Through this course, I was exposed to a new branch of study in the science field that uses the principle and language of chemistry to explain biology. I also learnt that biology and chemistry can be and are interconnected. I was also able to understand the connections between biology and chemistry and applied this knowledge to my daily life as well as in the Aquatic Science program.

Dr Hashimatul is a great lecturer. Not only was she approachable but her teaching methods were also effective which allows me to understand the subject better. She encourages critical thinking among her students to allow us to explore and understand the subject on our own terms and also encourage us to approach her, during or after class and through Whatsapp and email if we do not understand any of the topics or concepts taught in the course. In this way, it allows the students to be more independent and expressive in their opinions. Besides that, she makes learning the subject fun and interesting by making quizzes on the Kahoot! app. Plus, she makes her own lecture notes by adding additional information that cannot be found in the existing lecture notes which allows us to fully focus during the lecture in addition to being very useful during examinations.

Besides the lectures, we also did a few practical and problem-based learning (PBL) sessions which allows us to put the knowledge that we have acquired from the lectures to real-life situations. The practical sessions challenged us to complete experiments based on theory alone and also forces us to think critically when doing the experiments as well as gain more knowledge related to the topics that we learn in the course. It also exposed us to the types of work that will be done in the near future if we decided to pursue a job in the Biochemistry field. For PBL, we are presented with a real case which tests our problem-solving skills as it requires us to produce ideas and actions that are fact-supported to solve the problem. The two sessions also tested our ability to work with our peers and establish good communication and networking skills.

Furthermore, we are also required to complete our E-portfolio which is a reflection-based learning. This method is useful as it allows the students to reflect and express their understanding of the course to show their development and improvement throughout the semester. It also gives the opportunity to the students to show creativity in the way the wish to retain the information that they have learnt from each topic in the course by making infographics, videos and mind-maps.

As an Aquatic Resource Science and Management student, Biochemistry helps me to gain insights on biochemical processes occurring in the variety of aquatic species, which will be helpful during my final year project. The course also exposes me to the different elements and compounds that are useful in the study of genetics of aquatic species. I can also apply the knowledge that I have gained in my daily life to understand how life works in a fundamental way. Not only that, it also helps me to understand the nutritional contents in the food I eat on the daily basis and the importance of this elements in regulating the processes in my body as well as the biological processes that occurs within our body.

Lipids are organic compounds that are mostly insoluble in water. They are composed of fats and oils, yield high energy and have a chemical composition of carbon, hydrogen and oxygen. Lipids perform three primary biological functions within the body which are as energy stores, structural components of cell membranes and as intracellular and intercellular signaling molecules. Lipids can be further classified into different categories which are triacylglycerols (triglycerides), phospholipids, steroids, terpenes, eicosanoids and lipid soluble vitamins.

Triacylglycerols or triglycerides are the simplest form of lipids formed by fatty acid and is made up of three fatty acids ester linked to a single glycerol. Due to the ester linked between the polar hydroxyls of glycerol and the polar carboxylates of fatty acids, triacylglycerols have characteristics such as nonpolar, hydrophobic and insoluble in water. Triacylglycerols are commonly found in vegetable oils, animal fats and dairy products. Triacylglycerols are stored as fat droplets in large amounts in vertebrate fat cells and as oils in plant seeds. They are better energy source compared to carbohydrates because triacylglycerols produces more than twice as much energy compared to oxidation of carbohydrates. The fat content of normal humans allows them to survive starvation for 2 to 3 months. Besides that, triacylglycerol under the skin can function as thermal insulation and energy reserves. Triacylglycerols are also involved in the saponification which is the formation of soaps from triacylglycerols by converting triacylglycerols into fatty acid salts (soap) and glycerol.

Phospholipids are the amphipathic lipids or lipid bilayers commonly found in membranes. Due to their amphipathic nature, they are effective as emulsifying agents, compounds that make or stabilizes emulsion. For example, the lecithin in egg whites keeps mayonnaise, an oil-water emulsion from separating. There are two classes of phospholipids which are glycerophospholipids and sphingolipids. Glycerophospholipids are amphiphilic molecules with non-polar aliphatic tails and polar phosphoryl-X heads. One of the main functions of glycerophospholipids is the formation of cellular membranes of all organisms and organelles in cells. Their amphipathic nature drives the formation of lipid bilayer structure of membranes. Sphingolipids consists of a polar head group and two non-polar tails with an amino alcohol called sphingosine as its core. Sphingolipids are major membrane components, have a structural function and protect the cell surface from harmful environmental factors. They also serve as adhesion sites for extracellular proteins and play an important role in signal transmission and cell recognition.

