Biology Lab 5 and 6: Macromolecule Detection

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Questions and Answers

Which of the following statements is true about disaccharides?

  • Disaccharides consist of three or more monosaccharides linked together.
  • Disaccharides are simple sugars with a general formula of [CH2O] n.
  • Disaccharides are formed when two monosaccharides are chemically bonded together. (correct)
  • Disaccharides are formed through the hydrolysis of polysaccharides.

What is the primary function of carbohydrates?

  • Short-term energy storage (correct)
  • Long-term energy storage
  • Catalysts for biochemical reactions
  • Structural component of cell membranes

Which test is used for the detection of starch?

  • Biuret reagent test
  • Benedict’s test
  • Lugol’s iodine test (correct)
  • Sudan test

What is the primary role of glycogen in vertebrates?

<p>Storage product in the liver (A)</p> Signup and view all the answers

Which macromolecule is tested using the Sudan test?

<p>Lipids (C)</p> Signup and view all the answers

In the dehydration synthesis of carbohydrates, what is removed from the reacting monosaccharides?

<p>Water (C)</p> Signup and view all the answers

Which monosaccharide is an isomer of glucose?

<p>Fructose (A)</p> Signup and view all the answers

Which of the following is NOT a structural component found in carbohydrates?

<p>Triglycerides in adipose tissue (B)</p> Signup and view all the answers

What color change indicates a positive result in a Benedict's test?

<p>Light blue to orange-brown (C)</p> Signup and view all the answers

Which of the following compounds is NOT detected using Lugol's iodine solution?

<p>Glucose (A)</p> Signup and view all the answers

What is the primary role of lipids in organisms?

<p>Long-term energy storage (B)</p> Signup and view all the answers

What is the structural component of fats?

<p>Glycerol and fatty acids (D)</p> Signup and view all the answers

Which of the following is a characteristic of cellulose?

<p>Indigestible and a part of dietary fiber (B)</p> Signup and view all the answers

What is the role of Sudan III in biochemical tests?

<p>To identify the presence of lipids (C)</p> Signup and view all the answers

Which statement about proteins is false?

<p>They consist solely of lipids (C)</p> Signup and view all the answers

During which process are excess sugars converted into fats in animals?

<p>Lipid synthesis (C)</p> Signup and view all the answers

What role does the 'R-group' play in amino acids?

<p>It defines the unique characteristics and properties of each amino acid. (D)</p> Signup and view all the answers

Which of the following statements is true regarding peptide bonds?

<p>They connect the amino end of one amino acid to the carboxyl end of another. (D)</p> Signup and view all the answers

What color change indicates a positive test result for peptide bonds using Biuret reagent?

<p>From blue to violet (C)</p> Signup and view all the answers

In the reducing sugar detection procedure, which solution serves as the negative control?

<p>Distilled water (A)</p> Signup and view all the answers

What is the purpose of using Benedict's reagent in the test for reducing sugars?

<p>To induce a color change indicating sugar concentration (C)</p> Signup and view all the answers

Which statement describes enzymes accurately?

<p>They act as organic catalysts in biological systems. (D)</p> Signup and view all the answers

What should be recorded before heating the test tubes in the reducing sugar detection experiment?

<p>The initial color of each reaction mixture. (C)</p> Signup and view all the answers

Which option describes a characteristic of structural proteins?

<p>They maintain the integrity and shape of cells and tissues. (A)</p> Signup and view all the answers

What is used to indicate the presence of starch in the samples?

<p>Lugol's iodine (D)</p> Signup and view all the answers

In the starch detection procedure, what does a (+) symbol indicate?

<p>Presence of starch (C)</p> Signup and view all the answers

Which of the following substances is used as a negative control for lipid detection?

<p>Distilled water (C)</p> Signup and view all the answers

What should the consistency of palm oil be when tested with Sudan III dye?

<p>Soluble (D)</p> Signup and view all the answers

Which test tube label corresponds to the sample used to detect reducing sugars?

<p>G (B)</p> Signup and view all the answers

During the starch detection procedure, what is the sequence of adding solutions to the test tubes?

<p>Water, starch, glucose, potato juice, rice water (D)</p> Signup and view all the answers

What is indicated by an (-) symbol in the starch detection results?

<p>Absence of starch (C)</p> Signup and view all the answers

What is the purpose of agitating each spot with a stick during the lipid detection test?

<p>To help dissolve the Sudan III dye (D)</p> Signup and view all the answers

Which of the following correctly identifies the function of Benedict's solution in carbohydrate detection?

<p>It identifies reducing sugars by changing color. (D)</p> Signup and view all the answers

Which sample would show a positive result with Lugol’s solution?

