Chapter 3 - The Cell PDF

2023-09-20 THE CELL Chapter 3 1 Goals of Lesson Name and describe the areas & structures of a general cell and their functions Discuss the presence of various structures in different ce...

2023-09-20 THE CELL Chapter 3 1 Goals of Lesson Name and describe the areas & structures of a general cell and their functions Discuss the presence of various structures in different cell types (cell diversity) and the purpose of the diversity Explain the methods used to move items into and out of cells Discuss the process of protein synthesis 2 1  2023-09-20 The Generalized Cell 3 3 Main regions of The Generalized Cell Plasma Membrane Cytoplasm Nucleus 4 2  2023-09-20 5 The Nucleus Control Center Contains “necessary for life” information (DNA) Its purpose is to direct all cellular metabolism and cell replication Nucle = kernel Three main regions: Nuclear envelope Nucleoli Chromatin 6 3  2023-09-20 Three main regions of the Nucleus Nuclear Envelope (membrane): Double membrane barrier, fused at points to form nuclear pores Semi-permeable, large pores increase permeability Encloses jelly-like substance (nucleoplasm) that suspends other nuclear elements. 7 Nucleoli: Sites for ribosome assembly Small, dark staining, round bodies Chromatin: DNA + Protein Loose network of bumpy threads Scattered in the nucleus until cell division 8 4  2023-09-20 9 10 5  2023-09-20 PLASMA MEMBRANE Barrier for cell contents – semi- permeable Double phospholipid layer Hydrophilic heads (water lovers) Hydrophobic tails (water haters) Other materials in plasma membrane Protein Cholesterol Glycoproteins 11 12 6  2023-09-20 Plasma Membrane Features: Proteins: Span the membrane: involved in transport Cluster to form channels (pores) Carriers bind to items and move it through the membrane 13 Plasma Membrane Features: Proteins: Protrude from the surface: May be receptors for hormone or other chemical messengers May be binding sites for anchoring the cell to fibers or other structures (inside or out) 14 7  2023-09-20 Plasma Membrane Features: Cholesterol: Interwoven throughout the membrane aiding in stabilization Helps keep the membrane fluid and flexible Glycoprotein: Sugar molecules attached to proteins towards extracellular space Make cell surfaces fuzzy, sticky, sugar-rich Many roles – identification, Blood type, receptors, cell-to-cell recognition and interactions 15 Plasma Membrane Features: Some plasma membranes have specialized extensions. Microvilli: Tiny, finger-like extensions that project from exposed cell surface. Increase cell surface area thus aid in absorption Cilia: Whip-like cellular extensions that move substances along the cell surface Flagella: Longer projection, used for propulsion 16 8  2023-09-20 17 Sticking Together! Cells are often bound together in 3 ways: 1) Glycoproteins act as adhesive 2) Wavy contours of adjacent cells “fit” together 3)Membrane Junctions: Tight junctions: Desmosomes Gap junctions 18 9  2023-09-20 Membrane Junction type is KEY for effective roles and performance. Tight Junction: Impermeable, make leak-proof sheets of cells Fuse together like zipper Desmosomes: Anchors to prevent cells from moving apart/separating Link like buttons or train links Gap Junction: Neighbouring cells connected by hollow protein cylinders that span the width of both membranes 19 20 10  2023-09-20 Membrane Junctions 21 INSIDE THE CELL… 22 11  2023-09-20 23 THE CYTOPLASM Gel like filling Working area of the cell Contains 3 major elements; Cytosol Organelles Inclusions (inclusion bodies) 24 12  2023-09-20 THE CYTOPLASM Cytosol: semitransparent fluid, suspends other elements Inclusions: temporary structures for storage, varies with cell role Organelles: permanent, specialized “small organs” membrane bound metabolic machinery 25 Cytoplasmic Organelles Mitochondrion (-ia) Lysosomes Endoplasmic Peroxisomes Reticulum Lysosomes Smooth Centrioles Rough Ribosomes Golgi bodies (apparatus) 26 13  2023-09-20 27 Cytoplasmic Organelles Mitochondria: Enzymes within react with oxygen to produce ATP (energy) and heat Endoplasmic Reticulum: Fluid filled canal system for transport & production smooth: no ribosomes present, lipid metabolism & detoxification rough: ribosomes present, cell membrane factory 28 14  2023-09-20 29 Cytoplasm Organelles Ribosomes: site of protein synthesis Golgi apparatus: modify, package and distribute cellular proteins (from ER) Lysosomes: membranous sacs of digestive enzymes. 