Chemistry Test - 20

Explanation:

Tollen's reagent-

• Tollens Test is a very useful method to distinguish between aldehydes and ketones. This qualitative lab test is also referred to as the silver mirror test.
• Tollens Reagent refers to the chemical reagent used to detect an aldehyde functional group, an aromatic aldehyde functional group, or an alpha-hydroxy ketone functional group in a given test substance.
• Tollens test is generally given by compounds having an aldehydic group (aldehydes,alpha-hydroxy ketones, and formic acid-its -COOH behaves like an aldehydic group). It gives a white ppt of Silver (where the silver salt is reduced to silver metal and the aldehyde is oxidized to silver salt of carboxylic acid.

Given data and Analysis-

⇒ Aldehydes are oxidized easily but ketones do not quickly oxidize by Tollen's agent.

⇒ Only aldehydes can reduce Tollen’s reagent.

⇒ Fructose is a Ketone, so fructose is kept in an aqueous solution and enolized. And then converted into aldehyde in the basic medium or by the base.

⇒ The reaction of aldehydes with Tollen’s reagent is an oxidation reaction.

⇒ All aldehydes generally reduce Tollen's reagent.

⇒ It can be concluded that fructose reduces Tollen’s reagent due to the enolization of fructose followed by conversion to aldehyde by the base.

Explanation-

Tollens test-

• Tollens Test is a very useful method to distinguish between aldehydes and ketones. This qualitative lab test is also referred to as the silver mirror test.
• Tollens test is generally given by compounds having an aldehydic group (aldehydes,alpha-hydroxy ketones, and formic acid-its -COOH behaves like an aldehydic group). It gives a white ppt of Silver (where the silver salt is reduced to silver metal and the aldehyde is oxidized to silver salt of carboxylic acid.

Glucose-

• Glucose is a simple sugar with six carbon atoms and one aldehyde group. This monosaccharide has a chemical formula C₆H₁₂O₆.
• The aldehydic group is present in glucose and Tollen's reagent is the test for aldehydes.
• So Glucose in the blood can be quantitatively determined with Tollen's reagent.

Important Points

Benedict's solution-

⇒ Benedict’s test is a chemical test that can be used to check for the presence of reducing sugars in a given analyte.

Alkaline iodine solution-

⇒ When Iodine and sodium hydroxide are added to a compound that contains either a methyl ketone or secondary alcohol with a methyl group in the alpha position, a pale yellow precipitate of iodoform or triiodomethane is formed. It can be used to identify aldehydes or ketones

Bromine water-

⇒ Bromine water is a yellow mixture solution with high oxidizing properties, prepared by dissolving diatomic bromine (Br₂) in water (H₂O).

Explanation-

• Glucose is a simple sugar with six carbon atoms and one aldehyde group. This monosaccharide has a chemical formula C6H12O6.
• Glucose is a carbohydrate and an important biomolecule that helps in the metabolism of the body.
• The glucose is reacted with acetic anhydride to form pentadactyl derivatives. This simply shows the presence of five hydroxyl groups. As we know Glucose is a very stable compound, no two OH groups can be attached to the same carbon.
• Or in other words, we can say that the five OH groups are present on the different carbons.
• D - glucose and L - glucose yield the same dicarboxylic acid: This means that these two sugars differ only in respect of the position of the terminal groups (CHO and CH₂OH).

∴ The exchange of the terminal groups in D-glucose should be able to give a different aldohexose.

• L- (-) -glucose is the enantiomer of the more common D-glucose.

The structure of L- (-) -glucose is

Explanation:

Reagent-

• A reagent is a compound or mixture added to a system to start or test a chemical reaction. A reagent can be used to determine the presence or absence of a specific chemical substance as certain reactions are triggered by the binding of reagents to the substance or other related substances.

Schweizer's reagent-

• Schweizer's reagent is the metal ammine complex with the formula [Cu(NH₃)₄(H₂O)₂](OH)₂.This deep-blue compound is used in purifying cellulose.
• It is prepared by precipitating copper(II) hydroxide from an aqueous solution of copper sulfate using sodium hydroxide or ammonia, then dissolving the precipitate in a solution of ammonia.
• Schweitzer's reagent used for dissolving cellulose in the manufacture of artificial silk is [Cu(NH3)4]SO4.

Explanation:

Anomeric carbon-

• An anomeric carbon is a hemiacetal or hemiketal carbon of cyclic sugar. It is the carbon at which the alpha anomer or beta anomer is formed.
• An anomeric carbon can be identified as the carbonyl carbon (of the aldehyde or ketone functional group) in the open-chain form of the sugar. It can also be identified as the carbon bonded to the ring oxygen and a hydroxyl group in the cyclic form.

