MCAT Basics (from MedSchoolCoach)

In this episode, we focus on biosignaling and cover how cells communicate through systems like voltage-gated and ligand-gated ion channels, using real-world examples such as neuronal signaling and muscle contraction.
We also break down the role of enzyme-linked receptors, specifically receptor tyrosine kinases (RTKs), and explore how these pathways are involved in cell growth and cancer. Additionally, we take a detailed look at G-protein coupled receptors (GPCRs) and their role in activating secondary messenger systems like cyclic AMP (cAMP).
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Jump into the conversation:
(00:00) Intro
(00:32) Overview of Biosignaling
(01:05) Introduction to Biosignaling and its Importance
(01:49) Stimulus-Response Concept: Fight or flight, glucose homeostasis, transcription regulation
(02:34) Voltage-Gated Ion Channels: Activated by changes in membrane potential
(03:29) Action Potential: Sodium channels and signal propagation
(05:01) Ligand-Gated Ion Channels: Role in neuron-to-neuron signaling
(06:01) Muscle Contraction: Acetylcholine's role in skeletal muscle contraction
(07:29) Misconception on Calcium: Sodium initiates muscle cell depolarization, not calcium
(08:33) Enzyme-Linked Receptors: Focus on receptor tyrosine kinases (RTKs)
(09:39) RTKs and Cancer: How RTK signaling pathways are linked to cancer
(12:00) G-Protein Coupled Receptors (GPCR): Structure and function of GPCRs
(14:43) Adenylate Cyclase and cAMP: Role of GTP in activating adenylate cyclase and producing cAMP
(18:10) Quiz Question 1: Ion specificity in potassium channels
(22:54) Quiz Question 2: Hypertension treatment and G-protein pathways
(25:00) Biosignaling as the foundation for cellular responses

In this episode, guest host Alex Starks introduces the Metabolism series by examining glycolysis, a fundamental biochemical pathway for energy production. The discussion covers glucose digestion, the role of insulin and glucose transporters, and the step-by-step breakdown of glucose within cells. Alex also offers a detailed explanation of how glucose is processed to generate energy and outlines the key reactions involved. This episode provides a thorough overview of glycolysis offers valuable study strategies for mastering this topic on the MCAT.
Visit MedSchoolCoach.com for more help with the MCAT.
Jump into the conversation:
(00:00) Intro
(01:08) Overview of metabolism and starting the series
(02:41) Digestion and absorption of glucose into the bloodstream
(04:10) The liver’s role in glucose transport and GLUT2
(05:05) The role of insulin in glucose uptake by muscles and fat cells
(07:48) Trapping glucose in the cell with glucose phosphorylation
(09:32) Glycolysis Step-by-step breakdown of glycolysis
(17:41) NADH and ATP production during glycolysis
(22:30) Pyruvate and NADH fates in anaerobic and aerobic respiration
(25:12) Quiz: Metabolism quiz and study tips for the MCAT

One of the most fundamental biochemical processes is the Krebs cycle. This metabolic pathway plays a critical role in both the Chem Phys and Bio/Biochem sections of the MCAT, so understanding it is key.
In this episode, our guest host, Alex Starks, walks us through the transformation of pyruvate into acetyl CoA via the Pyruvate Dehydrogenase Complex (PDC). We’ll explore how thioester bonds help transfer energy within the cycle, how acetyl CoA combines with oxaloacetate to form citrate, the difference between enzymes like synthetases and synthases, and how GTP is produced. We’ll also make connections to the electron transport chain and discuss how the TCA cycle influences blood pH through CO2 production.
Visit medschoolcoach.com for more help with the MCAT.
Jump into the conversation:
(00:00) Intro
(01:05) Recap of glycolysis and pyruvate
(02:45) Pyruvate dehydrogenase complex (PDC)
(03:40) Role of acetyl CoA in the Krebs cycle
(05:37) How citrate is formed 
(07:17) How isocitrate is formed
(10:00) How alpha-ketoglutarate is formed
(13:42) How  succinate and GTP are formed
(16:28) How succinate, fumarate and oxaloacetate are formed
(18:23) Fumarate converted to malate
(21:53) Recap of the Krebs cycle and ATP yield
(25:00) Regulation of the Krebs cycle
(26:16) Quiz

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In this episode, we cover the respiratory system, an important topic for the MCAT Bio/Biochem section. We'll go over the anatomy of the respiratory system, highlighting key structures such as the lungs, bronchi, bronchioles, and alveoli, and explain how they contribute to respiratory functions.
You'll also learn about the main roles of the respiratory system, including gas exchange, thermoregulation, particle filtration, and maintaining blood pH. We’ll break down the mechanics of breathing, including the role of the diaphragm and intercostal muscles, and how pressure changes drive air into and out of the lungs. We also cover the importance of pulmonary surfactant in preventing alveolar collapse and how partial pressures influence gas movement.
Visit MedSchoolCoach.com for more help with the MCAT.
Jump into the conversation:
(00:00) Intro
(01:02) Overview: Functions of the respiratory system
(01:28) Main Functions: Gas exchange, thermal regulation, particle filtration, pH control
(02:20) Upper Respiratory Tract: Nose, nasal cavity, sinuses, larynx, trachea
(05:00) Lower Respiratory Tract: Lungs, bronchi, bronchioles, and alveoli
(09:28) Airflow Pathway: How air travels through the respiratory system
(10:23) Gas Exchange: Oxygenation and CO2 removal
(11:27) Breathing Mechanics: Diaphragm and intercostal muscles
(13:04) Pressure Differentials: How pressure changes drive airflow
(15:01) Surface Tension in Alveoli: Importance of pulmonary surfactant
(18:17) Lung Compliance and Elasticity: How lung tissue stretches and returns to shape
(21:48) Gas Exchange Process: Partial pressures of oxygen and carbon dioxide
(24:59) Partial Pressure Explained: Role in moving gases during respiration
(30:31) Thermoregulation: Maintaining body temperature through respiration
(35:59) Particle Filtration: Nasal hairs and mucous cilia system
(39:44) pH Regulation: How breathing controls blood pH
(41:18) Respiratory Control: Involuntary and voluntary mechanisms, brainstem functions