Bile Composition and Functions

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Questions and Answers

What is formed when barium chloride is added to urine containing sulfate radicals?

Barium phosphate (correct)

Barium bilirubinate

Barium chloride

Barium sulfate

Which color change indicates the presence of bilirubin when using Ferric chloride in the Fouchet’s test?

Yellow to green (correct)

Blue to violet

Green to blue

Pink to purple

What does the biuret test detect in proteins?

Presence of amino acids

Presence of peptide bonds (correct)

Presence of carbohydrates

Presence of lipids

Which amino acid does not yield a colored product in the ninhydrin reaction?

Proline Signup and view all the answers

What is the expected color reaction for proteins when treated with concentrated nitric acid in the xanthoproteic test?

Yellow solution or precipitate Signup and view all the answers

Which reagent is used in the biuret test to produce a color reaction with proteins?

Alkaline copper sulfate Signup and view all the answers

What does the presence of color in the ninhydrin reaction signify?

Presence of free alpha amino groups Signup and view all the answers

Which compound when heated yields biuret and is related to the biuret test?

Urea Signup and view all the answers

What is indicated by a positive Millon-Nasse test?

Presence of tyrosine and/or tryptophan Signup and view all the answers

What color does the solution turn during the Bromine Water Test for free tryptophan?

Pinkish lavender or violet Signup and view all the answers

Which reagent is used in the Pauly Reaction?

NaNO2 and sulfanilic acid Signup and view all the answers

What does a positive Lead Acetate test indicate?

Formation of a black precipitate Signup and view all the answers

What is the likely outcome when free tyrosine is tested?

Old rose complex Signup and view all the answers

Which amino acid is detected by the Hopkins-Cole test?

Tyrosine Signup and view all the answers

What reaction occurs with substances containing the guanidino group in the Sakaguchi Reaction?

Reaction with alpha-naphthol and an oxidizing agent Signup and view all the answers

What happens to a solution containing indole group in the presence of concentrated H2SO4?

Forms a violet ring Signup and view all the answers

What is the primary function of bile salts in digestion?

To emulsify dietary fats and facilitate their absorption Signup and view all the answers

Which substance is NOT an inorganic constituent of bile?

Cholesterol Signup and view all the answers

What color is a positive reaction for bile salts in Pettenkofer’s test?

Red Signup and view all the answers

What is a major function of lecithin in bile?

To emulsify fats and aid in fat absorption Signup and view all the answers

What happens to bile salts when there is an obstruction in the biliary tract?

They appear in the urine Signup and view all the answers

In Smith's test for bile salts, what indicates a positive result?

A green ring at the junction of two layers Signup and view all the answers

What is the daily output range of bile?

700-1200 ml Signup and view all the answers

What happens when sulfur powder is added to normal urine in Hay's test?

Sulfur particles float on the surface Signup and view all the answers

Which amino acid does not readily lose sulfur when treated with strong alkali?

Methionine Signup and view all the answers

What is the primary repeating unit in nucleic acids?

Mononucleotide Signup and view all the answers

Which of the following organisms contains 4% RNA by weight?

Saccharomyces cerevisiae Signup and view all the answers

What happens to nucleic acids when acids are added to alkaline solutions?

They are precipitated Signup and view all the answers

Which tissue is noted to be the best source of DNA due to a high nuclear/cytoplasmic ratio?

Thymus Signup and view all the answers

What is one property of nucleic acids in relation to their solubility?

Sparingly soluble in cold water Signup and view all the answers

What name is given to the process of breaking down proteins to release nucleic acids?

Denaturation Signup and view all the answers

Which method is not used in the purification of isolated nucleic acid?

Sublimation Signup and view all the answers

What is the purpose of heating with alkali like NaOH in RNA isolation from yeast?

To extract nucleic acids and inactivate nucleases Signup and view all the answers

Which method is NOT commonly used to prevent enzymatic browning?

Increasing substrate concentration Signup and view all the answers

What compound is formed when polyphenols react with PPO and oxygen?

1,2-Benzoquinone Signup and view all the answers

What is usually included in solvent mixtures to extract RNA or proteins?

Chloroform and isoamyl alcohol Signup and view all the answers

What happens during the acid extraction at pH 4-5 in RNA isolation?

Nucleic acids are separated from proteins Signup and view all the answers

Which of the following methods decreases contact with oxygen to prevent enzymatic browning?

Using syrup solution Signup and view all the answers

Which statement about enzymatic browning is incorrect?

