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Transcript
Cellular Level of Organization FTCE Biology 6-12 Day 1 Cell discovery timeline Hooke: 1660 – Cork, used term “cells” Van Leeuwenhoek: 1673’s – Wee beasties, protists Schleiden: 1839 – Plants made of cells Schwann: 1839 – Animals made of cells Cell theory Rudolf Virchow -1855 The cell theory 1. Cells are the units of structure & function in organisms. 2 . All cells come from pre-existing cells. Cells are 1µm to 20µm small. Why is small better? – 1000 µm = 1mm – Ex. on pg. 156 Microscopes Magnification: the ratio between the size of the image and the object Resolution: the smallest degree of separation at which 2 objects appear distinct Resolution (resolving power) The ability to see clearly between two points. – Limited by the wavelength of the source of illumination • Visible light is used for “light microscopes” • Beam of electrons for EM Two types of microscopes Light microscope – Visible light to see image – Parfocal – Highest magnification with decent resolution = about 1000x – Can observe living cells Electron microscope – Electrons bounced off object – Highest magnification with decent resolution = about 1,000,000x – Preparation is severe. Two types of electron microscopes Transmission electron microscope – (TEM) – 2-D image Scanning electron microscope – (SEM) – 3-D image Three Views of Red Blood Cells Light Microscope SEM Scanning Probe Microscope Parts of the microscope Eyepiece Arm Base Revolving nosepiece Stage – Clips – diaphragm Parts of the microscope cont. Nosepiece –Objective lenses • Low (book calls it scanning) –4x magnification • Medium (book calls it low) –10x magnification • High (book calls it same thing) –40x magnification Overall mag. 10x (eyepiece) x lens Parts of the microscope cont. Coarse focus knob – Only when using low power objective Fine focus knob – For small adjustments diaphragm Light switch & cord Two general types of cells Prokaryote – No true nucleus – No membrane- bound organelles – Ex. Monera /bacteria Eukaryotes – True nucleus – Membrane- bound organelles – Ex. Protist cells, fungi cells, plant cells, animal cells Prokaryote structure Cell wall Plasma membrane Cytoplasm Nucleoid Plasmid (some) flagellum Bacteria Shapes Cocci/sphere Bacilli/rod Spirilla/spiral Eurkaryotes (Protists, Fungi, Plant, Animal) • organelles •plasma membrane • cell wall of cellulose (plants) • nucleus w/nuclear membrane • nucleoli • cytoplasm amoeba Amoeba Paramecium Onion skin Elodea Studying Cells Cytology: Cyto-cell –ology study of Human body-2 types of cells 1. Sex cells: sperm (male) oocyte (female) 2. Somatic cells: all other cells Generalized Animal Cell Generalized Plant Cell Cell organelles Cell Organelles • Compartmentalize cell’s activities • improve efficiency • protect cell contents from harsh chemicals • Enable cells to: • secrete substances • perform cellular respiration • degrade debris • reproduce Cell Organelles Cell membrane: lipid bilayer containing phospholipids, steroids, proteins and carbohydrates F-isolation: keeping proteins inside protection: sensitivity: receptors that allow the cell to recognize and respond to specific molecules. Cell membrane (continued) Structural support: to stabilize (skin) Transport: control of entrance and exit of materials (ions, glucose, elimination of wastes) • • cytoplasm: entire contents of the cell, except the nucleus, bounded by the plasma membrane cytosol: gelatinlike portion of the cytoplasm that bathes the organelles of the cell Organelles of Eukaryotic Cells Organelles compartmentalize a cell’s activities. 