I achieved a perfect score on the MCAT (528) and since then I’ve made it my mission to pass on my test-taking strategies to other pre-meds.
Acid & Base RegulationVolatile acid is the product of aerobic cellular respiration, which releases carbon dioxide. As we've learned elsewhere, when carbon dioxide interacts with water in the body fluids, carbonic acid forms."Volatile" refers to the fact that carbon dioxide is expired by the lungs.Non-volatile acids are the products of protein and phospholipid metabolism; they include sulfuric acid and phosphoric acid, and they are excreted in the urine as titratable acids.Because enzymes and other proteins only function at particular pH values, the body must regulate the acidity of the intra- and extracellular fluids.Three lines of defense against acid-base imbalance:In the body, fluids (chemical mixtures), called buffers, minimize pH changes until hydrogen balance can be regained. The respiratory system expires carbon dioxide, the source of volatile acid.The urinary system excretes the non-volatile, aka, fixed, acids.These systems operate interdependently to maintain an arterial blood plasma pH of 7.4. Acid Production by Body TissuesBody tissues produce acids, including carbon dioxide, sulfuric acid, and phosphoric acid; each of these acids releases hydrogen ions that must be buffered in the body fluid compartments. Buffering in Fluid CompartmentsIntracellular compartment of body tissues = proteins and organic phosphates.Intracellular compartment of red blood cells = hemoglobin.Extracellular fluid = bicarbonate, which is the most important extracellular buffer, and, phosphate and proteins. Acid RemovalIn the Lungs: When carbonic acid reaches the lungs, it dissociates to form carbon dioxide, which is expired in ventilation. When pH falls, increased ventilation triggers to release excess carbon dioxide. Rapidly, the partial pressure of carbon dioxide drops, and the acidity of the blood is reduced. In the Kidneys:Nephrons reabsorb bicarbonate from the filtrate, and excrete hydrogen ions as tritratable acids and ammonium in the urine. Nearly all of the filtered bicarbonate is reabsorbed from the proximal tubule. Some hydrogen ions attach to ammonia and are secreted into the filtrate as ammonium; some of this ammonium is then reabsorbed from the thick ascending limb (where it participates in countercurrent multiplication in the renal interstitial fluid). In the alpha-intercalated cells of the distal nephron, ammonium is again secreted into the tubular fluid, along with phosphoric acid. Phosphoric acid forms when hydrogen ions attach to phosphate, and is often referred to as "titratable acid" Ammonium and phosphoric acid formation and secretion involve bicarbonate synthesis and reabsorption; this new bicarbonate contributes to the extracellular buffers. Both mechanisms are responsive to aldosterone, which is a hormone secreted by the adrenal cortex secreted in response to low pH. Clinical CorrelationsAldosterone deficiency inhibits ammonium excretion, and causes type 4 renal tubular acidosis. Because potassium excretion is also inhibited by aldosterone deficiency, this type of acidosis is characterized by hyperkalemia. Alkalosis is a consequence of excessive removal of hydrogen ions from the body fluids; as a result, the blood becomes more alkaline). Acidosis is the opposite: excessive hydrogen ions are added to the blood or retained; the blood becomes more acidic. Retention of acids can be a sign of renal failure. See Acid-Base Disorders
Hormonal Regulation of Digestion SummaryFour Major Digestive Hormones Gastrin • Stimuli: stomach expansion, protein and caffeine in the stomach, alkaline chyme in the stomach – Secretion Site: enteroendocrine cells of the stomach mucosa • Major Actions: – Stimulates gastric juice (HCl, mucus, pepsinogen) secretion – Stimulates gastric motility – Pyloric sphincter relaxation Secretin • Stimuli: acidic chyme in the duodenum – Secretion Site: enteroendocrine cells of the duodenal mucosa • Major Actions: – Stimulates pancreatic enzyme secretions into duodenum via the sphincter of Oddi (Pancreatic secretions = bicarbonate-rich, neutralize acidic chyme.) Cholecystokinin (CCK) • Stimulus: triglycerides, fatty acids, and amino acids (part of chyme) in the duodenum – Secretion Site: enteroendocrine cells of the duodenal mucosa • Major Actions: – Stimulates bile secretion from gallbladder – Stimulates pancreatic enzyme secretion – Promotes sphincter of Oddi relaxation.CCK and secretin potentiation: together stimulate a much greater release of pancreatic enzymes than if either hormone acts alone. Glucose-dependent insulinotropic peptide (GIP) • Stimulus: glucose (also: fatty acids and amino acids; all present in chyme) in the duodenum – Secretion Site: enteroendocrine