Carbohydrates Questions in English

(B) Starch is a polysaccharide that serves as the primary storage carbohydrate in plants. It is composed of two distinct glucose polymers: $1$. Amylose,which is a linear,unbranched chain of $\alpha-D$-glucose units linked by $\alpha-1,4$-glycosidic bonds. $2$. Amylopectin,which is a branched chain of $\alpha-D$-glucose units containing both $\alpha-1,4$-glycosidic bonds and $\alpha-1,6$-glycosidic bonds at the branch points. Therefore,both amylose and amylopectin are components of starch.

(A) Cellulose is a polysaccharide composed of a linear chain of several hundred to many thousands of $\beta-D-glucose$ units.
These glucose units are linked together by $\beta-1,4-glycosidic$ bonds.
Unlike starch (which contains amylopectin that is branched),cellulose is a strictly unbranched,linear polymer.
Therefore,the correct description is $\beta-1,4$ linkage and unbranched structure.

(B) Fructose is a naturally occurring monosaccharide found in many fruits,vegetables,and honey. It is known to be the sweetest among all naturally occurring carbohydrates,being significantly sweeter than glucose and sucrose.

(A) Glycogen is a polysaccharide that serves as the primary form of energy storage in animals.
It is synthesized and stored primarily in the liver and skeletal muscle cells.
In the liver,it helps maintain blood glucose levels,while in the muscles,it provides a ready source of energy for muscle contraction.

(C) Cellulose is a complex carbohydrate known as a polysaccharide.
It is a linear polymer of $D$-glucose units linked by $\beta-1,4$-glycosidic bonds.
It serves as the primary structural component of the plant cell wall,providing rigidity and strength to the cell.

(C) levorotatory sugar is one that rotates plane-polarized light to the left (anti-clockwise).
Fructose ($D-(-)$-fructose) is a naturally occurring levorotatory sugar,which is why it is also known as 'levulose'.
Glucose is dextrorotatory ($D-(+)$-glucose).
Sucrose itself is dextrorotatory,but the mixture obtained from its hydrolysis (invert sugar) is levorotatory.
Therefore,the correct answer is Fructose.

(B) Carbohydrates,specifically disaccharides and polysaccharides,are formed by the linkage of monosaccharide units.
These monosaccharide units are joined together by a covalent bond known as a glycosidic bond.
$A$ glycosidic bond is formed between the anomeric carbon of one sugar molecule and a hydroxyl group of another sugar molecule through a dehydration synthesis reaction (loss of a water molecule).
Therefore,the correct option is $B$.

(C) Lactose is a disaccharide sugar composed of galactose and glucose subunits. It is commonly known as 'milk sugar' because it is found in the milk of mammals. Therefore,it is the sugar characteristically found in mammals.

(A) Monosaccharides are the simplest form of carbohydrates that cannot be hydrolyzed into smaller carbohydrate units.
$Glucose$ $(C_6H_{12}O_6)$ is a classic example of a monosaccharide (a hexose sugar).
$Maltose$ and $Sucrose$ are disaccharides, which consist of two monosaccharide units linked together.
$Raffinose$ is a trisaccharide.
Therefore, the correct option is $A$.

(B) When an individual is starving,the body first utilizes the readily available stored carbohydrates to maintain blood glucose levels and energy requirements.
Glycogen is the primary storage form of glucose in animals,stored mainly in the liver and skeletal muscles.
Once glycogen stores are depleted,the body proceeds to utilize stored fats (lipids) and eventually proteins as energy sources.
Therefore,glycogen is the first substrate to be consumed during starvation.

(A) Carbohydrates are the primary and most readily available source of energy for the human body. During cellular respiration,glucose (a simple carbohydrate) is broken down through glycolysis and the Krebs cycle to produce $ATP$ (Adenosine Triphosphate),which is the energy currency of the cell. While fats provide more energy per gram,they take longer to metabolize compared to carbohydrates,making carbohydrates the preferred choice for immediate energy.

(D) The Benedict's test is used to detect the presence of reducing sugars.
Reducing sugars contain a free aldehyde or ketone group that can act as a reducing agent.
Glucose,maltose,and fructose are all reducing sugars because they possess a free anomeric carbon.
Sucrose is a non-reducing sugar because its anomeric carbons are involved in the glycosidic bond between glucose and fructose,leaving no free aldehyde or ketone group available to reduce the Benedict's reagent.
Therefore,sucrose does not give a positive Benedict's test.

