Module 1 - Cell Physiology 3-slides (1) PDF - Human Physiology I

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9/1/24 HH/KINE 2011 - HUMAN PHYSIOLOGY I FACULTY OF HEALTH KINESIOLOGY AND HEALTH SCIENCE Fall 2024 MODULE 1 – CELL PHYSIOLOGY Hum an Physiology: From Cells to System s, 5th Edition Lauralee Sherw ood; Christopher W ard; Chapter 2 1 Lecture 1: Learning Objectives By the end of today’s lecture, you should be able to: Understand the principle of cell theory Define the main structures and functions of a cell Identify the organelles present in all human cells and learn their function(s) Copyright © 2024 Dr. Abdul-Sater 2 Principles of cell theory Theodor S chw ann The cell is the smallest structural and functional unit capable of carrying out life processes. The functional activities of each cell depend on the specific structural properties of the cell. Cells are the living building blocks of all plants and animals organisms. The cell is the basic unit of life. An organism’s structure and function ultimately depend on the collective structural characteristics and functional capabilities of its cells. Because of this continuity of life, the cells of all organisms are fundamentally similar in structure and function. Copyright © 2024 Dr. Abdul-Sater 3 1  9/1/24 Cell Structure and Function Trillions of cells in the human body classified Peroxisome into ~ 200 cell types Mitochondria Free ribosome This is based on Vault specific variations in Nuclear pore structure and function Nucleus Rough ER Despite variations, Pair of centrioles cells still share many in centrosome Ribosome (attached to Endoplasmic rough ER) reticulum Lysosome common features: Smooth ER Plasma Microtubules radiating from Membrane centrosome Microfilaments Vesicle Cytosol Plasma membrane Nucleus Golgi complex Cytosol ❙ Figure 2-1 Diagram of cell structures visible under an electron microscope. Copyright © 2024 Dr. Abdul-Sater 4 sists of a different DNA molecule that contains a unique set of genes. Body cells contain 46 chromosomes that can be sorted into 23 pairs on the basis of their distinguishing features. DNA We next examine interactions of RNA with DNA in protein synthesis. has two important functions: Roles of RNA Three types of ribonucleic acid (RNA) play roles in protein synthesis (see p. A-14). First, DNA’s genetic 1. Serving as a genetic blueprint during cell replication. code for a particular protein is transcribed into a messenger Through this role, DNA ensures that the cell produces addi- RNA (mRNA) molecule, which exits the nucleus through the tional cells just like itself, thus continuing the identical type of nuclear pores. Within the cytoplasm, mRNA delivers the coded cell line within the body. Furthermore, in the reproductive message to ribosomes, which “read” the code and translate it cells (eggs and sperm), the DNA blueprint passes on genetic into the appropriate amino acid sequence for the designated characteristics to future generations. protein being synthesized. Ribosomal RNA (rRNA) is an 2. Directing protein synthesis. DNA provides codes, or “instruc- essential component of ribosomes. (We will discuss the struc- tions,” for directing synthesis of specific structural and enzy- ture and function of ribosomes in more detail later.) Transfer matic proteins within the cell. Proteins are the main structural RNA (tRNA) delivers the appropriate amino acids within the component of cells, and enzymes govern the rate of all chemical cytoplasm to their designated site in the protein under con- reactions in the body. By specifying the kinds and amounts of struction at the ribosome. Gene expression refers to the multi- proteins that are produced, the nucleus indirectly governs most stepped process by which information encoded in a gene is cell activities and serves as the cell’s control center. used to direct the synthesis of a protein molecule. (For further Unless otherwise noted, all content on this page is © Cengage Learning. Cell Physiology 23 Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Cell Structure and Function Plasma Membrane: thin membranous structure that encloses each cell composed mostly of lipid (fat) molecules (bilayer) studded with proteins barrier separates the cell’s contents from its surroundings selectively control movement of molecules into and out of the cell Copyright © 2024 Dr. Abdul-Sater 5 Cell Structure and Function Nucleus: surrounded by a double- layered membrane houses the cell’s genetic material, deoxyribo- nucleic acid (DNA) Serves as a genetic blueprint during cell replication Directs protein synthesis Copyright © 2024 Dr. Abdul-Sater 6 2  9/1/24 Cell Structure and Function: Organelles Endoplasmic reticulum Fluid filled membranous system Ribosomes a protein and lipid Where a messenger RNA fits through Rough ER Smooth ER producing factory Large a ribosome Small Rough ER: ribosomal subunit ribosomal subunit (c) Ribosome Studded with ribosomes Rough ER lumen Smooth ER lumen synthesizes proteins to be secreted to the exterior or to be Ribosomes incorporated into Tubules plasma membrane or Sacs other