Carbohydrates Questions in English

(C) Monosaccharides and disaccharides are generally soluble in water because they are small molecules with many hydroxyl $(-OH)$ groups that can form hydrogen bonds with water.
Polysaccharides,such as starch,cellulose,and glycogen,are large,complex polymers with high molecular weights.
Due to their large size and the way they are packed,they have limited interaction with water molecules,making them insoluble or only sparingly soluble in water.

(A) Starch is a storage polysaccharide in plants and is composed of two components: Amylose and Amylopectin.
Amylose is an unbranched,helical chain of $D$-glucose units linked by $\alpha-1, 4$-glycosidic bonds.
Amylopectin is a branched-chain polysaccharide consisting of $D$-glucose units linked by $\alpha-1, 4$-glycosidic bonds and $\alpha-1, 6$-glycosidic bonds at branch points.
Therefore,the unbranched component of starch is Amylose.

(B) The structure of $RNA$ (Ribonucleic Acid) and $ATP$ (Adenosine Triphosphate) contains a pentose sugar known as ribose.
Ribose is a five-carbon sugar (aldopentose) with the chemical formula $C_5H_{10}O_5$.
Among the given structures,the second option (represented by the image in option $B$) corresponds to the open-chain structure of ribose,which is an aldopentose with hydroxyl groups on the same side for carbons $2, 3,$ and $4$.
Therefore,the correct component found in $RNA$ and $ATP$ is ribose.

(C) glycosidic bond is a type of covalent bond that joins a carbohydrate (sugar) molecule to another group,which may or may not be another carbohydrate.
In the formation of common disaccharides like maltose or lactose,the bond typically forms between the anomeric carbon (the $1^{st}$ carbon) of one monosaccharide and the $4^{th}$ carbon of another monosaccharide.
This is known as a $(1 \rightarrow 4)$ glycosidic linkage.
Therefore,the correct option is $C$.

(C) Carbohydrates are classified based on their hydrolysis and sweetness.
Monosaccharides (e.g.,glucose,fructose) and disaccharides (e.g.,sucrose,lactose) are generally sweet in taste and are often called 'sugars'.
Polysaccharides (e.g.,starch,cellulose,glycogen) are complex carbohydrates consisting of long chains of monosaccharide units.
Due to their high molecular weight and complex structure,they are insoluble in water and are not sweet in taste.
Therefore,the correct answer is $C$.

(A) Ketose sugars are monosaccharides that contain a ketone functional group. The general structure of a ketone group is a carbonyl group $(>C=O)$ bonded to two carbon atoms. In contrast,aldose sugars contain an aldehyde group $(-CHO)$. Therefore,the functional group present in ketose sugars is the carbonyl group represented by $>C=O$.

(B) Sucrose is a disaccharide composed of two monosaccharide units: glucose and fructose.
When sucrose undergoes hydrolysis, the glycosidic bond between these two units is broken by the addition of a water molecule.
This reaction is typically catalyzed by the enzyme sucrase or invertase.
The chemical equation for the hydrolysis is: $C_{12}H_{22}O_{11} + H_2O \rightarrow C_6H_{12}O_6$ (Glucose) + $C_6H_{12}O_6$ (Fructose).
Therefore, the hydrolysis of sucrose yields one molecule of glucose and one molecule of fructose.

(D) Polysaccharides are long-chain polymers of monosaccharides linked by glycosidic bonds.
Most common polysaccharides,such as starch,cellulose,and glycogen,are polymers of glucose $(C_6H_{12}O_6)$.
During the formation of a polysaccharide,each glycosidic linkage involves the removal of a water molecule $(H_2O)$ between two monosaccharide units.
The general formula for a monosaccharide is $(CH_2O)_n$,but for a polymer formed by dehydration synthesis,the formula is $(C_6H_{10}O_5)_n$,where $n$ represents the number of repeating units.

