| Using the table below list the characteristics that are used to help describe and classify each of your specialization areas. Be sure to explain in as much detail as possible what traits and characteristics are used to identify and classify the specific organism or kingdom that you have become a specialist. |
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#2: ( Example – Protista Characteristics) |
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The Nobel Prize in Chemistry for 2002 is being shared between scientists in two important fields: mass spectrometry (MS) and nuclear magnetic resonance (NMR). The Laureates, John B. Fenn and Koichi Tanaka (for MS) and Kurt Wüthrich (for NMR), have contributed in different ways to the further development of these methods to embrace biological macromolecules. This has meant a revolutionary breakthrough, making chemical biology into the “big science” of our time. Chemists can now rapidly and reliably identify what proteins a sample contains. They can also produce three-dimensional images of protein molecules in solution. Hence scientists can both “see” the proteins and understand how they function in the cells.
Why study biological macromolecules?
All living organisms – bacteria, plants and animals – contain the same types of large molecules, macromolecules, which are responsible for what we call life. Events in the cells are controlled by nucleic acids (such as DNA) that may be termed the cells’ “directors”, while the various proteins are the cells’ leading actors. Each protein has a biological function that may vary with its environment. The protein hemoglobin, for example, transports oxygen to all the cells in the body.
Protein research itself is not new, but proteomics, i.e. studies of how different proteins and other substances act together in the cell, is a relatively new field of research that has grown enormously in the past few years. As the gene sequences of more and more organisms have been mapped and the research frontier has advanced, new questions have cropped up: how can it be that man’s 30,000-or-so genes code for hundreds of thousands of different proteins? What happens if a gene is damaged or is missing? How do diseases such as Alzheimer’s or mad cow disease originate? Can the new chemistry be used to diagnose and treat more quickly the diseases that are threatening mankind?
To be able to tackle questions such as these chemists are in constant pursuit of more knowledge of proteins and how they function together with each other and with other molecules in the cells. This is because small variations in a protein’s structure determine its function. The next step is to study the dynamics: what do protein molecules look like at the very moment when they are interacting with one another? What happens at the decisive moments? To understand, we need to see.
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| Fig 1. This protein consists of a long chain of amino acids that is pleated, folded and wound together like a ball of wool. It is this three-dimensional image of the protein one needs to achieve to be able to understand the function of that protein. This protein molecule, which was one of the first to have its structure determined with NMR, has a diameter of approximately one millionth of a centimeter (10-8 m). |
Mass spectrometry – a method of identifying molecules
Mass spectrometry now allows us to identify a substance in a sample, rapidly, on the basis of its mass. This technique has long been used by chemists on small and medium-sized molecules. The method is so sensitive that it is possible to trace very small quantities of each type of molecule. Doping and drug tests, foodstuff control and environmental analysis are examples of areas where mass spectrometry is now in routine use.
The foundations of mass spectrometry were already in place at the end of the nineteenth century. The first analyses of small molecules were reported in 1912 by Joseph J. Thompson. Several of the Nobel Prizes of the twentieth century depended directly on mass-spectrometric analysis. Examples are Harold Urey’s discovery of deuterium (Nobel Prize in Chemistry 1934) and the discovery of the fullerenes, “carbon footballs” that gave Robert Curl, Sir Harold Kroto and Richard Smalley the Nobel Chemistry Prize in 1996.
The goal of using mass spectrometry for macromolecules as well long attracted the scientists. During the 1970s a number of successes were achieved in transferring macromolecules to ions in the gas phase, termed desorption technology. These have formed the basis for the revolution in this field during the past twenty years.
Macromolecules may be large in comparison with other molecules but we are nevertheless dealing here with incredibly small structures. Hemoglobin molecules, for example, have a mass of a tenth of a thousand-millionth of a thousand-millionth of a gram (10-19 g). How to weigh something that is so small? The trick is to cause the individual protein molecules to let go of each other and spread out as a cloud of freely hovering, electrically charged protein ions. A common method of subsequently measuring the mass of these ions – and hence identifying the proteins – is to accelerate them in a vacuum chamber where their time of flight (TOF) is measured. They “reach their targets” in an order determined partly by their charge and partly by their mass. The fastest ones are those that are lightest and have the highest charge.
