The Cell.pptx

Captioning Statement Video and audio content at the University uses closed captions generated by automatic speech recognition (ASR). The ASR process is based on machine learning algorithms which automatically transcribe voice to text. According to our technology providers this process is approximate...

Captioning Statement Video and audio content at the University uses closed captions generated by automatic speech recognition (ASR). The ASR process is based on machine learning algorithms which automatically transcribe voice to text. According to our technology providers this process is approximately 70-90% accurate depending on the quality of the audio, and consequently video and audio closed captions may include some transcription errors. It is therefore important to recognise that the original recording is the most accurate reflection of the content, and not the captions. If you require accurate captions as part of your reasonable adjustments, please contact the Inclusion Centre to discuss your requirements 26/04/24 1 The Cell NU1303/NU1401 26/04/24 2 This topic relates to: Learning outcome: 1 Describe anatomy, physiology and homeostatic mechanisms of human development from conception to old age. Formative and summative assessment Any topic within this module could potentially have a question(s) in the exam paper Links with other topics in the module The cell is the fundamental building block of the whole body. This links with genetics, homeostasis, endocrinology. Links with other modules and stages It is important to understand the cellular level of life for pathophysiologies and psychopathophysiologies. Links to nursing and paramedic practice Many pathophysiologies/psychopathophysiologies and their treatment are linked to the cellular level. 26/04/24 3 Chapter 3 - Cells CHARLES J. WELSH 2021 HOLE’S ESSENTIALS OF HUMAN ANATOMY & PHYSIOLOGY Fourteenth Edition 26/04/24 4 3.1: Introduction A cell is the smallest unit of life A cell continually carries out metabolic activities essential for life, as well as specialized functions, and adapts to changing conditions Cells interact to form tissues, organs, and organ systems The human body consists of 30 trillion cells that vary considerably in shape and size, yet have much in common Differences in cell shape make different functions possible Examples: Nerve cells have long extensions that conduct electrical impulses, while epithelial cells in the mouth are flat, thin, and densely packed, to provide a protective barrier Genes control a cell’s actions and responses Cells Vary in Shape and Function 3.2: Composite Cell A composite cell includes many different cell structures; most cells contain most of these structures, but no cell contains all of them. A cell consists of three main parts: Nucleus: Contains DNA (genetic material) and directs cell’s activities Cytoplasm: Organelles and fluids that make up most of the cell; between nucleus and cell membrane Cell membrane: Boundary that encloses the cell Within the cytoplasm are specialized organelles (little organs) that perform specific functions for the cell Organelles are suspended in a fluid called the cytosol Illustration of a Composite Cell Cell Membrane Cell membrane is also called plasma membrane Boundary that contains the cell contents Regulates the movement of substances in and out of the cell Participates in signal transduction, a method of communication with other cells Helps cells adhere to other cells General Characteristics: Extremely thin, flexible, and elastic Selectively permeable – regulates entry/exit of substances Has complex surface features, with adaptations to increase surface area Cell Membrane Structure: Lipids Composed mainly of lipids and proteins, and some carbohydrates The basic framework of the cell membrane consists of a double layer (bilayer) of phospholipids, with fatty acid tails turned inward and the water-soluble heads facing the surfaces The phospholipids can move, forming a stable fluid film Lipid-soluble molecules (respiratory gases, steroid hormones) can pass through the phospholipid portion of the membrane Cell membrane is impermeable to water-soluble molecules Cell Membrane Structure: Many types of proteins are found in the cell membrane Proteins 1 Proteins are classified by their relationship to the phospholipid bilayer: Integral: span width of bilayer; may protrude on 1 or both sides Transmembrane: integral proteins that protrude on both sides Peripheral: associate with one side of bilayer Membrane proteins vary in shape: rodlike, globular, fibrous Membrane proteins vary in function: Some proteins function as receptors or growth factors on the cell surface, starting signal transduction Other proteins transport ions or molecules across cell membrane, such as ion channels Cell Membrane Structure: Proteins Other proteins have carbohydrates attached 2 (glycoproteins) and are used for cell identification; this helps identify cells as “self,” protecting them from attack by the immune system Proteins that protrude into the cell will anchor supportive rods and tubules, forming a cytoskeleton Membrane proteins called cellular adhesion molecules (CAMs) help determine a cell’s interactions with other cells Structure of the Plasma Membrane The Cytoplasm The cytoplasm makes up most of cell volume, and consists of a clear liquid (cytosol), a supportive cytoskeleton, and networks of membranes and organelles Organelles Ribosomes: Tiny, spherical structures composed of RNA and protein Provide structural support and enzyme activity for protein synthesis Not membranous Found in cytoplasm or bound to rough endoplasmic reticulum Organelles 1 Endoplasmic reticulum (ER): Made up of membrane-bound flattened sacs and vesicles Functions as a transport network throughout the cell 2 types of ER: Rough ER: contains ribosomes, and functions in protein synthesis Smooth ER: does not contain ribosomes, and functions in lipid synthesis, absorption of fats, and metabolism of drugs The Endoplasmic Reticulum. (a): Don