(B) triose sugar is a monosaccharide containing three carbon atoms.
The general formula for carbohydrates is $(CH_2O)_n$,where $n$ represents the number of carbon atoms.
For a triose sugar,$n = 3$.
Substituting $n = 3$ into the general formula: $C_3(H_2O)_3 = C_3H_6O_3$.
Therefore,the correct formula for a triose sugar is $C_3H_6O_3$.

(C) $PGAL$ stands for Phosphoglyceraldehyde,which is a $3$-carbon sugar.
It contains an aldehyde group at the first carbon position.
Since it has $3$ carbon atoms and an aldehyde functional group,it is classified as an aldotriose sugar.
Therefore,the correct option is $C$.

(A) Lactose is a disaccharide sugar composed of two monosaccharide units: $Glucose$ and $Galactose$.
It is commonly known as milk sugar and is linked by a $\beta-1,4-glycosidic$ bond.

(C) Glyceraldehyde is a simple sugar with the chemical formula $C_3H_6O_3$.
It contains $3$ carbon atoms in its structure.
Sugars with $3$ carbon atoms are classified as trioses.
Therefore,glyceraldehyde is a triose sugar.

(C) $Maltose$ is a disaccharide composed of two $Glucose$ units linked by an $\alpha-1,4-glycosidic$ bond.
Upon hydrolysis,$Maltose$ breaks down into two molecules of $Glucose$ $(C_6H_{12}O_6)$.
The chemical reaction is: $C_{12}H_{22}O_{11} + H_2O \rightarrow 2C_6H_{12}O_6$.

(C) Chitin is a complex carbohydrate,specifically a nitrogen-containing polysaccharide.
It is a polymer of $N$-acetylglucosamine units.
It serves as a structural component in the cell walls of fungi and the exoskeletons of arthropods like insects and crustaceans.
Therefore,it is classified as a polysaccharide.

(D) Carbohydrates are organic compounds composed of carbon $(C)$,hydrogen $(H)$,and oxygen $(O)$.
The general empirical formula for carbohydrates is $(CH_2O)_n$.
Nitrogen $(N)$ is typically found in proteins and nucleic acids,but it is not a constituent element of basic carbohydrate molecules.
Therefore,the correct option is $D$.

(C) Carbohydrates are classified based on the number of sugar units they contain into monosaccharides,disaccharides,and polysaccharides.
$A$. Monosaccharides are simple sugars.
$B$. Disaccharides consist of two sugar units.
$D$. Polysaccharides are complex carbohydrates consisting of many sugar units.
$C$. Polypeptides are chains of amino acids linked by peptide bonds,which are the building blocks of proteins,not carbohydrates.

(A) Carbohydrates are classified based on the number of sugar units they contain.
Monosaccharides are the simplest form of carbohydrates,consisting of a single sugar unit that cannot be further hydrolyzed into simpler sugars.
Examples include glucose,fructose,and galactose.
Disaccharides are composed of two monosaccharide units,while fatty acids are lipids and nucleotides are the building blocks of nucleic acids.

(A) The general formula $C_n(H_2O)_n$ represents the empirical formula for carbohydrates,which were historically referred to as 'hydrates of carbon'.
While this formula is a characteristic feature of many simple carbohydrates,it is most commonly associated with monosaccharides (e.g.,glucose $C_6H_{12}O_6$ where $n=6$).
However,in the context of general classification,this formula is the defining empirical representation for the class of carbohydrates.

(D) Monosaccharides are the simplest carbohydrates that cannot be further hydrolyzed into smaller sugar units.
Chemically,they are polyhydroxy aldehydes or polyhydroxy ketones.
If the monosaccharide contains an aldehyde group $( -CHO )$,it is called an aldose (e.g.,glucose).
If the monosaccharide contains a ketone group $( >C=O )$,it is called a ketose (e.g.,fructose).
Therefore,both aldehyde and ketone functional groups can be present in monosaccharides.

(C) Monosaccharides are classified based on the functional group they contain.
If a monosaccharide contains an aldehyde group $(-CHO)$,it is known as an aldose sugar.
If a monosaccharide contains a ketone group $(>C=O)$,it is known as a ketose sugar.
Therefore,a monosaccharide with a $-CHO$ group is called an aldose sugar.

