Structure and Function of Biological Molecules
The main content covered in this unit includes the Structure and Function of the biological molecules, the energy flow and the nutrients, Nutritional Facts Labels, and the My Plate concept. Proteins, nucleic acids, polysaccharides in carbohydrates are considered macromolecules, and the lipid molecules are considered as biomolecules. For clarity purposes, proteins, nucleic acids, carbohydrates, and fats will be referred to as “biological molecules” throughout the unit. The history of studying these biological molecules dates back to the early 19th century. British physician-chemist, William Prout (1785-1850) was the first to classify “foodstuffs or ingredients of life into saccharinous (carbohydrates), oleaginous (fats), and albuminous (proteins)” and urged that “a satisfactory diet should include carbohydrates, fats, protein, and water”3. Carl Schmidt coined the term “carbohydrates” in 1844.
Biological molecules are organic molecules that are present in living cells. They can be small or large molecules. Whereas, biomacromolecules are large molecules with a molecular weight of over a few thousand grams per mole. Biomacromolecules are often biopolymers that are made up of hundreds and thousands of smaller molecules called monomers4. The word monomer comes from the Greek word monas meaning single and meros meaning part. Polymerization is a process through which monomers are joined to form polymers. This process is often a dehydration (removal of a molecule of water) process in the formation of a biopolymer such as protein. On the other hand, the process of breaking down biopolymers into monomers is often hydrolysis (breaking down), e.g. digestion of protein. The four major groups of biological molecules that are found in living organisms are carbohydrates, proteins, fats, and nucleic acids. All living beings need these molecules to survive.
Carbohydrates are compounds that are made up of elements of carbon, hydrogen, and oxygen5. There are different types of carbohydrates, such as monosaccharide, disaccharide, and polysaccharides were mono- di- and poly- refer to one, two, and many, respectively. Some examples of monosaccharides are glucose and fructose. A combination of two monosaccharides results in disaccharides, e.g., sucrose and maltose. Polysaccharides are chains of thousands of monosaccharides. Some examples include cellulose that is present in the grass and starch that is present in bread products and rice. Carbohydrates not only are excellent sources of energy but also function as energy storage. Plants undergo the process of photosynthesis, where they intake carbon dioxide from the air, water from the ground, convert the light energy from the Sun into chemical energy (glucose), and release oxygen into the atmosphere. Animals store energy for short-term usage in the form of glycogen, another type of polysaccharides.
Biological Molecules
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Functions
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Food Examples
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Carbohydrates
Monomers: Monosaccharides/Simple Sugars

Glucose
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Sources of energy for cell activities, building structures. Cellulose constructing cell wall in plants.
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Pasta, bread, fruits, and vegetables
Simple sugars: table sugar, components of milk and fruits
Complex carbohydrates: Glycogen (or animal starch) and starch and cellulose in plants
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Lipids
Made up of Glycerol (backbone) and Fatty Acids

Fatty acids |

Glycerol |
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Long-term storage of energy, important parts of biological membranes and waterproof coverings
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Unsaturated fats such as olive oil and corn oil, and saturated fats such as butter and lard
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Proteins
Monomers: Amino Acids

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Enzymes controlling rates of reactions and regulating cell processes, muscle development, transport substances in and out of the cells or helping to fight diseases
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Beans, meats, fish, cheese, eggs, and dairy products
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Nucleic Acids
Monomers: Nucleotides (made up of sugar, phosphate, and a nitrogenous Base) Monomers of DNA and RNA are different

