SELF REFLECTION ON CARBOHYDRATES

(NAZRUL SYAZWAN BIN MOHD NAZERI 72461)

Today I learned about carbohydrates by Dr. Hashimatul Fatma. I really excited to learn because I already knows little bit about it as I learned during my foundation in UNIMAS last year. Carbohydrates are the most abundant biological molecules on earth. Carbohydrates being produced by through fixation process of carbon dioxide during photosynthesis. Generally we knew that carbohydrates functioned in energy storage, structural components, cellular recognition and carbohydrates derivatives. Carbohydrates formed in three : monosaccharides, oligosaccharides, polysaccharides. I learned also about stereochemistry of monosaccharides and classification each of them based of the number of carbon and arrangement of it. I also learned about Fischer projections and Haworth projections of monosaccharides. After that, I learned about oligo and polysaccharides of carbohydrates. Before this, I never know that polisaccharides also have its different division which are HOMOpolysaccharides and HETEROpolysaccharides. They funtions well as storage, structural and information. Example of polysaccharides are starch, glycogen and hemicellulose. So that’s all my reflection about carbohydrates lecture session with Dr. Hashimatul on that day.


(MUHAMMAD HANIF FIKRI BIN MOHAMAD KHIRUDIN 72417)

During our biochemistry class on week 9, our lecturer, Dr. Hashimatul gave a lecture and explained to us about Carbohydrates. Many new information that we get from her, especially about the properties of carbohydrates. At first, she were well explained to us about the introduction of carbohydrates. Carbohydrates is the most abundant biological molecules on Earth that consist of carbon, hydrogen and oxygen, with hydrogen : oxygen atom ratio of 2:1 (as in water). It is an organic compound with the empirical formula Cn(H20)n (with n>3). Carbohydrates also have several key function such as it act as energy storage, glycogen form in human body and in starch form in plants. Next, it is important for structural components for example cellulose and chitin. Besides, carbohydrates function for cellular recognition and carbohydrate derivatives. The basic unit for carbohydrates are called monosaccharides.

For more details about monosaccharides, it is the simplest carbohydrates and they cannot be hydrolyzed to smaller carbohydrates under mild conditions. Monosaccharides are polyhydroxyl aldehydes (aldoses) or ketones (ketoses) with two or more hydroxyl groups. Aldoses and ketoses contain aldehyde and ketone functions, respectively. There are four important monosaccharides structure that we need to know which is glucose, fructose, ribose and glyceraldehyde. Move to the stereochemistry of monosaccharides, it is in chiral which is asymmetrical. For Aldoses, it contains 3 carbon or more, and 4 carbon or more are chiral for Ketoses. Monosaccharides also exhibits enantiomers, diastereomers and epimers characteristics. Enantiomers is a stereoisomers that are minor images, as example the D-glucoes and L-glucose. For diastereomers, it is a stereoisomers that are not minor images, as example the D-ribose and D-xylose. Epimers is a diastereoisomers that differ around 1 carbon, as example the D-glucose and D-galactose.

Furthermore, Dr explained about the Fischer Projection of Monosaccharides. Fischer projection is a two dimensional representation for showing the configuration of tetrahydral stereoisomers. Besides, the Haworth Projection. In its ring forms, monosaccharides are also shown as Haworth Projections. Planar pentagons or hexagons viewed from the edge. Monosaccharides can cyclize to form Pyranose/Furanose forms, which is pyranose that has 6-membered ring and only 5-membered ring for Furanose. Back to the key function of carbohydrates, it says that monosaccharides act as reducing sugars. This condition happen when in the uncyclized form, where the monosaccharides will act as reducing agents. Free carbonyl group from aldoses or ketoses can reduce Cu2+ and Ag+ ions to insoluble products.

Other than that, Dr. Hashimatul told us about derivatives of monosaccharides. Because of the -OH, aldehyde and ketone groups, sugars are easily derivatized. Several derivations of sugars include the reduction and esterification process. For esterification, the hydroxyl group of alcohols can react with acids to produce esters. Other products from the derivatizations of sugars include sugar phosphate, deoxy acids, amino sugars and sugar alcohols.

Finished for our first section about carbohydrates. Move to the next lecture, also about carbohydrates but specifically explain about oligo and polysaccharides. Firstly, the glycosidic bonds. 2-10 monosaccharide units can be joined via O-glycosidic bonds. Glycosidic bond is linkage from the anomeric carbon to the –OR group. This glycosides formed between two monosaccharides, become disaccharides. There are large diversity of glycosidic possible such as different monosaccharide units, anometric configuration (α or β) and its diversity through different connectives. Some examples of glycosidic bond is maltose, the building block of starch and glycogen. Both glycogen and starch consist of D-glucose monomers in α(1-4) linkage. Besides, the cellobiose which is the building block of cellulose. β(1-4) linkage between 2 glucose monomers.

