N109 Objective 3 Part A (2023) (1).pdf

ANATOMY &PHYSIOLOGY PN 1109 O B J E C T I V E # 3 PA R T A CHAPTER 3 LEARNER OBJECTIVES • Define key terms related to cells, tissues, and systems • Identify the main structures of the cell • Identify the structure and functions of the plasma membrane • Discuss the processes that move substance a...

ANATOMY &PHYSIOLOGY PN 1109 O B J E C T I V E # 3 PA R T A CHAPTER 3 LEARNER OBJECTIVES • Define key terms related to cells, tissues, and systems • Identify the main structures of the cell • Identify the structure and functions of the plasma membrane • Discuss the processes that move substance across the cell membrane • Discuss the structure and functions of the cytoplasm • Discuss the structure and functions of the organelles • Discuss the structure and function of the cellular extensions • Discuss the structure and functions of the nucleus • Discuss the cell cycle and its importance in cellular reproduction CELL THEORY • Cell – structural and functional unit of life • Organismal functions depend on individual and collective cell functions • Structure and function are complementary • Biochemical activities of cells dictated by their shapes/forms, and specific subcellular structures • Continuity of life has cellular basis • Cells can only arise from pre-existing cells MAIN STRUCTURES OF THE CELL These are the 3 basic parts of a human cell: • Plasma Membrane – flexible outer layer • Cytoplasm – intracellular fluid containing organelles • Nucleus – DNA containing control center EXTRACELLULAR MATERIALS • Substances found outside of cells that contribute to body mass: – Body fluids – interstitial fluid (fluid in tissues), blood plasma, and CSF. All are transport and dissolving media. – Cellular secretions – substances that aid in digestion (intestinal/gastric fluids) and some that act as lubricants (saliva, mucus) – Extracellular matrix – largest of the 3; jelly-like material that serves as “cell glue” to hold cells together. PLASMA MEMBRANE – Separates two of the major compartments (ICF & ECF) – Controls what goes in and out of cell (selective permeability) – Fluid Mosaic Model: Plasma membrane is a bilayer of phospholipids and proteins • Phospholipids – largest component, each phospholipid is hydrophilic (head) and hydrophobic (tail); 75% • Glycolipids – found only on the outer surface of the membrane; accounts for 5% of total membrane lipids • Cholesterol – accounts for 20% of membrane lipids. It helps stabilize the membrane, decrease the mobility of phospholipids and the fluidity of the membrane MEMBRANE PROTEINS • Allow communication with environment • Most specialized membrane functions • Some float freely • Some tethered to intracellular structures • Two types: integral proteins & peripheral proteins MEMBRANE PROTEINS • Integral proteins -Firmly inserted on the lipid bilayer - have both hydrophilic (head) and hydrophobic (tail) regions - Function as a transport proteins (channels and carriers), enzymes or receptors • Peripheral proteins - Attach loosely to integral - Include filaments on intracellular surface for membrane support - Function as: - Enzymes - Motor proteins - Cell to cell connections for communicaton 6 FUNCTIONS OF MEMBRANE PROTEINS 1. Transport 2. Receptors for signal transduction 3. Attachment to cytoskeleton & extracelluolar matrix 4. Enzymatic activtity 5. Cell to cell joining (intercellular) 6. Cell-cell recognition MEMBRANE PROTEIN FUNCTIONS • Figure 3.3a Membrane proteins perform many tasks. MEMBRANE PROTEIN FUNCTIONS MEMBRANE PROTEIN FUNCTIONS Figure 3.3e Membrane proteins perform many tasks. MEMBRANE PROTEIN FUNCTIONS Figure 3.3c Membrane proteins perform many tasks. MEMBRANE PROTEIN FUNCTIONS • Figure 3.3f Membrane proteins perform many tasks. MEMBRANE PROTEIN FUNCTIONS Figure 3.3d Membrane proteins perform many tasks. GLYCOCALYX • Consists of sugars sticking out of cell surface – Attached to lipids and proteins in plasma membrane • Different patterns of this “sugar coating” found on all cell types – Functions as specific biological markers for cell to cell recognition – Allows immune