cells of the duodenal mucosa • Major Action: – Stimulates pancreas insulin secretion – Inhibits gastric acid secretion.Four Criteria of Gastrointestinal Hormone A substance must meet four different criteria to be considered a gastrointestinal hormone. • The substance is secreted into the bloodstream in response to a physiologic stimulus (in this case, ingestion of a meal) to a target site, resulting in a physiologic action (to regulate digestive actions). • The function of the substance acts independently of neural activity. • The substance can be isolated and purified for chemical identification as well as synthesized again. • The isolated substance, upon intravenous injection, can induce the same physiologic response as when it receives the appropriate stimulus. The four major digestive tract hormones meet all of these criteria.Candidate Hormones Candidate Hormone Description • Regulate digestion but fail to meet all four of the aforementioned criteria. – Considered to have putative roles in GI regulation.Key Candidate Hormones • Motilin – increases GI motility and specifically mediates the migrating myoelectric complex. • Pancreatic polypeptide – inhibits pancreatic bicarbonate and enzyme secretions. • Enteroglucagon – responds to low blood glucose concentration and stimulates glycogenolysis and glucagonogenesis by the liver. • Glucagon-like peptide-1 (GLP-1) – stimulates insulin secretion by the pancreas.Additional Note: There are many unique types of enteroendocrine cells, each of which secrete a specific hormone.* – For example, G cells are enteroendocrine cells that specifically secrete gastrin.
Need help getting started studying for the MCAT? Take advantage of this fully-personalized MCAT study schedule. This comes with continuous edits for 90 days after purchase to make sure it works for you! I scored a 519 (129/129/131/130) --97th percentile on the MCAT. I have been a peer tutor (online and in-person) in A&P, chemistry, organic chemistry, biochemistry and biology for 5 years! I have been an MCAT tutor for the last 2 years. I know how to design a manageable study schedule that will: -suit your needs -recommend study materials -cover all topics on the MCAT -best prepare you to score high Once you have purchased the item, I will email you a questionnaire to learn more about: - where you are in the process - test date - hours/day you have to study - preferred study methods - study materials you have available Lets get started on this journey together!
Welcome to the Zoë Huggett Tutorials website. Visit the online tuition page to find out more about me and how I might be able to help you with A-Level biology or A-Level chemistry (or GCSEs). This site provides A-Level biology revision resources to help you on your journey to a better understanding and your goal
Gas exchange requires the close physical association of ventilated alveoli and perfused pulmonary capillaries.However, in the dead spaces of the respiratory tract, one (or both) of these requirements is absent, and gas exchange does not occur. Anatomic dead space: conduction portion of the respiratory tract (we show the tracheobronchial tree in this image). Functional dead space: aka, alveolar dead space comprises alveoli where gas exchange does not occur (i.e., non-perfused alveoli). Physiologic dead space: includes the anatomical space and functional dead space; this is the total volume of the respiratory tract that does not participate in gas exchange. It can be calculated using the Bohr equation. Ventilation Rates Minute ventilation rate:The total rate of air-flow into and out of the lungs.Includes the air-flow through the tracheobronchial tree and to both the functional alveoli and non-functional alveoli. Alveolar ventilation rate:Refers to the rate of air-flow into and out of the functioning alveoli, only (not though the physiologic dead spaces). Partial pressures of Alveolar O2 Partial PressureMinute and alveolar ventilation rate can be used to calculate the partial pressure of alveolar oxygen, which is a key facet of clinical respiratory evaluations. Calculation Steps:Calculate the minute ventilation rate: VE = TD x Breaths/Min Tidal volume can be measured clinically using a spirometer.VA = VE - VD (clinically determined via the Bohr equation). Alveolar ventilation equation states that: PACO2 = (VCO2 x K)/VA K is usually 863 mmHg; this constant controls for variation in physical measurement conditions.Alveolar gas equation states: PAO2 = PIO2 - (PACO2/RQ) RQ = respiratory quotient (aka, respiratory exchange ratio) is typically 0.8; it describes the ratio of the amount carbon dioxide produced in metabolism to the amount of oxygen consumed. SummaryWhen alveolar ventilation rate decreases, the alveolar partial pressure of carbon dioxide increases while the part...