Next is the polysaccharides. There are two types of polysaccharides, homopolysaccharides that only have 1 type of monomers. Some example of this homopolysaccharides is glycogen, starch, cellulose and chitin. Another type is heteromonosaccharides which is consist of different types of monomers. For example is hemicelluloase, peptidoglycans and glycosaminoglycans. The several function of polysaccharides is it work as storage, glycogen in animals and bacteria, and starch in plants. Polysaccharides also important for structure such as cellulose, chitin, peptidoglycans and glycosaminoglycans. Besides, it also function as information for cell surface oligo and polysaccharides, on proteins/glycoproteins and on lipids/gylcolipids. For starch, it is the principal food reserve in plants that made of polymers of α-D-glucose units. There are two form of starch that is amylose and amylopectin. Move to glycogen, it is the storage polysaccharides in animals. Glycogen is slightly like amylopectin but even more highly compact and branched. Furthermore, Dr. Hashimatul explained to us about the structural of polysaccharides. For cellulose it is a homopolymer, a linear chain of several hundred to over ten thousand β(1→4) linked D-glucose units. Next, structural polysaccharides for chitin. Chitin is a main component of the cell walls of fungi, the exoskeletons of arthropods such as crustaceans, crabs, lobsters and shrimps, and also the insects. Furthermore, the glucoaminoglycans. Glycosaminoglycans (GAGs) or mucopolysaccharides are long unbranched polysaccharides made of repeating disaccharide units. This repeating units consists of a hexose or a hexuronic acid, linked to a hexosamine. Last but not least, the function in information of polysaccharides, the glycoproteins. Glycoproteins are proteins that contain oligosaccharide chains (glycans) covalently attached to polypeptide side-chains. It is often important integral membrane proteins, where they play a role in cell-cell interactions. Generally, there are two types of glycoprotein, the O-linked glycoprotein and the N-linked glycoprotein.

In a nut shell, from that previous lecture that were given by Dr. Hashimatul, there were so many new information that we got especially more details about the carbohydrates. We also were having so much fun at the end of the class when we play kahoot. Besides, group in 5 learning technique also give more benefits for us. We can discuss and have more brainstorming session when we were in group. The group member will help others member and support them if they cannot catch up the flow study. For overall, I think it felt more interesting to study biochemistry with this technique and I hope I can use this knowledge and apply it in my future.

(AQMAL SYABIL BIN ASMADY 72125)

I have learned that Carbohydrates are most abundant biological molecules on Earth. It also can be produced through CO2 fixation during photosynthesis. Carbohydrates have several key functions which are:-
1. Energy storage - glycogen, starch.
2. Structural components - cellulose, chitin.
3. Cellular recognition - glycoproteins, glycolipids.
4. Carbohydrate derivatives - DNA, RNA, co-factors.

I know that basic carbohydrate units called monosaccharides and its polymers of monosaccharides are called polysaccharides.Oligosaccharides means "a few" which usually 3 to 10.
Monosaccharides are the simplest carbohydrates and they cannot be hydrolyzed to smaller carbohydrates under mild conditions. Monosaccharides are classified according to the no of carbon. Important monosaccharides that I know are Glucose, Fructose, Ribose and Glyceraldehyde.
Monosaccharides have -OH and C=O group in the same molecules and exist almost entirely as 5- and 6- membered rings.

Monosaccharides are easily derivatized because of the -OH, aldehyde and ketone groups. Derivatizations of sugars include Reduction and Esterification. Other products from the dericatizations of sugars include:-
1.Sugar Phosphate
2. Deoxy Acids
3. Amino sugars
4. Sugar alcohols

I have learned that 2-10 monosaccharides units can be joined via O-glycosidic bonds. Glycosidic bond is linkage from the anomeric carbon to the -OR group. Glycosides formed between two monosaccharides which is disaccharides. Example of glycosides are Maltose and Cellobiose.
There are 4 dissacharides which are Maltose, Sucrose, Cellobiose and Lactose.

I have learned that there are two types of polysaccharides which are HOMOpolysaccharides and HETEROpolysaccharides. HOMOpolysaccharides are all polysaccharides with 1 type of monomer while HETEROpolysaccharides are polysaccharides that have different types of monomers. Example of HOMOpolysaccharides are glycogen, starch, cellulose and chitin and for HETEROpolysaccharides are hemicellulose, peptidoglycans and glycosaminoglycans.