cell components Smooth ER: Don W. Fawcett/Science Source packages the secretory product into transport vesicles, which bud off and move to the Golgi complex Copyright © 2024 Dr. Abdul-Sater Rough ER lumen Ribosomes Smooth ER lumen (a) Rough ER (b) Smooth ER 7 ❙ Figure 2-2 Endoplasmic reticulum (ER). (a) Diagram and electron micrograph of the rough ER, which consists of stacks of relatively flattened interconnected sacs studded with ribosomes. (b) Diagram and electron micrograph of the smooth ER, which is a meshwork of tiny interconnected tubules. The rough ER and smooth ER are connected, making one continuous organelle. (c) Diagram of an assembled ribosome. ribosomes, free ribosomes synthesize proteins for use within In most cells, the smooth ER is rather sparse and serves the cytosol. In this way, newly produced molecules destined for primarily as a central packaging and discharge site for mole- export out of the cell or for synthesis of new membrane or other cules to be transported from the ER. Newly synthesized pro- cell components (those synthesized by the ER) are physically teins and lipids move within the continuous lumen from the separated from those that belong in the cytosol (those produced rough ER to gather at specialized exit sites in the smooth ER. by the free ribosomes). About one third of the proteome is These exit sites then “bud off ” (that is, balloon outward on the typically synthesized in the ER. surface and then are pinched off), forming transport vesicles How do newly synthesized molecules within the ER lumen that enclose the new molecules (❙ Figure 2-3). (A vesicle is a get to their destinations if they cannot pass out through the ER fluid-filled, membrane-enclosed intracellular cargo container.) membrane? They do so by action of the smooth ER. How does the ER exit site bud off? Coat proteins of the type known as coat protein II (COPII) from the cytosol bind with specific proteins facing the outer surface of the smooth ER The smooth ER packages new proteins membrane at the exit site. The linking of these coat proteins into in transport vesicles. a cagelike assembly or “coat” causes the surface membrane at The smooth ER does not contain ribosomes, so it is “smooth.” the site to curve outward to form a dome-shaped bud around Lacking ribosomes, it is not involved in protein synthesis. the newly synthesized products to be exported out of the Instead, it serves other purposes that vary in different cell types. smooth ER. Eventually the surface membrane closes and 26 CHAPTER 2 Unless otherwise noted, all content on this page is © Cengage Learning. Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Cell Structure and Function: Organelles Golgi Complex Ubiquitin 1 Addition of ubiquitin to consists of a stack of a protein. Unwanted flattened, protein slightly curved, membrane-enclosed sacs closelyRegulatory associated with the particle Golgi complex ER Unfolding protein Transport Modifies, Proteasome Core packages, and2 Proteasome recognizes ubiquitin-tagged protein and vesicle from distributes (size of a ribosomal particle newly synthesized unfolds it. Enzymes that are part of the core digest ER, about to fuse with the Golgi subunit) Peptides Golgi membrane lumen proteins protein to small peptides. 3 Cytosolic enzymes Golgi degrade the released sacs Vesicles containing peptides to amino acids, finished product which are recycled for protein synthesis or used as an energy source. Golgi complex Proteasome and ubiquitin are recycled. Copyright © 2024 Dr. Abdul-Sater ❙ Figure 2-4 Proteasome. 8 each end with a regulatory particle. The regulatory particle rec- Don W. Fawcett/Science Source ognizes the ubiquitin-tagged protein, unfolds it, and feeds it into the core. The core cavity is lined with a variety of enzymatic sites that break down the protein into peptides (small chains of amino acids). After the peptides are released from the protea- some, cytosolic enzymes finish digesting them into their com- ponent amino acids. Ubiquitin is released and recycled. ❙ Figure 2-5 Golgi complex. Diagram and electron micrograph of a Golgi com- In addition to tagging misfolded proteins in the ER, ubiqui- plex, which consists of a stack of slightly curved, membrane-enclosed sacs. The tin also labels other damaged or unneeded intracellular pro- vesicles at the dilated edges of the sacs contain finished protein products pack- teins for degradation in proteasomes. aged for distribution to their final destination. Check Your Understanding 2.3 flattened sacs are thin in the middle but have dilated, or bulg- 1. Distinguish between the rough ER and smooth ER structurally ing, edges. The number of Golgi complexes varies, depending and functionally. on the cell type. Some cells have only one Golgi stack, whereas 2. Discuss the structure and function of a ribosome. cells specialized for protein secretion may have hundreds of 3. State the destination of proteins synthesized by the rough ER. stacks. 