<p>Starch solution (D)</p> Signup and view all the answers

Why is distilled water tested with each indicator during the experiment?

<p>To establish a negative control for all tests. (C)</p> Signup and view all the answers

What conclusion can be drawn if a brick red color is observed after testing starch with Benedict’s reagent?

<p>The starch has been converted into glucose. (A)</p> Signup and view all the answers

Which of the following indicators is specifically used to test for proteins?

<p>Biuret's solution (B)</p> Signup and view all the answers

Which of the following statements is true regarding lipid detection?

<p>Palm oil shows insolubility in water. (D)</p> Signup and view all the answers

What is the role of positive controls in the testing process?

<p>To provide a standard against which results can be compared. (B)</p> Signup and view all the answers

What is the expected result when testing a glucose solution with Biuret's solution?

<p>Negative result indicating no macromolecule presence. (A)</p> Signup and view all the answers

What is the purpose of adding Biuret reagent to the test tubes?

<p>To detect the presence of proteins (C)</p> Signup and view all the answers

Which solution serves as a positive control in the protein detection procedure?

<p>Egg white solution (C)</p> Signup and view all the answers

What is the expected observation when proteins are present in a solution after adding Biuret reagent?

<p>The solution turns violet or purple (B)</p> Signup and view all the answers

Which substance is used as a negative control in the experiment?

<p>Distilled water (A)</p> Signup and view all the answers

What is the first step in conducting the protein detection test?

<p>Label the test tubes (A)</p> Signup and view all the answers

How many drops of Biuret reagent are used in each test tube?

<p>5 drops (B)</p> Signup and view all the answers

What should be recorded in the data table after adding Biuret reagent?

<p>Color changes and presence of proteins (A)</p> Signup and view all the answers

Which of the following is NOT a material used in the protein detection procedure?

<p>Ethyl alcohol (D)</p> Signup and view all the answers

What does a (+) indicate in the final column of the data table?

<p>Presence of proteins (D)</p> Signup and view all the answers

Why is it important to include controls in the experiment?

<p>To validate the accuracy of the results (A)</p> Signup and view all the answers

If a solution remains colorless after adding Biuret reagent, what conclusion can be drawn?

<p>The solution has no proteins (B)</p> Signup and view all the answers

What could be a possible reason for an incorrect outcome when testing for proteins?

<p>Incorrectly labeling the test tubes (C)</p> Signup and view all the answers

During the procedure, what is the main role of glucose solution?

<p>To act as a reference solution for protein presence (A)</p> Signup and view all the answers

In what scenario would you expect to observe a violet color after the addition of Biuret reagent?

<p>In the milk test tube (A)</p> Signup and view all the answers

Flashcards

Biological Macromolecules

Large molecules (polymers) made up of smaller organic molecules (monomers).

Carbohydrates

Organic macromolecules with the general formula [CH₂O]ₙ, primarily used for energy storage and structural components.

Monosaccharides

Simple sugars, single units of carbohydrates.

Disaccharides

Two monosaccharides bonded together.

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Polysaccharides

Large molecules composed of many monosaccharide units.

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Benedict's test

A test to detect the presence of monosaccharides.

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Lugol's iodine test

A test to detect the presence of starch, a polysaccharide.

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Sudan test

A test to detect lipids.

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Biuret reagent test

A test to detect proteins.

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Dehydration synthesis

The chemical reaction that joins monosaccharides to form disaccharides and polysaccharides, releasing water.

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Amino acids

Building blocks of proteins, linked by peptide bonds.

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Peptide bond

Covalent bond formed between two amino acids.

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Protein

Large molecules crucial for structure and function in organisms.

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R-group

Variable part of an amino acid, determining its properties.

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Reducing sugar

Sugar that can reduce other compounds.

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Benedict's reagent

Chemical used to detect reducing sugars.

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Positive test (Biuret)

Violet color indicates presence of peptide bonds in protein.

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Negative test (Biuret)

Blue color indicates absence of peptide bonds in protein.

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Dehydration synthesis

Reaction where water is removed to form a bond.

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Reducing Sugar Test

A chemical test used to identify the presence of reducing sugars in a sample.

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Starch Detection

A chemical test used to identify the presence of starch, a polysaccharide.

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Positive Control (Starch)

A known sample containing starch used to verify the test's effectiveness.

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Negative Control (Water)

A sample without the substance being tested, used as a comparison.

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Lipid Detection

A chemical test for identifying lipids (fats) in a sample.

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Positive Control (Lipid)

A known sample containing a lipid (like vegetable oil), used to confirm the test.

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Negative Control (Water)

A sample without the substance being tested, used as a comparison to determine if the substance dissolves.

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Solubility

The ability of a substance to dissolve in another substance.