system to recognize “self” PLASMA MEMBRANE • Maintains integrity of cell\ • Facilitates contact with other cells • Determines blood group • Determines cell life span • Recognizes cell as “self” CELL JUNCTIONS • Some cells are not bound to other cells (“free”) • Blood cells, sperm cells • most cells are bound together to form tissues and organs • Three ways cells are bound (cell junctions): 1. Tight junctions 2. Desmosomes 3. Gap junctions CELL JUNCTIONS 1. Tight junctions – Adjacent Integral proteins fuse together forming an impermeable junction that encircles the cell. – Prevents molecules from passing through the space between cells – Ex: intestines CELL JUNCTIONS 2. Desmosomes – Anchoring junctions(“spots”) that anchor cells together at plaques • Reduces risk of tearing • Allow flexibility between cells to withstand tension – Ex: skin; contracting muscles of heart CELL JUNCTIONS 3. Gap Junctions – A communicating junction between adjacent cells through tunnels. – Allow ions and small molecules to spread between cardiac or smooth muscle cells – Allows electrical signals to be passed quickly from cell to cell – Ex: cardiac and smooth muscle cells PLASMA MEMBRANE • Cells surrounded by interstitial fluid • Plasma membrane allows cell to: – Obtain from interstitial fluid exactly what it needs, exactly when it is needed – Keep out what it does not need Membrane Transport ▪ The cell provides the medium through which substances enter and leave the cell ▪ Plasma membrane is selectively permeable ▪ Movement occurs through: 1) Passive transport – no ATP needed; substance moves down concentration gradient 2) Active transport - gets energy from the cell in the form of ATP; occurs only in living cell membranes 23 ▪ Passive Transport: 1) Diffusion: a) Simple diffusion b) Facilitated diffusion (carrier & channel-mediated) c) Osmosis 2) Filtration ▪ Active transport: a) Endocytosis b) Exocytosis 24 PASSIVE TRANSPORT • Molecule will passively diffuse through membrane if: – It is lipid soluble, or – Small enough to pass through, or – Assisted by a carrier molecule PASSIVE TRANSPORT a) Simple diffusion movement of particles from a region of high to low concentration down or with the concentration gradient ▪ No energy required. ▪ ▪ Results in uniform mixture – equilibrium ▪ Non polar lipid-soluble (hydrophobic) substance diffuse directly through phospholipid bilayer ▪ Ex: oxygen, carbon dioxide, fat-soluble vitamins b) Facilitated diffusion ▪ Certain hydrophobic molecules (glucose/AA/ion) requires a special carrier molecule to move passively down a concentration gradient. A) Carrier mediated facilitated diffusion (binding to protein carriers) B) Channel mediated facilitated diffusion (moving through water filled channels) 26 PASSIVE TRANSPORT A) Carrier-mediated facilitated diffusion • Transmembrane integral proteins are carriers • Carriers transport specific polar molecules too large for channels (ex: sugars/AA) • Example of specificity: glucose carriers will carry only glucose molecules nothing else • Binding of substrate causes shape change in carrier then passage across membrane • Binding is limited by number of carriers present PASSIVE TRANSPORT B) Channel-mediated facilitated diffusion – Aqueous channels formed by transmembrane proteins – Selectively transport ions or water – Two types; • Leakage channels : always open • Gated channels: controlled by chemical or electrical signals PASSIVE TRANSPORT C) Osmosis ▪ Movement of solvent (water) through a selectively permeable membrane ▪ Water diffuses through plasma membranes ▪ ▪ Through lipid bilayer ▪ Through specific water channels Equilibrium is reached when the solution on both sides of the membrane have the same concentration 29 PASSIVE TRANSPORT With osmosis, water concentration varies with number of solute particles because solute particles displace water molecules • Osmolarity – measure of total concentration of solute particles • Water moves by osmosis until hydrostatic pressure (back pressure of water on membrane) and osmotic pressure (tendency of water to move into cell by osmosis) equalize • When solutions