The Tour of the Cell
The Tour of the Cell Biology 1107
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This 8 page Class Notes was uploaded by Cheyenne prather on Wednesday February 24, 2016. The Class Notes belongs to Biology 1107 at East Georgia State College taught by Dr. Silva in Winter 2016. Since its upload, it has received 35 views. For similar materials see General Biology in Biological Sciences at East Georgia State College.
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Date Created: 02/24/16
A Tour of the Cell: Part 1 Fundamental units of life All living organisms are made of cells, which are the simplest level of matter that can be alive The Microscope Used as a tool for Biologists to study and visualize cells Observation of cells with a microscope is necessary because they are usually too small to be seen with the naked eye Parameters of Psychology Magnification: Ratio of an object’s image size to its real size Resolution: Measure of the clarity of the image or minimum distance of two distinguishable points Contrast: Visible differences in brightness between parts of the sample Microscope Types Electron Microscope (Ems): Used to study subcellular structures Scanning Electron Microscope (SEMs): Focus a beam of electrons onto a specimen’s surface, producing 3-D like imageries Transmission Electron Microscope (TEMs): Focus a beam of electrons through a specimen and mainly used to study a cell’s internal structure Cell Fractionation Separates the major organelles from one another Takes cells apart Enables scientists to determine the functions of organelles Biochemistry and Cytology o Help correlate cell function with structure 2 Types of Cells Prokaryotic o Archaea o Bacteria Eukaryotic o Protists o Fungi o Animals o Plants Basic Features of all Cells Plasma Membrane Cytosol Chromosomes Ribosomes Prokaryotic Cells No nucleus DNA in nucleoid: unbound region No membrane bound organelles Cytoplasm bound by plasma membrane Eukaryotic Cells DNA is nucleus bound by nuclear envelope Membrane bound organelles Cytoplasm between plasma membrane and nucleus Animal Cell Plant Cell Cell Type Eukaryotic Eukaryotic Cell Walls None Rigid Cell Walls Shape Round (irregular) Rectangular (Fixed) Organelles Cell Membrane Cell Wall Nuclear Membrane Nuclear Membrane One or more small Plasmodesma vacuoles Large Vacuole Centrioles Plastids Cytoplasm Chloroplasts Endoplasmic Reticulum Leucoplast Ribosomes Chromoplast Golgi Apparatus Golgi bodies Microtubules/Microfilame Ribosomes nts Endoplasmic Reticulum Flagella (some cells) Mitochondria Lysosomes Lysosome Nucleus Cytoplasm Cilia Nucleus DNA DNA Chromatin RNA Cytoskeleton Nucleolus A Tour of the Cell: Part 2 Endomembrane System – regulates protein traffic and performs metabolic functions in the cell Plasma Membrane Nuclear Envelope Endoplasmic Reticulum Lysosomes Vacuoles The Plasma Membrane Selective barrier that allows passage of: o Oxygen o Nutrients o Waste The Nucleus Contains eukaryotic cell’s genetic instructions (Most DNA) Nuclear Envelope A double membrane that encloses the nucleus, separating it from the cytoplasm Nucleolus Located in the nucleus Ribosomal synthesis takes place Chromosomes Composed of a single DNA molecule associated with proteins (chromatin) Condenses to form discrete chromosomes as a cell prepares to divide Ribosomes Made of protein and ribosomal RNA Carries out protein synthesis in 2 places Smooth ER Synthesizes lipids, metabolizes carbohydrates, detoxifies drugs/poisons, and stores calcium ions Rough ER Contain bound ribosomes that secrete glycoproteins Distributes transport vesicles Considered the membrane factory Golgi Apparatus Consists of flattened membranous sacs called cisternae Works to modify products of the ER Manufactures particular macromolecules Sorts/packages materials into transport vesicles Lysosomes Membranous sac of hydrolytic enzymes that can digest macromolecules Works best in lysosome’s acidic environment Phagocytosis can occur where some types of cells can engulf another cell Lysosome fuses with food vacuole and digests the molecule Also uses enzymes to recycle cell’s own organelles and macromolecules, called autophagy Vacuoles Large vesicles derived from the ER and Golgi Apparatus Functions depend