(A) Monosaccharides are classified based on the type of carbonyl group present in their structure.
If the carbonyl group is an aldehyde group $(-CHO)$,the sugar is called an aldose sugar.
If the carbonyl group is a ketone group $(C=O)$,the sugar is called a ketose sugar.
Therefore,a monosaccharide containing a $C=O$ functional group is known as a ketose sugar.

(D) Monosaccharides are the simplest form of carbohydrates and cannot be further hydrolyzed into smaller sugar units.
Option $D$ states that they undergo hydrolysis to form simpler forms,which is incorrect because they are already in their simplest form.
Monosaccharides are generally water-soluble and,due to their small size,can often pass through cell membranes.

(C) Monosaccharides are the simplest form of carbohydrates. They consist of a single sugar unit and cannot be hydrolyzed further into smaller sugar molecules. Disaccharides and polysaccharides are complex carbohydrates that can be broken down into monosaccharides through the process of hydrolysis.

(D) Monosaccharides are the simplest carbohydrates that cannot be hydrolyzed further into smaller sugar units.
They are classified based on the number of carbon atoms present in their structure.
For example,a monosaccharide with $3$ carbon atoms is called a triose,with $4$ carbons is a tetrose,with $5$ carbons is a pentose,and with $6$ carbons is a hexose.

(B) Monosaccharides are the simplest form of carbohydrates.
Biologically,$5$-carbon sugars known as pentoses are of immense importance.
Examples include ribose,which is a key component of $RNA$,and deoxyribose,which is a key component of $DNA$.
These sugars form the backbone of nucleic acids,which are essential for genetic information storage and transfer.
Therefore,pentose is the correct answer.

(C) Monosaccharides are the simplest form of carbohydrates that cannot be further hydrolyzed into smaller sugar units.
Examples include glucose,fructose,and galactose,which are all hexoses $(C_6H_{12}O_6)$.
Maltose and sucrose are disaccharides,while cellulose is a polysaccharide.
Therefore,hexose is the correct category representing a monosaccharide.

(C) triose sugar is a monosaccharide containing three carbon atoms.
The general formula for carbohydrates is $(CH_2O)_n$,where $n$ represents the number of carbon atoms.
For a triose sugar,$n = 3$.
Substituting $n = 3$ into the formula,we get $C_3(H_2O)_3$,which simplifies to $C_3H_6O_3$.
Therefore,$C_3H_6O_3$ is the molecular formula for a triose sugar.

(D) The molecular formula $C_6H_{12}O_6$ represents a sugar with $6$ carbon atoms.
Sugars are classified based on the number of carbon atoms present in their molecule.
- Triose: $3$ carbon atoms $(C_3H_6O_3)$
- Pentose: $5$ carbon atoms $(C_5H_{10}O_5)$
- Hexose: $6$ carbon atoms $(C_6H_{12}O_6)$
- Heptose: $7$ carbon atoms $(C_7H_{14}O_7)$
Therefore,$C_6H_{12}O_6$ is a hexose sugar,such as glucose or fructose.

(A) triose sugar is a monosaccharide containing three carbon atoms.
$Glyceraldehyde$ is a triose sugar with the chemical formula $C_3H_6O_3$.
$Fructose$ and $Galactose$ are hexose sugars $(C_6H_{12}O_6)$,while $Ribose$ is a pentose sugar $(C_5H_{10}O_5)$.

(C) An aldose sugar is a monosaccharide that contains an aldehyde group $(-CHO)$ at the end of the carbon chain.
Among the given options:
$1$. Dihydroxyacetone is a ketose sugar (contains a ketone group).
$2$. Ribulose is a ketose sugar.
$3$. Ribose is an aldose sugar (contains an aldehyde group).
$4$. Fructose is a ketose sugar.
Therefore,Ribose is the correct answer.