Today there are two principles for causing proteins to transform into the gas phase without losing their structure and form, and it is the discoverers behind these methods that are being rewarded jointly with half the Nobel Prize in Chemistry. In one of these methods, of which John B. Fenn is the originator, the sample is sprayed using a strong electrical field to produce small, charged, freely hovering ions. The other method, instead, uses an intense laser pulse. If this is done under suitable conditions (as to the energy, structure and chemical environment of the sample) the test molecules take up some of the energy of the laser pulse and become released as free ions. The first person to show that this phenomenon, soft laser desorption, could be used for large molecules such as proteins was Koichi Tanaka.
Fenn’s contribution – hovering through spraying
During 1988 John B. Fenn published two articles that were to mean a breakthrough for mass spectrometry with “electrospray” for macromolecules. In the first, studies of polyethylene glycol molecules of unknown mass showed that the method could handle large molecule masses with high charges. The second publication reported the use of the method on medium-sized whole proteins as well. The release of ions is achieved by spraying the sample using an electrical field so that charged droplets are formed. As the water gradually evaporates from these droplets, freely hovering “stark naked” protein molecules remain. The method came to be called electrospray ionization, ESI.
As the molecules take on strong positive charges, the mass/charge ratio becomes small enough to allow the substances to be analyzed in ordinary mass spectrometers. Another advantage is that the same molecule causes a series of peaks, since each can take up a varying number of charges. While this complicates the pattern, at first confusing the researchers, it also gives information that makes identification easier.
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Fig 2. The principles for mass spectrometry of biomolecules. |
Tanaka’s contribution – hovering through blasting
At the same time exciting things were happening in another part of the world. At the Japanese Shimadzu instrument company in Kyoto, a young Japanese engineer, Koichi Tanaka, reported an entirely different technique for the first critical stage. At a symposium in 1987 and a year later in print, Tanaka showed that the protein molecules could be ionized using soft laser desorption (SLD). A laser pulse strikes the sample which, unlike in the spray method, is in a solid or viscous phase. When the sample takes up the energy from the laser pulse it is “blasted” into small bits. The molecules let go of one another, released as intact hovering molecule ions with low charge which are then accelerated by an electrical field and detected as described above by recording their time of flight. Tanaka was the first to demonstrate the applicability of laser technology to biological macromolecules. The principle is fundamental for many of today’s powerful laser desorption methods, particularly the one abbreviated MALDI (Matrix-Assisted Laser Desorption Ionization) but also SELDI (Surface Enhanced Laser Desorption Ionization) and DIOS (Direct Ionization on Silicon).
Applications of mass spectrometry
Both electrospray ionization (ESI) and soft laser desorption (SLD) have many areas of application. The sophisticated biochemical analyses now possible were but dreams a few years ago. Interactions between proteins are very important to study in order to understand the signal systems of life. Such non-covalent biomolecule complexes can be examined with ESI. The method is superior to other methods in the rapidity, sensitivity and identification of the actual interaction. Mass spectrometric analytical methods are relatively cheap, enabling them to spread quickly to laboratories all around the world. Today soft laser desorption (in the form of MALDI) and electrospray are standard methods for structure analyses of peptides, proteins and carbohydrates which make it possible to quickly analyze the protein content of intact cells and living tissue. The following examples of current fields of research gives a picture of the application versatility generated by this year’s Nobel Prize. Applications include:
Pharmaceuticals development
The early phase of pharmaceuticals development has undergone a paradigm shift. Combined with fluid separation, ESI-MS has made it possible to analyze several hundreds of compounds per day.
Malaria
Scientists have recently discovered new ways of studying the spreading of malaria. Early diagnosis is possible thanks to the soft laser desorption method. The oxygen-bearing part of human hemoglobin is used here to absorb the energy of the laser pulse.
Ovarian, breast and prostate cancer
New methods for early diagnosis of different forms of cancer have been reported at a rapid rate during the past year. By having a surface that cancer cells adhere to – and then analyzing this with soft laser desorption – chemists can discover cancer faster than doctors can.
Foodstuff control
ESI technology has also made progress for small molecules. During the past few months we have learned that preparation of the food we eat can give rise to a number of substances hazardous to health, e.g. acrylamide which can cause cancer. With mass spectrometry, food is analyzed rapidly at various stages of production. By modifying the temperature and the ingredients, the harmful substances can be avoided or minimized.
