5.Transport, Endocytosis, and Phagocytosis Undergraduate – Graduate Histology Lecture Series Larry Johnson, Professor Veterinary Integrative Biosciences Texas A&M University College Station, TX VIBS 443 and VIBS 602

Cell membrane Cell membrane – plasmalemma – nm

Cell membrane Necessary for life Marks limits of cell (defines cell) Separates cell from its environment Can not be a complete barrier, some items must pass.

Cell membrane Four classes of items that must pass - Nutrients (AA, O 2, fatty acids, CHO, etc.,) - Waste (CO 2 and products of metabolism) - Informational molecules (hormones, growth and chemotaxic factors) - Cell products (secretions, bacteria, RBC {250 billion cells/day})

Cell membrane Plasmalemma nm Function Contain antigenic molecules, which are the basis of cell recognition and tissue specificity Regular internal environment - ion pumps

Cell membrane Plasmalemma nm Function Possess receptors for hormones Possess mechanisms for generating messenger molecules that activate the cell’s physiological responses to stimuli

HISTO 61

Transport of small molecules across membranes Simple diffusion (cross freely) Passive, facilitated, and Active transport

Simple diffusion (cross freely) Passive, facilitated, and Active transport

Specific (high affinity) but can be saturated

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Exocytosis - release of secretory products into extracellular compartment Membrane-bound granules move to surface Granule membranes fuse with plasma membrane Contents flow extracellularly Invaginating vesicles - remove excess membrane from cell membrane Minute vesicles like pinocytosis vesicles

Exocytosis Endocytosis Budding Cell membrane

Merocrine Apocrine

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Transport of macromolecules: endocytosis 1.Fluid (or bulk) flows 2.Receptor mediated endocytosis Specific receptor Coates pits (clathrin) Lysosomal fusion with endosomes

BULK FLOW

LDL and receptor separates at lower pH

Insulin receptors do not recycle! clathrin coated vesicle (dots label clathrin coat) uncoated vesicle (no dots)

Endocytosis - bulk uptake of materials Pinocytosis - cell drinking Phagocytosis - cell eating Attachment – binding of particle ligand to membrane receptors Interiorization by pseudopods

Ingestion of particles: phagocytosis Mononuclear phagocyte system macrophage Opsonized particles Membrane zippering mechanism

Primary lysosome Secondary

SER

U.S.A. Mexico

Cytoskeleton and cell motility Next time

Mexico USA

Bruce Alberts, et al Molecular Biology of the Cell. Garland Publishing, Inc., New York, NY. Bruce Alberts, et al Molecular Biology of the Cell. Garland Publishing, Inc., New York, NY. William J. Banks, Applied Veterinary Histology. Williams and Wilkins, Los Angeles, CA. Hans Elias, et al Histology and Human Microanatomy. John Wiley and Sons, New York, NY. Don W. Fawcett Bloom and Fawcett. A textbook of histology. W. B. Saunders Company, Philadelphia, PA. Don W. Fawcett Bloom and Fawcett. A textbook of histology. Chapman and Hall, New York, NY. Arthur W. Ham and David H. Cormack Histology. J. S. Lippincott Company, Philadelphia, PA. Luis C. Junqueira, et al Basic Histology. Lange Medical Publications, Los Altos, CA. L. Carlos Junqueira, et al Basic Histology. Appleton and Lange, Norwalk, CT. L.L. Langley, et al Dynamic Anatomy and Physiology. McGraw-Hill Book Company, New York, NY. W.W. Tuttle and Byron A. Schottelius Textbook of Physiology. The C. V. Mosby Company, St. Louis, MO. Leon Weiss Histology Cell and Tissue Biology. Elsevier Biomedical, New York, NY. Leon Weiss and Roy O. Greep Histology. McGraw-Hill Book Company, New York, NY. Nature ( Vol. 414:88,2001. A.L. Mescher 2013 Junqueira’s Basis Histology text and atlas, 13 th ed. McGraw Douglas P. Dohrman and TAMHSC Faculty 2012 Structure and Function of Human Organ Systems, Histology Laboratory Manual - Slide selections were largely based on this manual for first year medical students at TAMHSC Many illustrations in these VIBS Histology YouTube videos were modified from the following books and sources: Many thanks to original sources!