(D) ketose sugar is a monosaccharide containing one ketone group per molecule.
Among the given options:
$1$. Glyceraldehyde is an aldotriose (contains an aldehyde group).
$2$. Ribose is an aldopentose (contains an aldehyde group).
$3$. Galactose is an aldohexose (contains an aldehyde group).
$4$. Dihydroxyacetone is a ketotriose (contains a ketone group).
Therefore,Dihydroxyacetone is the correct example of a ketose sugar.

(A) Ribulose is a ketopentose sugar,which means it contains $5$ carbon atoms and a ketone functional group.
Since it has $5$ carbon atoms,it is classified as a pentose sugar.
It plays a crucial role in the Calvin cycle as the acceptor of $CO_2$ in the form of Ribulose-$1,5$-bisphosphate $(RuBP)$.

(A) hexose sugar is a monosaccharide containing $6$ carbon atoms,with the general chemical formula $C_6H_{12}O_6$.
Glucose,Fructose,and Galactose are all examples of hexose sugars.
Ribulose is a ketopentose sugar,which contains $5$ carbon atoms and has the chemical formula $C_5H_{10}O_5$.
Therefore,Ribulose is not a hexose sugar.

(B) ketohexose is a monosaccharide containing six carbon atoms and a ketone group.
Glucose and Galactose are aldohexoses (containing an aldehyde group).
Ribulose is a ketopentose (containing five carbon atoms).
Fructose is a ketohexose with the chemical formula $C_6H_{12}O_6$ and contains a ketone functional group at the $C-2$ position.

(C) Fructose is a simple monosaccharide found in many plants,where it is often bonded to glucose to form the disaccharide sucrose. It is commonly known as 'fruit sugar' because it is the primary sugar found in most fruits and fruit juices.

(D) An aldohexose is a $6$-carbon sugar containing an aldehyde group $(-CHO)$.
Glucose $(C_6H_{12}O_6)$ is an aldohexose because it has an aldehyde group at the $C_1$ position.
Galactose $(C_6H_{12}O_6)$ is also an aldohexose and is an epimer of glucose at the $C_4$ position.
Fructose $(C_6H_{12}O_6)$ is a ketohexose because it contains a ketone group $(>C=O)$ at the $C_2$ position.
Therefore,both glucose and galactose are aldohexoses.

(C) Disaccharides are carbohydrates formed by the condensation of two monosaccharide units through a glycosidic bond.
Common examples of disaccharides include sucrose,lactose,and maltose.
Sucrose is composed of glucose and fructose,while lactose is composed of glucose and galactose,and maltose is composed of two glucose units.
Glucose,fructose,and galactose are all $6$-carbon sugars,which are classified as hexoses.
Therefore,hexose monosaccharides are typically involved in the formation of disaccharides.

(B) The plasma membrane is selectively permeable. Monosaccharides like $Glucose$,$Galactose$,and $Fructose$ are small molecules that can pass through the plasma membrane via facilitated diffusion or active transport using specific transporters. However,$Maltose$ is a disaccharide (composed of two glucose units) and is too large to pass through the plasma membrane directly without being hydrolyzed into monosaccharides by enzymes like maltase located on the intestinal brush border.

(B) Sucrose is a disaccharide composed of two monosaccharide units: glucose and fructose.
Upon hydrolysis, the glycosidic bond between these two units is broken by the addition of a water molecule.
This reaction is represented as: $C_{12}H_{22}O_{11} + H_2O \rightarrow C_6H_{12}O_6$ (Glucose) + $C_6H_{12}O_6$ (Fructose).
Therefore, the hydrolysis of sucrose yields one molecule of glucose and one molecule of fructose.

(B) Lactose is a disaccharide formed by the condensation reaction between one molecule of $D-glucose$ and one molecule of $D-galactose$. This reaction involves the formation of a $\beta-1,4-glycosidic$ linkage between the two monosaccharides. Sucrose is formed from glucose and fructose,while maltose is formed from two molecules of glucose.

(C) Monosaccharides are the simplest form of carbohydrates.
When a large number of monosaccharide units are linked together by glycosidic bonds,they form complex carbohydrates known as polysaccharides.
Examples of polysaccharides include starch,glycogen,and cellulose.
Disaccharides are formed by the linkage of only two monosaccharide units.
Polypeptides are chains of amino acids linked by peptide bonds.
Polynucleotides are chains of nucleotides linked by phosphodiester bonds.