(D) Monosaccharides are the simplest form of carbohydrates that cannot be further hydrolyzed into smaller sugar units.
They are classified based on the number of carbon atoms they contain.
$1$. Pentose sugars (e.g.,Ribose,Deoxyribose) contain $5$ carbon atoms.
$2$. Hexose sugars (e.g.,Glucose,Fructose,Galactose) contain $6$ carbon atoms.
Since both Pentose sugars and Hexose sugars (including Glucose) are types of monosaccharides,the correct answer is 'All of the above'.

(B) Fructose is a monosaccharide and is known as the sweetest naturally occurring sugar. It is found in many fruits and is often referred to as fruit sugar. Its sweetness is significantly higher than that of glucose and sucrose.

(B) Glycogen is a polysaccharide that serves as a form of energy storage in animals and fungi.
It is a homopolymer of glucose,meaning it is composed entirely of glucose units,not a co-polymer of glucose and mannose.
Structurally,it consists of a long chain of glucose units linked by $\alpha-1, 4$-glycosidic bonds.
Branching occurs due to $\alpha-1, 6$-glycosidic bonds,typically appearing every $8$ to $12$ glucose units.
Therefore,the statement that it is a co-polymer of glucose and mannose is incorrect.

(B) non-reducing sugar is a carbohydrate that cannot act as a reducing agent because it lacks a free aldehyde or ketone group.
In $Sucrose$,the glycosidic bond is formed between the $C1$ of glucose and the $C2$ of fructose.
Since both the anomeric carbons (the carbons involved in the glycosidic linkage) are involved in the bond,there is no free aldehyde or ketone group available to reduce Benedict's or Fehling's reagent.
Therefore,$Sucrose$ is a non-reducing sugar,while $Glucose$,$Maltose$,and $Galactose$ are all reducing sugars.

(B) In animals,excess glucose is converted into a complex polysaccharide called glycogen for storage.
Glycogen is primarily stored in the liver and muscle cells.
It serves as a readily available energy reserve that can be broken down into glucose when the body requires energy.
Glucose is the immediate fuel,cellulose is a structural carbohydrate in plants,and $ATP$ is the energy currency of the cell,not a storage form.

(C) The question asks for a polysaccharide that provides maximum energy per unit volume.
$1$. Polysaccharides like $Starch$ and $Glycogen$ are storage carbohydrates.
$2$. However, $Lipids$ (fats) are not polysaccharides; they are macromolecules that provide more than twice the energy per unit mass compared to carbohydrates.
$3$. Among the given options, $Glycogen$ is the primary storage polysaccharide in animals, while $Starch$ is the primary storage polysaccharide in plants.
$4$. If the question strictly implies a polysaccharide, $Glycogen$ is the most compact form of energy storage in animals.
$5$. Note: If the question intended to compare energy density across all biomolecules, $Lipids$ would be the answer, but since the question specifies 'polysaccharide', $Glycogen$ is the correct biological answer.

(A) Polysaccharides are long-chain carbohydrates composed of many monosaccharide units linked together by glycosidic bonds.
$1$. Starch,glycogen,and cellulose are all examples of polysaccharides,which are polymers of glucose.
$2$. Sucrose is a disaccharide,which is composed of two monosaccharide units: one molecule of glucose and one molecule of fructose.
$3$. Therefore,sucrose is not a polysaccharide.

(C) Cellulose is a complex carbohydrate consisting of a linear chain of several hundred to many thousands of $\beta(1 \rightarrow 4)$ linked $D$-glucose units.
It is a structural polysaccharide found in the cell walls of plants.
Since it is composed of many monosaccharide units linked together,it is classified as a polysaccharide.

(A) Starch is a polysaccharide composed of a large number of glucose units linked together by glycosidic bonds.
During the formation of starch from glucose $(C_6H_{12}O_6)$,water molecules are removed during the polymerization process.
The general formula for a polysaccharide formed from hexose sugars like glucose is $(C_6H_{10}O_5)_n$,where $n$ represents the number of glucose units.
Therefore,the correct chemical formula for starch is $(C_6H_{10}O_5)_n$.

(B) In animals,carbohydrates are stored in the form of glycogen. Specifically,in the human body,glycogen is stored primarily in the liver and skeletal muscles. When the body requires energy,this stored glycogen is broken down into glucose through the process of glycogenolysis to provide fuel for muscle contraction and other metabolic activities. Therefore,the correct answer is $Glycogen$.