NMR for biological macromolecules
Where mass spectrometry gives answers to questions about e.g. a protein, such as “what?” and “how much?”. NMR in one sense answers the question “what does it look like?” Even the largest proteins are too small to be studied at sufficient resolution with any type of microscope. To be able to form a picture of what a protein really looks like, then, other methods must be used. NMR (Nuclear Magnetic Resonance) is one such method. By interpreting the peaks in an NMR spectrum one can draw a three-dimensional picture of the molecule being studied. One finesse is that the sample can be in a solution, in the case of proteins their natural environment in the cell.
Before the advent of NMR, X-ray crystallography was the only method available for determining the three-dimensional structure of the substance. In 1957 the first true three-dimensional structure of a protein, myoglobin, was presented. This was rewarded with a Nobel Prize in Chemistry to Max Perutz in 1962. X-ray crystallography is based on the diffraction of X rays in protein crystals, and has since contributed to a further series of Nobel Prizes. As a complement to X-ray crystallography, chemists long sought a method that would also function in a solution, i.e. an environment that better resembles the one the biomolecules surround themselves with naturally.
The physicists Felix Bloch and Edward Purcell discovered as early as in 1945 that some atom nuclei, through what is called their nuclear spin, absorb radio waves of a certain frequency when placed in a powerful magnetic field. This was rewarded with the Nobel Prize in Physics in 1952. A few years earlier it was discovered that the frequency for nuclear resonance depended not only on the strength of the magnetic field and the type of atom but also on the chemical environment of the atom. In addition, the nuclear spins of different nuclei could affect each other, generating fine structures, i.e. a further number of peaks in the NMR spectrum.
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| Fig 3. The sample to be examined is placed in a very strong magnetic field. The figure shows a super-conducting magnet cooled by liquid nitrogen and helium. Pulses of radio waves are sent into the sample which emits a radio wave “answer”. This response is analyzed electronically and the result is an NMR spectrum. |
The applicability of the NMR method was initially limited by its low sensitivity: it required incredibly concentrated solutions. But in 1966 the Swiss chemist Richard Ernst (Nobel Prize in Chemistry 1991) showed that this sensitivity could be increased dramatically if, instead of slowly varying the frequency, the sample was exposed to short and intense radio frequency pulses. He also contributed, during the 1970s, to the development of a way of determining what nuclei were adjacent to one another in a molecule, e.g. two atoms bound to each other. By interpreting the signals in an NMR spectrum it was thus possible to gain an idea of the appearance of the molecule, its structure. The method was successful for relatively small molecules but, for larger ones, it was hard to differentiate between the resonances of the different atom nuclei. An NMR spectrum of this kind could look like a grass lawn in section – thousands of peaks where it was impossible to decide which peak belonged to which atom. The scientist who finally solved this problem was the Swiss chemist Kurt Wüthrich.
Kurt Wüthrich – showed that NMR was possible for proteins
At the beginning of the 1980s, Kurt Wüthrich developed an idea about how NMR could be extended to cover biological molecules such as proteins. He invented a systematic method of pairing each NMR signal with the right hydrogen nucleus (proton) in the macromolecule (see fig. 4). The method is called sequential assignment and is today a cornerstone of all NMR structural investigations. He also showed how it was subsequently possible to determine pair wise distances between a large number of hydrogen nuclei and use this information with a mathematical method based on distance-geometry to calculate a three-dimensional structure for the molecule.
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| Fig 4. If one knows all the measurements of a house one can draw a three-dimensional picture of the house. In the same way, by measuring a vast number of short distances in a protein it is possible to create a three-dimensional picture of its structure, as shown schematically in the figure. |
The first complete determination of a protein structure with Wüthrich’s method came in 1985. At present 15-20% of all the thousands of known protein structures have been determined with NMR. The structures of the others have been determined chiefly with X-ray crystallography; a few with other methods such as electron diffraction or neutron diffraction.
