Carbohydrates - definition and classification - class-XII

Cellulose is a type of carbohydrate, containing chains of glucose rings. The cell walls, which are responsible for providing support and rigidity to the plants are made of cellulose. 

Carbohydrates undergo dehydration in the presence of sulphuric acid, giving aldehyde as a product which undergoes condensation in the presence of Molisch reagent ($\alpha-napthanol $ dissolved in ethanol) to give a purple colored compound. This forms the basis of Molisch test to detect carbohydrates. Since glucose, raffinose, and deoxyribose are all carbohydrates, they can be identified using Molisch reagent

Fehling's solution is used to distinguish between reducing sugars (like glucose) and non-reducing sugars (like sucrose/cane sugar). Glucose will give a positive test (red precipitate), while sucrose will not.

The two forms of D-glucopyranose (alpha and beta) differ only in the configuration at the anomeric carbon (C1). Such isomers are specifically called anomers.

Glucose is a dextrorotatory sugar (rotates plane-polarized light to the right) and is commonly found in fruits, often referred to as grape sugar.

Ribose and deoxyribose sugars commonly exist in furanose form in nucleic acids. Fructose, also known as fruit sugar, exists in furanose form in its cyclic structure.

Lactose $=$ Glycosidic bond $[1,4]$ between glucose and galactose 

Carbohydrates are used by body mainly as a source of energy. 

Sucrose, glucose and fructose all are sugars. Glucose and fructose are monosaccharides and sucrose is a disaccharide of the two combined with a bond. Glucose and fructose have the same molecular formula $(C _6H _{12}O _6)$ but glucose has a six member ring and fructose has a five member ring structure. Fructose is known as the fruit sugar as its source in the diet is fruits and vegetables. Honey is also a good source. Glucose is known as grape sugar, blood sugar or corn sugar as these are its richest sources. Sucrose is the sugar we know as sugar or table sugar. Typically extracted as cane or beet sugar. If sucrose is treated with acid or heat, it hydrolyses to form glucose and fructose. This mixture of sucrose, glucose and fructose is also called invert sugar.

Glucose is a source of instant energy because it is quick to act to create energy along with oxygen so our body does not need to convert the glucose to anything else. It also can be absorbed through the lining of the stomach.

Any carbohydrate will give water and $CO _2$ after combustion.

(A) carbon

Transition state is intermediate state produced during enzymatic biochemical reaction which is transition state and unstable state

$Glucose\underrightarrow { Zymase } Ethanal$
Zymase converts glucose to ethanal

Photosynthesis is the process by which plants utilize the energy from the sunlight in order to convert carbon dioxide and water into carbohydrates.

Formula of glucose is $C _6H _{12}O _6$ it is derived from the reaction of photosynthesis that is :

Sodium chloride, sodium bromide, and sodium acetate are all ionic compounds and hence, they dissociate into their respective ions in an aqueous solution. On the contrary, sugar is a covalent compound and hence does not dissociate into ions

Carbohydrates are polyhydroxy aldehydes or polyhydroxy ketones OR compounds which give aldehydic as well as ketonic groups on hydrolysis. Therefore the major functional groups are (carbonyl) Aldehyde, Ketone, and hydroxy groups. 

2 M glucose has a higher boiling point than 1 M of glucose.

$\rightarrow$ Carbohydrates are important source of instant energy in our body system.
$\rightarrow$ Honey has been used as instant source of enrgy in ayurvedic medicines.
$\rightarrow$ Carbohydrates are used as storage starch in plants and glycogen
$\rightarrow$ carbohydrates are also used in textile industry.

Invert sugar is a sucrose, partially or totally cleaved into fructose and glucose. Sucrose is converted into  invert sugar by chemical reaction called hydrolysis by heating a mixture or solution of table sugar.

Molisch test is a test for carbohydrate or compounds which can be dehydrated to furfural or furfural derivatives in the presence of the concentrated sulphuric acid .

Alpha and beta D-glucose are anomers, which are a type of stereoisomer that differ specifically in the configuration at the anomeric carbon (C-1).

Starch contains acetal linkages (glycosidic bonds) between glucose units. Acetals are acid-labile and readily hydrolyze by acid. Hemiacetals are more reactive but acetals are stable to base but hydrolyzed by acid, making starch susceptible to acid hydrolysis.

The rate of a chemical reaction is influenced by various factors including temperature, the presence of a catalyst, and the concentration of the reactants.

The dehydration of sucrose (C12H22O11) by concentrated sulfuric acid leaves behind a porous black mass of carbon known as sugar charcoal.

Glycolipids yeild fatty acids, glycerol and carbohydrates on hydrolysis. Monogalactosyldiglycerides are glycolipids which are commonly found in plant leaves and algae. They contain a high proportion of poly unsaturated fatty acids and appear to play a role in photosynthesis.

Carbohydrates are primarily produced by plants and form a very large group of naturally occurring organic compounds. Some common examples are cane sugar, glucose, starch, etc.
The carbohydrates may be defined as optically active polyhydroxy aldehydes or ketones or the compounds which produce such units on hydrolysis.