(C) The primary sugar found in the hemolymph of insects is $Trehalose$.
$Trehalose$ is a non-reducing disaccharide consisting of two glucose molecules linked by an $\alpha, \alpha-1,1-glycosidic$ bond.
It serves as a major energy source and a protectant against environmental stress in insects.

(A) $1$. Maltose is a disaccharide composed of two glucose units linked by an $\alpha-1,4$-glycosidic bond.
$2$. Upon hydrolysis,maltose breaks down into two molecules of glucose $(C_{12}H_{22}O_{11} + H_2O \rightarrow 2C_6H_{12}O_6)$.
$3$. Sucrose is a disaccharide that yields one molecule of glucose and one molecule of fructose upon hydrolysis.
$4$. Lactose is a disaccharide that yields one molecule of glucose and one molecule of galactose upon hydrolysis.
$5$. Therefore,the correct answer is Maltose.

(A) Sucrose is a disaccharide,which is a type of carbohydrate formed by the condensation of two monosaccharides.
Specifically,one molecule of sucrose is formed by the glycosidic linkage between one molecule of $D-glucose$ and one molecule of $D-fructose$.

(A) non-reducing sugar is a carbohydrate that cannot act as a reducing agent because it lacks a free aldehyde or ketone group.
In $Sucrose$,the glycosidic bond is formed between the $C1$ of glucose and the $C2$ of fructose.
Since both the anomeric carbons are involved in the glycosidic linkage,there is no free aldehyde or ketone group available.
Therefore,$Sucrose$ is a non-reducing sugar.
In contrast,$Glucose$,$Fructose$,and $Galactose$ are monosaccharides that possess free anomeric carbons,making them reducing sugars.

(A) In carbohydrates,monosaccharide units are linked together by a covalent bond known as a glycosidic bond.
This bond is formed by a dehydration reaction (loss of a water molecule) between the hydroxyl group of one sugar and the hydroxyl group of another sugar.
Therefore,the correct option is $A$.

(B) Saccharin is an artificial sweetener that is approximately $300-400$ times sweeter than sucrose (table sugar). Despite its intense sweetness,it is not a carbohydrate (sugar) and does not provide calories to the body. Therefore,it is commonly used as a sugar substitute.

(C) Raffinose is a trisaccharide with the chemical formula $C_{18}H_{32}O_{16}$.
It is composed of three monosaccharide units: galactose,glucose,and fructose.
These units are linked together by glycosidic bonds.
Therefore,it is classified as a trisaccharide.

(D) In mammals,carbohydrates are stored as glycogen,which is a polysaccharide. The primary storage sites for glycogen are the liver and skeletal muscles. The liver stores glycogen to maintain blood glucose levels,while muscles store it to provide energy for muscle contraction.

(A) Carbohydrates are primarily produced by photosynthetic organisms through the process of photosynthesis.
These organisms include green plants,algae,and certain types of bacteria (such as cyanobacteria) that possess chlorophyll or other photosynthetic pigments.
Fungi and viruses are heterotrophic or parasitic and do not perform photosynthesis to produce their own carbohydrates.
Therefore,the correct group is some bacteria,algae,and green plant cells.

(C) hexose is a monosaccharide with six carbon atoms,having the chemical formula $C_6H_{12}O_6$.
Mannose and galactose are both isomers of glucose and are classified as aldohexoses because they contain six carbon atoms and an aldehyde group.
Cellulose is a polysaccharide,not a monosaccharide.
Therefore,both mannose and galactose are hexose sugars.

(D) Glucose is a monosaccharide,which is the simplest form of carbohydrate.
Monosaccharides cannot be further hydrolyzed into simpler sugar units.
Therefore,glucose does not undergo hydrolysis to yield other sugar units like erythrose,ribose,or mannose.
Thus,the correct answer is $D$.

(D) Glycogen is a polysaccharide that serves as the primary form of energy storage in animals and fungi. It is a branched polymer composed of many glucose units linked together by $\alpha-1,4$ and $\alpha-1,6$ glycosidic bonds. Therefore,it is a polymer of glucose.

(A) 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 $(C_{12}H_{22}O_{11} + H_2O \rightarrow 2C_6H_{12}O_6)$.
Lactose,on the other hand,hydrolyzes into glucose and galactose.
Sucrose hydrolyzes into glucose and fructose.
Therefore,the correct option is $A$.

(C) Carbohydrates are chemically defined as polyhydroxy aldehydes or polyhydroxy ketones,or substances that yield these compounds on hydrolysis.
They are the primary source of energy in living organisms and are composed of carbon,hydrogen,and oxygen atoms.