of different osmolarity are separated by membrane permeable to all molecules, both solutes and water cross membrane until equilibrium reached • When solutions of different osmolarity are separated by membrane impermeable to solutes, osmosis occurs until equilibrium reached • Osmosis causes cells to swell and shrink • Change in cell volume disrupts cell function, especially in neurons Tonicity: ability of solution to alter cells water volume ▪ Isotonic solution - Concentration equal to that of cell - Water moves feely into and out of cell; cell stable ▪ Hypertonic solution - concentration higher than that of cell - the cell crenates (shrinks) as water is drawn out ▪ Hypotonic solute - concentration lower than that of cell - The cell swells as water is pulled in (lysis/hemolysis) 33 d) Filtration ▪ uses pressure to push substances through a membrane; ▪ Hydrostatic pressure (greater pushing force on one side of the membrane than the other) ▪ pores in the membrane filter determine the size of particles that will pass through it. ▪ Ex: kidneys 35 ACTIVE TRANSPORT ▪ move substances against a concentration gradient (from low to high) ▪ from a region of lower concentration to a region of higher concentration ▪ Requires ATP because: ▪ Solute too large for channels ▪ Solute not lipid soluble ▪ Solute not able to move down concentration gradient ▪ Requires carrier protiens: ▪ Bind specifically and reversibly with substance ▪ Ex: sodium-ion pump – Na pumped out, K pumped into cell 36 ACTIVE TRANSPORT • Vesicular transport is form of active transport • Transports large particles, macromolecules, and fluids across membrane in membranous sacs called vesicles • Requires cellular energy (ATP) • Includes exocytosis and endocytosis a) Endocytosis ▪ Brings substances into the cell ▪ Usually involves receptors so it’s a selective process ▪ Some pathogens are capable of hijacking receptor for transport into cell ▪ Once vesicle pulled inside cell, it may: ▪ Fuse with lysosome ▪ Undergo transcytosis ▪ Ex: ▪ Phagocytosis – cell eating; ex: wbc ▪ Pinocytosis – cell drinking; ex: small intestine b) Exocytosis ▪ Removes substances from the cell ▪ Substance being ejected is enclosed in secretory vesicle ▪ Ex: hormones, neurotransmitters, mucus 38 CELL COMPONENTS Cytoplasm • – Found between plasma membrane and nucleus – Cytosol: Gel-like fluid, primarily water – Inclusions: dissolved electrolytes, waste products and nutrients – Organelles: metabolic machinery of cell CELL COMPONENTS Mitochondria – Elongated, oval, fluid filled sacs in cytoplasm – Own DNA, RNA & ribosomes -reproduce themselves – “Power Plant” of the cell – Produce most of cells energy – Enclosed in double membranes; inner membranes has many folds (cristae) CELL COMPONENTS Ribosomes – Small granules of RNA and protein – Free in cytoplasm or attached to the endoplasmic reticulum (rough) – Synthesize proteins – Two forms found: • Free ribosomes: floating; site of synthesis of soluble proteins that function in cytosol or other organelles • Membrane-bound ribosomes: attached to ER; site of synthesis of proteins to be incorporated into membranes, lysosomes or exported from cell CELL COMPONENTS Endoplasmic Reticulum Complex series of membranous channels Interconnected membrane forms fluid filled sacs and canals (cisterns) Attached to plasma membrane, nuclear membrane and other organelles Rough Endoplasmic Reticulum-protein synthesis Smooth Endoplasmic Reticulum-lipid synthesis CELL COMPONENTS Golgi Apparatus Series of 4-6 flattened and stacked membranous cistern sacs Connected to the endoplasmic reticulum Shipping and receiving Packages products from endoplasmic reticulum for secretion Abundant in glands CELL COMPONENTS Peroxisomes • Membraneous sacs containing powerful detoxifying substances that neutralize toxins • Play a role in breakdown and synthesis of fatty acids CELL COMPONENTS Lysosomes – Membranous-enclosed sacs of digestive enzymes packaged by Golgi apparatus – Digest- material in cell, destroy debris from damaged cells and worn-out cells – Break down particles such as bacteria – Metabolic functions: break down & release glycogen and calcium NON-MEMBRANEOUS CELL COMPONENTS Cytoskeleton Elaborate series of rods throughout the cytoplasm 3 types: Microfilaments Intermediate filaments microtubules Made up of proteins Maintains shape of cell Aids in movement of organelles Role in muscle contraction MICROFILAMENTS • Thinnest of all cytoskeletal elements • Semi-flexible strands of protein actin • Each cell has a unique arrangement of strands although share common terminal web – Dense cross-linked network of microfilaments attached to cytoplasmic side of plasma membrane – Strengthens cell surface and helps to resist compression • Some are involved in cell mobility, changes in cell shape, or endocytosis and exocytosis INTERMEDIATE FILAMENTS • Size is in between microfilaments and microtubles • Tough, insoluble, ropelike protein fibers • Help cell resist pulling forces • Some have special name – Neurofilament = nerve cells – Keratin filaments = epithelial cells MICROTUBULES • Larges of cytoskeletal elements • Hallow tubes made of protein subunits called tubulins • Determine overall shape of cell and distribution of organelles – Many organelles are tethered to microtubules to keep organelles in place – Many substances are moved throughout cell by motor proteins which use microtubules as tracks NON-MEMBRANEOUS CELL COMPONENTS Centrosome • Located near nucleus • Makes microtubules • Houses centrioles Centrioles • Function in cell reproduction by aiding in distribution of chromosomes • Form the basis of cilia and flagella N O N M E M B R A N E OU S CELL COMPONENTS Cilia Short, cylindrical, hair-like processes projecting outward from cell membrane Wavelike pattern of movement that moves substances across the cell surface Found in respiratory tract where moves mucus up and away from lungs Flagella Similar in structure to cilia Move the cell itself Microvilli ❑ fingerlike projections that extend from surface of the cell to increase surface area for absoprtion NUCLEUS Largest organelle Spherical-located near center of cell Enclosed by membrane (nuclear envelope) Control centerregulates cell metabolic activity Contains DNA STRUCTURES OF NUCLEUS • Nuclear envelope • Nucleoli • chromatin THE NUCLEAR ENVELOPE • Double-membrane barrier that encloses the jelly-like fluid, the nucleoplasm – Outer layer is continuous with rough ER and, like the rough ER, is studded with ribosomes – Inner layer, called nuclear lamina, is a network mesh of proteins that maintains nuclear shape and acts as scaffolding for DNA • Nuclear pores allow substances to pass into and out of nucleus; they are guarded by the nuclear pore complex, which regulates transport of specific large molecules NUCLEOLI • Dark-staining spherical bodies within nucleus that are involved in ribosomal RNA (rRNA) synthesis and ribosome subunit assembly • Associated with nucleolar organizer regions that contain the DNA that codes for rRNA • Usually one or two per cell CHROMATIN • Consists of 30% threadlike strands of DNA, 60% histone proteins, and 10% RNA • Arranged in fundamental units called nucleosomes, which consist of DNA wrapped around histones – Chemical alterations of histones have an effect on DNA and therefore can help regulate gene expression • Chromosomes are condensed chromatin – Condensed state helps protect fragile chromatin threads during cell division CELL DIVISION ▪ Meiosis – cell division producing gametes ▪ Mitosis – produces clones ▪ Essential for body growth and tissue repair ▪ Occurs continuously in some cells (skin/intestine) ▪ None in most mature cells of nervous tissue, skeletal muscle, and cardiac muscle ▪ Repairs with fibrous tissue 58 Stages of Mitosis p. 100 ▪ Interphase ▪ Prophase ▪ Metaphase ▪ Anaphase ▪ Telophase 59 REVIEW 1. 2. 3. 4. 5. 6. 7. https://www.youtube.com/watch?v=o2abDVq4M84 https://www.youtube.com/watch?v=L0k-enzoeOM https://www.youtube.com/watch?v=51FkahHUBwc https://www.youtube.com/watch?v=dPKvHrD1eS4 Cell song: https://www.youtube.com/watch?v=wRZthGlzEUc Organelles song: https://www.youtube.com/watch?v=dngsFl2X3nc Mitosis song: https://www.youtube.com/watch?v=IlV9hExXZnM