Biogas is primarily composed of methane (typically 50-75%) and carbon dioxide, produced by the anaerobic digestion of organic matter.

For the reduction of glucose to n-hexane, the reagent used is $HI$.
Glucose is heated with $HI$, n-hexane is obtained which suggests that all the six carbons are linked in a straight chain.

Monosaccharides may contain 3 to 7 carbon atoms. They have chemical formula $(CH _2O) _{n}$, where conventionally $n=3$. Monosaccharides can be classified by the number of carbon atoms they contain: diose(2), triose(3), tetrose(4), pentose(5), hexose(6), heptose(7) and so on.

Raffinose is a trisaccharide and consists of 1 unit of glucose, fructose and galactose each. 

Saccharin, aspartame, dulcin all are synthetic sweetener. They have a sugar-like taste but with less food energy.

Option (A) is right. The incorrect statement is (II).
(II) Lactose is a disaccharide while glucose is an aldosic monosaccharide.

(I) Maltose is also known as malt sugar.

Monosaccharides, disaccharides and oligo saccharides are crystalline solids, water soluble and sweet in taste. They are called sugar.
Thus only statement III is incorrect.

Monosaccharide cannot be hydrolyzed to simpler compounds as it is itself the simplest unit.
Disaccharides, polysaccharides and oligosaccharides can be hydrolyzed to monosaccharides.

Aspartame is artificial sugar so it does not increases the calorie intake it only induces the sweetness.

False-Aidohexoses exist in $2^4(= 16)$ optical forms.

False-On hydrolysis, it gives three molecules of monosaccharide units one each of glucose, fructose and galactose

False-Fructose is more sweeter than glucose

Two-dimensional ascending chromatography has been employed to separate a mixture of monosaccharides.

Monosaccharide is single polyhydroxy aldehyde (aldose) or ketone (ketose) units. Glucose is a single polyhydroxy aldehyde, while fructose is a single polyhydroxy ketone. A monosaccharide contains a skeleton, of carbon atoms. The minimum number of carbon atoms is three and it can go up to seven.

A carbohydrate that cannot be hydrolysed further to give simpler unit of polyhydroxy aldehyde or ketone is called a monosaccharide. Some common examples are glucose, fructose, ribose, etc.
Carbohydrates that yield two to ten monosaccharide units, on hydrolysis, are called oligosaccharides. They are further classified as disaccharides, trisaccharides, tetrasaccharides, etc., depending upon the number of monosaccharides, they provide on hydrolysis. Amongst these the most common are disaccharides. The two monosaccharide units obtained on hydrolysis of a disaccharide may be same or different.

Glucose and fructose are both monosaccharides as they cannot be hydrolysed further to simple sugars.

$Glucose\rightarrow Ethanol$
Zymase enzymes can do above conversion.
(catalyzes fermentation of sugar into ethanol & $CO _2$).

All sugars are compared relative to sucrose on the basis of sweetness. Hence, sucrose is rated one in terms of sweetness. 

Carbohydrates are the biomolecules containing carbon, hydrogen, and oxygen respectively. They are also called hydrates of carbon.

Carbohydrates are polyhydroxy aldehydes or polyhydroxy ketone. Cellulose is a carbohydrate used to make a paper. Carbohydrates are also produced as an intermediate in the synthesis of protein.

Here Glucose, Maltose, and Fructose are carbohydrate. Glycine is not a carbohydrate. It is a protein.

• Polyhydroxy aldehydes or ketones are molecules with more than one hydroxyl group $(−OH)$, and a carbonyl group $(C=O)$ either at the terminal carbon atom (aldose) or at the second carbon atom (ketose) are called carbohydrates.
• Monosaccharides are polyhydroxy aldehydes and are called Simple Sugar, any of the basic compounds that serve as the building blocks of carbohydrates. 
  

$Br _2/H _2O$ being a mild oxidising agent can only oxidise aldose to carboxylic acids but cannot oxidise ketose.

Carbohydrates are polyhydroxy aldehydes or ketones, meaning they contain both hydroxyl (-OH) groups and a carbonyl (>C=O) group (which can be an aldehyde -CHO or a ketone).

 $\alpha$-D glucose has cyclic hemiacetal structure. Hemiacetal on hydrolysis gives free aldehyde group.
Maltose, sucrose and lactose are are disacharides which on hydrolysis gives monosaccharides in which aldehyde group becomes free.
Maltose  $\displaystyle \xrightarrow { \text { hydrolysis} }$ Glucose $\displaystyle + $ glucose.
Sucrose  $\displaystyle \xrightarrow { \text { hydrolysis} }$ Glucose $\displaystyle + $ fructose.
Lactose  $\displaystyle \xrightarrow { \text { hydrolysis} }$ Glucose $\displaystyle + $ galactose.

Colour and appearance are physical properties.
The remaining are chemical properties which include its composition, reaction with sulphuric acid and decomposition.