(C) Cellulose is a complex carbohydrate composed of a long chain of $D$-glucose units linked by $\beta-1,4$-glycosidic bonds.
Since it consists of many monosaccharide units linked together,it is classified as a polysaccharide.
It is the most abundant organic molecule in the plant kingdom and serves as a structural component of the plant cell wall.

(C) The primary sugar present in the hemolymph (blood) of insects is $Trehalose$.
$Trehalose$ is a non-reducing disaccharide consisting of two glucose molecules linked by an $\alpha, \alpha-1,1$-glycosidic bond.
It serves as a major energy source and a protectant against environmental stress in insects.

(A) Glucose is a simple sugar with the molecular formula $C_6H_{12}O_6$.
It is commonly known as 'Grape sugar' because it was first isolated from grapes.
Cane sugar is the common name for sucrose,while fructose and galactose are other types of monosaccharides.

(D) In mammals,excess glucose is converted into glycogen for storage. This process is known as glycogenesis. The primary sites for the storage of glycogen in the mammalian body are the liver and skeletal muscles. The liver stores glycogen to maintain blood glucose levels,while muscles store it to provide energy for muscle contraction.

(C) In the human body,excess glucose is converted into a complex carbohydrate called glycogen for storage.
This process is known as glycogenesis.
Glycogen is a polysaccharide,which serves as the primary storage form of glucose in animals,mainly found in the liver and skeletal muscles.
Therefore,the correct option is $C$.

(C) Polysaccharides are long-chain carbohydrates composed of many monosaccharide units linked together by glycosidic bonds.
$A$. Sucrose is a disaccharide composed of glucose and fructose.
$B$. Lactose is a disaccharide composed of glucose and galactose.
$C$. Glycogen is a polysaccharide,which serves as the primary storage form of glucose in animals.
$D$. Glucose is a monosaccharide.
Therefore,the correct answer is $C$.

(B) $ATP$ stands for Adenosine Triphosphate.
It consists of an adenine base,a ribose sugar,and three phosphate groups.
Therefore,the sugar present in $ATP$ is ribose.

(C) Honey is primarily composed of sugars,water,and small amounts of other substances. The main sugars present in honey are glucose and fructose (also known as levulose). Maltose is also present in trace amounts as a product of starch digestion by bees. Lactose,which is a disaccharide found in milk,is not present in honey.

(B) $Deoxyribose$ is a pentose sugar,which means it contains $5$ carbon atoms in its molecular structure. Its chemical formula is $C_5H_{10}O_4$. Therefore,the correct number of carbon atoms is $5$.

(B) Sugars are classified based on the number of atoms in their ring structure.
$1$. $A$ $5$-membered ring structure is known as a $Furanose$ ring,which consists of $4$ carbon atoms and $1$ oxygen atom.
$2$. $A$ $6$-membered ring structure is known as a $Pyranose$ ring,which consists of $5$ carbon atoms and $1$ oxygen atom.
$3$. $Dextrorotatory$ and $Levorotatory$ are terms used to describe the optical rotation of light,not the ring size.
Therefore,the correct option is $B$.

(A) Optical isomerism is exhibited by molecules that contain at least one chiral carbon atom (an asymmetric carbon atom bonded to four different groups).
Dihydroxyacetone $(CH_2OH-CO-CH_2OH)$ is the simplest ketose sugar.
In dihydroxyacetone,the central carbon atom is bonded to two identical $-CH_2OH$ groups,meaning it lacks a chiral center.
Therefore,dihydroxyacetone does not exhibit optical isomerism.
All other options (Glyceraldehyde,Erythrose,and Ribose) contain at least one chiral carbon atom and thus exhibit optical isomerism.

(B) Rice is a cereal grain and is a primary source of carbohydrates in the human diet. The major carbohydrate present in rice is $Starch$,which is a polysaccharide composed of glucose units. Therefore,a person who eats rice consumes a significant amount of $Starch$.

(B) Glucose,sucrose,and maltose are all carbohydrates.
Glucose is a monosaccharide,while sucrose and maltose are disaccharides.
Starch is a polysaccharide,which is also a type of carbohydrate.
Myoglobin and hemoglobin are proteins,and amino acids are the building blocks of proteins.
Therefore,starch is the correct answer as it belongs to the same chemical class (carbohydrates) as the others.

(B) In mammals,excess glucose in the blood is converted into glycogen through a process called glycogenesis. This glycogen is primarily stored in the liver and skeletal muscles to be used as an energy reserve when needed. Therefore,the correct form of storage is glycogen in the liver and muscles.