Question

long answer questions
q.1(ex. q. 1) what are carbohydrates? how are monosaccharides prepared? give their characteristics. (board 2016) 10213001
ans: carbohydrates:
carbohydrates are macromolecules defined as polyhydroxy aldehydes or ketones. they have general formula $c_n(h_2o)_n$.
classification of carbohydrates:
carbohydrates are classified as:
i. monosaccharides ii. oligosaccharides iii. polysaccharides
preparation of monosaccharides:
glucose is a monosaccharide which is synthesized by plants through photosynthesis process from carbon dioxide and water in the presence of sunlight and green pigment chlorophyll.
$6co_2 + 6h_2o \xrightarrowchlorophyll{sunlight} c_6h_{12}o_6 + 6o_2$
characteristics: (board 2021)
i- monosaccharides are white crystalline solids.
ii- they are soluble in water.
iii-they have sweet taste.
iv-they cannot be hydrolyzed.
v- they are reducing in nature, therefore, they are called reducing sugars.
q.2 what are monosaccharides? describe with an example. (board 2017) 10213002
ans. introduction:
monosaccharides are the simplest sugars which cannot be hydrolyzed. they consist of 3 to 9 carbon atoms. therefore, they are classified according to the number of carbon atoms in their molecules as trioses, tetroses, pentoses, hexoses, and so on.
example:
the important monosaccharides are hexoses like glucose and fructose, etc. glucose is a pentahydroxy aldehyde while fructose is pentahydroxy ketone having the open chain structures as follows and general formula $c_6h_{12}o_6$.

Explanation:

For Q.1:

Carbohydrates are defined as polyhydroxy aldehydes/ketones with the general formula $\text{C}_n(\text{H}_2\text{O})_n$, classified into monosaccharides, oligosaccharides, and polysaccharides. Monosaccharides like glucose are made by plants via photosynthesis. They have key physical and chemical traits.

For Q.2:

Monosaccharides are the simplest non-hydrolyzable sugars, grouped by their carbon count (3-9 carbons, e.g., trioses, hexoses). Glucose (a pentahydroxy aldehyde) and fructose (a pentahydroxy ketone) are common hexose examples, both with the formula $\text{C}_6\text{H}_{12}\text{O}_6$.

Answer:

Q.1:

1. Carbohydrates: Macromolecules defined as polyhydroxy aldehydes or ketones, with the general formula $\text{C}_n(\text{H}_2\text{O})_n$. They are classified into:

• i. Monosaccharides
• ii. Oligosaccharides
• iii. Polysaccharides

1. Preparation of Monosaccharides:

Plants synthesize the monosaccharide glucose via photosynthesis:
$$6\text{CO}_2 + 6\text{H}_2\text{O} \xrightarrow[\text{Chlorophyll}]{\text{Sunlight}} \text{C}_6\text{H}_{12}\text{O}_6 + 6\text{O}_2$$

1. Characteristics of Monosaccharides:

• i. White crystalline solids
• ii. Soluble in water
• iii. Have a sweet taste
• iv. Cannot be hydrolyzed
• v. Reducing in nature (reducing sugars)

Q.2:

1. Monosaccharides: The simplest form of carbohydrates that cannot be hydrolyzed further. They contain 3 to 9 carbon atoms, and are classified by their carbon count into trioses, tetroses, pentoses, hexoses, etc.
2. Example:

Glucose and fructose are common hexose monosaccharides (both with formula $\text{C}_6\text{H}_{12}\text{O}_6$):

• Glucose is a pentahydroxy aldehyde, with the open-chain structure:

$$\begin{align*} &\text{CHO} \\ &\mid \\ &\text{H}-\text{C}-\text{OH} \\ &\mid \\ &\text{HO}-\text{C}-\text{H} \\ &\mid \\ &\text{H}-\text{C}-\text{OH} \\ &\mid \\ &\text{H}-\text{C}-\text{OH} \\ &\mid \\ &\text{CH}_2\text{OH} \end{align*}$$

• Fructose is a pentahydroxy ketone, with the open-chain structure:

$$\begin{align*} &\text{CH}_2\text{OH} \\ &\mid \\ &\text{C}=\text{O} \\ &\mid \\ &\text{HO}-\text{C}-\text{H} \\ &\mid \\ &\text{H}-\text{C}-\text{OH} \\ &\mid \\ &\text{H}-\text{C}-\text{OH} \\ &\mid \\ &\text{CH}_2\text{OH} \end{align*}$$