Urinary and Digestive Systems & Protein Production Study Guide

Major Functions and Anatomy of the Urinary System

• Primary Functions of the Urinary System:     * Waste removal: Clearing the body of metabolic byproducts.     * Water balance: Regulating the volume of water in the body.     * Electrolyte balance: Maintaining proper levels of ions such as sodium, potassium, and calcium.     * pH balance: Managing acid-base levels in the blood.     * Hormone production: Secretion of hormones involved in blood pressure and red blood cell production.

• Path of Urine Leaving the Body:     * Urine is produced in the kidneys and travels through the following sequence of organs: Kidneys $→$ Ureters $→$ Bladder $→$ Urethra.

• The Urinary Bladder:     * Tissue Composition: The bladder is composed of transitional epithelium and elastic fibers.     * Functional Benefits: This specific tissue allows for expansion and shape-shifting as the bladder fills, providing protection and the ability to store urine under variable pressure.

• Kidney Anatomy and Structure:     * Renal Cortex: The outer layer of the kidney; the site of the glomerulus and Bowman’s capsule.     * Renal Medulla: The inner portion of the kidney containing the renal pyramids; the site of the loop of Henle and collecting ducts.     * Renal Pelvis: The central funnel-like structure that collects urine and directs it into the ureter.     * Renal Pyramid: Triangular-shaped structures in the medulla that help transport urine toward the calyx.     * Calyx: Cup-like structures that collect urine from the pyramids before it enters the renal pelvis.     * Renal Capsule: The fibrous outer membrane that surrounds the kidney for protection.     * Renal Artery: Carries oxygenated, unfiltered blood containing high levels of waste and excess water into the kidney.     * Renal Vein: Carries deoxygenated, filtered, and cleaned blood away from the kidney.     * Ureter: The tube that transports urine from the kidney to the bladder.

Nephron Physiology and Urinalysis

• Path of Urine through the Kidney:     * Once urine exits the collecting duct of the nephron, it follows this path: Papillary duct $→$ Calyx $→$ Renal Pelvis $→$ Ureter $→$ Bladder $→$ Urethra.

• Nephron Components and Functions:     * Glomerulus: A network of capillaries where filtration begins.     * Bowman’s Capsule: Surrounds the glomerulus and captures the filtrate.     * Proximal Convoluted Tubule (PCT): The site of primary filtration and reabsorption, specifically for glucose and water.     * Loop of Henle: Includes ascending and descending limbs; primary site for water reabsorption (specifically in the descending limb).     * Distal Convoluted Tubule (DCT): Involved in further secretion and reabsorption of ions.     * Collecting Duct: Final site for water reabsorption before urine exits toward the renal pelvis.     * Afferent Arteriole: Directs blood into the glomerulus.     * Efferent Arteriole: Directs blood out of the glomerulus.

• Glomerular Filtration Rate (GFR) Calculation:     * Example: A patient has a GFR of $100\,mL/min$. To find the daily rate in liters:     * $100\,mL/min \times 60\,min/hr \times 24\,hr/day = 144,000\,mL/day$     * $144,000\,mL/day \div 1000\,mL/L = 144\,L/day$

• Urinalysis Indicators for Disease:     * Gestational Diabetes: Detected by high glucose (glycosuria) levels in pregnant individuals.     * Urinary Tract Infection (UTI): Indicated by the presence of high nitrites and leukocytes (white blood cells) in the urine.     * Ketoacidosis: Indicated by the presence of ketone bodies, suggesting the body is breaking down fat for fuel instead of glucose.     * Diabetes Insipidus: Characterized by low urine specific gravity, indicating very dilute urine.     * Kidney Failure: Indicated by high protein levels (proteinuria) or low GFR, suggesting the filtration system is compromised.

• Experimental Variables:     * Independent Variable: The factor that is manipulated by the researcher.     * Dependent Variable: The observed factor or result that changes in response to the independent variable.     * Positive Control: A baseline sample expected to yield a positive result.     * Negative Control: A sample not expected to react to the independent variable, used to ensure the baseline is clear.

The Digestive System: Anatomy and Function

• Oral Cavity Digestion:     * Mechanical Digestion: Teeth break down food into smaller particles.     * Chemical Digestion: Saliva contains salivary amylase, which begins the breakdown of carbohydrates.