4. Describe the function of the ubiquitin–proteasome pathway. Transport vesicles carry their cargo to the Golgi complex for further processing. Most newly synthesized molecules that have just budded off Golgi Cell2.4 Complex and and Structure Function: from the smooth ER enterOrganelles a Golgi stack. When a transport Exocytosis vesicle reaches a Golgi stack, the vesicle membrane fuses with the membrane of the sac closest to the center of the cell. The The Golgi complex, a membranous organelle, is closely associ- vesicle membrane opens up and becomes integrated into the from the surface membrane. Besides bringing ECF into a cell, Lysosomes ated with the ER. Each Golgi complex consists of a stack of Golgi membrane, and the contents of the vesicle are released to pinocytosis provides a means to retrieve extra plasma mem- Peroxisome flattened, slightly curved, membrane-enclosed sacs (❙ Figure 2-5 the interior of the sac (see ❙ Figure 2-3). small, membrane-enclosed, and chapter opener photo). The sacs within each Golgi stack do These newly synthesized raw materials from the ER travel brane that has been added to the cell surface during exocytosis. degradative organelles not come into physical contact with one another. Note that the by means of vesicle formation through the layers of the Golgi Receptor-Mediated Endocytosis Unlike pinocytosis, which involves the nonselective uptake of the surrounding fluid, recep- break down organic 28 CHAPTER 2 Lysosome Unless otherwise noted, all content on this page is © Cengage Learning. tor-mediated endocytosis is a highly selective process that molecules with powerful Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. enables cells to import specific large molecules that it needs from its environment. Receptor-mediated endocytosis is triggered by hydrolytic enzymes the binding of a specific target molecule such as a protein to a surface membrane receptor specific for that molecule (❙ Figure digestive system of the cell: Oxidative 2-9b). This binding causes the plasma membrane at that site to destroy foreign substances Hydrolytic enzymes pocket inward and then seal at the surface, trapping the bound enzymes and cellular debris molecule inside the cell. The pouch is formed by the linkage of clathrin molecules, which are membrane-deforming coat proteins on the inner surface of the plasma membrane that bow inward, in contrast to the outward-curving coat proteins that form buds. The resulting pouch is known as a coated pit because it is coated with Don W. Fawcett/Science Source clathrin. Cholesterol complexes, vitamin B12, the hormone insu- lin, and iron are examples of substances selectively taken into cells by receptor-mediated endocytosis. Unfortunately, some viruses can sneak into cells by exploiting this mechanism. For instance, flu viruses and HIV, the virus that causes AIDS (see p. 426), gain entry ❙ Figure 2-8 Lysosomes and peroxisomes. Diagram and electron micrograph of lysosomes, which contain hydrolytic enzymes, and peroxisomes, which contain to cells via receptor-mediated endocytosis. They do so Copyright © 2024 Dr. Abdul-Sater oxidative enzymes. by binding with membrane receptors normally designed to trig- ger the internalization of a needed molecule. 9 Phagocytosis During phagocytosis (“cell eating”), large the Golgi complex for packaging in the budding lysosome (see multimolecular particles are internalized. Most body cells ❙ Figure 2-3). These enzymes catalyze hydrolysis, reactions that perform pinocytosis, many carry out receptor-mediated endo- break down organic molecules by the addition of water at a cytosis, but only a few specialized cells are capable of phago- bond site (hydrolysis means “splitting with water”; see p. A-14). cytosis, the most notable being certain types of white blood In lysosomes, the organic molecules are cell debris and foreign cells that play an important role in the body’s defense mecha- material, such as bacteria, that have been brought into the cell. nisms. When a white blood cell encounters a large particle, Lysosomal enzymes are similar to the hydrolytic enzymes that such as a bacterium or tissue debris, it extends surface projec- the digestive system secretes to digest food. Thus, lysosomes tions known as pseudopods (“false feet”) that surround or serve as the intracellular “digestive system.” Note that lysosomes engulf the particle and trap it within an internalized vesicle mostly degrade extracellular proteins brought into the cell, known as a phagosome (❙ Figure 2-9c). A lysosome fuses with whereas most unwanted intracellular proteins are degraded by the membrane of the phagosome and releases its hydrolytic the ubiquitin–proteasome pathway. enzymes into the vesicle, where they safely attack the bacte- Extracellular material to be attacked by lysosomal enzymes rium or other trapped material without damaging the remain- is brought into the cell through the process of phagocytosis, a der of the cell. The enzymes largely break down the engulfed 3 type of endocytosis. Endocytosis, the reverse of exocytosis, material into raw ingredients, such as amino acids, glucose, refers to the internalization of extracellular material within a and fatty acids, which the cell can use. cell (endo means “within”) (see ❙ Figure 2-6b). Endocytosis can be accomplished in three ways—pinocytosis, receptor-mediated endocytosis, and phagocytosis—depending on the contents of Lysosomes remove worn-out organelles. the internalized material. Cells typically live longer than many of their internal compo- nents. Lysosomes can fuse with aged or damaged organelles to  9/1/24 Cell Structure and Function: Organelles Peroxisomes Peroxisome from the surface membrane. Besides bringing ECF into a cell, pinocytosis provides a means to retrieve extra plasma mem- membrane-enclosed sacs brane that has been added to the cell surface during exocytosis. containing oxidative Receptor-Mediated Endocytosis Unlike pinocytosis, which enzymes Lysosome involves the nonselective uptake of the surrounding fluid, recep- tor-mediated endocytosis is a highly selective process that detoxify various wastes enables cells to import specific large molecules that it needs from its environment. Receptor-mediated endocytosis is triggered by produced within the cell or the binding of a specific target molecule such as a protein to a foreign toxic compounds Oxidative surface membrane receptor specific for that molecule (❙ Figure 2-9b). This binding causes the plasma membrane at that site to that have entered the cell Hydrolytic enzymes pocket inward and then seal at the surface, trapping the bound (e.g. alcohol consumed in enzymes molecule inside the cell. The pouch is formed by the linkage of clathrin molecules, which are membrane-deforming coat proteins beverages!) on the inner surface of the plasma membrane that bow inward, in contrast to the outward-curving coat proteins that form buds. The resulting pouch is known as a coated pit because it is coated with Don W. Fawcett/Science Source clathrin. Cholesterol complexes, vitamin B12, the hormone insu- lin, and iron are examples of substances selectively taken into cells by receptor-mediated endocytosis. Unfortunately, some viruses can sneak into cells by exploiting this mechanism. For instance, flu viruses and HIV, the virus that causes AIDS (see p. 426), gain entry ❙ Figure 2-8 Lysosomes and peroxisomes. Diagram and electron micrograph to cells via receptor-mediated endocytosis. They do so Copyright © 2024 Dr. Abdul-Sater of lysosomes, which contain hydrolytic enzymes, and peroxisomes, which contain oxidative enzymes. by binding with membrane receptors normally designed to trig- ger the internalization of a needed molecule. 10 Phagocytosis During phagocytosis (“cell eating”), large the Golgi complex for packaging in the budding lysosome (see multimolecular particles are internalized. Most body cells ❙ Figure ❙ Figure 2-3). 2-19 These enzymes Components catalyze of the hydrolysis, cytoskeleton. reactions that (a) Micro- perform pinocytosis, many carry out receptor-mediated endo- Keratin filament break down tubules, organic the largest of themolecules by the addition cytoskeletal elements, of water at a are long, hollow cytosis, but only a few specialized cells are capable of phago- bond tubessite (hydrolysis formed means by two slightly “splitting different variantswith water”; see p. A-14). of globular-shaped cytosis, the most notable being certain types of white blood Intubulin lysosomes, molecules.the(b)organic molecules the Most microfilaments, aresmallest cell debris of the and cy- foreign cells that play an important role in the body’s defense mecha- material, toskeletal such as bacteria, elements, thatchains consist of two haveofbeenactin brought molecules into the cell. nisms. When a white blood cell encounters a large particle, Lysosomal wrapped aroundenzymes are similar each other. to the hydrolytic (c) The intermediate enzymes that filament keratin, such as a bacterium or tissue debris, it extends surface projec- the founddigestive in skin, issystem made of secretes four keratinto digest food. protofibrils twisted Thus, together.lysosomes tions known as pseudopods (“false feet”) that surround or serve as the consists A protofibril intracellular “digestive of two strands, eachsystem. made up” of Note two that stag- lysosomes engulf the particle and trap it within an internalized vesicle gered rows mostly of keratin degrade subunits. The composition extracellular of intermediate proteins brought into the cell, known as a phagosome (❙ Figure 2-9c). A lysosome fuses with filaments, which are intermediate in size between the microtu- whereas most unwanted intracellular proteins are degraded by the membrane of the phagosome and releases its hydrolytic bules and microfilaments, varies among different cell types. Keratin the ubiquitin–proteasome pathway. enzymes into the vesicle, where they safely attack the bacte- subunit Extracellular material to be attacked by lysosomal enzymes rium or other trapped material without damaging the remain- Tubulin is brought into the cell through the process of phagocytosis, a subunit der of the cell. The enzymes largely break down the engulfed type of endocytosis. Endocytosis, the reverse of exocytosis, material into raw ingredients, such as amino acids, glucose, refers to the internalization