Immune System OverviewHere we will learn about the immune system, which combats disease-causing organisms.Pathogens Disease-causing or harmful microorganismsAntigens Material that can evoke an immune response Innate Immune BranchNon-specific, fastThe innate branch is non-specific (it reacts to a broad range of microbes) and is fast (responses occur within hours of infection).Actors of the Innate SystemPhysical barriers: - Epidermal cells create a slightly acidic surface and release enzymes and other antimicrobial peptides that make the skin surface inhospitable to microbes.Chemical barriers: - Some body surfaces (such as the respiratory pathways) are also covered in mucus, which can trap microbes before they can infect the body.Chemokines: Chemical signal produced by damaged cell to alert the body to danger and act as a homing signal for immune cellsNeutrophils: First type of phagocytic cell to arriveMonocytes: Arrive and mature into macrophages which engulf and destroy pathogensInflammation: Response to tissue damage, four clinical signs: redness, heat, swelling and pain.Innate System in ActionPathogens gain entry to the inside of the body through the wound.Chemokine chemical signals (chemotactic cytokines): Released by damaged cells to alert the body of trouble. Act as homing signals that stimulate cells of the immune system to migrate towards the source of the chemokines. Phagocytic cells are then attracted to the wound site from the blood. Neutrophils, monocytes, macrophages.Macrophages phagocytose pathogens: Phagocytosis is a type of bulk transport into the cell in which large extracellular cargo is brought into the cell and broken down. In our example, the bacterium will eventually be broken down and the macrophage will go on to engulf and destroy other pathogens.Clinical signs of inflammation Result from innate immunity activation. Redness, heat, swelling, and pain are all classically accepted signs of inflammation. Importantly, inflammation can result in impairment in function.If the innate branch is unable to fight off the invading pathogens on its own, the adaptive branch is called in to help. Adaptive Immune BranchSpecific, slow, systemic, memoryThe adaptive branch is: Specific (it can distinguish specific species of pathogens) Slow (responses occur within days of infection). Systemic (NOT restricted to the initial site of infection). Has memory (it mounts a faster and even stronger attack against repeat pathogens).Actors of the Adaptive SystemAdaptive immunity is further divided into humoral immunity and cell-mediated immunity.Humoral immunity: B cells (matured into plasma cells) producing antibodies (Y-shaped proteins)Cell-mediated immunity: Cytotoxic T cells recognize infected cells and kill them while helper T cells act as the general of the immune army and release chemical signals that activate various immune cell typesHumoral ImmunityLymphoid tissue is the home of many types of immune cells.Plasma cells reside in the lymphoid tissues: - Plasma cells are activated and matured B cells (B cells and T cells are the two adaptive immune cell types). - Plasma cells pump out antibodies.Antibodies are Y-shaped proteins that recognize antigens from the invading pathogen.The antibodies produced by plasma cells are released into the blood vessel where they travel throughout the body.In the tissues, we show an antibody binding two viruses. Neutralizing antibodies are able to bind to viruses and toxins in such a way as they are no longer able to infect or cause damage.Cellular ImmunityThe major cells of cell-mediated immunity are the T cells, which are divided into cytotoxic T cells or helper T cells.Cytotoxic T cells have receptors on their surfaces that bind infection signals on infected host cells. The cytotoxic T cell has a receptor on its surface that is able to bind the infected cell's signal. When this happens, the T cell releases death signals which kill the infected cell.Helper T cells act as the general of the immune army. They release activation signals (cytokines and chemokines) that help phagocytic cells to perform their job more efficiently. They also release signals that activate cytotoxic T cells. B cells also receive activation signals from helper T cells.With all of these cells working together, the immune system is usually able to destroy the invading pathogens.