(D) Polysaccharides are complex carbohydrates formed by the polymerization of many monosaccharide units.
$1$. They are not sweet in taste (unlike monosaccharides and disaccharides).
$2$. They are complex polymers,not simple carbohydrates.
$3$. Due to their large molecular size,they cannot easily pass through the cell membrane.
$4$. They are generally insoluble in water because of their high molecular weight and complex structure.

(B) polysaccharide is a long chain of monosaccharide units linked by glycosidic bonds.
$1$. Cellulose is a structural polysaccharide found in plant cell walls.
$2$. Glycogen is a storage polysaccharide found in animals.
$3$. Maltose is a disaccharide composed of two glucose units.
$4$. Lignin is a complex organic polymer deposited in the cell walls of many plants,but it is not a carbohydrate (polysaccharide).
Therefore,both Maltose and Lignin are not polysaccharides,but in the context of typical biology questions regarding carbohydrates,Maltose is a disaccharide and Lignin is a non-carbohydrate polymer. Given the options,Maltose is a disaccharide and Lignin is a complex polymer. However,Maltose is the most common answer for 'not a polysaccharide' in carbohydrate classification questions.

(A) Starch is a polysaccharide composed of two types of glucose polymers: Amylose and Amylopectin.
Amylose is a linear,unbranched chain of $\alpha$-$D$-glucose units linked by $\alpha(1\to4)$ glycosidic bonds.
Amylopectin is a branched-chain polymer of $\alpha$-$D$-glucose units containing both $\alpha(1\to4)$ and $\alpha(1\to6)$ glycosidic linkages.
Therefore,the unbranched component of starch is Amylose.

(B) Starch is a storage polysaccharide in plants and is composed of two components: Amylose and Amylopectin.
Amylose is a linear,unbranched polymer of $\alpha$-$D$-glucose units linked by $\alpha(1 \rightarrow 4)$ glycosidic bonds.
Amylopectin is a branched polymer of $\alpha$-$D$-glucose units,containing both $\alpha(1 \rightarrow 4)$ and $\alpha(1 \rightarrow 6)$ glycosidic bonds.
Therefore,Amylopectin is the branched polysaccharide chain of glucose.

(C) Plants synthesize glucose during photosynthesis. Since glucose is soluble and reactive,it is converted into a complex polysaccharide called $Starch$ for storage. $Starch$ is the primary storage carbohydrate in plants,typically stored in amyloplasts within cells. In contrast,animals store energy in the form of $Glycogen$.

(B) Starch is a polysaccharide that is composed of two types of glucose polymers: amylose and amylopectin.
Amylose is a linear,unbranched chain of $\alpha-D-glucose$ units linked by $\alpha-1,4-glycosidic$ bonds.
Since amylose is a major component of starch,starch is the correct answer among the given options.

(C) In animals,carbohydrates are stored in the form of $Glycogen$.
$Glycogen$ is a multi-branched polysaccharide of glucose that serves as a form of energy storage in animals,fungi,and bacteria.
$Starch$ is the storage form of carbohydrates in plants.
$Cellulose$ is a structural polysaccharide found in plant cell walls.
$Lignin$ is a complex organic polymer deposited in the cell walls of many plants,making them rigid and woody.

(B) Carbohydrates are the primary and most readily available source of energy for living organisms.
They are broken down into glucose,which is then used in cellular respiration to produce $ATP$ (Adenosine Triphosphate),the energy currency of the cell.
While lipids provide more energy per gram,carbohydrates are preferred for immediate energy requirements.

(D) glycolipid is a lipid molecule that has a carbohydrate chain attached to it.
These molecules are essential components of cell membranes,where the carbohydrate portion extends into the extracellular space to facilitate cell-cell recognition and communication.
Unlike phospholipids,which contain a phosphate group,glycolipids contain a sugar or carbohydrate moiety as their non-lipid component.