BIO101 Cell Physiology (Lecture) PDF

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All year-1 course materials, whether in print or online, are protected by copyright. The work, or parts of it, may not be copied, distributed, or published in any form, printed, electronic, or otherwise. As an exception, students enrolled in year 1 of St. George’s University School of Medicine and their faculty are permitted to make electronic or print copies of all downloadable files for personal and classroom use only, provided that no alterations to the documents are made and that the copyright statement is maintained in all copies. ‘View only’ files, such as lecture recordings, are explicitly excluded from download, and creating copies of these recordings by students and other users is strictly illegal. The author of this document has made the best effort to observe current copyright law and the copyright policy of St. George's University. Users of this document identifying potential violations of these regulations are asked to bring their concerns to the attention of the author.  Your Objectives will show here! 1. Identify and describe the three main parts of the cell. 2. Describe the basic structure and function of the cytoplasm a) Describe the structure and function of the Cytosol: include discussion of structure and function of cytoskeleton b) Describe the structure and function of the following organelles: ribosome, endoplasmic reticulum, Golgi complex, lysosome, peroxisome, proteasome, and mitochondria. c) Describe the structure and function of the nucleus: include brief discussion on the function of envelope, pores, nucleoli, genes, and chromosomes. 3. Describe the composition and function of the plasma cell membrane. a) List the different components in the plasma membrane. i. List the types of proteins found in the membrane and describe their function b) Explain the concepts of membrane fluidity and permeability and describe how it affects transport across the cell Session ID: rgeorge1  Your Objectives will show here! c) Explain the concept of concentration and electrical gradients and their contribution to the formation of electrochemical gradients. d) Describe the structure and function of the following cell specializations: cilia, flagella, microvilli i. Include function and typical locations 4. Describe the various types of transport across the cell membrane. a) Describe the passive processes of simple and facilitated diffusion b) Define and describe osmosis and osmotic pressure. c) Describe the active transport processes. Compare and contrast with each other and with the passive processes d) Describe the types (3) of vesicular transport. i. Endocytosis – describe the (3) types ii. Exocytosis iii. Transcytosis Session ID: rgeorge1 A 65-year-old female with a past medical history of Type 2 Diabetes mellitus is brought to the emergency department because she appeared confused and disoriented (altered mental status). During physical examination, she is drowsy and has dry oral mucosa. Lab studies show blood glucose levels of >600 mg/dL. (Normal is between 70 – 100 mg/dL. Her treatment regiment included IV fluids, IV insulin, electrolyte replacement. 1. Which symptom gave a direct indication of the state of the cells in the patient? 2. What is the major cause of the patient’s medical condition? 3. Which part of the cell presents a barrier between its surroundings and its contents? 4. What is the role of the membrane permeability in response to the IV fluids given to the patient? 5. What structure is responsible for providing the instructions for insulin production? 6. List the cell structures vital to the production of insulin in order of their involvement from synthesis to secretion. Session ID: rgeorge1 Cell:basic functional unit of the body 1. Plasma membrane ✓ outer surface of the cell ✓ selective barrier 2. Cytoplasm ✓ Cytosol - fluid portion of cytoplasm, containing H2O, dissolved solutes, suspended particles. ✓ Organelles- little organs, with diverse structures and special functions. 3. Nucleus - large organelle housing most of the cell’s DNA. Controls cellular structure and function How does the plasma membrane exercise its role in communication among cells and between cells and the external environment? Session ID: rgeorge1 1. Cytosol (Intracellular fluid) - Site of chemical reactions – glycolysis, protein synthesis (translation), meiosis, mitosis - 55% total cell volume, 75-90 % water - ions, glucose, amino acids, fatty acids, proteins, lipids, ATP, waste products, lipid droplets, glycogen granules 2. Organelles- Session ID: rgeorge1 Session ID: rgeorge1 Session ID: rgeorge1 Session ID: rgeorge1 Session ID: rgeorge1 3. Cytoskeleton -network of protein filaments extending throughout the cytosol -scaffold that helps determine a cell’s shape and organize the cellular contents. -aids movement of organelles within the cell, of chromosomes during cell division, and of whole cells such as phagocytes. - Filaments: microfilaments, intermediate filaments, microtubules Session ID: rgeorge1  Filaments Microfilaments Intermediate filaments Microtubules Size Thinnest Greater than Large microfilaments, less than microtubules Protein Actin, myosin Keratin(skin), Tubulin, neurofilaments( neurons), Glial fibrillary acidic protein (astrocytes) Function 1. Generate movement 2. 1. Stabilize position of 1. Help determine cell Provide mechanical organelles shape support(microvilli), shape 2. Attach cells to each 2. Function in and strength of cell other movement eg 1. Movement:Muscle Eg, keratin ensures 1. Movement of contraction, cell division, cell attachment to the secretory vesicles, locomotion. 