thin membrane that separates the interior of a living cell from its surroundings. This cell membrane (also called the plasma membrane) encloses the contents of the cell, which are mostly big, water-soluble, positively charged molecules such as proteins, nucleic acids, carbohydrates, and chemicals involved in cellular metabolism.
The cell’s water-based environment contains nutrients it needs to survive and thrive and ions, acids, and alkalis that are harmful to the cell. Thus, the cell membrane is a barrier to keep the cell’s constituents inside and unwanted substances out, as well as a gate to let in necessary nutrients and waste products (Goodman, 2008).
Lipids derived from fatty acids and proteins are the main components of cell membranes. Phospholipids and sterols comprise the bulk of membrane lipids (generally cholesterol). While both forms of lipids share the property of dissolving easily in organic solvents, which is the distinguishing characteristic of lipids, they also share an area that is attracted to and soluble in water.
To perform their function as membrane structural components, lipids must be “amphiphilic” or possess a dual attraction (i.e., comprise both a lipid-soluble and a water-soluble region). There are also two broad categories of membrane proteins.
The extrinsic proteins are one group that only has a weak connection to the phosphoryl surface of the bilayer through ionic interactions or calcium bridges. Another sort of protein, intrinsic proteins, to which they canbind As their name suggests, the intrinsic proteins are completely encased by the phospholipid bilayer. A higher percentage of protein is typically seen in membranes that play an active role in metabolism (Marie et al., 2014).
A membrane surrounds each living cell with a thickness of only a few nanometers (109). The cell membrane’s chemical composition makes it exceptionally malleable, making it a superb border for actively proliferating cells. However, the membrane also serves as a powerful barrier, controlling certain dissolved molecules’ passage while inhibiting others’ passage.
The membrane allows passage for molecules soluble in lipids and some small molecules. Still, it effectively blocks the passage of the numerous large, water-soluble molecules and electrically charged ions essential for the cell’s survival. Certain classes of intrinsic proteins form various transport systems to carry these crucial substances across the membrane.
These systems include open channels that allow ions to diffuse directly into the cell, facilitators that aid solute diffusion past the lipid screen, and pumps that force solutes through the membrane when their concentration is too low for them to diffuse spontaneously. The membrane opens and closes to ingest and expel particles too big to be dispersed or pumped.
To facilitate the transmembrane transport of big molecules, the cell membrane itself goes through coordinated movements in which either the extracellular fluid medium is taken within the cell (endocytosis) or the intracellular medium is released into the extracellular space (exocytosis). To accomplish these shifts, the surfaces of two membranes fuse and then reform into their original, unbroken shapes.
Structure of the Cytoskeleton
The cytoskeleton is a network of filaments and fibres found in the cytoplasm of all eukaryotic cells (cells containing a nucleus). The cytoskeleton coordinates the movement of the cell and its organelles and is responsible for the cell’s shape maintenance and ability to migrate. The cytoskeleton’s filaments are so minute that they have only been uncovered thanks to the enhanced resolution of the electron microscope (Goodman, 2008).
Actin filaments, microtubules, and intermediate filaments are the three main types of filaments that make up the cytoskeleton. Within a cell, actin filaments can be found as meshwork’s or bundles of parallel fibres; these filaments play an important role in shaping the cell and ensuring its stability on the substrate.
Actin filaments are arranged in dynamic patterns that aid cell movement and mediate cellular processes, such as cell division. Microtubules are dynamic, longer filaments that play a critical function in mitosis by transporting the daughter chromosomes to the newly developing daughter cells. They are also present in bundles in the cilia and flagella of protozoans and the cells of some multicellular mammals.
Unlike actin filaments and microtubules, intermediate filaments are extremely stable structures that make up the cell’s actual skeleton. They keep the nucleus in place and provide the cell with its elastic qualities, which it needs to tolerate tension.
The term “cytoskeleton” can refer to more than just the actin and tubulin proteins. Some proteins, such as septins, can self-assemble into filaments that serve as attachment sites for other proteins, and spectrin self-assembles along the intracellular surface of the cell membrane to aid in the preservation of the cellular structure (Xu et al., 2013).
This article is jointly authored by Kashif Hussain from the Department of Parasitology, University of Agriculture, Faisalabad; Talha Khan from the Department of Microbiology, University of Veterinary and Animal Sciences, Lahore; and Aqdas-Ul-Hassan from the Department of Applied Chemistry, Government College University, Faisalabad.