W. Fawcett/Science Source Organelles 2 Vesicles: Membranous sacs Store or transport substances within or between cells Golgi apparatus: Composed of flattened, membranous sacs Refines, packages, and transports proteins formed in the rough ER Vesicles formed in the ER travel to the Golgi apparatus, which may modify their contents by adding sugar molecules to the proteins, to stabilize their structure or to enable folding. A new vesicle pinches off the Golgi apparatus and may then move to the cell membrane to secrete its contents to the outside (exocytosis) The Golgi Apparatus (a): Biophoto Associates/Science Source Organelles 3 Mitochondria: Elongated fluid-filled sacs The inner membrane of the mitochondrion is folded into cristae, which increase surface area House many chemical reactions that extract energy from nutrients (cellular respiration) and produce ATP Store the energy in the chemical bonds of ATP Very active cells contain thousands of mitochondria Mitochondria have their own DNA and reproduce by dividing Mitochondria (a): Bill Longcore/Science Source Organelles 4 Lysosomes: Membranous sacs Formed by budding off Golgi apparatus Contain enzymes that break down nutrients, ingested materials, debris, worn out cell parts, cholesterol (in some cells), toxins, and drugs Peroxisomes: Also membranous sacs Contain a different set of enzymes than lysosomes Their enzymes function in the breakdown of fatty acids and hydrogen peroxide, and detoxification of alcohol Other Cellular Structures 1 In the cytoplasm, there are several structures, which are not organelles, but rather part of the cytoskeleton. Microfilaments and microtubules are thin, threadlike structures that serve as the cytoskeleton of the cell: Microfilaments: made of the protein actin; cause various cellular movements; group together to form myofibrils in muscle Microtubules: made of the globular protein tubulin, are attached in a spiral to form a long tube; important in cell division Intermediate fibers: made of different proteins in different cells, are abundant in skin cells and neurons Other Cellular Structures 1 In the cytoplasm, there are several structures, which are not organelles, but rather part of the cytoskeleton. Microfilaments and microtubules are thin, threadlike structures that serve as the cytoskeleton of the cell: Microfilaments: made of the protein actin; cause various cellular movements; group together to form myofibrils in muscle Microtubules: made of the globular protein tubulin, are attached in a spiral to form a long tube; important in cell division Intermediate fibers: made of different proteins in different cells, are abundant in skin cells and neurons The Cytoskeleton (a): Dr. Gopal Murti/Science Source Other Cellular Structures 2 Centrosome: A non-membranous structure, made up of two hollow cylinders called centrioles, that function in the distribution of chromosomes during cell division; made of nine groups of three microtubules Cilia: Motile extensions from the cell; short cilia are abundant on the free surfaces of certain epithelial cells and move in a wave (respiratory linings, for example) to move fluids or whole cells Flagella: Another type of motile extension from cell; usually a cell only has 1 flagellum; the only human cell with a flagellum is a sperm cell; the flagellum allow the sperm to swim toward the egg cell The Centrosome (Centrioles) (a): Don W. Fawcett/Science Source Cilia and Flagella (a): Oliver Meckes/Science Source; (b): Brand X Pictures/Getty Images The Cell Nucleus 1 The nucleus contains genetic material, DNA, which controls cell activities The fairly large nucleus is surrounded by a double-layered nuclear envelope, containing relatively large nuclear pores that allow the passage of certain substances Contains a fluid called nucleoplasm The nucleolus is a small, dense body in the nucleus, composed of RNA and protein; it is the site of ribosome production Chromatin consists of loosely coiled fibers of protein and DNA found in the nucleus Condensed DNA is referred to as chromosomes; this form of DNA is present during cell division The Cell Nucleus (b): Dr. Gopal Murti/Science Source 2 Structures and Functions of Cell Parts TABLE 3.1 Structures and Functions of Cell Parts 1 Cell Part(s) Structure Function Cell membrane Membrane composed of protein and lipid molecules Maintains integrity of cell and controls passage of materials into and out of cell Ribosomes Particles composed of protein and RNA molecules Synthesize proteins Endoplasmic reticulum Complex of interconnected membrane-bounded sacs and canals Transports materials within the cell, provides attachment for ribosomes, and synthesizes lipids Vesicles Membranous sacs Contain and transport various substances Golgi apparatus Stack of flattened, membranous sacs Packages protein molecules for transport and secretion Mitochondri a Membranous sacs with inner partitions Release energy from nutrient molecules and change energy into a usable form Lysosomes Membranous sacs Digest worn cellular parts or substances that enter cells Structures and Functions of Cell Parts TABLE 3.1 Structures and Functions of Cell Parts 2 Cell Part(s) Structure Function Peroxisomes Membranous sacs House enzymes that catalyze diverse reactions, including breakdown of hydrogen peroxide and fatty acids, and alcohol detoxification Microfilaments and microtubules Thin rods and tubules Support the cytoplasm and help move substances and organelles within the cytoplasm Centrosome Nonmembranous structure composed of two rodlike centrioles Helps distribute chromosomes to new cells during cell division Cilia and flagella Motile projections attached beneath the cell membrane Cilia propel fluid over cellular surfaces, and a flagellum enables a sperm cell to move Nuclear envelope Double membrane that separates the nuclear contents from the cytoplasm Maintains integrity of nucleus and controls passage of materials between nucleus and cytoplasm Nucleolus Dense, nonmembranous body Site of ribosome synthesis