# Category: stem

## Calculus: Methods for Solving Limits with Explanations, Practice Questions, and Answers [AP Calculus, Calculus 101, Math]

In this calculus article, we will talk about the methods for actually solving or evaluating limits. There are practice questions included, labeled PRACTICE, and they are there for you to test your understanding of the different methods. The answers are at the very bottom. Enjoy!

## 2022 National Teacher Appreciation Week: Free Stuff and Teacher Discounts

A huge thank you to all the teachers around the world! May 3 is Teacher Appreciation Day, also known as National Teachers Day, and Teacher Appreciation Week lasts from May 2 – May 6. Teachers are invaluable to our communities. They nurture the growth of our students, both young and old, and inspire us to succeed with the gift of learning and education.

## Immunology 101: Stages of B-cell Development [Biology, MCAT, USMLE Medicine]

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.

## 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.

## Gastrointestinal System: Pathophysiology of Diseases and Cancers [Biology, MCAT, USMLE]

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.

• Illustrate the function of the endoplasmic reticulum in the cotranslational translocation of proteins made on membrane bound polysomes and their co- and post-translational modifications. Explain the function of the endoplasmic reticulum in protein folding and discuss the fate of misfolded proteins.
• ## Biology 101: Gel Electrophoresis

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.

## Chemistry 101: At Home Awesome Chemistry Experiments

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!

## Calculus: Two Important Theorems – The Squeeze Theorem and Intermediate Value Theorem

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.

## Working out …for your brain? – The Neuroscience and Benefits of Playing An Instrument

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.

## Central Chemoreceptor vs Peripheral Chemoreceptor in Respiration [Biology, MCAT, USMLE]

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.

## Say… Cheese! A Look Into Fermentation – History and Making of Cheese

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!

## Biology Unit 5 Study Guide: Evolution

Biology Unit 5 Study Guide: Evolution. After his visit to the Galapagos Islands, Darwin came up with the theory of evolution.  This theory stated that organisms change over time.  The way that organisms change is through the process of natural selection. With examples, practice questions, and answers to help make evolution respiration easy to learn!

## Pushing Life’s Boundaries: Extremophiles Archaea

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 Study Guide Book Just Published and on Sale! [Free Chapters]

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!

## TB Tests, Drugs and Side Effects for Tuberculosis: [USMLE, MCAT, Biology]

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.

## What is Maladaptive Daydreaming Disorder?

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.

## Hypertension: Causes and Health Effects of High Blood Pressure [Biology, MCAT, USMLE]

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.

## Direct Hernia vs Indirect Hernia

Direct vs Indirect Hernia: What is the difference between direct and indirect inguinal hernias? In this easy-to-understand lesson, we explore the differences between direct inguinal hernias and indirect inguinal hernias. Overall, an inguinal hernia is a medical condition, where protrusion or bulge of abdominal contents into the groin area and/or inguinal canal. There are two types of inguinal hernias: 1) direct inguinal hernia and 2) indirect inguinal hernia.

## Embryogenesis: Definition, Stages, and Development [MCAT]

Sonic Hedgehog Gene. CNS development and Limb development. In embryology and developmental biology, embryogenesis is the development of an animal or plant embryo, starting with fertilization of an egg cell by a sperm cell. After fertilization, the ovum becomes a diploid zygote. orms forebrain, separates right and left brain, and establishes midline. f there’s a mutation, then we have a whole brain with no separation of right and left, which is bad. This is called holoprosencephaly. Left and right hemispheres fail to separate. There are also facial abnormalities, cleft lip/palate and even severe cyclopia (single eye like a cyclops).

## The Rise of Tech: Tech Trends of the COVID-19 Pandemic

The recent COVID-19 pandemic has turned our world upside down. From the way we greet each other to the schedule of our daily routines, it’s safe to say that everything that was considered the norm at the beginning of 2020 has completely changed. While most people’s eyes are on health officials, tech giants and start-up companies have been using this time to create new inventions to propel society further – or so they say. Here we will analyze the new products and tech trends that have arisen in the wake of this pandemic, what they do, and if they actually serve to help society.