Explanation-

Lactose-

⇒ Lactose is a disaccharide that upon hydrolysis gives two saccharides, glucose and galactose. It was discovered by Fabriccio Bartoletti and is a solid carbohydrate that is white in color. 2-8% of milk contains lactose and this is the natural form of sugar present in it.

⇒ The structural formula of lactose is as shown in the figure.

(+) Lactose, C12H22O11 contains 8-OH groups.

⇒ On hydrolysis (+) Lactose gives an equal amount of D(+) glucose and D(+) galactose.

⇒ (+) Lactose is a β-glycoside formed by the union of a D(+) glucose and a molecule of D(+) galactose.

⇒ (+) Lactose is a reducing sugar and all reducing sugar shows mutarotation.

Explanation-

• A reagent is a substance or compound added to a system to cause a chemical reaction, or added to test if a reaction occurs. Sanger's reagent is 1-Fluoro-2,4-dinitrobenzene (commonly called, dinitrofluorobenzene, DNFB, or FDNB).
• Sanger’s reagent reacts with the peptide chain and undergoes nucleophilic aromatic substitution (NAS) with the N-terminal amino group of a peptide or protein, resulting in a chemical tag on the terminal amino acid residue.
• Then the product is hydrolyzed into individual amino acids, the peptide or protein's terminal amino acid can be identified by the specific wavelength of light absorbed (i.e., colorimetric analysis).
• Sanger’s reagent reacts with the N-terminal of the amino acid.
• So Sanger's reagent is used for the identification of the N-terminal amino acid of the peptide chain.

 Important Points

Colorimetric analysis-

• A colorimeter is a device that is used in Colorimetry. It refers to a device that helps specific solutions to absorb a particular wavelength of light.
• The colorimeter is usually used to measure the concentration of a known solute in a given solution with the help of the Beer-Lambert law.
• There are two types of colorimeters — color densitometers, which measure the density of primary colors, and color photometers, which measure the color reflection and transmission.

Explanation-

Denaturation of protein-

Denaturation implies the destruction of the tertiary structure of a protein molecule and the formation of random polypeptide chains.

• Secondary, tertiary and quaternary protein structure is easily changed by a process called denaturation. These changes can be quite damaging.
• Heating, exposure to acids or bases and even violent physical action can cause denaturation to occur.
• The albumin protein in egg white is denatured by heating so that it forms a semisolid mass. Almost the same thing is accomplished by the violent physical action of an egg beater in the preparation of meringue.
• Heavy metal poisons such as lead and cadmium change the structure of proteins by binding to functional groups on the protein surface.
• Denaturation of proteins can be done by bringing in physical changes as well as the introduction of chemicals.
• Most of the denaturation processes are irreversible, but it has been seen (in very few cases) that some of the denaturation processes can be reversed; it is then called as renaturation of protein.
• Some of the common cases of denaturation of proteins are coagulation of egg white when an egg is subjected to boiling. Here the denaturation occurs due to a change in temperature.

Explanation-

⇒ Enzymes can be defined as biological polymers that catalyze biochemical reactions.

⇒ Most enzymes are proteins with catalytic capabilities crucial to performing different processes. Metabolic processes and other chemical reactions in the cell are carried out by a set of enzymes necessary to sustain life.

⇒ Enzymes are a linear chain of amino acids, which give rise to a three-dimensional structure. The sequence of amino acids specifies the structure, which in turn identifies the catalytic activity of the enzyme.

⇒ Upon heating, the enzyme’s structure denatures, resulting in a loss of enzyme activity, which typically is associated with temperature.

⇒ Enzymes are said to possess an active site. The active site is a part of the molecule that has a definite shape and the functional group for the binding of reactant molecules.

⇒ The molecule that binds to the enzyme is referred to as the substrate group. The substrate and the enzyme form an intermediate reaction with low activation energy without any catalysts.

⇒ The effectiveness of a catalyst is maximum at its optimum temperature. The activity of the biochemical catalysts declines at either side of the optimum temperature.

Explanation:

Enzyme catalysis:

⇒ Catalysis is a phenomenon in which the rate of the reaction is altered with the help of a substance called a catalyst (the catalyst does not participate in the reaction; its concentration and composition remain unchanged).

⇒ The substance used to change the rate of the reaction is called a catalyst. Enzymes are a class of catalysts that are responsible for facilitating and increasing the rate of many vital biochemical reactions in plants and animals.

The catalysis in which enzymes act as a catalyst is called enzyme catalysis.

• A single molecule of the enzyme catalyst can transform up to a million molecules of the reactant per second. Hence, enzyme catalysts are said to be highly efficient.
• These biochemical catalysts are unique to certain types of reactions, i.e. the same catalyst cannot be used in more than one reaction.
• The effectiveness of a catalyst is maximum at its optimum temperature. The activity of the biochemical catalysts declines at either side of the optimum temperature.
• Enzymes are mostly proteinous in nature. Enzymes are denatured by ultraviolet rays and at high temperatures.