Areas of application for NMR with macromolecules
In many respects, the NMR method complements X-ray crystallography for structural determination. If the same protein is investigated with both methods, in the one case in solution and in the other crystallized, the same result is generally obtained, with the exception of certain superficial areas that are affected by the environment in both cases – in the crystals by the tightly packed protein molecules, in solution by the surrounding molecules of the solvent. While the strength of X-ray crystallography lies in being able to determine accurately really large three-dimensional structures, the NMR method has other unique advantages. The fact that the investigation takes place in a solution means that physiological conditions can be approximated. A particular strength of NMR is its ability to demonstrate unstructured and very mobile parts of a molecule. It is possible to elucidate the mobility, the dynamics, and how it varies along a protein chain. Isotope labeling can also be used to facilitate the identification of the atoms.
One example of NMR-determined protein structures comes from studies of the prion proteins involved in the development of a number of dangerous diseases such as mad cow disease (Nobel Prize in Medicine to Stanley Prusiner in 1997). Here Wüthrich and coworkers have shown with NMR methodology that the healthy form of prion proteins has two parts: approximately half of the protein chain assumes a well-ordered, fairly rigid three-dimensional structure in a water solution (121-231 in the picture below), while the other half is without structure and very mobile (23-120).
NMR can also be used in studies of structure and dynamics of other biological macromolecules such as DNA and RNA.
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| Fig 5. Structure of prion protein, determined with NMR. Half of the protein chain (23-120) is disordered and quite flexible in water solution. |
NMR is also used in the pharmaceuticals industry to determine the structure, and hence the properties, of proteins and other macromolecules that can be interesting target molecules for new pharmaceuticals. Pharmaceutical molecules are designed to fit into the structure of the protein – like a key in a lock. The perhaps most important industrial use of NMR is in the search for small potential pharmaceutical molecules that can interact with a given biological macromolecule. If the small molecule binds to the large one, the NMR spectrum of the large molecule is normally changed. This may be used to “screen” a large number of pharmaceuticals candidates at an early stage of the development of a new drug.
| The Laureates | |||
| John B. Fenn Virginia Commonwealth University Dept. of Chemistry 1001 W. Main St. P.O. Box 842006 Richmond, VA 23284-2006 USA www.has.vcu.edu/che/people/fenn.html |
US citizen. Born 1917 (85 years) in New York City, USA. PhD in chemistry 1940 and Professor at Yale University 1967–1987. Professor Emeritus 1987 at Yale University, Connecticut, USA. Since 1994 Professor at Virginia Commonwealth University, Richmond, Virginia, USA.
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| Koichi Tanaka Shimadzu Corp. 1. Nishinkokyo Kuwabaracho Nakagyou-ku Kyoto 604-8511 Japan www.shimadzu.com |
Japanese citizen. Born 1959 (43 years) in Toyama City, Japan. B. Eng 1983 at Tohoku University, Japan. R&D engineer at Life Science Business Unit, Analytical & Measuring Instruments Division, Shimadzu Corp., Kyoto, Japan.  |
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| Kurt Wüthrich Swiss Federal Institute of Technology Zürich ETH Hönggerberg, HPK CH-8093 Zürich Schweiz and The Scripps Research Institute 10550 North Torrey Pines Rd, La Jolla, CA 92037 USA www.mol.biol.ethz.ch/wuthrich www.scripps.edu/mb/wuthrich/people/kw/kw.html |
Swiss citizen. Born 1938 (64 years) in Aarberg, Switzerland. PhD in inorganic chemistry 1964 at The University of Basel. Since 1980 Professor of Molecular Biophysics at ETH, Zürich, Schweiz. Visiting Professor of Structural Biology at The Scripps Research Institute, La Jolla, California, USA
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Source: http://nobelprize.org/nobel_prizes/chemistry/laureates/2002/public.html
| AP Biology: CHAPTER 1 |
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THEMES IN THE STUDY OF LIFE
1. Why do Biology courses build their content around themes and major concepts? __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 2. List each major theme and briefly describe. a. ________________________________________________________________________ b. ________________________________________________________________________ c. ________________________________________________________________________ d. ________________________________________________________________________ e. ________________________________________________________________________ f. ________________________________________________________________________ g. ________________________________________________________________________ h. ________________________________________________________________________ i. ________________________________________________________________________ j. ________________________________________________________________________ 3. What is the primary model for regulation? __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 4. List and give an example of the three domains. __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 5. How does biology account for the unity and diversity of life? __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ 6. What is meant by the statement that science is a process? __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________
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Found at the Biology Corner Name __________________ Period ______
Sponges – A Coloring WorksheetSince sponges look like plants, it is understandable why early biologists thought they were plants. Today, we know that sponges are simple, multicellular animals in the Kingdom Animalia, Phylum Porifera. This phylum is thought to represent the transition from unicellular animals to multicellular animals. Most (but not all) sponges are asymmetrical and have no definite shape. Sponges, like all animals, are eukaryotic – meaning their cells have a nucleus. Porifera in Latin means “pore-bearer” and refers to the many pores or openings in these animals. Because of these pores, a sponge can soak up and release water. At one time, real sponges were used for cleaning and bathing. Today, most are artificially made.