• Salivary Glands: Produce saliva to lubricate food for swallowing, moisten the mouth, and provide an initial defense against bacteria while starting starch digestion.

• Liver and Bile:     * Liver Functions: Produces bile, metabolizes toxins, and stores nutrients (converts glucose to glycogen for storage).     * Bile Function: Breaks down fats into smaller droplets for easier absorption.     * Entry Point: Bile is produced in the liver, stored in the gallbladder, and enters the digestive tract in the duodenum.

• Pancreas and Connection to Digestion:     * Enzymes Produced:         * Lipase: Breaks down fats.         * Protease: Breaks down proteins.         * Amylase: Breaks down carbohydrates.     * Connection: The pancreas connects to the rest of the digestive system via the pancreatic duct, which opens into the duodenum.

• The Small Intestine Sections:     * Duodenum: The site where digestion is completed; receives bile and pancreatic juices via the Sphincter of Oddi.     * Jejunum: The primary site of nutrient absorption.     * Ileum: Absorbs remaining nutrients and connects to the large intestine.

• The Large Intestine Sections:     * Cecum: Receives material from the small intestine.     * Colon: Divided into Ascending, Transverse, Descending, and Sigmoid sections. Its primary roles are absorbing water and electrolytes and housing the gut microbiome.     * Rectum: Stores feces before defecation.

• Special Medical Tubes and Procedures:     * J-Tube (Jejunostomy tube): A feeding tube inserted directly into the jejunum.     * G-Tube (Gastrostomy tube): A feeding tube inserted directly into the stomach.     * Ostomy: A surgical procedure that creates a stoma (opening) in the abdominal wall for waste removal.     * Endoscopy: Use of a camera to view the upper gastrointestinal (GI) tract.     * Colonoscopy: Use of a camera to view the entire colon via insertion into the rectum.     * Biopsy: Removal of a small piece of tissue for laboratory analysis.

• Gut Microbiome: The collective population of microorganisms (bacteria, fungi, viruses) living in the intestine that are essential for digestion and immune system health.

Digestive Diseases and Conditions

• Colon Polyp: A small clump of cells forming on the lining of the colon; most are benign, but some can become cancerous.
• Celiac Disease: An immune reaction to eating gluten that causes damage to the small intestine over time.
• GERD (Gastroesophageal Reflux Disease): A chronic digestive disease where stomach acid flows back into the esophagus.
• Peptic Ulcers: Open sores that develop on the inner lining of the stomach or the upper portion of the small intestine.
• Crohn's Disease: A type of inflammatory bowel disease (IBD) that causes chronic inflammation of the digestive tract.
• Whipple's Disease: A rare bacterial infection that most often affects the gastrointestinal system, impairing nutrient absorption by affecting the interior wall of the small intestine.

Molecular Biology and Bacterial Transformation

• Genes, Proteins, and Traits:     * Genes (DNA): Segments of DNA acting as a recipe or code for specific proteins.     * Proteins: Built from amino acid chains that fold into specific shapes; these shapes enable proteins to perform specific functions.     * Visible Traits: The outward expression or physical function determined by these active proteins.

• Bacterial Transformation:     * Definition: A mechanism of horizontal gene transfer where a bacterial cell takes up free, "naked" DNA from its surroundings.     * Conjugation: Requires direct cell-to-cell contact through a sex pilus to transfer a plasmid.     * Transduction: Involves a virus acting as a vector to inject bacterial DNA into a cell.

• pGFP Plasmid Components:     * AmpR (Ampicillin Resistance): A gene producing beta-lactamase, which breaks down ampicillin. It serves as a selectable marker, allowing only transformed bacteria to grow on ampicillin-infused plates.     * GFP (Green Fluorescent Protein): A reporter gene originating from jellyfish; it glows under UV light, allowing researchers to visually identify successful transformation.     * T7 Promoter: An inducible promoter sequence acting as a "switch." It binds RNA polymerase to initiate the transcription of the GFP gene when induced.

• Transformation Success and Failure:     * Low Competence: Cells may not be properly prepared to take up DNA, reducing the intake rate.     * DNA Degradation: Enzymes (nucleases) may cut or destroy foreign DNA before it is integrated.     * Poor Expression: The gene may be taken up but not effectively translated into a protein.

