ANEQ305 Week 3 notes
ANEQ305 Week 3 notes ANEQ305
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This 5 page Class Notes was uploaded by Andrew Everitt on Saturday September 10, 2016. The Class Notes belongs to ANEQ305 at Colorado State University taught by Dr. Hyungchul Han in Fall 2016. Since its upload, it has received 19 views. For similar materials see Functional Large Animal Anatomy/Physiology in Animal Science at Colorado State University.
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Date Created: 09/10/16
ANEQ305 9-7-16 Starting on Slide 3.3 Phospholipid bilayer is impermeable to - Large and or poorly lipid-soluble molecules (proteins, glucose, and amino acids) - Small, charged molecules (ions) Mechanisms for transporting these molecules into or out of the cell - Channel transport - Carrier-mediated transport - Vesicular transport Channel Transport - Transmembrane proteins form narrow channels - Highly selective - Permit passage of ions or water (aquaporins) - Gated channels can be open or closed - Leak channels are open at all times - Movement through channels is faster than carrier-mediated transport Carrier- mediated transport - Transmembrane proteins that can undergo reversible changes in shape - Binding sites can be exposed to either side of membrane - Transport small water-soluble substances - Facilitated diffusion or active transport - Characteristics of carrier-mediated transport systems o Specificity – each carrier protein is specialized to transport a specific substance o Saturation – limit to the amount of a substance that a carrier can transport in a given time (transport maximum or T sub m) o Competition – closely related compounds may compete for the same carrier Facilitated Diffusion - Passive carrier-mediated transport from high to low concentration - Does NOT require energy - Ex: glucose transport into cells Diabetes melatus – latin name for Sweet Pee – sweet urine because there’s glucose/sugar in the urine Active Transport - Carrier-mediated transport that moves a substance against its concentration gradient - Requires energy - Primary active transport o Energy is directly required o ATP is split to power the transport process - Secondary active transport o ATP is not directly used o Carrier uses energy stored in the form of an ion concentration gradient built by primary active transport o EX: Glucose binding to sodium to diffuse into the cell Na+-K+ ATPase pump - Pumps 3 Na+ out of cell for every 2 K+ in - Splits ATP for energy - Phosphorylation induces change in shape of transport proteins - Maintains Na+ and K+ concentration gradients across the plasma membrane - Also helps regulate cell volume Secondary Active transport - Simultaneous transport of a nutrient molecule and an ion across the plasma membrane by a cotransport protein o Nutrient molecule is transported against its concentration gradient o Driven by simultaneous transport of an ion along its concentration gradient o Ex: cotransport of glucose and Na+ across the luminal membrane of intestinal epithelial cells Vesicular transport - Caveolae – protein which plays role in pinching of membrane - Endocytosis - Exocytosis Direct Intercellular communication - Gap junctions - Transient direct linkup of surface markers - Nanotubes Indirect intercellular communication - Intercellular chemical messengers - Synthesized by specialized cells to serve a designated purpose - Bind with specific receptors on target cells Categories of Chemical messengers - Paracrine: local chemical messengers whose effect is exerted only on neighboring cells - Neurotransmitters: used by neurons which communicate directly with the cells they innervate - Hormones: long-range chemical messengers that are secreted into the circulation by endocrine glands - Neurohormones – hormones released into the circulation by neurosecretory neurons - Pheromones – chemical signals released into the environment to reach sensory cells of other animals - Cytokine – regulatory peptides made by almost any cell, generally involved in development and immunity 9-9-16 - Signal Transduction o Extracellular chemical messengers bind with receptors to trigger a biochemical chain of events inside the target cell o Signal transduction is the process by which incoming signals are conveyed to the target cell’s interior for execution o Response is specific for specific chemical messenger received o Lipophilic extracellular messengers Pass through the target cell’s plasma membrane to bind to intracellular receptors Produce second messenger, Cyclic GMP or Alter gene transcription o Lipophobic extracellular messenger Cannot pass through the target cell’s plasma membrane; bind with surface membrane receptors Open or close specific membrane channels to regulate ion movement or Activiate an enzyme that phosphorylates a cell protein Transfer the signal to an intracellular second messenger - Opening and closing of membrane receptor-channels o Chemically gated (ligand gated) Responds to binding of an extracellular chemical messenger to a specific membrane receptor o Voltage gated Respond to changes in the electrical current in the plasma membrane Inside of membrane is -70mV When charged, changes to +30mV o Mechanically gated Respond to stretching or other mechanical deformation of the channel - Phosphorylating enzymes o Protein kinase phosphorylates a target cell protein o Phosphorylated protein changes shape and function o Tyrosine kinase phosphorylates its own tyrosine residues o Activated protein kinase sites phosphorylate cytoplasmic proteins to lead to the cellular response - G protein-coupled membrane receptors (GPCRs) o Inactive G protein on inner surface of plasma membrane contains alpha, beta and Gamma subunits with a GDP bound to the alpha subunit o When hormone binds with its receptor, the receptor attaches to G protein, releasing GDP and attaching GTP to the alpha subunit o Activated alpha subunit links with an effector protein in the membrane and alters its activity o 300 different receptors use the G protein mechanism - Cyclic AMP second-messenger GPCR pathway o Binding of hormone (first messenger) to its receptor activates a G protein o Activated alpha subunit links with adenylyl cyclase in the membrane o Activated adenylyl cyclase converts intracellular ATP to cyclic AMP o Cyclic AMP activates protein kinase A o Protein kinase A phosphorylates intracellular proteins, leading to the cellular response - Diacyglycerol-inositol triphosphate-Ca2+ second messenger pathway o Binding of hormone (first messenger) to its receptor activates a G protein o Activated alpha subunit activates phospholipase C on inner surface of membrane o Activated phospholipase C converts phospatidylinositol biphosphate (PIP2) to diacylglycerol (DAG) and inositol triphosphate (IP3) o IP3 diffuses into cytosol and mobilizes intracellular Ca2+ stores o Ca2+ serves as second messenger leading to cellular response o DAG activates protein kinase C o Protein kinase C phosphorylates intracellular proteins leading to the cellular response - Second messenger systems o Shared by many cell types o Multiple steps lead to amplification of initial signal o Receptors are subject to regulation Downregulation or upregulation of receptor number o Drugs and toxins alter communication pathways Antagonists block a step in the pathway Agonists activate a step in the pathway Steroid hormone are all made from cholesterol Key Highlighted = extra lecture information Underlined = important info Bold= slide header Bold and underlined = chapter title
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