Human Nutrition: Macronutrients

Human Nutrition 

By Naomi Keddy

Why Do Organisms need Food?

Well Organisms need food to maintain metabolism and the continuity of life for all living things. We need to maintain metabolism to maintain homeostasis. We need nutrients to carry out metabolic reactions, as a source of energy and for growth and repair. Nutrition is the study of food, its composition, structure, properties. amounts required and its effects on the body.

What are Macronutrients? 

Macronutrients are the nutrients that are required in large amount in the body and they are Protein, Carbohydrates and Lipids.

What is protein? 

Protein is composed of the elements Carbon, Hydrogen, Oxygen and Nitrogen. Protein is the only nutrient that contains Nitrogen, which is essential for growth in the body. Sometimes protein contains smaller amounts of sulfur, phosphorus and other elements. The basic structure of protein is a build up with amino acids. Peptide bonds are formed when amino acids join together. In this reaction a H2o molecule is lost. The reserve of this reaction is called hydrolysis and it involves the addition of water and enzyme action and this occurs in digestion. There are two sources of protein. Protein that comes from animals and protein that comes from plants. Examples of plant source protein are soya beans, peas and beans. Examples of animal source protein are Chicken, milk, eggs and meat. Structural role of protein is to form structures such as hair, nails and muscles. 

Denaturation  is the unfolding of the protein chain resulting in an irreversible change in shape and the lost of its function. 

Deamination is using protein as a source of energy to control reactions. Excess protein that is not required for growth and repair is deaminated in the liver. An Excess amount of Nitrogen in the body can be toxic the body so that is why excess amount of protein has to be deaminated in the liver. Metabolic role of protein in the body is is used by enzymes to control reactions. 

The laboratory test for protein is the biuret test. If Protein is present it would change to a purple colour and if absent it would result in a blue colour.

What are Carbohydrates?

Carbohydrates are composed of the elements Carbon, Hydrogen and Oxygen. Carbohydrates are mainly found in plant foods. Plants makes their own food from a process call photosynthesis resulting in the production of glucose which is a carbohydrate. Carbohydrates are really good in the diet because they are a slow releasing energy. Carbohydrates are made up of sugar units. There are three types of carbohydrates which are broken into how many sugar units. 

Monosaccharide is one sugar unit. e.g Glucose and fructose. 

Disaccharide is two sugar units. e.g sucrose and maltose. 

Polysaccharide is many sugar units. e.g Starch and glycogen. Carbohydrates carry out several functions such as heat and energy to the body; they are stored as fat to the body. Fibre is good in the diet, because it is a substance that is plentiful in the outside layers of fruit and vegetables and the husks of grains. It is not digested or absorbed by the body but moves quickly through the small intestine and it is excreted out as waste. This helps prevent bowel disease. Sources of carbohydrates are bread, potatoes, rice and flour. 

The laboratory test for carbohydrates is Benedict's test (For Reducing Sugar) and Iodine test (Test for Starch). 

 The Benedict's test, if sugar is present it would result in a brick red colour and it is negative it would result in a blue colour.

The iodine test, if starch is present it would change to a blue-black colour and if absent it would result in a red-yellow colour.

What are Lipids?

Lipids are fats and oils that are composed of the elements Carbon, Hydrogen and Oxygen. Fats are solid at room temperature and oils are liquid at room temperature. Fats are divided into two types: Saturated fats and unsaturated fats. Saturated fats are fats that come from an animal . Saturated fats are known as the bad kind of fats. Unsaturated fats are fats that come from plant sources. 

The structure of lipids is glycerol and three fatty acid which is called triglyceride. 

Glycerol and two fatty acids and a phosphate  are called phospholipid. 

The structural role of lipids is heat and energy and protection of organs. The overuse of lipids may lead to stokes, heart disease and obesity. The metabolic role of lipid is to be broken down in respiration to release energy. The laboratory test for lipids is using brown paper, if it is a lipid it would stain a wet look and it isn't it won't be visible.