Clinical Pathophysiology of the Cell PDF

Clinical Pathophysiology of the Cell Calli Cook, DNP, FNP-C, FAANP Objectives Part 1: Identify cellular organelles, their structure, and their function Describe the structure and function of the cell membrane Cell Componen ts Cell Membrane Phospholipid bilayer...

Clinical Pathophysiology of the Cell Calli Cook, DNP, FNP-C, FAANP Objectives Part 1: Identify cellular organelles, their structure, and their function Describe the structure and function of the cell membrane Cell Componen ts Cell Membrane Phospholipid bilayer Separates intra and extracellular fluids Polar/hydrophilic "heads" Nonpolar/hydrophobic "tails" Functions as: Barrier Electrical Insulator Interface  Cell Components Cytoplasm Protein synthesis Movement proteins Nucleus Houses cell DNA Synthesis Ribosomes Typically only 1 Ribosomes & Rough ER Protein synthesis Protein folding programming Smooth ER Metabolic processing Steroid hormone synthesis Ca+ homeostasis  Cell Components Golgi Apparatus Packages proteins and lipids Mitochondria Energy power house Initiates apoptosis Lysosomes Break down aging cells phagolysosome Peroxisome Free radicals are generated and scavenged here Cytoskeleton Protein filaments responsible for movement Question 1 Which of the following organelles is made in the nucleus and attach to messenger RNA (mRNA) for protein synthesis? a. Rough endoplasmic reticulum (ER) b. Smooth ER c. Golgi apparatus d. Ribosome Mechanism s of Membrane Transport  Briefly describe membrane transport mechanisms: Diffusion Endocytosis Objectives Exocytosis Facilitated diffusion Part 2: Active Transport Primary Secondary Ion channels  Concentration Gradients in a typical Cell Solutes and pH Extracellular Concentration Intracellular Concentration pH 7.4 7.2 Solutes Sodium 135–147 mEq/L 10–15 mEq/L Potassium 3.5–5.0 mEq/L 120–150 mEq/L 2.1–2.8 mmol/L (total) Calcium ~10−7 mmol/L (ionized) 1.1–1.4 mmol/L (free, ionized) Chloride 95–105 mEq/L 20–30 mEq/L 1.0–1.4 mmol/L (total) Phosphate 0.5–0.7 mmol/L (ionized) 0.5–0.7 mmol/L (ionized) Bicarbonate 22–28 mEq/L 12–16 mEq/L 1 mmol/L (ionized) Magnesium 0.6 mmol/L (ionized) 18 mmol/L (total) Glucose 5.5 mmol/L Very low Diffusion No specific transport protein required Down gradient Small, hydrophobic, non-polar chemical structure Flick’s first law of diffusion:  ENDOCYTOSIS Extracellular fluid is engulfed and brought into the cell Three processes: Phagocytosis: Macrophages or neutrophils engulf large particles and destroy them Pinocytosis: surveillance of the environment Receptor mediated endocytosis: interaction between cellular membrane and cytoskeletal proteins. Familial Hypercholesterolemia  EXOCYTOSI S Extracellular release of intracellular contents General: Ongoing process Examples: Liver: albumin and coagulation proteins Plasma cells: immunoglobulins Regulated: Protein or molecule are held intracellularly until triggered. Neuron: Action potential Axon effected receptor protein release of neurotransmitter Facilitated Diffusion Many substances that need to move into the cell are polar and hydrophilic Membrane transport proteins allow this movement down the molecule's concentration gradient Example: GLUT (1-5) transporters in the gut GLUT Facilitated Diffusion SGLT is a sodium dependent glucose transporter GLUT is a facilitated glucose transporter Active Transport Sodium– potassium (Na+/K+) pump Protein Found on all cells of the body Always active Transports sodium out of the cell and potassium into the cell Both ions are moving against their concertation gradients Helps support potential energy needed for secondary active transport  Protein Found on cell Calcium membranes and the membrane of the ATPase ER pump Maintains the calcium gradient Restores low intracellular calcium levels  Protein Found on gastric parietal cells Involved in the Proton secretion of pump hydrochloric acid into the stomach Maintain acid-base balance Drug target  Based on the gradient established by the Na+/K+ Pump. Does not require ATP but allows Na+ to sneak back into the Secondary cell Two types: Active Cotransport/ Transport symport: both Na+ and another molecule are moving into the cell Antiport/counter transport: Na+ is moving into the cell; however, another molecule is moving out Secondary Active Transport Examp les: COtransport Question 2 Drugs that inhibit gastric acid secretion target which of the following types of transport? a. Osmosis b. Facilitated diffusion c. Primary active transport d. Ion channels ION CHANNELS Transmembrane proteins Allow movement down a concentration gradient Selective for one ion On all body cells, very prominent