2. Support underlying basement chromosomes microvilli, anchor membrane and cell-cell during cell division, cytoskeleton to the plasma contact in the cilia and flagella membrane keratinocytes Session ID: rgeorge1 -prominent spherical oval-shaped structure in the cell -Absent in red blood cells -More than one is present in some cells(eg skeletal muscles, hepatocytes (liver cells)) Function: -Controls cellular structure (genes) -Directs cellular activities (genes) -Produces ribosome subunits (nucleolus) Features -Double membrane lipid nuclear envelope with nuclear pores -Pores allow passive diffusion of small molecules and ions. Proteins and RNA are actively transported through pores Session ID: rgeorge1 Features Nucleolus -spherical bodies within the nucleus without a membrane, -cluster of protein, DNA, and RNA -synthesizes rRNA, assembles rRNA and proteins into ribosomal subunits Genes -Hereditary units located in the nucleus -Controls cellular structure -Directs cellular activities -DNA-double helix -DNA is packaged as nucleosomes which give rise to chromatin (DNA, proteins, RNA) and highly coiled to form chromosomes (46) Session ID: rgeorge1 Session ID: rgeorge1 -flexible barrier that surrounds and contains the cytoplasm of a cell, -fluid mosaic model Function: -Acts as a barrier separating inside and outside of the cell. -Controls the flow of substances into and out of the cell. -Helps identify the cell to other cells (e.g., immune cells). -Participates in intercellular signaling. Structure: Lipid bilayer - three types of lipid molecules—phospholipids, cholesterol, and glycolipids -polar (facing outward) and (nonpolar components) Session ID: rgeorge1 Integral proteins -are amphipathic -extend into or through the lipid bilayer and are firmly embedded in it -most integral proteins are transmembrane proteins -many are glycoproteins -form ion channels, act as carriers/transporters, serve as receptors, act as enzymes, act as linkers -glycoproteins & glycolipids constitute the glycocalyx -glycocalyx -enables cells to recognize one another -enables cells to adhere to one another in some tissues -protects cells from being digested by enzymes in the extracellular fluid -attracts a film of fluid to the cell’s surface -makes red blood cells slippery as they flow through narrow blood vessels -protects cells from drying out Session ID: rgeorge1 Peripheral proteins -not as firmly embedded in the membrane -they are attached to the polar heads of membrane lipids or to integral proteins at the inner or outer surface of the membrane. -act as enzymes and linkers -support the plasma membrane, -anchor integral proteins, -participate in mechanical activities (moving materials and organelles , changing cell shape, attaching cells to one another) Session ID: rgeorge1  Permeable- allows the passage of a substance Impermeable-does not allows the passage of a substance Selective permeability- some substances pass more readily than others Membrane oxygen (O2), carbon water and urea ions and portion dioxide (CO2), and large, uncharged steroids polar molecules, such as glucose lipid bilayer highly moderately impermeable (hydrophobic) permeable permeable Session ID: rgeorge1 Selective permeability -major determinant of concentration of substances on either side of the plasma membrane concentration gradient- difference in the concentration of a chemical from one place to another electrical gradient (membrane potential)- difference in electrical charges between two regions, inner surface is more negatively charged, outer surface is more positively charged electrochemical gradient- combined influence of the concentration gradient and the electrical gradient on movement of a particular ion Session ID: rgeorge1  Cilia and Flagella - motile projections of the cell surface -Narrow, long hair-like structures -Formed by basal bodies. -Cilia move fluid along the cell surface (respiratory tract) -flagella move an entire cell (sperm cell). -Made up of microtubules, “9+2” structure Microvilli -Microscopic protrusions of folds of the cell membrane -Increases surface area for absorption, “brush border” -Contain actin filaments -Location: digestive system Session ID: rgeorge1 Session ID: rgeorge1 Session ID: rgeorge1  Transport process Passive Active Process Down concentration/ electrical ‘Uphill’/against concentration gradient gradient Energy Kinetic 1. Primary active transport - Adenosine triphosphate (ATP) 2. Secondary active transport -ionic concentration gradient (H, Na), indirectly uses ATP, Eg. Simple diffusion-O2, CO2, N, Fatty 1.Active transport- Na, K, Cl, H, acids, steroids, Vit A,D,E & K, H2O Ca, I, amino acids, , Urea, small alcohols monosaccharides Facilitated diffusion:glucose, fructose, galactose, K, Na, Ca, Cl, 2.vesicle (endo/exo –cytosis) Osmosis:H2O through selectively permeable membrane Membrane structure involved Simple diffusion- plasma membrane 1.Integral membrane protein gradient (carrier proteins)-Primary active Facilitated diffusion- Integral transport-pumps membrane protein (carrier proteins/ ion channels) 2.Integral membrane protein (carrier proteins)-Secondary active transport- symporters, antiporters Factors influencing rate Steepness of the concentration gradient, temperature, mass of substance, surface area, diffusion Session ID: rgeorge1 distance  Vesicle- small spherical sac substances are transported in vesicles from one structure to another within cells Vesicles also import materials from and release materials into extracellular fluid Types of vesicle transport Endocytosis -receptor-mediated endocytosis -phagocytosis -bulk-phase endocytosis Exocytosis Session ID: rgeorge1  Receptor-mediated endocytosis highly selective type of endocytosis by which cells take up specific ligands vesicle forms after a receptor protein in the plasma membrane recognizes and binds to a particular particle in the extracellular fluid Eg LDLs, transferrin (an iron- transporting protein in the blood), some vitamins, antibodies, and certain hormones Session ID: rgeorge1  Phagocytosis the cell (neutrophils, macrophages) engulfs large solid particles Protects the body from disease Pseudopods (projections of the plasma membrane and cytoplasm)- surround the particle and fuse forming a phagosome eg of material phagocytosed worn- out cells, whole bacteria, or viruses Session ID: rgeorge1  Bulk-phase endocytosis (pinocytosis) Carried out by most body cells tiny droplets of extracellular fluid are taken up plasma membrane folds inward and forms a vesicle which is then pinched off in the cytosol Session ID: rgeorge1 Exocytosis Release of material from the cell Eg secretory cells - digestive enzymes, hormones, mucus, etc Eg , nerve cells – neurotransmitters Waste- Transcytosis Substances are moved into, across, and out of a cell eg epithelial cells. 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