30 15  2023-09-20 More Cytoplasmic Organelles  Peroxisomes  Membranous sacs of oxidase enzymes  Detoxify harmful substances  Break down free radicals (highly reactive chemicals)  Replicate by pinching in half Free radicals  Highly reactive chemicals with unpaired electrons that can scramble the structure of proteins & nucleic acids if allowed to accumulate 31 More Cytoplasmic Organelles  Centrioles  Paired, rod-shaped bodies made of microtubules  Involved in cell division and generating microtubules 32 16  2023-09-20 Cytoplasmic Organelles Figure 3.4 33 Steps of Production and Distribution within a cell Request for product Recipe found in coded DNA sequence in nucleus Change to understandable format (details later) Recipe instructions sent to Ribosome(s) Ribosome(s) follow directions and build product (protein) in Endoplasmic Reticulum or cytoplasm 34 17  2023-09-20 Product migrates to the ER for transport and modifications (shape change, additions) Packaged in tiny sac = transport vesicle Transport vesicle migrates to and fuses with Golgi Apparatus Modification, Packaging and distribution completed here Final Product distributed in specialized sac based on destination 35 36 18  2023-09-20 Packaging products: Figure 3.5 Copyright © 2003 Pearson Education, Inc. publishing as Benjamin Cummings 37 38 19  2023-09-20 CYTOSKELETON Elaborate network of protein structures Found throughout the cytoplasm An internal framework Determines cell shape Provides support and machinery for cell Contains: Microtubules, Intermediate filaments, Microfilaments, 39 40 20  2023-09-20 41 42 21  2023-09-20 The Life of a cell https://www.youtube.com/watch?v=wJyUtbn0O5Y 43 CELL DIVERSITY 44 22  2023-09-20 Cell Specialists 1) Cells that connect body parts (connective) 2) Cells that cover and line organs (epithelial) 3) Cells that move organs and body (Skeletal and smooth muscle) 45 1) Cells that store nutrients (fat cells) 2) Cells that fight disease (macrophages) 3) Cells that gather information and control function (nerve cells) 4) Cells of reproduction (Oocytes & sperm) 46 23  2023-09-20 47 CELL PHYSIOLOGY 48 24  2023-09-20 CELL PHYSIOLOGY The study of how the cell functions. Most cells can perform (or aid to perform) the following: Metabolism Growth Food digestion Waste disposal Reproduction 49 CELL PHYSIOLOGY ALSO… Membrane Transport Protein Synthesis Cell Division Stimuli Response (irritability) Locomotion 50 25  2023-09-20 Today Focus on: Membrane Transport Protein Synthesis Cell Division (minimal) 51 Necessary Life Function: MAINTAIN BOUNDARIES 52 26  2023-09-20 Compartments  Intracellular compartment –refers to the inside of the cell  Extra-cellular compartment –refers to anything that is outside of the cell  In humans there are at least 2 extra-cellular compartments  Interstitial – which lies around the cell  Intravascular –in the vessels 53 Intracellular Fluid: The nucleoplasm and cytosol Contains small amounts of gases, nutrients, and salts dissolved in water Interstitial Fluid: Fluid that continually bathes the exterior of our cells Contains thousands of ingredients Including nutrients (vitamins, amino acids), hormones, neurotransmitters, salts and waste 54 27  2023-09-20 PLASMA MEMBRANE Recall the plasma membrane is a phospholipid bilayer contains proteins, glycoproteins and cholesterol acts as a barrier, semi-permeable 55 SELECTIVE PERMEABILITY A barrier that allows some substances to pass through while excluding others i.e. allows nutrients to enter the cell but keeps many undesirable substances out. Valuable proteins and cell components are kept IN the cell while wastes are allowed to exit through the membrane 56 28  2023-09-20 MEMBRANE TRANSPORT PASSIVE MEMBRANE TRANSPORT: Substances move across the membrane without the expenditure of energy. i.e. diffusion and filtration ACTIVE MEMBRANE TRANSPORT: The use of energy to move substances across the cell membrane i.e. active transport and vesicular transport 57 PASSIVE TRANSPORT Diffusion : Movement of particles (solutes) from an area of high concentration to an area of low concentration 58 29  2023-09-20 Recall Solution: Homogeneous mixture of two or more components Solvent: The substance present in the largest amount, often the dissolving medium (water) Solute: Substance(s) present in smaller amounts 59 60 30  2023-09-20 PASSIVE TRANSPORT SIMPLE DIFFUSION Unassisted movement (diffusion) of solutes through a semi-permeable membrane (plasma membrane). Lipid soluble molecules (fats, oxygen, carbon dioxide) Small molecules able to pass through membrane pores (small ions i.e. Chloride ion) 61 PASSIVE TRANSPORT Osmosis: The diffusion of water through a selectively permeable membrane. In the plasma membrane water passes through special pores (aquaporins) created by membrane proteins, thus is occurring all the time (down concentration gradient!) 