All questions of Carbohydrates for MCAT Exam

Lactose intolerance is the inability to break down a type of natural sugar called lactose. Lactose is commonly found in dairy products, such as milk and yogurt. A person becomes lactose intolerant when his or her small intestine stops making enough of the enzyme lactase to digest and break down the lactose.

Hydrolysis of sucrose is inversion because the angle of specific rotation of the plane polarized light changes from positive to negative value due to the presence of optical isomers of mixture of glucose and fructose sugar...

It forms glucose pentaacetate. The acetic anhydride esterifies with all the alcohol groups on the glucose ring.

All sacchrides /carbohydrates form glycosidic bond by eliminating water molecule

Glucose and C2 of fructose, which does not have a free aldehyde or ketone group to undergo oxidation and reduction reactions.
c)Sucrose does not react with Benedict's reagent, which is used to detect the presence of reducing sugars.
d)Sucrose cannot be hydrolyzed by acid or enzyme into its constituent monosaccharides.

Non-reducing sugars do not have an OH group attached to the anomeric carbon so they cannot reduce other compounds. All monosaccharides such as glucose are reducing sugars. A disaccharide can be a reducing sugar or a non-reducing sugar. Maltose and lactose are reducing sugars, while sucrose is a non-reducing sugar.

Because it is in the ratio of 1:2:1

It is called invert sugar because the angle of the specific rotation of the plain polarized light changes from a positive to a negative value due to the presence of the optical isomers of the mixture of glucose and fructosesugars.

It shows that glucose exists as n-hexane...i.e. it has straight linear chain...

Carbohydrates
Carbohydrates are organic compounds that are composed of carbon, hydrogen, and oxygen atoms. They are one of the three main macronutrients, along with proteins and lipids, and are essential for providing energy to the body.

Composition of Carbohydrates
Carbohydrates consist of carbon, hydrogen, and oxygen atoms. The general formula for carbohydrates is (CH2O)n, where "n" represents the number of carbon atoms in the molecule. This formula indicates that carbohydrates are composed of carbon and water (H2O).

Primary Sources of Carbohydrates
Carbohydrates are primarily found in plant tissues. Plants produce carbohydrates through photosynthesis, where they convert sunlight into energy. Common sources of carbohydrates in the human diet include fruits, vegetables, grains, legumes, and dairy products.

Classification of Carbohydrates
Carbohydrates are a distinct group of compounds and are not classified as lipids or proteins. They have their own classification system, which includes monosaccharides, disaccharides, and polysaccharides. Monosaccharides are single sugar units, while disaccharides are composed of two monosaccharide units joined together. Polysaccharides are long chains of monosaccharides linked together.

Solubility of Carbohydrates
Carbohydrates are generally soluble in water. This solubility is due to the presence of hydroxyl groups (-OH) in their structure, which can form hydrogen bonds with water molecules. However, some carbohydrates, such as insoluble fiber, may be partially or completely insoluble in water.

Summary
In summary, carbohydrates contain carbon, hydrogen, and oxygen atoms. They are primarily found in plant tissues and are not classified as lipids or proteins. Carbohydrates are generally soluble in water, although some types may be insoluble.

Monosaccharides such as glucose can be linked together in condensation reactions. For example, sucrose (table sugar) is formed from one molecule of glucose and one of fructose, as shown below. Molecules composed of two monosaccharides are called disaccharides. 

Lactose is the carbohydrate that is commonly known as milk sugar. It is a disaccharide composed of two sugar molecules, galactose and glucose, linked together by a β-glycosidic bond. Lactose is found in the milk of mammals, including humans, and is an important source of energy for infants.

Here is a detailed explanation of why lactose is called milk sugar:

Lactose in Milk:
- Lactose is primarily found in the milk of mammals. It is the main carbohydrate present in milk, accounting for about 4-5% of its composition.
- It provides energy for the growing infant and is essential for their development.
- As mammals produce milk to nourish their young, lactose is present in varying amounts in the milk of different species, including humans.

Structure of Lactose:
- Lactose is a disaccharide, which means it is composed of two sugar molecules linked together.
- It consists of one molecule of glucose and one molecule of galactose.
- The glucose and galactose molecules are joined by a β-glycosidic bond, which is a specific type of chemical bond between the two sugars.

Digestion of Lactose:
- Lactose is digested by the enzyme lactase, which is produced in the small intestine.
- Lactase breaks down lactose into its individual sugar components, glucose and galactose.
- These simple sugars can then be absorbed into the bloodstream and used as a source of energy by the body.

Intolerance to Lactose:
- Some individuals have a reduced ability to produce lactase, resulting in lactose intolerance.
- Lactose intolerance is characterized by symptoms such as bloating, gas, and diarrhea after consuming milk or dairy products.
- This occurs because undigested lactose reaches the large intestine, where it is fermented by bacteria, leading to the production of gas and other byproducts.

In conclusion, lactose is called milk sugar because it is the main carbohydrate found in milk. It consists of glucose and galactose linked together by a β-glycosidic bond. Lactose provides energy for infants and is digested by the enzyme lactase. Lactose intolerance can occur when there is a reduced ability to produce lactase, leading to digestive symptoms after consuming milk or dairy products.