B-Cell Development Stages. stem cell –> early pro-B cell –> late pro-B cell –> large pre-B cell –> [1st checkpoint – selects for functional heavy chains] –> small pre-B cell –> [2nd checkpoint – select for functional light chains] –> Immature B cell (has surface IgM, no surface IgD). Somatic recombination is the process in which different individual gene segments of the H (heavy) chain combine with rearranged gene segments of the L (light) chain. The enzymes responsible for somatic recombination are the recombinase enzymes (RAG-1 and RAG-2) that recognize specific sequences (RSS) or recombination signal sequences. RAG-1 and RAG-2 are only expressed in B or T lymphocytes. These specific sequences recognized by the RAG-1 or RAG-2 enzymes are either a 1) heptamer or 2) nonamer. The heptamer literally contains 7 nucleotides, and the nonamer literally contains 9 nucleotides. There are typically 12 or 23 nucleotides in between the heptamer and nonamer to separate them.
In the midst of the COVID-19 pandemic, many people have been forced to quarantine themselves in their homes. Although countries are starting to open and people are exiting quarantine, social distancing is still common and previously planned summer activities such as trips, internships and summer jobs have been postponed or cancelled. With summer having arrived, students will no longer be distracted by their classes. This raises the question, what can we do over a quarantined summer?
Reproductive System: Medical Anatomy and Histology of Male vs Female Reproductive Organs [Biology, MCAT, USMLE]
In this quick and easy lesson, explore the histology of key reproductive system organs in females and males. Female Reproductive System: Histology and Organs. Male Reproductive System: Histology and Organs. Medicine. Medical School.
In this quick and easy guide, learn about Gastrointestinal System: Pathophysiology of Diseases and Cancers [Biology, MCAT, USMLE]. Topics include heptobiliary disease, understanding liver functions and cirrhosis, liver function tests, causes of liver injury, alcoholic hepatitis, NAFLD, NASH, viral hepatitis, autoimmune hepatitis, durg-induced liver injury, hereditary hemochromatosis, Wilson’s disease, Alpha-1 Antitrypsin Deficiency, PSC, PBC, cholelithiasis, cholecystitis, cholangitis, hepatocellular carcinoma, and more.
Cell Biology 101 – Function and Biogenesis of Cellular Membranes: The Endoplasmic Reticulum [Biology, MCAT, USMLE]
In this quick and easy lesson guide, learn about cell biology – the function and biogenesis of cellular membranes. Explain the metabolic and protein biosynthetic functions of the endoplasmic reticulum. Define key metabolic functions of the endoplasmic reticulum.
In this educational lesson, we learn about the purpose of gel electrophoresis and how gel electrophoresis works. Gel electrophoresis in a method of separating DNA. It can be used to separate the size of DNA, RNA, and protein. You first start with a variety of different fragments of DNA all mixed together. The gel is a porous matrix like a sponge and separates the DNA based on two main things: 1) size and 2) charge. The charge on DNA is what makes it move through the gel. DNA is a negatively charged molecule, so it will move towards a positive charge.
Chemical reactions happen around us all the time. These reactions occur when we cook or bake and even in our bodies, like when we breathe. Everyday objects are able to react and cause incredible reactions. Here are some easy science experiments you can create using things you can find around the house. Make sure you act safely during the experiment and have fun!
Learn about two very cool theorems in calculus using limits and graphing! The squeeze theorem is a useful tool for analyzing the limit of a function at a certain point, often when other methods (such as factoring or multiplying by the conjugate) do not work. This theorem also has other names like the Sandwich Theorem or the Pinch Theorem, but it is most commonly called the Squeeze Theorem. The Intermediate Value Theorem, often abbreviated as IVT, deals with a single function unlike the Squeeze Theorem.
Digoxin: How does Digoxin treat heart failure? Mechanism of Action and Side Effects [USMLE, Biology, MCAT, Medicine]
Digoxin is a drug that treats heart arrhythmias, left ventricular systolic dysfunction, and heart failure. In this succinct educational lesson, we learn about how digoxin works in treating heart arrhythmias and heart failure, digoxin toxicity and common side effects, and treatment for digoxin toxicity. We also have a mini quiz at the end, so you can test your knowledge on the pharmacology of digoxin.