It can improve flavor and nutritional value. Signup and view all the answers

What enzyme is primarily responsible for enzymatic browning?

Polyphenoloxidase (PPO) Signup and view all the answers

Study Notes

Bile

Bile is a golden greenish-yellow, viscous liquid
It's intermittently discharged into the duodenum
Daily output ranges from 700-1200 ml
Bile aids digestion by breaking down fats into fatty acids
These fatty acids are absorbed by the digestive tract

Organic Constituents of Bile

Bile Salts (Sodium & Potassium Salts): Major organic component, emulsify fats, aid intestinal absorption. Appear in urine with biliary tract obstruction.
Cholesterol: Converted into bile acids, secreted or transported into bile via ABCG5/G8
Lecithin: Third major lipid component, primary source of choline in the body.
Bile Pigments (Bilirubin and Diglucuronide): Third major lipid component of bile, main source of choline in the body.

Inorganic Constituents of Bile

Sodium Ions
Potassium Ions
Chloride Ions
Bicarbonate Ions

Tests for Bile Salts & Pigments

Pettenkofer's Test: Red color indicates bile salts
Smith's Test: Green ring at the junction of layers, indicates bile salts
Hay's Test: Sulfur particles sink in urine with bile salts present; otherwise they float.
Fouchet's Test: Oxidation of bilirubin to bilverdin using ferric chloride in trichloroacetic acid.

Color Reactions of Proteins & Amino Acids; Detection of Proteins, Lipids, and Carbohydrates

Proteins are polymers of amino acids joined by peptide bonds.
Hydrolysis of proteins yields amino acids.
Proteins are essential for protoplasm, enzymes, and hormones.
Amino acids and proteins react with reagents to produce colored products.

Color Reactions for Proteins & Amino Acids (continued)

Ninhydrin Reaction: Used to estimate amino acids; results in a purple color for most amino acids, a yellow color for proline and hydroxyproline.
Biuret Test: Detects peptide bonds, produces a violet color with increasing peptide bonds.
Xanthoproteic Test: Detects aromatic rings in proteins via nitric acid reaction, forming a yellow color, which turns more intense with alkali.
Millon-Nasse Test: Detects tyrosine, phenol, and thymol. Produces a colored complex.
Hopkins-Cole Test: Detects tryptophan; results in a violet ring.
Bromine Water Test: Detects tryptophan; produces a pinkish-lavender violet color in the alcohol layer.

Pauly Reaction

Positive for histidine or tyrosine
Reaction with NaNO2 and sulfanilic acid
Gives red or orange color based on amino acid

Lead Acetate

Positive for sulfur-containing amino acids (e.g., cysteine) when boiled with KOH and then treated with lead acetate (Pb(OAc)2)

Sakaguchi Reaction

Positive for guanidino-containing compounds, such as arginine
Uses alpha-naphthol and an oxidizing agent (e.g., sodium hypobromite)
Gives a red or orange color

Nucleic Acids

Biopolymers with mononucleotides as repeating units
DNA and RNA are major components in cells (5-15% of dry weight)
Nucleic acids are abundant in spleen, liver, and thymus.
Nucleic acids have properties like being sparingly soluble in cold water, insoluble in alcohol, soluble in weak alkali, and precipitated with acids.

Isolation of Nucleic Acids

Step 1: Cell membrane disruption to release nucleic acids
Step 2: Treatment with reagents to dissociate nucleoproteins and denature proteins (e.g., detergents with phenol, solvent mixtures)
Step 3: Purification of isolated nucleic acids (e.g., gradient centrifugation, gel electrophoresis, chromatography)

Isolation of RNA from Yeast

Step 1: Heating with alkali (e.g., NaOH) to extract nucleic acids and water-soluble proteins, inactivating nucleases.
Step 2: Acid extraction (pH 4-5) to separate nucleic acids from proteins and other substances.
Step 3: Precipitation of RNA with alcohol, ether, or other organic solvents to remove lipids.

Enzymatic Browning

Enzymatic activity causes rapid darkening of fruits and vegetables, especially after cutting or slicing
The mechanism involves oxygen, polyphenoloxidases (PPOs), and phenolic compounds.
Browning occurs when phenolic compounds come into contact with oxygen and PPO.
Prevention methods include blanching, use of inhibitors, and lowering of pH.

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Description

Explore the vital role of bile in digestion, including its organic and inorganic constituents. This quiz covers essential functions such as fat emulsification and the tests used for bile salts and pigments. Gain a deeper understanding of bile's impact on health and digestion.