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UPSEE: Important Questions & Study Notes for Bimolecules

Jan 11, 2018 17:43 IST
    UPSEE/UPTU 2018: Biomolecules
    UPSEE/UPTU 2018: Biomolecules

    As competition is getting tougher day by day, students don’t want to waste their precious time in reading the topics from the book just before any engineering entrance examination. They want to study only the concepts which are very important from the examination point of view.

    To fulfil this need of engineering aspirants we bring the study notes and important previous years’ solved questions of chapter Bimolecules for coming UPSEE/UPTU examination.

    Read about the following topics here:

    1. Definition of Bimolecules

    2. Examples of some common biomolecules like Carbohydrates, Proteins, Lipids, Nucleic acids, ATP molecules

    3. Types of carbohydrates like Monosaccharide, Disaccharides and Polysaccharides

    4. Some important chemical reactions of Monosaccharides  

    UPSEE: Important Questions and Preparation Tips – Solid State

    Important Concepts:

    Bimolecules

    They are the organic molecules that are involved in the maintenance and metabolic processes of living organisms. Thus, they build up the living system and are responsible for their growth and maintenance.

    Some of the common biomolecules are given below:

    •    Carbohydrates

    •    Proteins

    •    Lipids

    •    Nucleic acids

    •    ATP molecules

    Carbohydrates:

    On the basis of hydrolysis, carbohydrates are classified as follows:

    (a) Monosaccharide

    (b) Disaccharides

    (c) Polysaccharides

    Monosaccharide: These are the simpler carbohydrates which cannot be hydrolysed further to its constituent aldehyde or ketone.

    For example glucose,fructose, galactose etc.

    UPSEE Bimolecules Concepts 1

     

    Disaccharides: It is a sugar which can be hydrolysed into two monosaccharides.

    For example sucrose, lactose, maltose.

    UPSEE Bimolecules Concepts 2

    Polysaccharides: These are carbohydrates which on hydrolysis yield many monosaccharide units.

    For example starch, cellulose, glycogen, gums, etc.

    Monosaccharides and oligosaccharides are crystalline solids, soluble in water and sweet in taste. These are called sugars. Polysaccharides are amorphous, insoluble in water and tasteless. These are called non-sugars.

    D and L configuration of Sugar:

    For defining D and L configuration of sugar the compound glyceraldehydes, HOCH2CH(OH)CHO was chosen as the standard.

    UPSEE Bimolecules Concepts 3

    Compounds that resembles D-glyceraldehyde at one terminal is known as D-sugar. Similarly, compound that resembles L-glyceraldehyde at one terminal is known as L-sugar.

    Note: Natural sugar are D-sugar and synthetic sugar are L-sugar.

    Cyclic Structure of Monosaccharides:

    Some monosaccharides adopt cyclic structures. This conversion occurs because of the ability of aldehydes and ketones to react with alcohols:

    UPSEE Bimolecules Concepts 4

    Reactions of monosaccharides

    Oxidation Reaction:

    (a) Reaction with Br2 – H2

    The oxidation of monosaccharides with Br2 – H20 is shown as follows:

    UPSEE Bimolecules Concepts 5

    Note: Ketose is not oxidized by Br2 – H20 because it causes epimerization.

    (b) Reaction with dilute HNO3

    The oxidation reaction of monosaccharide with dilute HNO3 is as follows:

    UPSEE Bimolecules Concepts 6

    (c) Tollen’s Test:

    Ammonical AgNO3 is called Tollen’s reagent. It oxidizes aldehyde group of sugar into carboxylic acid.

    UPSEE Bimolecules Concepts 7

    Note: Ketose also give Tollen’s test because of basic medium. In basic medium Ketose is first of all epimerized to aldose and aldose gives Tollen’s test.

    Reducing and non reducing Sugars:

    Reducing Sugar: Those sugar which reduces Tollen’s reagent are called reducing sugar.

    Non Reducing Sugars: Those sugar which fail to reduce Tollen’s reagent are called non reducing sugar.

    Reaction with Phenylhydrazine:

    Both glucose and fructose react with phenylhydrazine whose chemical formula is C6H5NHNH2 to form osazone.

    Glucose and Fructose react as shown below:

    UPSEE Bimolecules Concepts 8

    Reduction: Sugar are reduced either with NaBH4 or with H2/Ni into sugar-alcohol.

    UPSEE Bimolecules Concepts 8

    UPSEE: Important Questions and Preparation Tips – Periodic Classification & Periodicity in Properties

    Some previous years’ solved questions are given below:

    Question 1:

    UPSEE Bimolecules Question 1

    Solution 1:

    UPSEE Bimolecules Solution 1

    Hence, the correct option is (B).

    UPSEE: Important Questions and Preparation Tips – Solutions

    Question 2:

    A solution of D-glucose in water rotates the plane of polarised light

    (A) To the left

    (B) To the right

    (C) To either side

    (D) None of these.

    Solution 2:

    D-glucose rotates the plane polarised light to the right.

    Hence, the correct option is (B).

    UPSEE: Important Questions and Preparation Tips – Thermodynamics (Part 1)

    Question 3:

    Which of the following pairs give positive Tollen’s test?

    (A) Glucose, Sucrose

    (B) Glucose, Fructose

    (C) Hexanal, Acetophenone

    (D) Fructose, Sucrose

    Solution 3:

    Aldehyde gives positive Tollen’s test. However under the strongly basic condition of the test α-hydroxy ketones can isomerise to aldehydes so that’s why they also give a positive Tollen's test α - hydroxy ketones.

    Hence, the correct option is (B).

    UPSEE: Important Questions and Preparation Tips – Equilibrium

    Question 4:

    The two forms of D-glucopyranose obtained from the solution of D-glucose are called

    (A) enantionier

    (B) epimer

    (C) anomer

    (D) isomer

    Solution 4:

    The two forms of D-glucopyranose obtained from the solution of D-glucose are called anomers. They are: α-D(+) glucopyranose and β-D(+)-glucopyranose. Anomers are a pair of stereoisomer which differs in configuration only around first carbon atom.

    Hence, the correct option is (C).

    UPSEE: Important Questions and Preparation Tips – States of Matter

    Conclusion:

    Students will find every important topic related to Bimolecules here. They can refer the topics mentioned in these notes instead of reading the complete theory from the books to save their time. It is presented in a systematic manner to help students in grasping the content easily.

    Mathematics all chapters complete notes for UPSEE/UPTU 2018

    DISCLAIMER: JPL and its affiliates shall have no liability for any views, thoughts and comments expressed on this article.

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