Biomolekul • Part 1: Susunan dan Penggolongan Karbohidrat

Summary

In this educational video, the Science Window Channel dives into the topic of biomolecules, focusing on carbohydrates. The video explores their composition, classification, and different types, including monosaccharides, disaccharides, oligosaccharides, and polysaccharides. It explains the structure and examples of each type, covering the functional groups, carbon atoms, and the concept of optical isomers. The video also touches on important reactions such as hydrolysis, reducing properties of monosaccharides, and their behavior in tests like Fehling’s, Tollens’, and Benedict’s. The content is designed to provide a clear understanding of carbohydrates and their role in biology and chemistry.

Takeaways

• 😀 Carbohydrates are polyhydroxy aldehydes or polyhydroxy ketones with the general formula CnH2nOn.
• 😀 Initially, scientists thought carbohydrates were compounds that bind several water molecules, but this theory was disproven in the 19th century.
• 😀 The term 'saccharides' refers to carbohydrates, but not all carbohydrates are sugars. Sugar is a subset of carbohydrates.
• 😀 Carbohydrates are classified into four groups: monosaccharides, disaccharides, oligosaccharides, and polysaccharides.
• 😀 Monosaccharides are the simplest carbohydrates that cannot be hydrolyzed further. They are categorized based on their functional group and the number of carbon atoms.
• 😀 Aldoses contain an aldehyde group, and ketoses contain a ketone group. The number of carbon atoms can range from three to six, forming triose, tetrose, pentose, and hexose sugars.
• 😀 Optical isomers (D and L forms) exist due to the chiral nature of monosaccharides, meaning they can be mirror images of each other.
• 😀 Fischer projections are used to depict the structural arrangement of chiral molecules, like monosaccharides, without needing to write each carbon atom explicitly.
• 😀 Monosaccharides are reducing sugars and can react positively with Fehling's, Tollen's, and Benedict's reagents.
• 😀 Ketoses can rearrange to form aldoses, allowing them to undergo oxidation reactions with reagents that target aldehyde groups.
• 😀 Monosaccharides are soluble in water due to their ability to form hydrogen bonds, making them polar and easily dissolved.

Q & A

What are carbohydrates and what is their general formula?

Carbohydrates are polyhydroxy aldehydes or polyhydroxy ketones, with the general formula CnH2nOn. Initially, carbohydrates were thought to be carbon compounds that bind several water molecules, but later it was understood that they are not just carbon bound to water molecules.

Why were carbohydrates initially thought to be hydrate compounds?

Carbohydrates were initially thought to be hydrate compounds because they were believed to be carbon compounds that bind several water molecules. This assumption was later disproven at the end of the 19th century.

What are the four classifications of carbohydrates?

Carbohydrates are classified into four categories: monosaccharides, disaccharides, oligosaccharides, and polysaccharides. Monosaccharides are the simplest, while polysaccharides are the most complex.

What is the difference between monosaccharides, disaccharides, oligosaccharides, and polysaccharides?

Monosaccharides are the simplest carbohydrates that cannot be hydrolyzed further. Disaccharides consist of two monosaccharide units, oligosaccharides have 3-10 monosaccharides, and polysaccharides are long chains of monosaccharide units formed by polymerization.

What are the results of hydrolysis for each type of carbohydrate?

Hydrolysis of disaccharides results in two monosaccharides, oligosaccharides result in 3-10 monosaccharides, and polysaccharides break down into many monosaccharide units.

Can you give examples of monosaccharides, disaccharides, oligosaccharides, and polysaccharides?

Examples of monosaccharides include glucose, fructose, and galactose. Disaccharides include maltose and sucrose. Oligosaccharides include raffinose, and polysaccharides include starch, glycogen, and cellulose.

What is the classification of monosaccharides based on?

Monosaccharides are classified based on their functional group (either aldehyde or ketone) and the number of carbon atoms. For example, if the functional group is aldehyde, it is an aldose; if it is ketone, it is a ketose.

What is the difference between aldoses and ketoses?

Aldoses are monosaccharides with an aldehyde functional group, while ketoses have a ketone functional group. Aldoses are named with 'aldo-' (e.g., aldotriose), and ketoses are named with 'keto-' (e.g., ketotriose).

What are optical isomers, and how do they relate to monosaccharides?

Optical isomers, or enantiomers, are compounds that are mirror images of each other. Monosaccharides can have optical isomers, such as D- and L-glyceraldehyde, where the positions of the OH and hydrogen atoms are reversed.

What are the properties of monosaccharides?

Monosaccharides are white solids that are easily soluble in water due to their polar OH groups. They are also reducing sugars, which means they can react positively with reagents like Fehling's, Tollens', and Benedict's reagents, indicating their ability to undergo oxidation.