The main difference between reducing sugar and starch is that reducing sugar can be either a mono- or disaccharide containing a hemiacetal group with an OH group and an OR group on the same carbon, while starch is a polysaccharide . composed of numerous glucose units linked by glycosidic bonds . In addition, all monosaccharides and many disaccharides such as cellobiose , lactose and maltose are reducing sugars, while glucose polymers such as starch and starch derivatives such as dextrin, glucose syrup, maltodextrin, etc. are macromolecules that start with a reducing sugar.
Reducing sugars and starches are two types of carbohydrates that are one of the three types of macronutrients in animals. In addition, carbohydrates contain carbon, hydrogen and oxygen; Hydrogen to oxygen ratio of 2: 1.
Key areas covered
1. What is a reducing sugar - definition, structure, meaning 2. What is starch - definition, structure, meaning 3. What are the similarities between reducing sugar and starch - overview of the common characteristics 4. What is the difference between reducing sugar and strength - comparison of key differences
key terms
Aldehyde groups, disaccharides, monosaccharides, reducing sugars, starch
What is a reducing sugar ?
Reducing sugars are the carbohydrates that can act as reducing agents. Therefore, they contain either a free aldehyde or a free ketone group. Significantly, all monosaccharides are reducing sugars. In addition, some disaccharides, oligosaccharides, and polysaccharides also have some reducing properties. In general there are two types of monosaccharides; Aldoses with an aldehyde group and ketoses with a ketone group. However, ketone groups must convert to aldose groups in order to become a reducing sugar. Usually hemiacetal groups containing an OH group and an OR group bonded to the same carbon have this ability to interconvert. Some of the examples of monosaccharides are also glucose, galactose, and fructose.
In addition, disaccharides have two monosaccharides linked by a glycosidic bond. In non-reducing disaccharides such as sucrose, however, a glycosidic bond is formed between anomeric carbons, as a result of which it is converted into the open-chain structure without an aldehyde group. In reducing disaccharides such as lactose and maltose , however, the open-chain structure has an aldehyde group. For example, in starch such as starch and starch derivatives, the polymer begins with reducing sugar that contains a free aldehyde. Significantly, more hydrolysis of starch creates more reducing sugar moieties.
Figure 1: Balance between cyclic and open forms of maltose
In addition, open-chain forms with aldehyde groups serve as reducing agents that oxidize metal ions. Therefore, in the Benedict test and in the Fehling's solution, Cu2 + ions oxidize to a brick-red color due to reducing sugars. Ag + is also oxidized in the Tollen test.
What is strength
Starch is the most important storage form of carbohydrates in plants. It is generally found in large quantities in staple foods like potatoes , wheat , corn (Corn), rice and cassava . Also, starch is a white color that is tasteless, odorless, and insoluble in cold water and alcohol. In plants, for example, glucose-1-phosphate is first converted into ADP-glucose, which polymerizes via 1,4-alpha-glycosidic bonds . Significantly, new ADP-glucose molecules are added to the non-reducing end of the polymer. On the other hand, the polymer is branched via 1,6-alpha- glycosidic bonds.
Figure 2: Amylose and amylopectin
In addition, because of its structure, there are two types of starch found in plants. They are linear amylose and branched amylopectin. In general, plants contain 25% amylose and 75% amylopectin. In industry, however, starch is important for fermenting ethanol to make beer, whiskey, and biofuel. Starch is also used in non-food industries.
Similarities Between Reducing Sugar and Starch
- Reducing sugars and starches are two types of carbohydrates made up of carbon, hydrogen, and oxygen.
- Their ratio of hydrogen to oxygen is 2: 1.
- They are the most common constituents of carbohydrate diets.
- Significantly, they play an important role as fuel for cell respiration.
Difference between reducing sugar and starch
definition
Reducing sugar refers to any sugar that can act as a reducing agent due to the presence of a free aldehyde or ketone group, while starch refers to an odorless, tasteless, white substance that is widely found in plant tissues such as cereals and potatoes.
structure
Reducing sugar can be either a mono- or disaccharide containing a hemiacetal group with an OH group and an OR group attached to the same carbon, while starch is a polysaccharide. composed of numerous glucose units linked by glycosidic bonds .
Reducing properties
All monosaccharides and many disaccharides like cellobiose , lactose and maltose are reducing sugars, while glucose polymers such as starch and starch derivatives such as dextrin, glucose syrup, maltodextrin, etc. are macromolecules that start with a reducing sugar.
Result of the Benedictine Trial
Reducing sugars give positive results for the Benedict test, while starch reacts very poorly with Benedict's reagent due to the presence of a small number of reducing sugar units.
diploma
Reducing sugars are either monosaccharides or disaccharides with a hemiacetal group with a free aldehyde or ketone group. Significantly, this group acts as a reducing agent and oxidizes metal salts. For example, all monosaccharides and some disaccharides including lactose and moltose are reducing sugars. In contrast, starch is the main form of storage polysaccharide in plants. It also consists of glucose units linked by glycosidic bonds. However, it starts with a reducing sugar with a free aldehyde group. Therefore it only has reducing properties to a small extent. Hence, the main difference between reducing sugars and starches is in their structure and properties.
References:
1. "What does sugar reduce?" Master's in Organic Chemistry, June 19, 2019, available here. "Strength." Encyclopædia Britannica, Encyclopædia Britannica, Inc., Available here.
Image courtesy:
1. “Maltose balance” By NEUROtiker - Own work ( Public Domain ) via Commons Wikimedia 2. “Figure 03 02 06” By CNX OpenStax ( CC BY 4.0 ) via Commons Wikimedia