Deoxyadenosine monophosphate (dAMP)
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Dictate the amino acid sequence of proteins, store and transmit hereditary or genetic information for traits
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All plant and animal products
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Figure 1: Biological Molecules. Downloaded from Wikipedia, Public Domain https://en.wikipedia.org
Lipids or triglycerides are biological molecules. They are hydrophobic and thus not miscible with water. They contain abundant non-polar chemical bonds and are mostly made up of elements of carbon, hydrogen, and oxygen atoms6. They are made up of glycerol backbone and fatty acids. The functions of lipids include long-term storage of energy. There are several types of triglyceride molecules: saturated fats, unsaturated fats, trans fats, and omega-3 fats. Saturated fats are triglycerides made of fatty acids that contain C-C single bonds. They are solids at room temperature, examples include butter and lard. Unsaturated fats are triglycerides containing fatty acids with C=C double bonds. These double bonds give a few kinks in fatty acid chains, making unsaturated fats as liquids at room temperature. Examples include vegetable oils, such as corn oil. Trans fats are harmful to health while omega-3 fats are essential to heart health. Both can be obtained in food. Phospholipids are formed when one of the fatty acids in a triglyceride fat molecule is swapped with a phosphate group. Phospholipids make up the cell membranes in living organisms. They are unique due to the hydrophilic (water-loving) heads and hydrophobic (water-fearing) tails. Thus, they are amphipathic.
Proteins are mainly made up mostly of elements of carbon, hydrogen, oxygen, and nitrogen but also contain sulfur. Some of their functions include controlling the rates of reactions, regulating cell processes, forming important cellular structures, transporting substances in or out of the cells, helping to fight diseases, forming protein hormones, etc. The monomers of proteins are called amino acids which contain an amino group on one end and a carboxylic group on the other end of the carbon atom which is bonded to a hydrogen atom and an R group. There are 20 types of natural amino acids and they differ in the R group as side chains. Hence, the side chains distinguish the characteristics of the amino acids. Some side chains make the amino acids acidic and others basic. Some side chains are polar yet others are nonpolar. Out of the 20 amino acids, human beings cannot make 9 of them and hence have to obtain them through food. The amino acids are bonded together by peptide bonds to make proteins. Proteins are complex and fold into well-defined 3-dimensional structures according to the protein sequence. Protein structures can be described at different levels: primary, secondary, tertiary, and quaternary structures.
Lastly, the nucleic acids are made up of elements of carbon, hydrogen, oxygen, nitrogen, and phosphorus. They include deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). The monomers of the nucleic acids are nucleotides, which are made up of sugar (deoxyribose in DNA and ribose in RNA), phosphate, and nitrogenous bases. The nitrogenous bases in DNA include adenine, thymine, cytosine, and guanine, and the nitrogenous bases in RNA include adenine, uracil, cytosine, and guanine. The major functions of the nucleic acids are to carry genetic information and pass it from generation to generation (from parents to offsprings). The DNA sequence dictates the amino acid sequence of proteins. Thus, DNA stores and transmits hereditary or genetic information for traits and contains information that is important for the structure and function of the organism.
In conclusion, biological molecules include carbohydrates, lipids, proteins, and nucleic acids. These molecules have different structures and functions. They make up the food that we ingest daily. The knowledge of the elements that these molecules are composed of, examples of foods that contain these molecules, and the process through which these molecules are built and broken down, and how they contribute to the metabolism of foods and the survival of living organisms is valuable for students.
Energy and Nutrients
Allliving organisms need energy to survive. Living organisms convert chemical energy obtained from the biological molecules that they produce or consume into energy7. All living cells need a constant source of energy to perform work and other bodily functions, such as growth, repair, building muscles, transporting chemicals, and so forth. Different living organisms obtain this energy in different ways. Organisms, such as trees and blue-green algae that produce their food through the process of photosynthesis are called autotrophs (auto in Greek means self). Autotrophs or producers capture energy from the sun and absorb inorganic materials and other chemicals from the surroundings to produce organic compounds. On the other hand, heterotrophs (hetero in Greek means other and troph means feeding) are organisms that obtain energy by eating other organisms either living or dead. Heterotrophs or consumers are organisms that obtain their energy from producers or other organisms that eat producers, for example, humans that consume plants, fruits, and meat. Lastly, decomposers are organisms, such as fungi and certain bacteria, which obtain their energy from breaking down dead materials from plants and animals.
Both heterotrophs and autotrophs undergo cellular respiration, a set of chemical reactions where the organic or biological molecules that they consume are broken down to release chemical energy. As we know, the food that we consume consists of biological molecules, such as carbohydrates, proteins, lipids, and nucleic acids. During the process of digestion, the food is further broken down into simple organic compounds, for example, glucose, amino acids, fatty acids, nucleotides such that they could be absorbed. These organic compounds are then transported by the blood to every cell in the body.
The cellular respiration is a set of chemical reactions where these organic compounds are broken down in the presence (aerobic respiration) or absence (anaerobic respiration) of oxygen, resulting in the release of energy in the form of adenosine triphosphate (ATP) and waste products, such as carbon dioxide and water vapor. ATP is the energy currency for all living beings. This energy is then used for cellular work such as muscle contraction, growth, movement, etc. One needs to keep in mind that not all energy derived from food is used in its entirety. For example, one Oreo cookie contains 55 calories. When we eat an Oreo cookie, some of the energy is spent on chewing the cookie and digesting. In the end, our body might obtain fewer calories than intended. Some of the energy is lost or released to the surrounding environment as heat energy. It is helpful to note this information to understand the energy obtained from the food we consume.
In conclusion, energy flow highlights information about how different organisms obtain their energy. Producers convert light energy from the sun to chemical energy. Consumers obtain energy from producers or other consumers. Decomposers obtain energy from dead producers or consumers. The process of cellular respiration involves a set of chemical reactions where the biological molecules are converted into energy either in the presence or absence of oxygen.
The Nutrition Facts Label
The Food and Drug Administration (FDA) is a U.S. government agency that is responsible for developing policies and regulations with regards to nutrition labeling and food standards8. The FDA created the Nutrition Fact Labels (food labels) to educate and enlighten the consumer about the important information about the food products that they consume. According to the FDA, the main idea of introducing the Nutrition Fact Label to students is to set the stage for good nutrition and better health.