62 31  2023-09-20 PASSIVE TRANSPORT Facilitated Diffusion: Using protein carriers or channels to move substances down their concentration gradient 63 PASSIVE TRANSPORT Filtration When water and solutes are pushed through a membrane (i.e. capillary wall) by an increase in pressure (hydrostatic pressure) Not very selective – large molecules (blood cells and proteins) cannot fit 64 32  2023-09-20 65 MEMBRANE TRANSPORT PASSIVE MEMBRANE TRANSPORT: Substances move across the membrane without the expenditure of energy. i.e. diffusion and filtration ACTIVE MEMBRANE TRANSPORT: The use of energy (ATP) to move substances across the cell membrane i.e. active transport and vesicular transport 66 33  2023-09-20 ACTIVE MEMBRANE TRANSPORT ENERGY INPUT REQUIRED BECAUSE: Molecule is too large Lack of special protein carrier Not fat soluble Moving against concentration gradient 67 ACTIVE TRANSPORT Active transport/Solute Pumping The use of a protein carrier and energy to move a substance across a membrane Often against a gradient (concentration or electrical) – thus the need for an input of energy 68 34  2023-09-20 69 ACTIVE TRANSPORT Sodium-Potassium Pump Simultaneously moves sodium ions out and potassium ions into the cell. (fig 3.11) 70 35  2023-09-20 ACTIVE TRANSPORT Bulk (Vesicular) Transport Exocytosis: “Condition of out of the cell” Actively secrets products via vesicles moves products OUT of cell 71 72 36  2023-09-20 73 ACTIVE TRANSPORT Bulk (Vesicular) Transport Endocytosis: “Condition of into the cell” Take in or engulf extracellular substances. Need ATP to enclose extracellular substances in a small vesicle 74 37  2023-09-20 75 ACTIVE TRANSPORT Endocytosis: vesicle formed around substances. detaches from wall moves into cytoplasm often fuses with lysosomes that digest contents and releases them into cytosol OR digestion occurs then moves to wall and expels via exocytosis 76 38  2023-09-20 77 ENDOCYTOSIS Pinocytosis: “cell drinking” Cell “gulps” droplet of extracellular fluid Plasma membrane indents to form a pit Edges fuse around the droplet (often filled with dissolved proteins or fats from GI tract) Used often by most cells especially impt in cells whose function is absorption 78 39  2023-09-20 ENDOCYTOSIS Phagocytosis: “cell eating” Often used with large particles (bacteria, dead body cells) Cytoplasmic extensions (pseudopods) separate the target from external environment Protective mechanism (rather than for obtaining nutrients) 79 ENDOCYTOSIS Receptor Mediated: Main mechanism for uptake of specific substances Receptor proteins on the plasma membrane bind to specific substances Receptors and attached target molecules are internalized via a vesicle 80 40  2023-09-20 CELL DIVISION 81 CELL LIFE CYCLE 2 major phases: Interphase: Cell growth and usual metabolic activities Very active and longer phase Cell Division: When cell replicates itself 82 41  2023-09-20 CELL DIVISION A complex series of events The purpose is to produce identical cells for growth and repair 83 CELL DIVISION DNA strand separates and replicates (during interphase) MITOSIS: division of the nucleus CYTOKINESIS: division of cytoplasm See Page 81-85 in text! 84 42  2023-09-20 85 Preparing for CELL DIVISION During Interphase: Trigger (unknown) tells DNA to uncoil and separate into its 2 nucleotide chains Each chain then acts as a template to build a new strand. Remember the new strand will be a complement of the “old” strand Result is 2 identical double helix DNA molecules 86 43  2023-09-20 CELL DIVISION 2 EVENTS: Mitosis: The division of the nucleus Cytokinesis: The division of the cytoplasm 87 88 44  2023-09-20 CELL DIVISION At the end of the process: 2 genetically identical daughter cells exist Each is smaller and has less cytoplasm than the original (mother) Each daughter cells grow and carry out normal cell activities until it is their turn to divide 89 PROTEIN SYNTHESIS 90 45  2023-09-20 Recall Deoxyribonucleic Acid (DNA) Deoxyribose sugar and phosphate make the “side rails” of the ladder Each of these nucleotides also contain a a nitrogen-containing base. Bases are: Adenine (A), Guanine (G), Cytosine (C), Thymine (T), and Uracil (U) 91 92 46  2023-09-20 DNA DNA is the master blueprint for all protein synthesis Contains all genetic material to build an organism and control the growth and development Each segment of DNA carries the directions for building 1 protein of the body Genetic material is stored in a “coded” form 93 Protein Synthesis Gene – A DNA segment that carries a blueprint for building one protein of the organism Proteins are key substances for all aspects of cell life i.e. Building materials for cells and enzymes For “safety” the information is stored in a coded and scrambled format! Need a decoder! - RNA 94 47  2023-09-20 RNA Ribonucleic Acid Single stranded Ribose sugar (not deoxyribose as in DNA) Uracil base (replaces Thymine) Act to decode the DNA message and carry it to the production area! 95 RNA 3 types of RNA (based on function) 1)Transfer RNA (tRNA) 2) Ribosomal RNA (rRNA) 3) Messenger RNA (mRNA) 96 48  2023-09-20 PROTEIN SYNTHESIS Two major phases Transcription: the transfer of information from DNA format to the complementary format of mRNA Occurs in the nucleus Translation: the information in base sequence is translated into amino acid sequence (proteins) in the cytoplasm 97 98 49  2023-09-20 99 Multiple Individual Cells work together for the same purpose and form the next level of structure: TISSUES 100 50  2023-09-20 101 51