Misunderstood Body: Vitamin D
After reading the lecture, consider what you learned about certain body parts or chemical compounds that are really rather misunderstood (for example, lipids are often thought to be all bad, but that's not the case).
Identify a lipid, mineral, protein, or other chemical compound that isn't always what it might seem on the surface. Explain how it is often perceived, and explain why that perception isn't the whole story.
Vitamin D is a “fat-soluble vitamin produced in the skin on exposure to UV (ultraviolet) radiation; necessary for normal bone growth and function” (Marieb, 2012, p. 46). Vitamin D is also a lipid and a steroid. There are a few misconceptions which surround vitamin D such as: people get enough vitamin D just from being outside, that there is no such thing as too much vitamin D, and that vitamin D is not that important to a person’s well-being. Some people incorrectly believe that they are receiving enough vitamin D merely by being outside. The human body does not produce vitamin D on its own and unless you work outside year-round you may not be getting enough vitamin D; to determine a person’s vitamin D level a blood test can be ordered by a physician.
Another misconception is that there is no danger from too much of a vitamin, but that is incorrect. Too much vitamin D can cause a person to develop vitamin D toxicity, also known as hypervitaminosis. A person who has hypervitaminosis can experience poor appetite, nausea, vomiting, weakness, frequent urination and kidney problems due to the buildup of calcium in their blood (Zeratsky, 2014).
It is a huge fallacy that Vitamin D is not as important in comparison to other vitamins. Vitamin D is very significant for the continued function of the human body; it is involved in regulating the levels of minerals such as phosphorus and calcium (WebMD, 2014). It also helps boost the immune system in order to prevent autoimmune diseases, and some types of cancer (WebMD, 2014). Vitamin D also contributes in the prevention of high blood pressure, high cholesterol, muscle weakness, multiple sclerosis, rheumatoid arthritis, chronic obstructive pulmonary disease, tooth and gum disease, and some skin conditions (WebMD, 2014).
Marieb, E. (2012). Essential of Human Anatomy and Physiology (10th Ed.). San Francisco: Pearson Education.
VITAMIN D. (n.d.). WebMD. Retrieved October 29, 2014, from http://www.webmd.com/vitamins-supplements/ingredientmono-929-vitamin%20d.aspx?activeingredientid=929&activeingredientname=vitamin%20d
Young, L. (n.d.). 5 myths and truths about vitamin D | Health | Get Healthy | Best Health. Best Health. Retrieved October 29, 2014, from http://www.besthealthmag.ca/get-healthy/health/5-myths-and-truths-about-vitamin-d
Zeratsky, K. (n.d.). Vitamin D toxicity: What if you get too much?. Mayo Clinic. Retrieved October 27, 2014, from http://www.mayoclinic.org/healthy-living/nutrition-and-healthy-eating/expert-answers/vitamin-d-toxicity/faq-20058108
Basic Body Chemistry
In order to understand the body’s structure and function, we must examine how it is arranged at its most basic levels. Chemicals are composed of atoms, which are the smallest unit of any pure substance. Atoms combine to form molecules, and similar molecules join together to form the basic components of cells. The cell is the most fundamental structural unit of all living things.
We have more day-to-day exposure to chemistry than people realize, and it plays a hugely important role in the body. For example, most people have had blood drawn or urine tested at some point in their life so a doctor could evaluate the quality of their health or diagnose disease. The reason for ordering these tests is because of the instrumental role chemistry plays in the body’s function. Abnormal levels of some chemicals, or the absence or presence of others, can indicate a problem.
Checking a body’s levels of various proteins, for example, can assess how well the kidneys and liver are functioning and can help diagnose certain types of cancers. The presence of wastes in the blood can tell about the kidneys’ ability to eliminate them, and elevated levels of glucose can indicate diabetes mellitus. The levels of calcium or enzymes, which are proteins that speed up chemical reactions, can indicate conditions that affect the liver, parathyroid glands, or bones. They can even be used to monitor the effectiveness of treatment for certain conditions: a doctor might analyze potassium levels if your blood pressure is high or if you have symptoms of heart problems.