of extracellular material within a and fatty acids, which the cell can use. cell (endo means “within”) (see ❙ Figure 2-6b). Endocytosis can be accomplished in three ways—pinocytosis, receptor-mediated endocytosis, and phagocytosis—depending on the contents of Lysosomes remove worn-out organelles. Cell Structure and Function: OrganellesCells typically live longer than many of their internal compo- Actin Keratin the internalized material. protofibril nents. Lysosomes can fuse with aged or damaged organelles to subunit Pinocytosis In pinocytosis (“cell drinking”), a droplet of remove these useless parts of the cell. Lysosomal enzymes Centrioles ECF is taken up nonselectively. First, the plasma membrane dips inward, forming a pouch that contains a small bit of ECF degrade the dysfunctional organelle, making its building blocks available for reuse by the cell. This selective self-digestion, (a) Microtubule A (b)pair of cylindrical Microfilament (c) Keratin, an intermediate filament (❙ Figure 2-9a). The plasma membrane then seals at the surface of the pouch, trapping the contents in a small, intracellular known as autophagy (auto means “self ”; phag means “eating”) makes way for new replacement parts. In most cells, all organ- structures at right angles to endocytic vesicle, or endosome. Dynamin, the protein respon- elles are renewable. each other sible for pinching off an endocytic vesicle, forms rings that wrap around and “wring the neck” of theCentrioles pouch, severing the vesicle When cells are starving, they often induce autophagy of healthy cellular components that can be spared. This self- Microtubules help formmaintain and asymmetric organize cell shapes and play a role in complex cell Unless otherwise noted, all content on this page is © Cengage Learning. Cell Physiology 31 movements. microtubules during assembly of the mitotic Microtubules are the largest of the cytoskeletal elements. They Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. are slender (22 nm in spindle diameter), during cell long, hollow, division unbranched tubes composed primarily of tubulin, a small, globular, protein form cilia and flagella molecule (❙ Figure 2-19a). Microtubules arise from the centrosome and its associated centrioles. The centrosome, or cell center, located near the nucleus, consists of the centrioles surrounded by an amorphous mass of proteins. The centrioles, which are nonmembranous organelles, are a pair of short cylindrical structures that lie at right angles to each other at the centrosome’s center (❙ Figure 2-20). The centrosome is the cell’s main microtubule organizing Microtubule center. When a cell is not dividing, microtubules are formed triplet from the amorphous mass and radiate outward in all directions Copyright © 2024 Dr. Abdul-Sater from the centrosome (see ❙ Figure 2-1, p. 23). Centrioles form microtubules under special circumstances, as you will see as we 11 turn attention to microtubule functions. Microtubules position many of the cytoplasmic organelles, such as the ER, Golgi complex, lysosomes, and mitochondria. They are also essential for maintaining the shape of asymmetric cells, such as nerve cells, whose elongated axons may extend up to a meter in length from where the cell body originates in the spinal cord to where the axon ends at a muscle (❙ Figure 2-21a). Don W. Fawcett/Science Source ❙ Figure 2-20 Centrioles. The two cylindrical centrioles lie at right angles to each other as shown in the diagram. The electron micrograph shows a centriole in cross section. Note that a centriole is made up of nine microtubule triplets that form a ring. 46 CHAPTER 2 Unless otherwise noted, all content on this page is © Cengage Learning. Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s). Editorial review has deemed that any suppressed content does not materially affect the overall learning experience. Cengage Learning reserves the right to remove additional content at any time if subsequent rights restrictions require it. Cell Structure and Function: Organelles much of the energy in food into a usable form. The generous Mitochondria folds of the inner membrane greatly increase the surface area available for housing these important proteins. The matrix con- rod-shaped or oval structures sists of a concentrated mixture of hundreds of different dis- about the size of bacteria solved enzymes that prepare nutrient molecules for final extrac- tion of usable energy by the cristae proteins. enclosed by a double Mitochondrion membrane Mitochondria form a mitochondrial reticulum in some cell types. inner membrane forms a In skeletal muscle and many other cell types, mitochondria series of infoldings called Intermembrane space rarely exist separately but instead are interconnected in a net- work, the mitochondrial reticulum (❙ Figure 2-10b). This orga- cristae Cristae nized system efficiently distributes materials essential for gener- ating energy—for example O2 and food derivatives such as fatty Cristae project into an inner acids—from the cell surface to deep within the cell. O2 and fatty cavity filled with a gel-like