Steroids are biologically active organic compounds with three 6-membered rings and one 5-membered rings arranged in a specific molecular configuration made naturally in the human body. Cholesterol is the most common steroid and is mainly synthesized in the liver and a precursor to all other steroid hormones such as testosterone which are secreted by the gonads. Cholesterol is also the precursor to vitamin D and bile salts, which help in the emulsification of fats and their subsequent absorption by cells. Cholesterol is a necessary for proper functioning of the body as it is a component of the plasma membrane found within the phospholipid bilayer. Steroid hormones serve many functions including salt balance, metabolic and sexual functions.

Terpenes are major biosynthetic building blocks within nearly every living creature. Some examples of terpenes are vitamin A and steroids which are derivatives of the triterpene squalene. Terpenes are derived biosynthetically from units of isoprene, which has the molecular formula C₅H₈. Its activated forms, isopentenyl pyrophosphate (IPP) and dimethylallyl pyrophosphate (DMAPP) are the building blocks. The functions of terpenes include producing color and odors associated with plants (essential oil), as vitamin and precursors, in visual pigments and chloroplast pigments.

Eicosanoids are signaling molecules made by oxidation of C₂₀ essential fatty acids (EFAs) which are produced and used locally or on site. Eicosanoids derive from either omega-3 or omega-6. There are four families of eicosanoids which are prostaglandins, prostacyclins, thromboxanes and leukotrienes. These eicosanoids are derived from membrane lipids, with arachidonic acid being the most important precursor in humans. Eicosanoids exert complex control over many bodily systems, mainly in inflammation or immunity, and as messengers in the central nervous system. It acts at low concentration and are involved in the production of pain and fever, regulation of blood pressure, blood coagulation and reproduction.

Some vitamins are lipid soluble. These vitamins are known as vitamin A, D, E and K. Vitamin A is a group of unsaturated organic compounds that includes retinol, retinal, retinoic acid, and several provitamin A carotenoids and beta-carotene. Vitamin A serves as the site of the primary photochemical reaction in vision. The active molecule is retinal which is a vitamin A aldehyde. Retinal forms an imine with an -NH₂ group of the protein opsin to form visual pigment called rhodopsin. The primary chemical event of vision in rod cells is absorption of light by rhodopsin followed by isomerization of the 11-cis double bond to the 11-trans double bond. Vitamin D is a group of structurally related compounds that play a role in the regulation of calcium and phosphorus metabolism. The most abundant form in the circulatory system is vitamin D3. Vitamin E is a group of compounds of similar structure and the most active is α-tocopherol. Vitamin E is an important antioxidant, necessary for reproduction in rats and may be necessary for reproduction in humans that functions to trap HOO• and ROO• radicals formed as a result of oxidation by oxygen of unsaturated hydrocarbon chains in membrane phospholipids. Meanwhile, vitamin K has a regulatory function in blood clotting.

Carbohydrates are organic compounds consisting of carbon, hydrogen and oxygen atoms with the empirical formula C_n(H₂O)_n, usually with the hydrogen to oxygen atom ratio of 2:1. The carbohydrates are technically hydrates of carbons, therefore it is structurally more accurate to view them as aldoses and ketoses. It is the most abundant biological molecules on Earth and mostly produced through carbon dioxide fixation during photosynthesis.  Carbohydrates have several key functions in living organisms such as energy storage in the form of glycogen in animals and starch in plants. These organic compounds also play an important role in structural components of plant cell walls, immune responses, cell-cell recognition and form derivatives that are important backbone of genetic molecules such as DNA and RNA. Carbohydrates can be classified into three types which are monosaccharides, disaccharides and polysaccharides.