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Cellulose

A polysaccharide found in plant cell walls, providing structural support and indigestible fiber.

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Benedict's test

A lab test used to detect reducing sugars (monosaccharides and most disaccharides except sucrose).

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Reducing sugars

Sugars that can be oxidized (lose electrons), showing a positive result in Benedict's test.

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Lipids

Energy-storage molecules, structural components (like phospholipids), and signaling molecules (like hormones).

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Sudan III test

A test used to detect lipids, as they are visible due to dye solubility in fats.

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Protein monomer

Amino acid, with both an amino group (NH2) and a carboxyl group (COOH).

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Starch

A polysaccharide used by plants for energy storage. Detected by Lugol's iodine solution.

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Glycerol

A 3-carbon alcohol that is a component of fats and oils.

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Fatty acids

Varying-length chains that combine with glycerol to form fats and oils.

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Lugol's iodine

A solution used to detect starch producing a purple/black color.

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Disaccharide

Two monosaccharides linked together (e.g., sucrose, lactose).

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Monosaccharide

Simple sugar, the basic unit of carbohydrates.

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Biuret Reagent

A chemical solution used to test for the presence of proteins.

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Protein Detection

Process of identifying if a sample contains proteins using a specific chemical reaction.

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Test Tubes

Small, glass tubes used to hold liquids or samples in lab tests.

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Biuret Reagent Test

Method to identify proteins by observing color change when Biuret Reagent is added.

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Reducing sugar test

A test to identify sugars that can reduce other chemical compounds.

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Starch test

A test to identify the presence of starch (a complex carbohydrate).

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Lipid test

A test to identify the presence of lipids (fats and oils).

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Protein test

A test to identify the presence of proteins.

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Positive control (carbohydrate)

A sample known to contain the target macromolecule, used to verify the test's effectiveness.

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Positive control (starch)

A sample known to contain starch, used to verify the test's effectiveness.

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Positive control (protein)

A sample known to contain protein, used to verify the test's effectiveness.

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Benedict's solution

Chemical used to detect reducing sugars.

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Lugol's iodine

Chemical used to detect starch.

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Biuret reagent

Chemical used to detect proteins.

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dH₂O

Distilled water

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Negative control

A sample known to not contain a target macromolecule, used to confirm that the test is valid and free of contamination/interference.

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Study Notes

Lab 5 and Lab 6: Detection of Biological Macromolecules

  • Cells are composed of organic macromolecules (carbohydrates, lipids, proteins, & nucleic acids).
  • This lab demonstrates qualitative tests to detect these macromolecules.

Objectives

  • Test for monosaccharides (e.g., glucose, fructose) using Benedict's test.
  • Test for starch (a polysaccharide) using Lugol's iodine test.
  • Test for lipids using Sudan III test.
  • Test for proteins using Biuret reagent test.
  • Identify unknown substances by detecting the presence of organic macromolecules.

Introduction

  • Biological macromolecules are large molecules made of smaller organic molecules (monomers).
  • Four classes of macromolecules: carbohydrates, lipids, proteins, and nucleic acids.

1) Carbohydrates

  • Monomer: monosaccharide (e.g., ribose, glucose, fructose, galactose).
  • General formula: (CH₂O)ₙ
  • Function: short-term energy storage (glucose), intermediate-term energy storage (starch/glycogen), and structural components (cellulose/chitin).
  • Disaccharides: formed by bonding two monosaccharides (e.g., sucrose, lactose, maltose).

2) Lipids

  • Function: long-term energy storage, structural components (e.g., cell membranes), and messengers (e.g., hormones).
  • Insoluble in polar substances (like water).
  • Examples: fats, oils, phospholipids.

3) Proteins

  • Monomer: amino acids (with an amino end, carboxyl end, and variable R-group).
  • Linked together by peptide bonds (dehydration synthesis).
  • Function: control and structural elements (e.g., proteins in cell membranes, muscles), enzymes (biological catalysts), and some hormones.

4) Polysaccharides

  • Large molecules formed from individual monosaccharide units.
  • Examples: starch (plants), glycogen (animals), cellulose (plant cell walls).

Tests

  • Benedict's test: detects reducing sugars (all monosaccharides, and most disaccharides except sucrose).
  • Lugol's (IKI) test: detects starch (produces a purple/black color).
  • Sudan III test: detects lipids (based on solubility).
  • Biuret test: detects proteins (violet color indicates presence of peptide bonds between amino acids).

Additional Information

  • Waxes are lipids important for structural components (plant cuticles/animal coverings).
  • The chemical reaction between reducing sugars and Benedict's reagent (Cu²⁺ ions are reduced to Cu⁺, forming a colored precipitate.)

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