PAR3623_F2024 - Lecture 2.pdf

PAR3623 Paramedicine – Medical Physiology I F2024 Lecture 2 Cellular basis of physiological function – Part II  Copyright / Intellectual Property Notice Materials posted to courses are subject to Intellectual Property and Copyright pr...

PAR3623 Paramedicine – Medical Physiology I F2024 Lecture 2 Cellular basis of physiological function – Part II  Copyright / Intellectual Property Notice Materials posted to courses are subject to Intellectual Property and Copyright protection, and as such cannot be used and posted for public dissemination without prior permission from the College. For clarity, these protections are automatic once a work is created, and applies whether or not a copyright statement appears on the material. Students are bound by College policies, including AA 34 - Copyright, and SA 07 - Student Code of Conduct, and any student found to be using or posting course materials for public dissemination without permission is in breach of these policies and may be sanctioned.  Using Wiley Resources To use the Wiley resources and to access the e-text, please go through Brightspace. You may be able to see the e-text via www.wileyplus.com but the correct assignment will not show there. For the assignments associated with Wiley, use only the BS link. If you haven’t accessed the Wiley content yet, please go to BS, click on the Wiley/Derrickson Course Resources tab and click the associated link. You should then be able to register and get access to the Wiley Dr. Pasan Fernando content. 3  Homeostasis and cells and medical terminology ECF – normal ranges Homeostasis in action – feedback mechanisms positive vs negative feedback Cell specialization and differentiation Overall body plan – critical points to understand Directional terms Organelles and their functions Dr. Pasan Fernando  Muddy Points – Negative and positive feedback Both negative and positive feedback work to put the body and variables back to a normal working range Both are good things! Negative feedback is most common § Works opposite to the change to restore normal Positive feedback is less common § Counters the change by enhancing an effect Dr. Pasan Fernando § Normal is restored after the positive effect has limited the change 5  Homeostatic Imbalance Do you think this person is in homeostasis? Can you link the concept of homeostasis to this patient? Dr. Pasan Fernando 6  Muddy Points –Differentiation and specialization of cells Dr. Pasan Fernando https://www.nature.com/articles/cddis2017504 7  Muddy Points – Simplified body plan Critical components of the simplified body plan: § Borders – formed from phospholipid membranes at many levels, ex. on the surface and within the body § The external environment has immediate access to the internal environment via a few entry points (lungs, mouth – intestine, excretory organs, ocular membranes…. others? § Within the body, there are more borders that separate internal (ex. intracellular) from external (extracellular) § Crossing the border requires PERMISSION § Nutrients and gasses: Ø must be brought into the body Dr. Pasan Fernando Ø Must move around the body and brought into cells Ø Must move out of cells Ø Must be eliminated from the body 8  Directional Terms Superior Cranial or Cephalic Proximal § Directional terms describe one Posterior Anterior body structure relative to or Dorsal or Ventral another § Based on the anatomical Lateral Medial position § Right and left refer to the body Proximal Caudal being viewed, not right and left Distal Right Left of the observer Dr. Pasan Fernando Distal Inferior Anterior view Lateral view 9  Muddy Points - Organelles Be happy! This is not a course in the Biology of the Cell. But, we need to focus on only a handful of organelles and cellular structures. These help us understand the cellular functions. The most immediate ones include: § The cell membrane § Nucleus § Mitochondria Endoplasmic reticulum (rough and smooth) Dr. Pasan Fernando § § The cytoskeleton (microfilaments, intermediate filaments, microtubules) § Junctional elements (gap junctions, desmosomes, tight junctions) § There will be others but I can’t think of them all right now J. 10 A/an _______ is a structure composed of two or more different types of tissues. a) tissue system b) organ c) organ system d) organism e) cellular system Copyright © 2019 John Wiley & Sons, Inc. All rights reserved. 11 What kind of tissue detects and responds to changes in the body’s external or internal environment? a) skeletal muscle b) nervous c) connective d) epithelial e) cardiac muscle Copyright © 2019 John Wiley & Sons, Inc. All rights reserved. 