role in cells that are electrically excitable Contribute to resting membrane potential  Transport Mechanism Mode of Transport Examples Transporter Names and Locations GLUT1—red blood cells, blood–brain barrier, many other cells GLUT2—liver, pancreatic β cells, renal tubules Glucose GLUT3—neurons Facilitated diffusion GLUT4—muscle and adipose cells (insulin- sensitive) Fructose GLUT5—gastrointestinal tract Several transporter types found on most cells, Amino acids enriched in small intestine and kidney tubules Sodium–potassium (Na+/K+) Membranes of all cells Active transport (primary active pump transport) Calcium pump Cell and endoplasmic reticulum membranes Potassium–hydrogen pump Renal tubules, stomach parietal cells Transport Mechanism Mode of Transport Examples Transporter Names and Locations SGLT1 (gastrointestinal) Sodium–glucose cotransport SGLT2 (renal) Sodium–calcium exchange NCX Sodium–potassium–2 chloride NKCC cotransport Secondary active transport Sodium–chloride cotransport NCC Sodium–hydrogen exchange NHE Sodium–serotonin cotransport SERT Sodium–norepinephrine cotransport NET Sodium–dopamine cotransport DAT Many cells—set resting membrane Potassium leak channels potential Electrically excitable cells—action Delayed potassium channels potential repolarization Ion channels Electrically excitable cells—action Fast sodium channels potential initiation and propagation Muscle cells—some action potential Slow calcium channels initiation, provide calcium for contraction Mechanisms of Cellular signaling  Explain the roles and functions of plasma membrane receptors Correctly identify the proteins and sequence of Objectives events occurring in signal transduction by the adenylyl cyclase and phospholipase C–linked Part 3: pathways Describe the mechanisms and sequence of signaling of receptors linked to tyrosine kinase enzymes. Illustrate how intracellular receptors differ from plasma membrane receptors  Autonomic nervous system is a rapid regulatory system Autonomic Parasympathetic Preganglionic neuron located in brainstem and Nervous sacral spinal cord Postganglionic neurons are cholinergic, System releasing acetylcholine Signaling: Sympathetic Preganglionic neuron located in thoracic and GPCRS lumbar spinal cord Postganglionic neurons are adrenergic, releasing norepinephrine Both branches have strong cardiovascular effects and neurotransmitters can work via G-protein coupled receptors GPCRs Generates a cascade of intracellular reactions that create a second messenger signal, altering target cell activity G-PROTEIN COUPLED RECEPTORS (GPCR) Common structural elements Found on all cells Long protein that crosses the cell membrane seven times Signaling pathway: Ligand binding When binding occurs —conformational change occurs GPCR: Adenylyl Cyclase (AC) Example: Cardiac cell with β-adrenergic receptor Norepinephrine binds to the receptor The receptor undergoes a conformational change The G protein dissociates The α subunit moves to the AC and increases its activity GPCR: Adenylyl Cyclase Activated AC converts ATP to cAMP, amplifying the signal cAMP diffuses through the cytoplasm and activates protein kinase A (PKA) PKA adds a phosphate group to the target protein and further amplifies cellular change —in this example, increases the heart rate GPCR: Phospholipase C (PLC) Example: α1-adrenergic receptor on vascular smooth muscle Sympathetic nerve releases norepinephrine binds to the receptor The receptor undergoes a conformational change The G protein dissociates The α subunit moves to the PLC and activates it GPCR: Phospholipase C (PLC) Activated PLC splits the membrane phospholipid phosphatidylinositol bisphosphate (PIP2) into diacylglycerol (DAG) and inositol trisphosphate (IP3) DAG stays in the membrane IP3 diffuses into the cytoplasm IP3 binds to receptors in the endoplasmic reticulum, stimulating the release of calcium In this example this will cause cell contraction leading to vasoconstriction and increasing blood pressure DAG activates protein kinase C which phosphorylates target proteins  Review of GPCR Second Excitatory/ System First messenger Outcome messenger/effector Inhibitory An array of M2-- inhibitory cellular functions depending on Adenylyl Norepinephrine cAMP/protein β-adrenergic receptor type. For Cyclase Acetylcholine kinase A receptor— this class we will excitatory focus on the heart rate effect. diacylglycerol (DAG)/Protein kinase C inositol α-adrenergic Increases Norepinephrine trisphosphate receptor— intracellular Acetylcholine (IP3)/works directly excitatory Phospholipase C calcium to carry Glutamate on the SER. out an array of (CNS) calcium/ M1, M3, M5— cellular