Whether it’s a violin or a harmonica, learning to play an instrument takes time and effort to “perfect.” Musicians put hours and hours of hard work to perform in concerts, participate in competitions, or even just practice for fun at home. It can be frustrating to play the same piece hundreds and hundreds of times, especially if you still can’t get one section down. However, all of these hours of practicing actually do more than just putting on a perfect performance or impressing your family; playing an instrument can help your physical and mental state.
Immunology: Treatments for Rheumatoid Arthritis – NSAIDs vs DMARDs vs Glucocorticoids [Biology, Medicine, MCAT, USMLE]
Rheumatoid arthritis is an autoimmune disease characterized by chronic inflammation in the joints of hands, feet, knees, etc. In this quick and easy lesson, we explain the standard medical treatment for patients with rheumatoid arthritis at the USMLE immunology level, including DMARDS (synthetics and biologics), NSAIDS, and glucocorticoids.
There are two types of chemoreceptors that help control and regulate our respiratory rate: 1) central chemoreceptors and 2) peripheral chemoreceptors. Both central chemoreceptors and peripheral chemoreceptors send signals to the main respiratory center in the brain that unconsciously tells our bodies to increase or reduce pulmonary ventilation. In this lesson, we describe the differences and similarities of central chemoreceptors and peripheral chemoreceptors for the pulmonary system.
From sour, sweet, and savory, cheese is a delicacy that connects people of all ages. It’s in hamburgers, pizza, salads, spaghetti, and desserts. Many of the world’s most popular dishes contain cheese, a food item that has been around humans for a long time. In this article, you will learn the incredible science that makes cheese possible. Although the exact origins of cheese are unknown, it is thought that cheese originated when humans first began domesticating milk-producing animals like cows and goats. In fact, there is a legend that the first person to discover cheese was a merchant who found his milk curdled inside his container made of a sheep’s stomach. To his surprise, the curdled milk had a unique flavor that quenched his hunger. Cheesemaking is also shown in the artwork of a number of ancient civilizations including the Roman Empire and Ancient Egypt. However, the cheeses that are popular today were not made until cheesemaking became widespread across European countries around 500 years ago and then came to America when Pilgrims brought cheesemaking techniques with them. Since then, the cheese industry boomed in America and as of 2017, Americans consumed an average of 37 pounds of cheese every year per person!
Native to New Guinea, bananas prefer tropical climates and can be grown year round. In terms of produce, the biggest distinction is between bananas and plantains, both of which belong to the same genus (Musa) and come in a range of cultivars, or varieties. Bananas are generally eaten raw or as part of a dessert or baked good. Plantains are a staple crop, culinary distinct due to their higher starch content, predisposing them to being cooked and fried as part of meals or snacks.
Moderate and extreme are relative terms. What many assume to be the normal conditions for life do not apply equally across all species. Habitability can be thought of in terms of the Goldilocks principle. For example, to survive people need an environment that is not too cold and not too hot. Ranges like this exist for other factors as well, such as pressure. However, what is just right for us and most other creatures can be too much or too little for some. Animals that live on the sea floor provide an illustrative example in this regard. Where people need submersibles to maintain their equilibria, creatures that natural selection has adapted to thrive in the ocean’s depths are right at home. Cold, highly pressurized environments are the norm for them. When deep sea creatures are brought to the surface through accident or scientific curiosity they often either melt, as with glacial ice worms, or fatally decompress, like with blobfish. In this way the term extremophile is a relative one and is used to describe organisms that live in environments that are extreme to us. Beyond their novelty, extremophiles are important objects of study as they challenge and expand our notions of life and its necessities.
Biology Unit 4 Study Guide: Genetics, Meiosis, DNA and Protein Synthesis. With examples and answers to help make meiosis, DNA replication, and RNA translation easy to learn!
