Lesson Notes By Weeks and Term - Senior Secondary 3

Giant Molecules 3

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TERM׃ IST TERM

WEEK ELEVEN

Class: Senior Secondary School 3

Age: 17 years

Duration: 40 minutes of 5 periods each

Date:

Subject: Chemistry

Topic: Giant molecules 3

SPECIFIC OBJECTIVES: At the end of the lesson, pupils should be able to

  1. Test for the presence of sugar and starch
  2. Define protein and explain its properties
  3. Test for the presence of protein
  4. Identify the uses of protein.

INSTRUCTIONAL TECHNIQUES: Identification, explanation, questions and answers,

demonstration, videos from source

INSTRUCTIONAL MATERIALS: Videos, loud speaker, textbook, pictures

INSTRUCTIONAL PROCEDURES

PERIOD 1-2

PRESENTATION

TEACHER’S ACTIVITY

STUDENT’S

ACTIVITY

STEP 1

INTRODUCTION

The teacher introduce protein to the students and discusses it's properties.

 

Students pay

attention

STEP 2

EXPLANATION

Teacher guide students to test for the presence of sugar, starch and protein.

Students pay

attention and

participate

 

STEP 3

DEMONSTRATIO

N

Teacher explain the uses of protein to the students.

 

Students pay

attention and

participate

STEP 4

NOTE TAKING

The teacher writes a summarized

note on the board

 

The students

copy the note in

their books

NOTE

GIANT MOLECULES 3

Test for starch and sugar

The iodine test is commonly used to detect the presence of starch. When iodine is added to a substance containing starch, it forms a blue-black color complex. The chemical reaction can be represented as follows:

 Starch + Iodine  Blue-black complex

On the other hand, for testing the presence of sugars, such as glucose, the Benedict's test or Fehling's test can be employed. These tests rely on the reduction of copper ions by reducing sugars. The resulting color change indicates the presence of sugars.

The Benedict's test involves heating the sample with Benedict's reagent, and if reducing sugars are present, the solution changes from blue to green, yellow, orange, or even red, depending on the concentration of reducing sugars.

The Fehling's test is similar, involving the reaction of reducing sugars with copper ions. A positive result is indicated by the formation of a reddish precipitate of copper(I) oxide.

Below is a table summarizing the tests for starch and sugar:

Test

Indicator

Procedure

Inference for starch

Inference for sugar

Starch test

Iodine solution        

Add iodine solution to the sample. 

Blue-black color complex indicates the presence of starch.

 No specific reaction with iodine.   

Sugar Test

Benedict's solution or Fehling's solution

For Benedict's: Heat with Benedict's solution.

For Fehling's: Mix with Fehling's A and B solutions, then heat.

No specific reaction with iodine.

Benedict's: Color change from blue to green, yellow, orange, or red indicates the presence of reducing sugars. Fehling's: Formation of a reddish precipitate of copper(I) oxide indicates the presence of reducing sugars

 

Uses of starch and glucose

Starch and glucose have various uses

Starch:

  1. Commonly used as a thickening agent in soups, sauces, and gravies.
  2. Used in the sizing of fabrics to provide stiffness.
  3. Applied in papermaking to increase paper strength.
  4. Starch-based materials are used as alternatives to traditional plastics.
  5. Used in the production of capsules and tablets.

Glucose:

  1. Primary source of energy for the human body through cellular respiration.
  2. Used in intravenous solutions to provide a quick energy source for patients.
  3. Sweetener in various food and beverage products.
  4. Used in fermentation processes for the production of various products, including biofuels and enzymes.
  5. Essential for photosynthesis in plants, contributing to their growth and development.

Protein

Proteins are large biomolecules composed of amino acid chains. They play crucial roles in various biological processes, serving as structural components, enzymes, antibodies, and more. Proteins are essential for the structure, function, and regulation of tissues and organs in the human body.

The structure of a protein is hierarchically organized:

  1. Primary Structure: The sequence of amino acids in a polypeptide chain.
  2. Secondary Structure: Localized folding patterns, like alpha helices or beta sheets.
  3. Tertiary Structure: Overall three-dimensional shape of a single polypeptide chain.
  4. Quaternary Structure: Arrangement of multiple polypeptide chains in a functional protein.

Properties of Protein

Proteins are large, complex molecules with crucial roles in the body. They have diverse functions and exhibit various properties:

  1. Proteins have a unique three-dimensional structure determined by their amino acid sequence. This structure is essential for their function.
  2. Proteins are made up of amino acids linked together by peptide bonds. The sequence of these amino acids dictates the protein's properties and function.
  3. Proteins serve numerous functions, such as enzymes catalyzing biochemical reactions, antibodies defending against infections, and structural proteins providing support to cells and tissues.
  4. Exposure to heat, pH extremes, or certain chemicals can alter a protein's structure, causing denaturation and loss of function.
  5. Proteins often exhibit specificity in their interactions, recognizing and binding to specific molecules, like substrates for enzymes or antigens for antibodies.
  6. Proteins can vary in solubility, with some being water-soluble and others lipid-soluble. This property influences their distribution and function in the body.
  7. Enzymes, a type of protein, act as biological catalysts, speeding up chemical reactions in living organisms without being consumed in the process.

Test for protein

The Biuret test is a common method to test for the presence of proteins. A tabulated summary of the Biuret test for proteins is described below.

Test

Principle

Reagents

Observation

Explanation

Biuret Test

Formation of a colored complex between copper ions and peptide bonds in proteins.

Biuret reagent (copper sulfate and alkaline sodium or potassium hydroxide).

Color change from blue to violet or pink.  

The coordination of copper ions with peptide bonds in proteins results in a colored complex, indicating the presence of proteins.

 

Uses of protein

Proteins play crucial roles in the body, serving various functions such as:

  1. Essential for the growth and repair of tissues, including muscles, skin, and organs.
  2. Act as catalysts for biochemical reactions, facilitating processes like digestion and metabolism.
  3. Regulate various physiological processes, including insulin for glucose regulation and growth hormone for development.
  4. Carry important molecules, such as oxygen by hemoglobin in red blood cells.
  5. Antibodies, a type of protein, help defend the body against pathogens.
  6. Contribute to the structure of cells, tissues, and organs, maintaining their integrity.
  7. Essential for communication between nerve cells, influencing mood, cognition, and other brain functions.

EVALUATION:  1. Identify 5 properties of protein                     

  1. Identify 2 uses of starch and glucose.
  2. Describe the test for protein in simple terms.
  3. Mention 4 uses of protein.

CLASSWORK: As in evaluation

CONCLUSION: The teacher commends the students positively