12 Which of the following statements about homeostasis is true? a) Each regulated parameter can change over a narrow range that is compatible with life. b) Energy is needed to keep a regulated parameter at a relatively constant level. c) The internal environment of the body is kept relatively constant despite continual changes in the external environment. d) All of the choices about homeostasis are true. Copyright © 2019 John Wiley & Sons, Inc. All rights reserved. 13 Most of the water in the body is contained within the a) intracellular fluid b) plasma c) interstitial fluid d) extracellular fluid Copyright © 2019 John Wiley & Sons, Inc. All rights reserved. 14 Effectors in feedback systems include a) muscles only b) glands only c) neurons only d) muscles or glands e) muscles, glands, or neurons Copyright © 2019 John Wiley & Sons, Inc. All rights reserved. 15 A/an ______ feedback system serves to enhance a controlled variable. a) positive b) neutral c) negative d) enhancing Copyright © 2019 John Wiley & Sons, Inc. All rights reserved. 16  Dr. Pasan Fernando 17  Lecture 2 Objectives for Lecture 2 1. Describe the components of the plasma membrane that confer cell specific activity. 2. Describe different modes of membrane transport and identify their relevance to cellular function 3. Identify and describe the function of select cellular components Dr. Pasan Fernando 18  Components of a cell Objective: ü Describe the three main components of a cell Dr. Pasan Fernando  The three main components of the cell Plasma membrane § Forms the cells outer surface Cytoplasm § Consists of the cellular contents between the plasma membrane and nucleus Nucleus § Large organelle that houses most of the cell’s DNA Dr. Pasan Fernando  Plasma Membrane Objectives: ü Describe the composition of the plasma membrane ü Describe the classes of membrane proteins associated with the plasma membrane Dr. Pasan Fernando 21  Plasma Membrane § Acts as an active barrier separating intracellular fluid (ICF) from extracellular fluid (ECF) § Plays dynamic role in cellular activity by controlling what enters and what leaves cell § Two back-to-back layers made up of three types of lipids: Ø Phospholipids Ø Cholesterol Dr. Pasan Fernando Ø Glycolipids § Cell membrane = plasma membrane Coursepics.com 22  Plasma Membrane Proteins Arrangement: § Integral Ø Transmembrane § Peripheral § Glycoproteins § glycocalyx Dr. Pasan Fernando 23  Structure of Plasma Membrane § Consists of membrane lipids that form a flexible lipid bilayer § Specialized membrane proteins float through this fluid membrane, resulting in constantly changing patterns Ø Referred to as fluid mosaic (made up of many pieces) pattern § Surface sugars form glycocalyx § Membrane structures help to hold cells together through cell junctions Dr. Pasan Fernando 24  Glycocalyx Consists of sugars (carbohydrates) sticking out of cell surface § Some sugars are attached to lipids (glycolipids) and some to proteins (glycoproteins) Every cell type has different patterns of this “sugar coating” § Functions as specific biological markers for cell- to-cell recognition § Allows immune system to recognize “self” vs. “nonself” Dr. Pasan Fernando 25  Membrane Lipids Lipid bilayer is made up of: § 75% phospholipids, which consist of two parts: Ø Phosphate heads: are polar (charged), so are hydrophilic (water- loving) Ø Fatty acid tails: are nonpolar (no charge), so are hydrophobic (water- hating) § 5% glycolipids Ø Lipids with sugar groups on outer membrane surface § 20% cholesterol Ø Increases membrane stability Dr. Pasan Fernando  Membrane Proteins § Allow cell communication with environment § Make up about half the mass of plasma membrane § Most have specialized membrane functions § Some float freely, and some are tethered to intracellular structures § Two types: Ø Integral proteins; peripheral proteins Dr. Pasan Fernando  Membrane Proteins (cont.) Integral proteins § Firmly inserted into membrane § Most are transmembrane proteins (span membrane) § Have both hydrophobic and hydrophilic regions Ø Hydrophobic areas interact with lipid tails Ø Hydrophilic areas interact with water § Function as transport proteins Dr. Pasan Fernando (channels and carriers), enzymes, or receptors  Membrane Proteins (cont.) Peripheral proteins § Loosely attached to integral proteins § Include filaments on intracellular surface used for plasma membrane support § Function as: Ø Enzymes Ø Motor proteins for shape change during cell division and muscle contraction Ø Cell-to-cell connections Dr. Pasan Fernando  Membrane Proteins - Notes Phospholipids make the basic structure of membrane § Forms barrier