Figure-2: Highlights of the new changes made to the Nutrition Facts Labels (created by the Food and Drug Administration, Public Domain)
The New Nutrition Facts label highlights the following:
- Serving Sizes appear in a large bolder font so that the consumers know exactly how many servings are included in the packet
- Calories are now displayed in larger bolder fonts and ensure that the calorie needs of individuals vary according to age, sex, height, and levels of physical activity “2,000 calories a day is used as a guide for general nutrition advice”. A calorie is traditionally the unit of measure for energy. It is the amount of energy required to raise the temperature of one gram of water by one degree Celsius. The unit of measurement of food energy in kilocalories (kcal or Cal), which is equal to 1000 calories.
- Daily values have been updated. The Percent Daily Value (%DV) shows how much a nutrient in a serving of food contributes to a total daily diet.
- The amounts of added sugars (consuming too much-added sugars can make it hard to meet nutrient needs while staying within calorie limits), and vitamin D and potassium, which can reduce the risk of osteoporosis and high blood pressure, respectively are included.
- Lastly, the FDA, suggests the consumers to use the new labels to support their personal dietary needs, e.g. choosing healthier options of food, such as higher dietary fiber and lower in saturated fats that help reduce the possibility of developing certain health conditions such as high blood pressure, cardiovascular disease, osteoporosis, and anemia.
In conclusion, according to the Food and Drug Administration (FDA), The Nutrition Facts Label is an accessible tool with nutrient information to help make healthy food choices. Consumers can refer to the labels to make healthy decisions, understand the importance of good nutrition, maintain healthy lives, and avoid diseases. One of the goals of this unit is to teach students how to apply information from the food labels and make healthy food choices.
The My Plate Concept
The United States Department of Agriculture (USDA) first created a guide to food groups in 1918 9. We are all aware of the food guide pyramids in the early 1990s. The My Plate concept was created in 2011 with the main idea to grab consumers’ attention with a new visual cue and added the word “My” to create a personalized feeling. This concept portrays a visual guide of what kinds of foods fall under different categories, such as fruits, vegetables, grains, dairy, and proteins. This concept ensures that we are consuming a balanced diet that will provide our bodies with the energy to perform work and live healthily. The My Plate concept website is interactive and caters to the needs of children, teens, young adults, college students, families, adults, and professionals. One can also have a variety of selections from the food groups (classification of food, daily amounts to be consumed, as well as the portion sizes), physical activity, meal planning, budget, shopping, recipes, and food safety. The information is also available in Spanish. My Plate concept encourages consumers to find a healthy eating style and build upon it throughout their lifetime.
By using this concept, teachers will be able to break down the menu according to several categories such as fruits, vegetables, grains, protein foods, and dairy. The students will have a visual representation of the portion sizes and amounts of each of the above-mentioned categories they are required to consume based on their age, height, weight, and activity levels. They will then have a clear idea about what they could eat for breakfast, lunch, and dinner. Once this is established, the plate could be personalized based on dietary needs, religious and cultural beliefs, and health-related issues, such as lactose-intolerant, vegan, kosher, and other meal categories. This would help K-12th grade students to understand what exactly they are required to eat and how much. The students then will have several opportunities to share this information with their friends as well as family members.

Figure 3: The My Plate Concept, created by the U.S. Department of Agriculture (USDA), Public Domain.
In conclusion, the My Plate Concept will provide the readers a visual description of the amount as well as the types of foods such as fruits, vegetables, grains, protein foods, and dairy that one needs to consume daily. This information could be further researched in the United States Department of Agriculture (USDA) website. This website is interactive and will allow students as well as teachers to determine their My Plate meal plan. For example, a 14-year female student weighed 110 pounds at a height of 5 feet 5 inches, who performs moderate activities for 30 to 60 minutes per day, needs to consume around 2000 calories per day. Students could also obtain recipes and design their breakfast, lunch, and dinner menus for not only themselves but also their friends, family, and community. This knowledge has the potential to impact lifelong decisions concerning eating style. It is therefore pertinent to instill this knowledge to young adults.