All adult sponges are sessile, meaning they are attached to some surface. Since they cannot move, sponges cannot pursue their food. Instead, they are filter feeders, meaning they obtain their food by straining the water for small bits of food like bacteria, algae or protozoans.
Sponges exhibit less specialization (adaptation of a cell for a particular function) of cells than most invertebrates. The primitive structure of a sponge consists of only two layers of cells separated by a non-living jelly like substance. The outer layer of the sponge is the epidermis which is made of flat cells called epithelial cells. Color all the epithelial cells (B) of the epidermis peach or pink.
The inner layer consists of collar cells (A) whose function is to circulate water through the sponge. They do this by swishing their flagella which pulls water through the incurrent pore – water then travels out the osculum at the top of the sponge. As water passes through the sponge in this way, cells absorb food and oxygen and waste is excreted. Color the osculum (D) dark blue, the incurrent pores (C) light blue. Color the inside of the sponge where water circulates the same light blue as you colored the incurrent pores. Color all the collar cells (A) red.
In the jelly-like substance between the epidermis and the collar cells are cells called amebocytes – because they look like amebas. The job of the amebocytes is to travel around distributing food and oxygen to the cells of the epidermis. Because of the amebocytes, scientists believe that sponges evolved from protists. Color all of the amebocytes (E) green – look for them carefully.
The body of the sponge would collapse if it did not have some type of supporting structure. Some sponges have a soft network of protein fibers called spongin. Others have tiny, hard particles called spicules. Many of these spicules also stick out of the epidermis and provide the sponge with protection. Most sponges have a combination of spicules and spongin, the ratio often determines how soft or hard the sponge is. Search for and color all the pointy spicules (F) brown.
Reproduction for sponges can be accomplished both sexually and asexually. There are three ways for a sponge to reproduce asexually: budding, gemmules, and regeneration. Sponges can simply reproduce by budding, where a new sponge grows from older ones and eventually break off. Color the adult sponge (J) pink and all the buds (G) you can find red. Sponges can also reproduce by regeneration, where missing body parts are regrown. People who harvest sponges often take advantage of this by breaking off pieces of their catch and throwing them back in the water, to be harvested later. Finally, sponges can reproduce by creating gemmules – which is a group of amebocytes covered by a hard outer covering. Color the gemmule (H) yellow.
Sexual reproduction occurs when one sponge releases sperm into the water. This sperm travels to another sponge and fertilizes its eggs. The larva form will then swim to another location using its flagella where it will grow into an adult sponge. Most sponge species are hermaphrodites, they can produce both eggs and sperm.
Questions:
1. What did early biologists think sponges were? ______________________
2. Sponges belong to the Kingdom _________________ and the Phylum _______________
3. Sponges are [ unicellular or multicelluar ] and [ prokaryotic or eukaryotic ]
4. What type of symmetry do sponges have? ___________________________________
5. What does it mean to be sessile? ____________________________________
6. How do sponges get their food? ___________________________________
7. Water enters the sponge through the _____________________ and leaves through the
_____________________.
8. What is the job of the amebocyte? ________________________________________
9. What two substances give the sponge support? _________________________________
10. Tiny sponges growing from the main body of the sponge are called _________________
11. What is a gemmule? ___________________________________________________
12. What is a hermaphrodite? ______________________________________________
Label the letters on the diagrams
Label the letters on the diagrams
Found at www.biologycorner.com
Click here to view an animation of the endocrine system
The endocrine system is a set of hormone secreting glands within the body of an animal. The function of the endocrine system is homeostasis, communication and response to stimuli. The endocrine system regulates the internal environment of the animal for growth, survival and reproduction as well as allowing it to respond to changes in its external environment.