functions. calmodulin excitatory Multiple second messengers in this system Question 3 Which of the following is a characteristic of G protein–coupled receptors (GPCRs)? a. Primary messengers turn on protein kinase enzymes to change the function of intracellular proteins b. Phosphorylation only increases the activity of proteins c. Inhibitory receptors limit the strength and duration of the effects of GPCRs d. The action of second messengers is terminated by off-switches Enzyme-linked receptors Intrinsic enzyme activity instead of requiring a G protein These receptors have tyrosine kinase activity, phosphorylating target proteins Properties of ligand binding: 1. Dimerization- two receptors are drawn together at the membrane 2. Autophosphorylation- each chain phosphorylates the other 3. Tyrosine kinase phosphorylates additional proteins on the intracellular portion of the receptor Can you think of a process where this would be important? Epidermal Growth Factor Receptor (EGFR) Activity of EGFRs turns on signaling pathways that leads to gene expression, transcription, and translation Require dimerization for activation Extracellular portion has a ligan binding site Intracellular portal contains the tyrosine kinase component, this is activated by the ligand binding. EGFR is well studied Mutated version is involved in several cancers Mutation can occur with the receptor or downstream proteins, like the Ras family Cytokine Receptors Cytokines are protein messengers of the immune system The immune response requires a rapid response to foreign invaders Cytokine receptors do not have intrinsic tyrosine kinase activity, they are activated by extracellular binding. Their intracellular portion undergoes a conformation change to bind to Janus Kinase (JAK) JAK targets are signal transducer and activator of transcription (STAT) proteins JAKs are mutated in some cancers and targets for some anti-neoplastic drugs Question 4 Activation of an epidermal growth factor receptor (EGFR) is followed by cell activity changes due to: a. Phosphorylation of cell proteins on serine residues b. Phosphorylation of cell proteins on threonine residues c. Phosphorylation of cell proteins on tryptophan residues d. Phosphorylation of cell proteins on tyrosine residues Mechanis m of Contractil e Cells  Describe the basics of interactions between the Objectives contractile proteins myosin and actin Compare the mechanisms of contraction of Part 4: striated (skeletal and cardiac) and smooth muscle cells. Types of Contractile Cells 1. Cardiac 2. Smooth- no striations or sarcomeres 3. Skeletal Sarcomeres of skeletal and Cardiac Muscle Striated appearance, dark bands alternating with light A bands (dark) I bands (light) Sarcomeres span from Z disc to Z disc Actin: protein made of repeated subunits Myosin: 2 light chains and 2 heavy Chains These proteins make up myofibrils MECHANISM OF MYOFIBRIL CROSSBRIDGE FORMATION Goal: shortening of the muscle When Myosin binds to Actin there is pulling toward the center of the sarcomere Actin bind spots are blocked by tropomyosin Troponin helps to support the tropomyosin 1. Troponin I- high sensitivity cardiac 2. Troponin C- binds Ca++ 3. Troponin T- high sensitivity cardiac Steps of crossbridge FORMATION 1. At rest, Myosin binds to ADP and a free phosphate 2. Muscle fiber is stimulated, depolarization occurs 3. The sarcoplasmic reticulum rapidly increases intracellular Ca++ 4. Ca++ bind to Troponin C 5. The Troponin/Tropomyosin complex shifts, actin is exposed 6. Myosin binds to Actin, crossbridge formation is complete What is Unique About This Fish?  Characteristic Skeletal Muscle Fibers Cardiac Muscle Cells Cell Long fibers Short cells linked morphology Contain many nuclei mechanically and Connect to tendons to electrically generate force across Contain one nucleus joints Action Acetylcholine released Pacemaker cells in the potential from motor neuron sinoatrial node generate Compariso generation terminals at the neuromuscular junction action potentials that propagate along cardiac n of generates action potentials that propagate conduction pathways Skeletal Metabolism along the membrane Anaerobic and aerobic Primarily aerobic, contain and greater numbers of mitochondria Cardiac Length–tension The longer the muscle relationship fiber at the start of The greater the filling of the cardiac chamber Muscle contraction, the greater will be the tension it can at the start of contraction, the develop greater will be the tension it can develop Smooth Muscle Contractile Cells Found in the GI tract, uterus, bladder, blood vessels, and airway No striations or sarcomeres; loosely