Monosaccharides are simple sugars and the most basic unit of carbohydrates. They cannot be hydrolyzed to smaller carbohydrates under mild conditions. Monosaccharides is a type of monomer that can be combined with like monomers through glycosidic bonds to form larger polymers. Monosaccharides are classified according to the number of carbon atoms in the backbone and categorized as aldoses and ketoses. The sugar is an aldose if it contains the aldehyde functional group and ketose if it contains the ketone functional group. The aldoses and ketoses contain aldehyde and ketone functions respectively. Monosaccharides consists of glucose, fructose, galactose, ribose and glyceraldehyde.

Glucose is an important monosaccharide as it provides energy and precursors for cellular respiration through glycolysis. It is stored as starch in plants and glycogen in animals. Glucose also provides structure in that it can be connected in long strings of monosaccharides to form polysaccharides that resemble fibers known as cellulose. Cellulose are used by plant cells to create rigid cell walls that helps the plants to stand tall and remain turgid.  Fructose are similar to glucose in its chemical formula but has different molecular structure. Fructose is mostly found in fruits therefore it is sometimes called fruit sugar. Fructose is also an important source of energy for the body. Galactose is also an important energy-providing nutrient as it is mainly converted to glucose and an important monomer in production of milk as it forms lactose when bonded to glucose by glycosidic bond. Ribose primarily occurs as D-ribose, which forms the backbone structure of DNA and RNA as well as creation of ATP for cellular respiration. Glyceraldehyde is an important intermediate compound in carbohydrate metabolism

Disaccharides are formed when two monosaccharides are joined by glycosidic bonds through condensation reaction, which involves the removal of water molecule from the functional group only. Much like monosaccharides, disaccharides are also soluble in water. Disaccharides are divided into two classes which are reducing sugars and non-reducing sugars. Reducing sugars are sugars that has free aldehyde or ketone functional group to act as a reducing agent whereas non-reducing sugars do not have a free aldehyde or ketone group. There are three common examples of disaccharides which are sucrose, lactose and maltose. All three have the same general formula of C₁₂H₂₂O₁₁ but differ in atomic arrangements within the molecules. Other less common disaccharides are cellobiose, lactulose and trehalose.

Sucrose is a non-reducing sugar that is made up of glucose and fructose and commonly found in plants. Sucrose is an important component in the human diet as sweetener and as energy provider when it is digested and broken down into simpler sugars. Lactose, a milk sugar is made of galactose and glucose and commonly found in breast milk and provide nutrition to infants. Maltose is made up of two glucose molecules. In humans, further broken down into energy by various maltase enzymes or stored as glycogen. Maltose is also used in the malting process of barley to make beer and a low-cost sugar source in the form of high-maltose corn syrup. Trehalose is made up of two glucose molecules which are linked differently than in maltose. They occur in large variety of organisms, ranging from bacteria to invertebrate animals, where they serve as energy provider or stress protectant. Lactulose is made up of fructose and galactose, used to treat constipation and liver disease as well as to test for overgrowth of bacteria in the small intestines. Cellobiose, like maltose and trehalose are made up of two glucose molecules yet arranged in another different way. It is obtained from partial hydrolysis of cellulose and is used as an indicator carbohydrate for Crohn’s disease and malabsorption syndrome.

Polysaccharides are long chained polymeric carbohydrates composed of monosaccharide units bound together by glycosidic linkages. They ranged in structure from linear to highly branched. There are two types, homopolysaccharides which are composed of a single type of monomer and heteropolysaccharides which are composed of two or more different types of monomers. Examples of homopolysaccharides are the storage polysaccharides consisting of glycogen and starch and structural polysaccharides consisting of cellulose and chitin. Heteropolysaccharides consists of hemicellulose, peptidoglycans, glycosaminoglycans and information polysaccharides which are glycoprotein and glycolipids.

For storage polysaccharides, starch is made up of α-D-glucose units. There are two forms of starch which are amylose, a linear polymer of α(1 to 4) linked glucose residues and amylopectin, a branched polymer of α (1 to 4) linked glucose residues with α(1 to 6) linked branches. The main function of starch is as energy storage and food reserve in plants. It is also used in food processing as additives, thickeners and stabilizers in foods such as puddings and to make pastas and noodles. Besides that, starch can also be used to make glue, paste and a new type of bio-batteries. Glycogen are branched polymer like amylopectin but even more highly compact and branched. It is mainly stored in the liver and muscles of animals and provides the body with a readily available source of energy when blood sugar level decrease.

