Protein Isolation: Casein and Glutenin

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Questions and Answers

What is the primary mechanism by which isopropyl alcohol denatures proteins?

Forming cross-links with sulfur-containing amino acids

Disrupting hydrophobic interactions (correct)

Forming insoluble complexes with negatively charged groups

Interacting with certain functional groups

Which reagent can cause protein coagulation by forming cross-links with sulfur-containing amino acids?

Zinc sulfate

Copper sulfate (correct)

Mercuric chloride

Isopropyl alcohol

What is the primary effect of zinc sulfate on proteins?

Coagulation through cross-linking with sulfur-containing amino acids

Precipitation of proteins with negatively charged groups (correct)

Formation of insoluble complexes with certain functional groups

Denaturation through disruption of hydrophobic interactions

Which reagent does not have a significant effect on protein denaturation or precipitation under normal conditions?

Sodium ferrocyanide Signup and view all the answers

What is the primary mechanism by which mercuric chloride induces protein precipitation?

Forming insoluble complexes with certain functional groups Signup and view all the answers

What is the result of adding a salt to a protein solution, leading to a decrease in solubility?

Salting out Signup and view all the answers

Which of the following is NOT a type of protein?

Carbohydrate Signup and view all the answers

What is the purpose of adding ammonium sulfate in protein purification?

To precipitate proteins Signup and view all the answers

What is the main component of gluten found in wheat flour?

Glutenin Signup and view all the answers

What is the purpose of ninhydrin in biochemical reactions?

To detect the presence of amino acids Signup and view all the answers

What is the result of adding a base to an amino acid solution?

The amino acid becomes more basic Signup and view all the answers

What is the effect of heat on protein structure?

It denatures the protein Signup and view all the answers

What is the purpose of gel filtration in protein purification?

To separate proteins based on size Signup and view all the answers

What is the result of adding ZnSO4 to a protein solution?

The protein is precipitated Signup and view all the answers

What is the purpose of isoelectric precipitation in protein purification?

To precipitate proteins at their isoelectric point Signup and view all the answers

What is the characteristic structure of an osazone when viewed under a microscope?

Crystalline structure Signup and view all the answers

Which of the following sugars is NOT a reducing sugar?

Cellulose Signup and view all the answers

What is the purpose of the indole-3-acetic acid (IAA) test?

To identify fructose in the presence of glucose Signup and view all the answers

Which of the following sugars is a disaccharide of glucose and galactose?

Lactose Signup and view all the answers

What is the primary component of starch?

Glucose Signup and view all the answers

Which of the following sugars gives a negative result in the IAA test?

Xylose Signup and view all the answers

What is the primary function of polysaccharides in higher plants?

To serve as structural support and as food reserves Signup and view all the answers

What is the classification of polysaccharides based on the type of sugar units they contain?

Homopolysaccharides and heteropolysaccharides Signup and view all the answers

What is the result of complete acid hydrolysis of polysaccharides?

Formation of glucose, fructose, galactose, and other monosaccharides Signup and view all the answers

What is the characteristic of amylose?

It is a linear polysaccharide with alpha 1-4 glucosidic bonds Signup and view all the answers

What is the purpose of the Molisch test?

To detect the presence of carbohydrates in general Signup and view all the answers

What is the result of the Selivanoff test for ketoses?

Formation of a cherry-red color Signup and view all the answers

What is the purpose of the Bial's test?

To differentiate between pentoses and hexoses Signup and view all the answers

What is the result of the Tollen's phloroglucinol test for pentoses?

Formation of a blue-green color Signup and view all the answers

What is the characteristic of glycogen?

It is a branched polysaccharide with alpha 1-6 glucosidic bonds Signup and view all the answers

What is the result of the anthrone test for carbohydrates?

Formation of a blue-green color Signup and view all the answers

What is the primary characteristic of enantiomers that affects their reactions with other chiral substances?

Their optical activity Signup and view all the answers

Why are glycosidic linkages broken during the hydrolysis of polysaccharides?

To break down the polymer chain Signup and view all the answers

What is the purpose of saponification in the analysis of lipids?

To break down ester bonds in triglycerides Signup and view all the answers

What is the significance of the Lieberman-Burchard reaction in the detection of cholesterol?

It detects the presence of a hydroxyl group and unsaturation in the adjacent fused ring Signup and view all the answers

What is the primary difference between saturated and unsaturated fatty acids?

The presence of double bonds Signup and view all the answers

What is the purpose of the ammonium molybdate test in the detection of phospholipids?

To detect the presence of phosphate groups Signup and view all the answers

What is the significance of the Rosenheim's test for choline?

It detects the presence of choline in phospholipids, cerebrosides, and sphingomyelins Signup and view all the answers

What is the purpose of using petroleum ether in lipid extraction?

To solubilize non-polar lipids Signup and view all the answers

What is the significance of the Beer-Lambert law in spectroscopy?

It describes the relationship between the concentration of a substance and its absorbance Signup and view all the answers

What is the primary purpose of DNA extraction?