The Body’s Organic Compounds
Now that we see how important chemistry is, let’s start with a basic lesson. Chemicals that contain both carbon and hydrogen atoms are referred to as organic compounds. The main types of organic compounds in the body are proteins, lipids, carbohydrates, and nucleic acids.
Proteins are abundant in the body; in fact, over half of the body’s organic matter is composed of proteins. They are present in many hormones; the body’s organs produce them to regulate the actions of cells and other organs. Hormones are essential for growth, the digestion and use of nutrients taken in by the body, and reproduction. Proteins also regulate and speed up the rate of chemical reactions. They are in the outer layer of the cell
Module One: Building Blocks of the Amazing Human Body
(the plasma membrane) to regulate the passage of substances both into and out of the cell. They are present in muscle tissue, allowing us to move. Not only are the roles of proteins functional, but they are structural as well. They help to hold cells together and provide support and strength to our tissues.
Proteins are composed of amino acids, which contain an amine group (NH₂) and an acid group (COOH). Any molecular formulas that contain nitrogen, carbon, hydrogen, and oxygen are most likely a protein or protein derivative.
Lipids are also known as fats, waxes, and oils. Examples include triglycerides, phospholipids, and steroids. Even though lipids have had some bad press, they are essential for the structure and function of living things. Triglycerides are an important source of stored energy. They are mobilized into the bloodstream when needed and travel to cells such as skeletal muscle to act as fuel. Fats also insulate the body and protect its organs. Phospholipids are present in the cell membrane to maintain the cell’s shape and play a role in regulating how substances pass into and out of the cell. The body uses this substance, together with cholesterol, to make bile acids, which digest and absorb fats. Steroids are present in hormones such as testosterone and estrogen; they cannot be manufactured without cholesterol. The body makes cholesterol, and it is also taken into the body by way of the foods we eat. Cell membranes depend on cholesterol for their structure. Cholesterol is also the precursor to vitamin D; the body cannot make this essential vitamin without it.
Lipids contain carbon, hydrogen, and oxygen. If a molecular formula contains mostly carbon and hydrogen atoms and very few oxygen atoms, it is most likely a lipid.
Carbohydrates, more commonly known as sugars, are made up of monosaccharides, or simple sugars, such as glucose, fructose, and galactose. Two monosaccharide units joining together form disaccharides. Examples of disaccharides are sucrose, lactose, and maltose. Sucrose is made by the linkage of a glucose unit and a fructose unit; lactose is made from the combination of a glucose unit and a galactose unit; and maltose forms when a glucose unit combines with another glucose unit. A polysaccharide, or starch, is created as a result of the combination of many monosaccharide units.
Carbohydrates, like lipids, contain carbon, hydrogen, and oxygen. To determine if the molecular formula is that of a carbohydrate, check out the hydrogen to oxygen ratio; it should be 2:1.
Nucleic acids are composed of nucleotides, sometimes referred to as bases. DNA (deoxyribonucleic acid) and RNA (ribonucleic acid) are examples of nucleic acids. A gene is a specific section of DNA on a chromosome that contains the instructions for cell division. DNA contains the instructions for the creation of all of the parts of the body. It ultimately affects how our genes are expressed, and it does this by way of protein formation. RNA
transfers information stored in the DNA to the areas of the cell that build proteins, thereby playing an essential role in protein formation.
The base pairs of DNA are held together by weak hydrogen bonds, and the sugar-phosphate backbones are joined by strong covalent bonds. The reason for this difference is so the DNA molecule can split apart in order to replicate (make copies of its genetic material).
A.D.A.M. Editorial Team & Dugdale, D. C. (updated 2011, August 30). Comprehensive metabolic panel. Bethesda, MD: National Library of Medicine, US. Retrieved from http://www.nlm.nih.gov/medlineplus/ency/article/003468.htm
Marieb, E. N. (2012). Essentials of human anatomy and physiology (10th ed.). San Francisco: Pearson Education, Inc.