Chapter 4: Proteins

After studying this chapter, you will be able to:

(a) identify the sources and functions of proteins.

(b) identify how proteins need to be prepared and cooked to form a healthy diet.

(c) manage the effects of the imbalanced intake of proteins in the body.

(d) explain the characteristics of protein foods.

Keywords

• Amino
• acids healthy
• diet
• protein
• protein deficiency

Introduction

A healthy diet is important for all ages and proteins form the core of the meal. It is the main dish in a meal and other dishes accompany it since it is very important. Have you ever eaten a meal where a protein dish was lacking? Do you observe the kind of foods that are served to young babies in your community? It is important to eat a variety of food that provides different nutrients.

Proteins are body building nutrients made up of carbon, hydrogen, oxygen and nitrogen. They are responsible for growth of body cells and tissues. Our bodies contain millions of cells that need to be made and repaired. As the body grows, new cells are added. Others die and have to be replaced. You, therefore, need protein in your daily diet even when you stop growing. During the growth period of life, you need proteins in higher amounts.

4.1: Sources and functions of proteins

What are the sources of proteins? Are there any differences in these sources? Proteins from animals are first-class proteins. They are also called complete proteins because they contain all the essential amino acids needed for growth. Amino acids are the smallest unit of protein.

Plant proteins on the other hand are second-class proteins. They are also known as incomplete proteins because they lack one or more amino acids. It is important that you eat a mixture of incomplete proteins to provide all the essential amino acids. You can also serve incomplete proteins in larger quantities than complete proteins to be satisfactory.

Activity 4.1 Identifying the sources and Functions of proteins

1. In pairs, identify the sources of proteins eaten in your school, home and community.

2. Write down examples of animal sources and plant sources of proteins in your exercise books.

3. Discuss the sources of proteins in class.

4. In groups, use internet or textbooks to identify the functions of proteins. Write them on a manila paper and share with the class.

5. Explain the functions of proteins to the class and demonstrate using pictorial graphics.

4.2: Preparation and cooking of proteins to form part of a healthy diet

A healthy diet is that which consists of all the five important nutrients in their right amounts. Which nutrients do you think you should include in your diet daily? When you prepare or cook foods that contain protein foods, do you notice any changes in them? Protein foods need to be prepared and cooked well to aid digestion.

Activity 4.2 Preparation and cooking of proteins

1. In small groups,

(I) Identify some protein foods.

(ii) Select, prepare and cook a simple protein food.

(iii) Display the cooked protein foods in class.

4.3: Effects of imbalanced intake of proteins

When you eat an inadequate amount of food, it results to a deficiency disease. Malnutrition is a nutritional disorder which occurs when you take in less or more of a nutrient. Malnutrition is a deficiency of proteins and energy giving nutrients like carbohydrates and fats. If you do not get enough food containing proteins and carbohydrates, a condition known as marasmus results.

Kwashiorkor is a deficiency disease which occurs due to inadequate intake of proteins. These conditions are common in children between 1-5 years who are poorly weaned.

Figure 4.1: Child having kwashiokor

Who needs proteins? To some people, eating protein foods is of very great importance than to others. This is determined by the body requirement or demand. It is important that your body gets the right amounts of proteins for it to function well. Sometimes, your body may get too little or too much protein. This creates an imbalance in the body. Look at the picture in Figure 4.1.

What condition do you think the child is suffering from? What do you think would happen when you do not get the right amounts of protein in your diet?

Activity 4.3 Managing effects of protein imbalance

1. Have you ever seen a child suffering from kwashiorkor? Share with your groupmates about it.

2. Share also how that child was helped / treated.

3. Identify the signs and symptoms of kwashiorkor.

4. Discuss the ways of managing the effects of imbalanced intake of protein.

5. Present your work to the class.

If there is a deficiency of protein in the body, there is need to increase supply of protein of good quality in the diet. If there is excess protein, you need to reduce the amount of protein supplied in the diet to avoid over working the kidneys.

Activity 4.4 Practical way of Preventing protein imbalances in children individually

1. Design a message that you would deliver to a group of women about weaning their children to avoid the effects of protein imbalance.

2. Come up with two recipes/foods that you can use to feed a child that is suffering from the effect of kwashiorkor.

4.4: Characteristics of protein foods

Have you ever beaten an egg in a plate and poured it on a hot frying pan containing a little cooking oil or squeezed lemon juice in a glass of milk or poured baking powder accidentally on milk in a pan? What did you observe? Proteins are therefore affected by heat, acids and alkali.

Activity 4.5 Discovering the effects of heat, acids and alkali on protein

In groups,

1. Carry out the preparation of egg omelette to find out the effects of heat on protein.

2. Cut lemon and squeeze it in a glass of milk and note your observation.

3. Get a spoonful of baking powder and stir in a cup of milk and observe what happens.

4. Heat a cup of milk in a saucepan and observe the changes that take place until boiling point.

5. Discuss your observation in class and write in your notebook.