Chapter 3-4-5 Quiz

Foods that nourish the body provide calories which come from the carbohydrates, fats and protein. The food also provides water, vitamins and minerals but these will be discussed later as they do not provide calories.

Carbohydrates provide about half of the calories you eat every day. Carbohydrates include sugars, starches and fibers. Some sugars occur naturally in some food, other sugars are refined and added to foods. Starches include potatoes, corn or bread but this in inclusive to all the starchy foods. Many starchy foods also contain a carbohydrate called fiber. Fiber is non-caloric but very important to the health of the digestive system. Most carbohydrates come from plant foods. Plants make their own carbohydrates which then are used by humans as a nourishing source of calories. There are some carbohydrates that are not providing nutritious calories due to the processing, the processed carbohydrates are typically considered empty calories. The body requires carbohydrates. The most important carbohydrate for the human body is glucose. The brain and central nervous system preferentially require glucose as an energy source.

Lipids (aka Fat) refers to a number of things. Fats are in the category of lipids. We often think about fat or overweight or having too much body fat.  Fat is not all bad as it adds to the taste of food but too much is a problem. There are different types of fat and it is not as much the amount of fat but the type of fat that that has an effect on the body.  The fats found in most vegetable oils, nuts and fish are healthy but too much animal fat is a concern. Compounds in the category of lipids include fat and oils, sterols and phospholipids. Fats are usually provided by animal sources. Oils generally come from plant sources.  In food, lipids enhance the taste, flavor, aroma, crispiness (in fried foods), juiciness (in meats), and tenderness (in baked products). Most of the fat in foods is in the form of triglycerides. Triglycerides are made of three fatty acids and a glycerol backbone. Triglycerides may be saturated or unsaturated. Unsaturated triglycerides may be mono-unsaturated or poly-unsaturated. Sterols include the most well-known as cholesterol. Cholesterol only comes from animal products and is not essential. Essential nutrients are those that must come from the food you eat. Cholesterol is not essential as the body is able to produce its own cholesterol without eating any food that has cholesterol. Lipids provide essential fatty acids, omega-3 fatty acids and cholesterol. These will be further defined in the chapter.

Protein is most abundant in meat, poultry and seafood.  Plant sources also provide protein and a plant based diet is able to provide adequate protein even without any animal choices. Protein is unique in that unlike carbohydrates and lipids which contain carbon, hydrogen and oxygen, protein contains these and it is the only macro-nutrient to contain nitrogen. Protein is found in all living cells in animals and plants and have a lot of important roles. Protein is made from chains of amino acids. There are 20 different amino acids that can be used to make a protein. Of these, 9 are considered essential. Essential nutrients must come from food and can not be made by the body. The other 11 are usually non-essential but there are specific instances in which they are labeled as conditionally essential.  Protein foods are also identified as complete or incomplete proteins. A complete protein provides all 9 essential amino acids in proportions needed by the body. Incomplete proteins are missing one or more of the essential amino acids. It is possible to get all the essential amino acids by combining 2 or more incomplete sources, these are called complimentary proteins. The basic shape of an amino acid is a back bone with an acid end and an amino end. In addition, each amino acid has a different side chain.  Amino acids combine in a stand that then spirals and folds to make different shapes to provide the body to use them for building the body and doing work in the body. There are 2 types of proteins, structural proteins and working proteins. Structural proteins provide structure to the body, these include skin, hair, nails, bones, tendons and ligaments. Working proteins perform a task in the body; these include hormones, antibodies and enzymes. The proteins in foods and the body will be reviewed in the textbook in chapter 5.