To isolate DNA for further analysis or manipulation Signup and view all the answers

Study Notes

Here are the study notes:

Effect of Various Substances on Proteins*
Isopropyl alcohol:
- Denatures casein and gliadin
- Coagulates egg white
ZnSO4:
- Causes precipitation of casein
- Coagulates gliadin and egg white
CuSO4:
- No effect on casein
- Coagulates gliadin and egg white
HgCl2:
- Causes precipitation of casein
- Coagulates gliadin and egg white
Na4Fe(CN)6:
- No effect on casein and gliadin
- No effect on egg white
Denaturation of Proteins*
Denaturation: loss of native structure and biological activity
Causes of denaturation:
- Heat: disrupts non-covalent bonds, leading to unfolding of protein structure
- pH: extreme pH values disrupt electrostatic interactions
- Chemicals: detergents, urea, guanidine hydrochloride, and beta mercaptoethanol disrupt hydrophobic and electrostatic interactions
Reversibility of denaturation: some denaturations can be reversed, while others are permanent
Properties of Amino Acids*
Zwitter ions: amino acids exist as zwitter ions in the body, with both acidic and basic properties
Acid-base properties: amino acids have pK1, pI, and pK2 values, which describe the pH ranges for different ionic forms
Tertiary structure: 3-dimensional shape of amino acids, influenced by interactions between side chains and prosthetic groups
Color Reactions of Amino Acids*
Ninhydrin test:
- Positive result: purple or violet color, indicates presence of amino acids or proteins
- Used to detect amino acids, peptides, and proteins
Biuret test:
- Positive result: yellow color, indicates presence of phenols or imines
- Used to detect tyrosine, tryptophan, and other aromatic amino acids
Pauli's test:
- Positive result: violet color, indicates presence of guanidine or amino groups
- Used to detect arginine, histidine, and other amino acids with guanidine or amino groups
Sakaguchi's test:
- Positive result: red color, indicates presence of guanidine or amino groups
- Used to detect arginine, histidine, and other amino acids with guanidine or amino groups
Ehrlich's test:
- Positive result: pink color, indicates presence of aromatic amino acids
- Used to detect tryptophan, tyrosine, and other aromatic amino acids
Xanthoproteic test:
- Positive result: yellow or orange color, indicates presence of aromatic amino acids
- Used to detect tryptophan, tyrosine, and other aromatic amino acids
Lipids*
Solubility:
- Lipids are insoluble in polar solvents, but soluble in non-polar organic solvents
- Examples of non-polar solvents: petroleum ether, hexane, chloroform
Extraction methods:
- Hexane extraction: used for non-polar lipids
- Chloroform-methanol extraction: used for polar lipids
Types of triglycerides:
- Saturated: solid at room temperature, examples include lard and butter
- Unsaturated: liquid at room temperature, examples include olive oil and cod-liver oil
Protein Isolation and Analysis*
Isolation of casein and glutenin:
- Casein: can be isolated from milk using acidification, rennet, or heat
- Glutenin: can be isolated from wheat flour using organic solvents
Color reactions:
- Ninhydrin test: used to detect amino acids, peptides, and proteins
- Biuret test: used to detect phenols or imines
- Pauli's test: used to detect guanidine or amino groups
- Sakaguchi's test: used to detect guanidine or amino groups
- Ehrlich's test: used to detect aromatic amino acids
- Xanthoproteic test: used to detect aromatic amino acids### Carbohydrates and OsaZone
OsaZone is a product formed from sugars, characterized by a crystalline structure when viewed under a low-power microscope.
The time required for OsaZone formation is a specific property of a sugar.

Sugar Classification and Tests

Reducing sugars: Arabinose, Fructose, Galactose, Glucose, Xylose
Non-reducing sugars: Cellulose, Inulin, Lactose, Maltose, Starch, Sucrose
IAA (Indole-3-Acetic Acid) test: detects Fructose and Sucrose
Iodine test: detects Starch

Polysaccharides

Long chains of monosaccharides
Classification:
- Homopolysaccharides: Starch, Glycogen, Cellulose (contain same sugar units)
- Heteropolysaccharides: Pectin, Chitin, Agar (contain different sugar units)
- Mucopolysaccharides: Glycosaminoglycans (repeating sugar units)

Starch and Glycogen

Starch: mixture of Amylose and Amylopectin
Amylose: 20% of Starch, 300 units of D-glucose linked by alpha 1-4 glucosidic bonds, forms a helix
Amylopectin: major constituent of Starch, branched, majority of units linked by alpha 1-4 glucosidic bonds
Glycogen: analogous to Amylopectin, larger and more branching

Color Reactions of Carbohydrates

Molisch test: detects Carbohydrates, purple/red-violet color with alpha-napthol and concentrated sulfuric acid
Anthrone test: detects Carbohydrates, blue-green color with anthrone and concentrated sulfuric acid
Selivanoff test: differentiates aldoses and ketoses, cherry red color for ketoses, yellow to faint pink color for aldoses
Bial's test: differentiates pentoses and hexoses, blue-green color for pentoses, purple-red color for hexoses

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Description

Learn about the structure and properties of proteins, including fibrous and globular proteins, and how to isolate them. This quiz covers the basics of protein chemistry and the isolation of casein and glutenin.