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Science (English Medium) Class 12 - CBSE Important Questions

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Deficiency of which vitamin causes scurvy?

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Vitamins >> Classification of Vitamins

What type of linkage is responsible for the formation of proteins?

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Nucleic Acids >> Chemical Composition of Nucleic Acids

Write the product formed when glucose is treated with HI ?

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Nucleic Acids >> Chemical Composition of Nucleic Acids

 Write one example of a Natural polymer.

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Proteins >> Denaturation of Proteins

 Write one example of a thermosetting polymer.

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Proteins >> Denaturation of Proteins

Differentiable between the following: 
Essential amino acids Non-essential amino acids 

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Proteins >> Amino Acids

Differentiate between the following :

Peptide linkage and Glycosidic linkage 

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Proteins >> Structure of Proteins

Define the following term:
Denaturation of protein

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Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Proteins >> Denaturation of Proteins

Define the following term:
Vitamins

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Vitamins >> Classification of Vitamins

Write the reactions involved when D-glucose is treated with the following reagent:
H2N-OH

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Carbohydrates >> Structures of Glucose

Given below are two statements labelled as Assertion (A) and Reason (R).

Assertion (A): Proteins are found to have two different types of secondary structures viz alpha-helix and beta-pleated sheet structure.

Reason (R): The secondary structure of proteins is stabilized by hydrogen bonding.

Select the most appropriate answer from the options given below:

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Proteins >> Structure of Proteins

Account for the following:

There are 5 OH groups in glucose

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Carbohydrates >> Structures of Glucose

Account for the following:

Glucose is a reducing sugar

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Classification of Carbohydrates

Account for the following:

What happens when D – glucose is treated with the following reagents

Bromine water

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Carbohydrates >> Structures of Glucose

Account for the following:

What happens when D – glucose is treated with the following reagents

HNO3

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Carbohydrates >> Structures of Glucose

Read the passage carefully and answer the questions that follow:

Strengthening the Foundation: Chargaff Formulates His "Rules"

Many people believe that James Watson and Francis Crick discovered DNA in the 1950s. In reality, this is not the case. Rather, DNA was first identified in the late 1860s by Swiss chemist Friedrich Miescher. Then, in the decades following Miescher's discovery, other scientists- notably, Phoebus Levene and Erwin Chargaff- carried out a series of research efforts that revealed additional details about the DNA molecule, including its primary chemical components and the ways in which they joined with one another. Without the scientific foundation provided by these pioneers, Watson and Crick may never have reached their groundbreaking conclusion of 1953: that the DNA molecule exists in the form of a three-dimensional double helix.
Chargaff, an Austrian biochemist, as his first step in this DNA research, set out to see whether there were any differences in DNA among different species. After developing a new paper chromatography method for separating and identifying small amounts of organic material, Chargaff reached two major conclusions:
(i) the nucleotide composition of DNA varies among species.
(ii) Almost all DNA, no matter what organism or tissue type it comes from maintains certain properties, even as its composition varies. In particular, the amount of adenine (A) is similar to the amount of thymine (T), and the amount of guanine (G) approximates the amount of cytosine (C). In other words, the total amount of purines (A + G) and the total amount of pyrimidines (C + T) are usually nearly equal. This conclusion is now known as "Chargaff's rule."
Chargaff’s rule is not obeyed in some viruses. These either have single-stranded DNA or RNA as their genetic material.

Answer the following questions:

  1. A segment of DNA has 100 adenine and 150 cytosine bases. What is the total number of nucleotides present in this segment of DNA?
  2. A sample of hair and blood was found at two sites. Scientists claim that the samples belong to same species. How did the scientists arrive at this conclusion?
  3. The sample of a virus was tested and it was found to contain 20% adenine, 20% thymine, 20% guanine and the rest cytosine. Is the genetic material of this virus (a) DNA-double helix (b) DNA-single helix (c) RNA? What do you infer from this data?
    OR
    How can Chargaff’s rule be used to infer that the genetic material of an organism is double-helix or single-helix?
Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Nucleic Acids >> Structure of Nucleic Acids

Why tryptophan is an essential amino acid?

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Proteins >> Amino Acids

An α-helix is a structural feature of ______.

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Proteins >> Structure of Proteins

Proteins are polymers of ______.

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Proteins >> Structure of Proteins

When D-glucose reacts with HI, it forms ______.

Appears in 1 question paper
Chapter: [10] Biomolecules
Concept: Biomolecules in the Cell > Carbohydrates >> Structures of Glucose
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