• Lab Plate Expectations (-DNA vs +DNA):     * -DNA (No plasmid): Growth on LB agar (control); No growth on LB/Amp (control confirming ampicillin works).     * +DNA (With plasmid): Growth on LB/Amp (indicates successful transformation); Glows on LB/Amp/IPTG (indicates induction of GFP).     * IPTG: Acts as the inducer to turn on genes controlled by the T7/lac promoter system.

Protein Production and Analysis

• Steps in Protein Production and Purification:     1. Transformation: Inserting a plasmid into host bacteria.     2. Selection: Growing bacteria on antibiotic plates to isolate transformed cells.     3. Expression: Culturing bacteria in a broth and adding an inducer (e.g., IPTG) to start protein synthesis.     4. Cell Lysis: Breaking down the bacterial cell wall to release internal proteins.     5. Centrifugation: Spinning the lysate to separate cell debris from the protein-containing liquid (supernatant).     6. Chromatography: Using a column to separate the target protein from other proteins based on specific properties.     7. Gel Electrophoresis (SDS-PAGE): To confirm protein presence and purity.     8. Buffer Exchange: Removal of salts used during the purification process.

• Size-Exclusion Column Chromatography:     * Separates proteins based on molecular weight/size rather than chemical interactions.     * Large molecules bypass the resin beads, while small molecules enter the pores of the beads and are delayed, exiting the column later.

• SDS-PAGE (Protein Gel Electrophoresis):     * SDS Detergent Role: Unfolds (denatures) proteins by breaking non-covalent bonds, turning 3D shapes into linear chains. It also masks proteins with a negative charge.     * Mechanism: Uses an electric field to move molecules toward a positive anode based strictly on size.     * Comparison to DNA Agarose Gel Electrophoresis: Both use electric fields and separate by size. However, DNA gel electrophoresis is for large nucleic acids, while SDS-PAGE uses polyacrylamide gels for smaller protein molecules.

• Protein Folding and Denaturation:     * Folding Properties: Driven by Hydrophobic interactions, Hydrogen bonding, and Hydrophilic properties.     * Denaturation: The loss of a protein's complex 3D shape due to external stressors like heat, pH changes, or chemicals. A denatured protein is non-functional because function depends on shape; the process disrupts weak bonds but leaves the primary amino acid sequence intact.

Macromolecules and Biochemical Processes

• Four Macromolecules:     1. Carbohydrates (Polysaccharides): Such as glycogen, which are polymers of sugars.     2. Lipids (Triglycerides): Fats used for energy storage.     3. Proteins: Chains of amino acids.     4. Nucleic Acids: DNA and RNA.

• Antidiuretic Hormone (ADH): Produced in the pituitary gland; it "opens the doors" of the collecting ducts in the nephron, causing the body to reabsorb more water.

• Enzyme Summary:     * Pepsin: Found in the stomach; breaks down proteins.     * Trypsin: Found in the small intestine (from pancreas); breaks down proteins.     * Amylase: Found in saliva and pancreatic juice; breaks down carbohydrates.     * Bile: Not an enzyme, but digests/emulsifies fats.

• Chemical Reactions:     * Dehydration Synthesis: Joins monomers into polymers by removing a water molecule.     * Hydrolysis: Breaks down polymers into monomers by adding a water molecule.

Tissue Engineering and Xenotransplantation

• Tissue Engineering: A field that combines scaffolds, cells, and biologically active molecules to restore, replace, or enhance bodily tissues or organs.

• Organ Scaffold: A structural frame (often made of collagen) that provides a physical structure for cells to grow on in the lab.

• Clinical Advantage: Utilizing lab-grown tissue reduces the risk of organ transplant rejection compared to traditional human donor transplants.

• Xenotransplantation:     * Definition: The process of transplanting organs, tissues, or cells from one species to another (e.g., pig to human).     * Biological Risks:         * Immune Rejection: Hyperacute rejection is common as the human immune system immediately attacks animal tissue.         * Xenosis (Infection): The risk of introducing unknown animal pathogens or viruses into the human population.     * Ethical Risks:         * Animal Welfare: Concerns regarding the breeding and sacrificing of animals solely for organ harvesting.         * Patient/Public Safety: Risks of potential disease transfer to the patient's family and the public.