on the type of cell 3 Types of Vacuoles Food Vacuoles: formed by phagocytosis Contractile Vacuoles: pump excess water out of cell Central Vacuoles: hold organic compounds and water A Tour of the Cell: Part 3 Cytoskeleton Network of fibers that: o Support o Motility o Organize structures and activities o Anchors many organelles o Maintains shape Composed of 3 molecular structures: o Microtubules o Microfilaments o Intermediate Filaments Roles: o Interacts with motor proteins to create motility Microtubules Thickest component of cytoskeleton Hollow rods made of tubulin Functions o Shape cell o Guide movement of organelles o Separate chromosomes during cell division Centrosomes and Centrioles Animal Cells o Microtubules grow out from a centrosome near the nucleus o The centrosome has a pair of centrioles, each with nine triplets of microtubules arranged in a ring Cilia and Flagella Microtubules control the beating of the cilia and flagella: microtubule- containing extensions that project from some cells Differ in beating patterns Share common structure o A core of microtubules sheathed by a plasma membrane o A basal body that anchors the cilium or flagellum o A motor protein, Dynein, that drives the bending movements of a cilium or flagellum Microfilaments Solid rods made of actin and myocin Role o Bear tension, resisting pulling forces within the cell o Help support the cell’s shape Bunches of microvilli make up the core of microvilli of intestinal cells Intermediate Filaments Mainly made of Keratin Support cell shape and fix organelles in place More permanent cytoskeleton fixtures than microfilaments and microtubules Extracellular Components and Connections Between Cells Help coordinate cell activities Cell walls of plants Extracellular matrix of animal cells Plant’s Cell Wall Distinguish plant cells from animal cells Function o Protects plant cell, maintain shape, and prevents the uptake of excessive water Made up of: o Cellulose fibers embedded in other polysaccharides and protein Animal Cell’s Extracellular Matrix (ECM) Bind to receptor proteins in the plasma membrane called integrans Made up of: o Glycoproteins such as collagen, proteoglycans, and fibronectin Cell Junctions Neighboring cells in tissue, organs, or organ systems often adhere, interact, and communicate through direct physical contact Plant cells o Plasmodesmata Animal cells o Tight junctions o Desmosomes o Gap junctions Plasmodesmata Channels that perforate plant cell walls During the process o Water and small solutes can pass from cell to cell Tight junctions, Desmosomes, and Gap Junctions Animal cells Tight junctions o Pressed cells together preventing leakage of extracellular fluid Desmosomes o Anchoring junctions o Fasten cells together into strong sheets Gap junctions o Communicating junctions o Provide cytoplasmic channels between adjacent cells Mitochondria and Chloroplasts Change energy from one form to another Mitochondria o Sites of cellular respiration, a metabolic process that uses oxygen to generate ATP Chloroplasts o Sites of photosynthesis Mitochondria and Chloroplasts Evolutionary Origin Similarities with bacteria o Enveloped by double membrane o Contain free ribosomes and circular DNA molecules o Grow and reproduce somewhat independently in cells Endosymbiont Theory Suggests and early ancestor of eukaryotes engulfed an oxygen-using non- photosynthetic prokaryotic cell Engulfed cell becomes the endosymbiont The endosymbiont evolved into mitochondria At least one of these cells may have then taken up a photosynthetic prokaryote, which evolved into a chloroplast Mitochondria Structure o Outer membrane o Inner membrane folded into cristae and creates two compartments called: Intermembrane space Mitochondrial matrix Chloroplasts Contain chlorophyll and other enzymes and molecules that function in photosynthesis Found in leaves and other green plant and algae organs One of a group of plant organelles called plastids Structure o Thylakoids and granum o Stroma: internal fluid Peroxisomes Oxidative organelles Produce hydrogen peroxide and convert it to water Unknown how its related to other organelles Specialized metabolic compartments bounded by a single membrane
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