1. Nucleus – surrounded by a double membrane two phospholipid bilayers (nuclear envelope), perforated with nuclear pores – contains DNA & nucleolus (stores RNA nucleotides) – functions to separate DNA from rest of cell Nucleus Functions (Continued) Controls metabolism Stores and processes genetic information Controls protein synthesis Nucleolus Dense region in nucleoplasm of nucleus Site of rRNA synthesis and assembly of ribosomal units Nucleolus Cytoskeleton Network of protein filaments throughout the cytosol Functions – cell support and shape – Site of some chemical reactions – cell & organelle movement Continually reorganized Ribosomes Packages of Ribosomal RNA & protein Free ribosomes are loose in cytosol – make proteins used inside the cell Membrane-attached ribosomes – attached to endoplasmic reticulum or nuclear membrane – make proteins needed for plasma membrane and/or for export Inside mitochondria, synthesize mitochondrial proteins Ribosome Large + small subunits – made in the nucleolus – assembled in the cytoplasm 2. Endoplasmic reticulum (ER) –interconnected network of membranes extending from nucleus to plasma membrane Rough ER - studded with ribosomes – site of protein production (most will be exported out of the cell) Free ribosomes in the cytoplasm produce proteins that remain in cell. Smooth ER - lacks ribosomes – site of lipid production – contains enzymes that detoxify drugs & poisons 3. Golgi apparatus –stacks of membrane-enclosed sacs Golgi apparatus functions: – Forms membranes/vesicles (renews/modifies cell membrane) – links simple carbohydrates together to form starch – links simple carbohydrates to proteins (glycoprotein) or lipids (glycolipid) – completes folding of proteins – temporarily stores secretions – Storage, alteration and packaging of secretory products and lysosomal enzymes. Organelle interaction in a mammary gland cell. 4. Mitochondria – double-membrane • outer is smooth • inner is highly folded (cristae) – #/cell varies with energy demands of that cell (bone cedll have few, muscle cell has thousands) – contain DNA (some mitochondrial genes, rest in nuclear DNA) – Contains some ribosomes for own protein synthesis – inherited only from female parent – site of cellular respiration (production of ATP) – Takes in short carbon chains and oxygen to generate carbon dioxide and ATP Plant cells also have... • Cell wall: made of cellulose, provides rigidity and allows for turgor pressure • Vacuole: contains water and digestive enzymes, stores nutrients and wastes •Chloroplast: photosynthesis Chloroplasts #/plant cell varies (few-hundreds) contain DNA (some chloroplastic genes, rest in nuclear DNA) –found in plants & protists –function photosynthesis 6. Lysosomes (suicide sacs) apoptosis programmed cell death – vesicles containing > 40 types of digestive enzymes – function to recycle damaged organelles, break down cellular byproducts, destroy cell & kill invading microbes Centrioles Found near nucleus –Involved in cell divison Structurally similar to cilia and flagella Cilia and Flagella Differences – cilia • short and multiple – flagella • longer and single Movement of Cilia and Flagella Cilia – Move material over cell surface – Respiratory tree & oviduct Flagella – single flagella wiggles in a wavelike pattern – propels sperm forward The Endosymbiont Theory Lynn Margulis – eary 1960’s Proposes that chloroplasts and mitochondria evolved from once freeliving bacteria engulfed by larger prokaryotes, but not digested. Based on fact that mitochondria & chloroplasts resemble certain bacteria (size, shape, membrane structure,have own DNA and ribosomes) Multicellular Organization Each cell must do their own basic activities (protein synthesis, cellular respiration, cell division, etc.) Also show a division of labor or specialization and cooperationcontribute to the well being of other cells/tissues/organs etc. Some form of intercellular communication – Either chemical (hormone) or electrical (nervous) Levels of Organization Subatomic Atom Molecule Macromolecule Organelle Cell Tissue Organs System Organism Population Community Ecosystem Biosphere Levels of Structural Organization Chemical Level – Subatomic, atomic and molecular level Cellular level – smallest living unit – Tissue level – group of cells that work together on one task Levels of Structural Organization Organ level – groups of 2 or more tissue types into a recognizable structure with a specific function. Organ system – collection of related organs with a common function – sometimes an organ is part of more than one system Organism level – one living individual Levels of Structural Organization Population – Group of same specie in a given area Community – All specie in a given area Ecosystem – Biotic and abiotic in a given area Biosphere – All ecosystems combined