between the inside and outside of cell § Water soluble substances cannot easily pass § Protein channels allow substances (other proteins, water, biomolecules) to pass Ø Water can move through by osmosis or more readily through protein channels (pores) called aquaporins or water channels – Cholesterol adds fluidity to membrane structure § Decreases the permeability of membrane to water Integral membrane proteins embed or integrate within the membrane § Cannot dissociate without disrupting the bilayer § Connect with both the lipid bilayer and the aqueous environment § Polar surfaces of the protein face the aqueous environment (cytosol, ECF, or both) § Nonpolar surfaces embed within the lipid bilayer Transmembrane proteins § Span the lipid bilayer and face both the cytosol and the ECF § Usually cross the membrane at several places (transmembrane domains) Peripheral membrane proteins Dr. Pasan Fernando § Loosely bound to the membrane § Can dissociate without disrupting the phospholipid bilayer § Found usually on the cytosolic side Form part of cytoskeleton – internal structure 30  The Cytoplasm Objectives ü Explain the purpose of the cytosol ü Describe the functions of select organelles Dr. Pasan Fernando 31  Organelles § Tiny specialized structures within the cell that have characteristic shapes § Perform specific functions in cellular growth, maintenance, and reproduction. § Types Ø Ribosomes Ø Endoplasmic reticulum Ø Golgi complex Ø Mitochondria Ø Lysosomes, peroxisomes, and proteasomes Ø Cytoskeleton Dr. Pasan Fernando  Ribosomes § Sites of protein synthesis § Have high content of one type of ribonucleic acid, ribosomal RNA (rRNA) § Each one includes about 80 proteins. Dr. Pasan Fernando  Endoplasmic reticulum Network of membranes in the form of flattened sacs or tubules § Rough Ø Has ribosomes Ø Site of protein synthesis § Smooth Ø Extends from rough Ø Does not have ribosomes Ø Site of lipid synthesis Dr. Pasan Fernando  Cytosol § Site of many chemical reactions within the cell § Constitutes 55% of total cell volume Ø Mostly water Ø Various solutes (dissolved particles) – Ions – Glucose – Amino acids – Fatty acids – Proteins – Etc. Dr. Pasan Fernando 35  Golgi Complex Function § Further modifies proteins made by the rough ER Dr. Pasan Fernando  Golgi Complex: Protein Modification Involves 6 major steps 1. Transport vesicles made in rough ER 2. Transport vesicles move to Golgi complex 3. Proteins enter lumen of Golgi 4. Proteins are modified as they travel through cisternae 5. Modified proteins are packaged and sorted 6. Secretory vesicles are Dr. Pasan Fernando formed  Mitochondria § Makes cellular energy – ATP § Highly metabolic cells, i.e. cells with high activity, will have more mitochondria Dr. Pasan Fernando 38  Lysosomes, peroxisomes, proteasomes Lysosomes § Membrane-enclosed vesicles containing digestive enzymes that digest a wide variety of substrates Peroxisomes § Smaller than lysosomes § Contain oxidases that help metabolize amino acids and fatty acids Proteasomes § Degrades unwanted or damaged proteins that are in the cytosol Important for cell function and metabolic control Dr. Pasan Fernando Ø 39  Cytoskeleton Network of protein filaments that extends through cytosol § Provides structural framework § Aids in movement Three types § Microfilaments § Intermediate filaments § Microtubules Dr. Pasan Fernando  Microfilaments § Thinnest elements, made up of actin § Most prevalent at the edge of the cell § Functions Ø Help generate movements Ø Provide mechanical support Ø Form microvilli Dr. Pasan Fernando  Intermediate filaments Intermediate in size § Smaller than microtubules § Larger than microfilaments Functions § Found in places where cells encounter stress § Help position organelles § Attach cells to one another Dr. Pasan Fernando  Microtubules Largest of the cytoskeletal components Hollow tubes composed mainly of tubulin Functions § Determine cell shape § Movement of organelles § Found in cilia and flagella Dr. Pasan Fernando  Cilia and flagella Cilia § numerous, short, hair-like projections that extend from the surface of certain types of cells Ø Propel fluid across surface of cells Flagella § Similar in structure to cilia but are typically much longer Ø Flagella usually move an entire cell Dr. Pasan Fernando  Nucleus Structure and Function § Spherical most prominent cell component § Houses most DNA of the cell § DNA contains genes Dr. Pasan Fernando  Describe how the plasma membrane facilitates homeostasis. What features of the plasma membrane contribute to this function? Describe a homeostatic reaction that occurs within the body Dr. Pasan Fernando 46