To answer this question we will first have to review the physical properties of light and go over the basics of optics, which is the study of the relationship between sight and light. Visible light is a section of the electromagnetic spectrum, and it is the only portion that people can see. While electromagnetic radiation can be measured via its various prosperities, such as frequency or energy, it is most commonly categorized by wavelength. Taking one step back, radiation is the transfer of energy in the form of waves or particles. For electromagnetic radiation, wavelength is determined by measuring photons. Put simply, photons are massless particles that also exhibit the characteristics of waves. To measure wavelength a point is designated on one wave (usually a peak or trough) and the length between it and that same point on the next wave gives you the wavelength.
Hi Everyone! My friend just published a biology study guide book and it’s currently on sale! This book on biology study guides contains practice review questions and answers. Study Guides: Biology Unit Review Practice Questions and Answers . This interactive study guide of worksheets contains questions and answers to help you understand biology. Each unit contains information on key topics to review to further your understanding of biology. The units covered in this book include: ecology, biomolecules and cell biology, energy, photosynthesis, cellular respiration, cell division, mitosis, meiosis, protein synthesis, genetics, and evolution. Award-winning author and teacher Dr. Sam J. Alex created this study guide while inspired by students and teachers. All proceeds donated! Hope you find this book helpful on your journey into the wonderful world of biology and beyond!
Earth has experienced at least five Ice Ages: the Huronian, the Cryogenian, the Andean-Saharan, the Karoo, and the Quaternary. The latest of these is the Quaternary Ice Age, which began 2.6 million years ago and is still ongoing. That might sound off given that the popular conception of an ice age is of a world blanketed in snow and roaming with wooly mammoths, but the scientific definition only requires that a substantial ice sheet be present on the Earth’s surface, and Antarctica fits the bill. While their causes vary, ice ages are typified by periods of sustained global cooling and glacial expansion. Going by this, the Little Ice Age qualifies, though it is also an ice age within an ice age, making it a sort of matryoshka doll climate event. The Little Ice Age is not the only lesser ice age, though it is the best known as it occurred the most recently and within recorded history. After having touched on similarities, our next logical step is to examine what makes the Little Ice Age different.
Drugs for TB: What drugs treat tuberculosis TB? In this quick and easy lesson, we will explain the main drugs -rifamycin, isoniazid, pyrazinamide, ethambutol, and streptomycin – that treat Mycobacterium tuberculosis or TB and provide study aid mnemonics to aid in your USMLE learning.
Retroviruses are a class of viruses that not only infect host cells but also integrate their genetic material into the host genome, establishing a permanent infection that cannot be cured. The most common retrovirus is the human immunodeficiency virus or HIV, which targets and destroys helper T-cells.
Daydreaming is a common human phenomenon, one that we all experience in our daily lives. Studies show that we actually spend around 47% of our waking time in the dream world. We utilize this important tool to think-out different scenarios, re-visit special times in our lives, imagine new ones, or even just to pass time. Daydreaming is vital to the human experience. But one may wonder, what happens when one daydreams a little too much?
Sleep 101: Brain Activity and Sleep Disorders, Sleep Apnea, Circadium Rhythms, and How to Sleep Better at Night
Sleep and Brain Activity Sleep disorders affect up to 70 million people and cost around $15.9 billion annually. EEG stands for electroencephalography, which was used to examine human brain waves in the 1950s. Sleep Disorders: Insomnia, OSA, Apnea, Narcolepsy. Regulation of Sleep. Sleep-Wakefulness Cycle: Circadium Rhythm and Homeostatic System. Tips to sleep better at night.
Primary Essential Hypertension vs Secondary Hypertension: Causes and Health Effects of High Blood Pressure [Biology, MCAT, USMLE]
In this quick, easy-to-understand lesson, we learn about secondary hypertension for USMLE and medicine. Secondary hypertension is defined as high blood pressure (>140/90 or >130/80) caused by an underlying disease, medical condition, or drugs. While primary essential hypertension comprises of the majority of hypertension cases (90%), only 10% of patient cases is secondary hypertension.
In this quick, easy lesson, we learn about hypertension, also known as high blood pressure, for USMLE and medicine. Hypertension is defined numerically as >140/90 and more recently as >130/80. Primary Hypertension vs Secondary Hypertension. Hypertension Effects. Hypertensive Urgency vs Hypertensive Emergency.