The endocrine system’s glands secrete chemical messages we call hormones. These signals are passed through the blood to arrive at a target organ, which has cells possessing the appropriate receptor. Exocrine glands (not part of the endocrine system) secrete products that are passed outside the body. Sweat glands, salivary glands, and digestive glands are examples of exocrine glands.
The other communication method in the body is the nervous system. Although there are differences between them, they complement each other in many responses, e.g., response to danger.
The difference between nervous and endocrine control are as follows:
1. Nervous response is faster.
2. Nervous response is shorter in duration.
3. Nervous response stops quicker.
Hormones
Most hormones are made of protein. They are called peptides. Peptides are short chains of amino acids; most hormones are peptides. They are secreted by the pituitary, parathyroid, heart, stomach, liver, and kidneys.
Some hormones are steroid based. Steroids are lipids derived from cholesterol. Testosterone is the male sex hormone. Estradiol, similar in structure to testosterone, is responsible for many female sex characteristics. Steroid hormones are secreted by the gonads, adrenal cortex, and placenta.
Hormones are usually slow to act but, once they act, they remain active for long periods of time and, also, their effects remain for a long time.
Endocrine Glands
There are 10 endocrine glands. As stated previously, other organs such as the stomach, intestines, kidneys, heart, brain, and placenta also make hormones.
Click here to take an online quiz on the location of the endocrine glands
The Pituitary Gland
The pituitary gland is often called the master gland. That is because the pituitary gland produces hormones that regulate other endocrine glands. Some hormones produced by the pituitary gland are:
1. Follicle Stimulating Hormone (FSH): Will be discussed in a later Chapter of the syllabus.
2. Luteinising Hormone (LH): Will be discussed in a later Chapter of the syllabus.
3. Growth Hormone (GH): Causes body cells to absorb amino acids and form protein for growth. The main function is to cause the elongation of bones.
4. Prolactin: stimulates milk formation by the breast after the birth of the baby.
5. Oxytocin: stimulates muscle contraction of uterus during birth, stimulates muscle contraction in the milk ducts during breast-feeding.
6. Antidiuretic Hormone (ADH): causes increased water reabsorption by kidneys.
7. Thyroid Stimulating Hormone (TSH): Combines with iodine at the thyroid gland to produce thyroxine.
Overproduction of GH causes gigantism and underproduction causes dwarfism.
The Hypothalamus
The hypothalamus links the nervous system with the endocrine system. It produces hormones that control the pituitary gland’s responses to messages from the brain and other hormones. Some these hormones, called releasing hormones, stimulate the pituitary gland to make other hormones. Others, called release inhibiting hormones, prevent the production of pituitary hormones.
An example is growth hormone releasing factor. This causes the production of growth hormone (GH) by the pituitary gland.
The Pineal Gland
This gland is in the brain. One hormone produced there is melatonin. Synthesis and release of melatonin is stimulated by darkness and inhibited by light. But even without visual cues, the level of melatonin in the blood rises and falls on a daily (circadian) cycle with peak levels occurring in the wee hours of the morning. Melatonin is readily available in drug stores and health food stores, and it has become quite popular. Ingesting even modest doses of melatonin raises the melatonin level in the blood to as much as 100 times greater than normal. These levels appear to promote going to sleep and thus help, insomnia to hasten recovery from jet lag, and to not to have dangerous side effects.
The Thyroid Gland
The thyroid gland produces the hormone called thyroxin. Thyroxin controls the rate of all the body’s internal reactions. In other words, thyroxin controls the rate of the body’s metabolism.
Physical conditions related to abnormal thyroid function are:
Hypothyroidism- Under Production of Thyroxine
1. Cretinism– Under production of thyroxin in young children. This results in low metabolic rates and results in retarded physical and mental development.
2. Myxoedema- Under production of thyroxin in adults. Characteristics are tiredness, lack of energy, slow mental and physical activity, and weight gain.
3. Goitre- Swelling of the thyroid caused by myxoedema.
Goitre
In cases of low production of thyroxine tablets are available to increase the thyroxine in the body. Since thyroxine needs iodine to be produced iodine is also administered to boost thyroxine levels.
