Shown below in the table is the cost (£) and percentage (%) of the weekly social welfare allowance required to purchase the foods necessary for healthy eating for households using three different grocery store outlets - Leaving Cert Home Economics - Question 1 - 2014

Several factors contribute to the variation in the percentage of income spent on food:

1. Age: Younger individuals require more energy, leading to higher food purchasing to meet daily caloric needs compared to elderly individuals who may have lower energy requirements. Thus, households with young children often spend a larger percentage of their income on food.

2. Nutritional Knowledge: Those with better nutritional awareness are more likely to make informed food choices, potentially at a higher cost. Consumers familiar with the importance of balanced diets may opt for higher-quality, and therefore, pricier foods. Conversely, households with limited nutritional knowledge may spend less and purchase lower-cost options.

3. Family Circumstances: Factors such as the presence of children, special dietary requirements, or health issues can influence food expenditure. Families with dietary restrictions or children with specific nutrition needs may have to allocate more of their income toward food.

Low-cost protein foods can be both affordable and nutritious. Here are some options along with recommendations on their incorporation into a healthy eating plan:

1. Eggs: A versatile and inexpensive source of protein, they can be included daily in breakfasts or as part of salads and stir-fries.

2. Legumes (Beans and Lentils): Cost-effective and rich in nutrients, they can be incorporated into soups, stews, or as side dishes to provide protein and fiber.

3. Chicken Thighs: Generally cheaper than breast meat, they can be used in stir-fries or baked dishes, keeping the fat content in check while adding flavor.

4. Tofu: A great plant-based protein source, suitable for stir-fries, salads, or soups, allowing for varied meal preparations.

5. Canned Tuna: Affordable and convenient, it can be added to salads, sandwiches, or pasta dishes serving as a quick protein boost.

Classification of Proteins

1. Simple Proteins: These consist only of amino acid residues and can be classified further into:

   • Animal Proteins: e.g., collagen (found in connective tissues), globulin (found in blood plasma), and albumin (found in egg whites).
   • Plant Proteins: e.g., gliadin from wheat and zein from maize.

2. Conjugated Proteins: These contain additional groups that contribute to their structure and function.

   • Examples include lipoproteins, which contain fats, and glycoproteins, which combine proteins with carbohydrates. These conjugated forms are crucial for various biological functions within the body.

The supplementary value of protein foods occurs when different sources combine to provide complete nutrition. For instance, when consuming bread with beans, they complement each other by fulfilling the essential amino acid profiles that may be lacking in each food alone. In this interaction, one food compensates for the deficiencies of the other, providing a more balanced nutrient profile.

Structure of Proteins

1. Primary Structure: This refers to the specific sequence of amino acids in the polypeptide chain, determined by genetic code. The order is crucial for the protein's overall functionality.

2. Secondary Structure: This describes the folding or coiling of the polypeptide chain, often stabilized by hydrogen bonds, forming structures like alpha helices and beta sheets.

3. Tertiary Structure: This offers a three-dimensional organization of the folded polypeptide chain into a compact unit. The interactions among the side chains of amino acids result in the protein's final shape, facilitating its specific function.