For structural polysaccharides, cellulose is a homopolymer with linear chain of several hundred to over ten thousand of β (1 to 4) linked D-glucose units. It is the primary component of plant cell walls and green algae. Chitin is a homopolymer of β (1 to 4) linked N-acetylglucosamine residues that serves as a main component of the cell walls of fungi and the exoskeletons of arthropods such as crustaceans and insects. Hemicellulose is a heteropolymer, present along with cellulose in almost all terrestrial plant cell walls. It interacts with cellulose to help strengthen the cell walls. In more vascular plants, hemicellulose interact with lignin to provide structural tissue support. Peptidoglycans or murein are polymers made up of sugars and amino acid. They are mostly found in bacterial cell walls, providing structural strength, essential for osmotic stability in bacterial cells and involved in binary fission during bacterial cell reproduction.

For information polysaccharides, glycoproteins are proteins that contain oligosaccharide chains covalently attached to polypeptide side chains.  Generally, there are two types of glycoproteins which are O-linked glycoprotein and N-linked glycoprotein. Glycoproteins are important integral membrane proteins, where they play a role in cell-cell interactions. Glycolipids are lipids attached with carbohydrates linked by glycosidic bonds. They play a crucial role in maintaining stability of cell membrane and to facilitate cellular recognition which are important in immune response and in the connections that allow cells to connect to one another to form tissues.

In chapter 2: Water and Hydrogen Bonds, I learnt that water is an important component in cells, being the most abundant component and accounting for 60% to 90% of the mass of the cells. Some of the most important properties of water arises from its angled shaped, the intermolecular bonds it can form and its hydrogen bonding characteristics.

The general shape of a water molecule is V-shape. This is due to the H-O-H bond angle in free water molecule being 104.5° which is formed from the strong repulsion between the lone electron pairs pushing the covalent bond orbitals closer. Within the water molecules, there is an uneven distribution of charge occurs within each O-H bond in which the oxygen is more electronegative than hydrogen, therefore oxygen have higher tendency to attract electrons. Hence, the oxygen becomes partially negative while the hydrogen becomes partially positive. This uneven distribution of charge within a bond is known as a dipole and the bond is said to be polar. The angled arrangement of the polar O-H bonds of water creates a permanent dipole for water molecules. The polarity of water molecules causes it to attract one another and the attraction between one positive hydrogen atoms and the negative electron pairs produces a hydrogen bond. However, compared to other covalent bonds, hydrogen bonds are weak interactions as only +20 kj mol^-1 is required to disrupt hydrogens between water molecules.

Besides that, water molecules are considered unusual because they can form four O-H-O aligned hydrogen bonds with four other water molecules when is solid phase (ice). Each of the hydrogen bonds point to the oxygen atom of an adjacent water molecule, forming a tetrahedron. Freezing causes the ‘net’ to become rigid tetrahedral lattice. When melted, some of the lattice is released and water molecules move closer together. This makes liquid water denser than solid, therefore ice floats.

Liquid water molecules also usually can form two to three bonds at any given moment and this contributes to water’s two additional properties which are specific heat and heat of vaporization in which large amount of heat is required to raise the temperature of water because of the multiple hydrogen bonds that must be broken in order to release water molecules. These properties help in minimizing temperature fluctuations within cells. It is a universal solvent in biological systems due to its polarity. The polarity in water molecules is caused by an uneven charge distribution within each O-H bond, Due to the uneven charge distribution, water becomes ionic compound with covalent bond. Sodium chloride (NaCl) is an ionic compound, where Na is positively charge and Cl is negatively charge. Therefore, it dissolves readily in water. When NaCl is added into water (H2O), the negative charge side of water molecule is attracted to the Na and the positive charge side of water is attracted to Cl. Because the covalent bond of H2O is stronger compared to the ionic bond of NaCl, the ionic bond is pull apart and eventually break, causing the Na ion and Cl ion to be surrounded by water molecules and dissolving the salt resulting in homogenous solution.