arranged in the cytoplasm Generally weaker force with lower ATP requirements Latch-bridge mechanism Smooth Muscle: Crossbridge Formation Steps for contraction: 1. Smooth muscle depolarization occurs 2. Voltage gated Ca++ channels open 3. GPCR and PLC generate IP3 4. Ca++ is released from the sarcoplasmic reticulum 5. Ca++ binds to calmodulin, this actives calmodulin 6. The complex binds to Myosin light chain kinase 7. Phosphorylation occurs 8. Myosin head moves closer to actin, crossbridge formation occurs Smooth Muscle Example Question 5 How is the strength of contraction in striated muscle cells modulated? a. By the amount of calcium in the cytoplasm b. Prior shortening to rest the sarcomeres strengthens the contraction c. A smaller load decreases the strength and speed of the contraction d. Initial stretching generates a greater force of contraction Cell Renewal, Stress, and Cell Death  Objectives Part 5: Describe Identify Describe Explain Describe cell Identify the Describe cell Explain the renewal, cell major types of responses to purpose and stress, and cell severe injury examples of mechanisms adaptations and their physiological of cell stress and their biochemical apoptosis and common mechanisms the reasons causes why a programmed death pathway is necessary for optimal body function  Cell renewal, Maintenance, and adaption Many cells will die and be replaced by self-renewing stem cells Other cells can undergo renewal through removal of damaged proteins through new protein synthesis Injured, infected, or malnourished cells may be repaired or will undergo the various routes of cell death Cell may also adapt: Hypertrophy Atrophy Hyperplasia Metaplasia Dysplasia Cell Death Pathways  Cellular death is caused by a lack nutrient supply Stroke Myocardial Infarction Necrotic Cell Creates inflammation that leads to scar formation Death: resulting in: Noncontractile tissue (heart) Response to Reactive gliosis and neuronal loss and atrophy (brain or spinal cord) severe The following pathway represents cell death via necrosis: ischemia Rapid loss of ATP production, resulting in diminished membrane potential Depressed Na+/K+ pump activity Intracellular calcium overload Cell swelling Membrane rupture Loss of antioxidant function Accumulation of oxygen-derived free radicals Acidosis Activation of degradative enzymes that contribute to membrane rupture and spread of the damage to adjacent cells  Necrotic Cell Death: reperfusion injury Restoring blood flow too quickly can worsen the injury Increase in reactive oxygen species (ROS) Increase in inflammatory markers Think of releasing a crimped hose This Photo by Unknown author is licensed under CC BY-SA.  Apoptosis Very common, contributes to normal cellular turnover Programmed cell death Example: Autoreactive lymphocytes can undergo apoptosis centrally in the bone marrow or thymus depending on cell type Cytotoxic T cells can recognize infected cells or cancerous cells and initiate death pathway through apoptosis Two mechanisms: Intrinsic: Intracellular signals of abnormal cell function stimulate the release of the enzyme cytochrome C from mitochondria—cytochrome C then triggers a cascade of increases in pro-apoptotic proteins that activate the apoptotic enzymes Extrinsic: Extracellular signal bind to membrane tumor necrosis factor (TNF), causing assembly of intracellular Protein that activate apoptotic enzymes  Characteristic Necrosis Apoptosis Cell size Cells swell Cells shrink Fate of nucleus Ruptures Small packages containing fragmented DNA DNA Fragment size Fragment size Necrosis varies Cell membrane Ruptures uniform Removed in small Vs. fragments by blebbing Apoptosis Cell contents Enzymatic Enzymatic digestion and digestions, then leakage into tissue packaged into apoptotic bodies Adjacent Frequent No inflammation Physiological Invariably Often physiological or pathological pathological role  Autophagy Adaption to malnourishment Vacuole forms within the cell and takes up cellular contents The content are digested back into building blocks—amino acids, carbohydrates or sugars, and fats If malnutrition is severe enough the cell will die Response is on a continuum, mild to severe Question 6 Cells that undergo a hypoxic insult and become acidic, lose adenosine triphosphate (ATP) production, and accumulate reactive oxygen species undergo which type of cell death? a. Apoptosis b. Autophagy c. Necrosis d. Death program Question 7 Which of the following is not seen in necrotic cell death? a. Generation of reactive oxygen species b. Loss of calcium homeostasis c. Activation of new protein synthesis d. Release of lysosomal hydrolase enzymes