Thyroxine Excess (Hyperthyroidism)
Thyroxine secretion is above normal. This causes a raised level of metabolism. Symptoms of over production of thyroxin are bulging eyes, weight loss heat production, nervousness, irritability, and anxiety. This condition is called Grave’s Disease. Corrective measures for Grave’s Disease are:
1. Drugs to suppress thyroid activity
2. Surgically remove part of the gland
3. Use radioactive iodine to destroy some of the gland.
The Parathyroids
There are 4 parathyroid glands. They are located within the thyroid gland. The hormone they produce is called parathormone. This hormone stimulates the release of calcium from the bones. That is why we must continue to include calcium in our diet even when our bones are fully grown.
The Thymus Gland
This gland is located behind the breastbone. It produces the hormone thymosin. This hormone causes white blood cells (lymphocytes) to become mature and active. These blood cells, as previously discussed in the Blood web page, are involved in the body’s immune system.
The Adrenal Glands
Click here to view an animation of the adrenal glands
The adrenal glands are located on top of each kidney. They secrete the hormone called adrenaline (also called epinephrine). This hormone prepares the body for stress and is released when we are frightened or feel stress. It does the following:
1. Increases blood flow to the heart, muscles, and brain.
2. Reduces blood flow to the kidneys. This helps reduce blood loss if we are cut. It causes us to get pale.
3. Opens the bronchioles allowing us to get more air.
4. Increases glucose levels in the blood.
5. Increases heartbeat rate.
6. Increase muscular contraction and strength.
7. Increases mental alertness.
Pancreas
As discussed in the Human Nutrition web page the pancreas secretes pancreatic juice for the digestive system.
In addition, the pancreas produces the hormone called insulin. This hormone is produced in groups of cells called Islets of Langerhans. 
Insulin is needed because it reduces blood glucose levels in the blood. It causes cells, especially fat and muscle cells, to absorb glucose from the blood. The glucose is needed for cellular respiration or converted into glycogen. The glycogen is stored in the liver or the muscles for future use in cellular respiration.
Diabetes is a serious condition that results from 1 of 2 causes. In type 1 diabetes, the pancreas no longer makes insulin and therefore blood glucose cannot enter the cells to be used for energy. In type 2 diabetes, either the pancreas does not make enough insulin or the body is unable to use insulin correctly. Symptoms of diabetes are high glucose levels in the blood and urine, the production of large amounts of urine, severe thirst, loss of weight, and tiredness.
Injections of insulin, which are taken daily, the control of carbohydrate intake, exercise, and weight control treat diabetes.
Anabolic Steroids
Anabolic steroids are hormone supplements that habe been used. They build up muscle, speed up recovery of muscle from injury, and help strengthen bones. There are many serious side effects such as liver and adrenal gland failure, infertility, impotence, and the development of male characteristics in females that can result if they are misused. They are also, sometimes given to animals to promote increased lean muscle (meat) production. This practice is banned in the EU.
Control of Thyroxine Level
Control of thyroxine level as well as many other hormones is done by negative feedback. If the thyroxine level is normal the pituitary gland is inhibited from releasing thyroid stimulating hormone (TSH). As a result, no further thyroxine is produced. When thyroxine levels are low the pituitary gland produces TSH. This causes more thyroxine to be produced by the thyroid gland.
An Example of negative feedback in the role of the thyroid in maintaining body temperature at 37°C.:
OR:
| Where the Hormone is Produced | Hormone(s) Secreted | Hormone Function |
| Adrenal Glands | Adrenalin | Causes Emergency Responses (fight/flight) |
| Pituitary Gland | Growth hormone | Affects growth and development; stimulates protein production |
| Pancreas | Insulin | Lowers blood sugar levels; stimulates metabolism of glucose, protein, and fat |
Hypothalamus |
Growth Hormone Releasing Factor | Causes growth hormone to be made |
| Pineal Gland | Melatonin | Controls body rhythms |
| Parathyroid Glands | Parathyroid hormone (Parathormone) | Affects bone formation and excretion of calcium and phosphorus |
| Thyroid | Thyroxine | Controls Metabolism |
| Thymus | Thymosin | Matures white blood cells |