Read Antibody by BioTecNika on Issuu and browse thousands of other publications on our platform. Start here!
Brief guide to understanding the hard bits of the immune system A-level Biology Specification. Lots of questions and markschemes on the immune system. if you use then please like or share
Reactions of alcohols are one fo those must-know topics for anyone who's taking organic chemistry and is planning to take MCAT in the future.
Polygenic inheritance Single phenotypic character that is affected by multiple genesQuantitative characters Characters that exist along a spectrumTo understand this, we draw two average sized people, each with a genotype: big A, little a, big B, little b, big C, little c. How many potential genotypes can we have? • For each gene there are 2 possible alleles, and we are exploring a trait governed by three genes: - So 2^3 (8) independently assorted gamete possibilities from each parent so when crossed, there are a total of 64 possible genotypes in the offspring (8 times 8). - However, for our purposes when discussing the contribution to height, functionally all that matters is the total number of dominant alleles in the genotype (not which alleles are dominant), so we will reduce the number of genotypes to 7. • Write seven possible genotype combinations of their offspring (these aren't all of the possible combinations, but for our purposes they are enough). • So big A, big A, little b, little b, little c, little c gives the same amount of "height" as little a, little a, big B, little b, big C, little c. - As a simplification of how height is controlled in humans, consider that each dominant allele gives an equivalent amount of "height" to an offspring. • Draw the range of height that the offspring have. • The tallest is big A, big A, big B, big B, big C, big C. • The shortest is little a, little a, little b, little b, little c, little c. We apply these principles to our analysis of polygenic inheritance to simplify complex possibilities. • Finally, a clearer way to visualize this is to draw a box with six circles in it in line with each of the genotypes of the offspring. • Fill in one circle in each box per dominant allele in the offspring. So those with the most filled in circles end up being the tallest.Lastly, it is important to note that genes alone do not explain all of a phenotype. The environment, including socioeconomic status, plays a significant role in many phenotypes. For example, prenatal and childhood nutrition and stress influence height.
Read Regulation-of-enzyme-activity by BioTecNika on Issuu and browse thousands of other publications on our platform. Start here!
Medicine and Moscato | The MCAT is one of the toughest hurdle a premed goes through. Luckily, I've done it twice so you can learn from my mistakes!
Cytokines are the unsung heroes of the immune system, often acting as the first responders to a pathogen infection.
Prokaryotes And Eukaryotes Worksheet. All prokaryotes have plasma membranes, cytoplasm, ribosomes, and DNA that's not membrane-bound. Once you find your worksheet, click on on pop-out icon or print icon to worksheet to print or obtain. The prox
Full time MCAT tutor banned from taking the MCAT. Here's how I use this to my advantage to best help YOU the premed student when it comes to helping you craft your own personal MCAT prep journey.
Many of my private tutoring students have requested to see the MCAT study plan spreadsheet that I personally used.
Read Enzyme Kinetics by BioTecNika on Issuu and browse thousands of other publications on our platform. Start here!
Read Photoreceptors in plants by BioTecNika on Issuu and browse thousands of other publications on our platform. Start here!
Mind Help brings to you a detailed guide on what is Bipolar Disorder, types of BD, its signs and symptoms, and other frequently asked questions.
Click to enlarge When you think of chemical reactions, you might think of them as irreversible, permanently changing one substance into another. While this is true in some cases, some chemical reactions are reversible, and we can take the...
Attachment Theory describes the attachmentstages of close relationships.
Organic Chemistry Molecular Representations and Bonding in Organic Molecules Resonance By resonance in organic chemistry we mean an interaction of multiple p-orbitals making a long π-bond spanning multiple atoms. A case of a simple π-bond results from the interaction of the two p-orbitals connecting two atoms. However, there are situations when three or more orbitals...
Read Transcription RNA Synthesis by BioTecNika on Issuu and browse thousands of other publications on our platform. Start here!
Read Regulation of carbohydrate metabolsim by BioTecNika on Issuu and browse thousands of other publications on our platform. Start here!
Effective techniques how to stimulate your lymphatic system with our guide. Boost lymphatic circulation and enhance your well-being!
