Chapter 6 Concept 6 1 complex Microscopy size Though usually too small to be seen by the unaided eye cells can be Scientists use microscopes to visualize cells Light Microscope LM Visible light passes through specimen Magnification Ratio of object s size in an image compare to in s original Resolution Image Clarity Contrast Visible differences in parts of a sample Electron Microscopy Two types of Electron Microscopes surface providing 3D like image Scanning Electron Microscope SEM Focus beam of electrons on Transmission Electron Microscope TEM Focus beams of electrons Used to study mainly internal structure of a cell through a specimen Cell Fractionation Takes cells apart and separates the major organelles from each other Ex Centrifuges Helps to determine functions of organelles Biochemistry and cytology help correlate cell function and structure Concept 6 2 Prokaryotic Cells vs Eukaryotic Cells Prokaryotic Only Bacteria and Archea No Nucleus DNA is an area called nucleoid No Membrane Bound organelles Eukaryotic Cells DNA in a nucleus Membrane bound organelles Surface are relative to volume of a cell is critical Surface are increase by a factor of n 2 and volume increases by a factor of n 3 Nucleus conspicuous organelle Nucleus Contains most of the cell s genes and is usually the most Nuclear Envelope Encloses the nucleus separating it from the cytoplasm Double membrane lipid bilayer Nuclear Pores Regulate the entry and exit of molecules from the nucleus Shape of the nucleus is maintained by the nuclear lamina net like array of Chromatin DNA and proteins of chromosomes are together only when cell Nucleolus located within the nucleus and is the site of ribosomal RNA protein filaments is not dividing synthesis Concept 6 4 The Endomembrane system regulates protein traffic and preforms metabolic functions in the cell 1 Nuclear Envelope 2 Endoplasmic reticulum 3 Golgi Apparatus 4 Lysosomes 5 Vacuoles 6 Plasma Membrane Related either through physical continuity or connected via transfer by Accounts for more than half of the total membrane in many eukaryotic cells is continuous with nuclear envelope vesicles Endoplasmic Reticulum Two parts 1 Rough ER 2 Smooth ER Functions of smooth ER 1 Synthesis of Lipids Oils phospholipids or steroids 2 Metabolizes carbohydrates 3 Detoxifies drugs and poisons enzymes Liver cell s use hydroxyl groups 4 Stores calcium ions seen in muscle cells Induces proliferation of Smooth ER and associated detoxification Functions of Rough ER from cell carbohydrates Bound ribosomes produces proteins into the lumen of the ER Secreted Pancreatic Beta cells produce insulin Secretory proteins are glycoproteins Proteins covalently bonded to Carrier proteins from ER in transport vesicles proteins surrounded by membranes separated from proteins produced in cytosol Membrane factory of cell Produces membrane proteins Enzymes can assemble phospholipids from cytosolic pressure Golgi Apparatus Flattened membranous sacs called cisternae Distinct polarity Cis and Trans Region Cis Packaging Trans Transport Extensive cells specialized in secretion functions Functions 1 Modifies products of ER Carbohydrate component of Glycoproteins 2 Manufactures certain macromolecules Polysaccharides none cellulose polysaccharides 3 Sorts and packages materials Sorted by molecular ID tags such as phosphorylation 2 Models of substances move from Cis to Trans Vesicular transport model Macromolecules from one cisternae to Cisternae maturation Model Cisternae actually progress from Cis to trans face carrying and modifying their cargo another by vesicles Lysosomes Membranous sac of hydrolytic enzymes that can digest macromolecules Can hydrolyze proteins fats polysaccharides and nucleic acids Enzymes are produced in rough ER Acidic Environment Will not work on membrane protein found on lysosomes since their 3D structure protects them from enzyme attachment Lysosomes also use enzymes to recycle the cell s own organelles and macromolecules in a process called autophagy A human liver cell recycles it s own macromolecules once a week Lysosomes fuse with food vacuole Lysosomal Storage disease rare lack functioning hydrolytic enzymes in Tay Sachs disease lipid digesting enzyme missing or inactive resulting in a build up of lipids in brain cells Causes Mental retardation and childhood death Food Vacuole Phagocytosis Contractile Vacuole Water removing pump found in some prokaryotic Central Vacuole found in many mature plant cells holds organic compounds and water lysosomes Vacuoles Cells Endomembrane system Complex and dynamic player in cells compartments and organization Concept 6 5 Mitochondria and chloroplasts change energy from one form to another Mitochondria Cellular respiration uses oxygen to generate ATP Chloroplasts Found in plants and algae are the sites of photosynthesis Peroxisomes Oxidative organelles Evolutionary origins of Mitochondria and Chloroplast Similarities to bacteria Double membrane Free ribosomes and circular DNA molecules Grow and reproduce somewhat independently in cells Have proteins made up by free ribosomes Endosymbiont theory Endosymbiont relationship Ancient Eukaryotic cell engulfed prokaryotic cell causes an Merged into a single cell Mitochondria and Chloroplast Mitochondria Smooth outer membrane and inner membrane folded into cristae Composed of phospholipids 2 Compartments 1 Inter membrane space 2 Mitochondrial Matrix Some metabolic steps of cellular respiration are catalyzed in the mitochondrial matrix mDNA ribosomes and enzymes that catalyze cellular respiration reside in the mitochondrial matrix Cristae present a large surface area for enzymes that synthesis ATP More mitochondria mean more metabolic activity Chloroplasts Capture of light energy The chloroplast is a member of a family of organelles called plastids Chloroplast contains the green pigment chlorophyll as well as enzymes and other molecules that function in photosynthesis Chloroplasts is found in leaves and grass Structure Double membrane with intermediate Space Thylakoids membranous sacs stacked to form granum Stroma internal fluid of the chloroplast surrounding outside of DNA ribosomes and enzymes are found in the Stroma thylakoids Peroxisomes Oxidation Specialized metabolic compartments bound by a single membrane Preform reactions with many different functions Removal of hydrogen atoms from various substrates and transfers Used to break down fatty acids for use in the mitochondria and them to oxygen
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