Cell Structure (4.1-4.5)
Cell Structure (4.1-4.5) BIOL 201L 004
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BIOL 201L 004
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This 9 page Class Notes was uploaded by Feben Notetaker on Wednesday September 30, 2015. The Class Notes belongs to BIOL 201L 004 at Towson University taught by Dr. Sarah Texel in Fall 2015. Since its upload, it has received 141 views. For similar materials see Introduction to Cell Biology and Genetics in Biology at Towson University.
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Date Created: 09/30/15
Section 4.1: The Cell Theory Tuesday, September29, 206:47 PM • Cells are microscopic ○ Eukaryotes are 10μm-100μm ○ Prokaryotes are 1μm-10μm • Cells weren't discovered until microscopes were. • Matt Schleiden 1839 German physiologist discovered importance of cell CELL THEORY 1. All organisms are composed of one or more cells. Life processes and hereditary happen in these cells 2. Cells are the smallest living thing/are the base of life 3. Cells arise only by division f a previously existing cell • Cells are small because of relations of substance ability to diffuse in and out of the cell. • Rate of diffusion is affected by: ○ Surface area available for diffusion ○ Temperature ○ Concentration gradient of diffusing substance ○ Distance in which diffusion occurs. The bigger the cell the longer the diffusion time Larger cells have more macromolecules to synthesize □ Takes up more energy □ Produces more waste SURFACEAREA-TO-VOLUMERATIO • Surface area-to-volume ratio: as a cell size increases the volume increases much more rapidly than its surface area • The smaller the cell the larger surface area: volume ratio • If two cells differ by a factor of 10 one will be 100x surface area and 1000x volume • Membrane plays an important role in cell function • When cells are smaller they have more control over their content ○ Large cells adapted to solve problem Two nuclei Long and skinny structure permits diffusion to be rapid RESOLUTION • Resolution: minimum distance points can be apart and still be separate points. • If less than 100μm, they strike same photoreceptor and seem as one point • To identify samples easier, they can be altered by chemical stains ○ EX: Hershey-Chase experiment labeling DNA as 32P and protein as 35S CELLULAR STRUCTURES • All cells have: ○ A nucleus or nucleoid- storage for genetic material ○ Cytoplasm ○ Ribosome-protein synthesis ○ A plasma membrane ○ DNA • Prokaryotes: simplest organism that has a circular DNA (in the nucleoid) • Nucleoid: non-membrane bound nucleus that stores genetic info. • Nuclear envelope: double-membrane structure that surrounds nucleus in eukaryotes. • Cytoplasm: semi-fluid matrix that fills interior of cell ○ Has sugars, amino acids, and proteins that cells use in everyday activities. ○ High concentration of molecules and protein give jello form • Organelle: discrete macromolecules specialized for a function • Cytosol: part of cytoplasm that contains organic molecules and ions in solution. Section 4.2: Prokaryotic Cells Tuesday, September 29, 7:07 PM STRUCTURES • Prokaryotes have simple organization • Sizes range from 1 m-10μm diameter • Cytoplasm surrounded by plasma membrane • Has a cell wall • No membrane bound organelles. ○ Areas of function but no boundaries • No elaborate cytoskeletons ○ Made of actin and tubulin Gives rod-like structure • Strength and shape given by cell wall ○ Made of peptidoglycan- carb matrix (polymer + sugar) cross-linked by short polypeptide units (only in bacteria NOT archaea)http://ccyangyan.files.wordpress.com/2012/02/bio1001-image- FUNCTIONS & PROCESSES prokaryote.jpg • Harvest light through photosynthesis • Break down dead organisms and recycle them • Cause diseases • Have 2 domain ○ Archaea (can survive extreme conditions) ○ Bacteria • Move by a rotating flagella • Flagella: long threadlike structure of protein fibers that extend from cell. ○ Used in locomotion Section 4.3: Eukaryotic Cells Tuesday, September 29, 207:17 PM • More complex than prokaryotes • Endomembrane system : organelles are compartmentalized to perform own process simultaneously. • Central vacuole: membrane-bound organelle found in plant cells, ○ Stores proteins, pigments, and waste materials • Vesicles: both in animal and plant cells. Smaller sacs of phospholipid bilayer membrane that stores and transport materials in and out of cell ○ Endocytosis ○ Exocytosis • Chromosomes: compact units of DNA wrapped in proteins ○ Nucleus stores info to synthesize proteins ○ Most eukaryotes have one nucleus ○ Fungi and some other groups have several nuclei ○ Red blood cells lose nucleus when matured http://media.web.britannica.com/eb- • Nucleolus: region in nucleus with intensive rRNA synthesized. media/03/114903-004-924BAFBD.gif • Nuclear envelope: two phospholipid bilayer membrane surrounding nucleus ○ Outer membrane is continuous w/ Endoplasmic Reticulum (ER) • Nuclear pores: scattered shallow depressions in electron micrograph. All over nuclear envelope. ○ 50-80nm apart from each other where 2 membranes come together. ○ Allows ions and small molecules in and out Proteins and RNA protein complexes RIBOSOMES • Protein synthesis is done outside nucleus in ribosomes • Ribosomes are the most complex macromolecular assemblies in cells ○ Composed of rRNA and protein ○ To fully function, mRNA and tRNA join to initiate protein synthesis. ○ mRNA & tRNA carry amino acids ○ Ribosomes recieves info and converts it to protein. http://micro.magnet.fsu.edu/cells/plants/images/plantcell.jp g Cell Structure Page 4 Section 4.4: The Endomembrane System Tuesday, September29, 207:58 PM ENDOPLASMICRETICULUM (ER) • Endoplasmic reticulum (ER): internal membrane; a phospholipid bilayer embedded w/ protein • Rough ER: site of protein synthesis ○ Takes place on ribosomes sitting on RER ○ Protein is exported either: out of cell, to lysosome • Glycoproteins: Proteins + short chains of carbons • Smooth ER: has embedded enzymes ○ Enzymes aid in synthesis of lipids (phospholipid bilayer/ cell membrane, steroids) and carbs ○ Stores intracellular Ca2+ Keeps cytoplasmic levels low Associated with muscle contraction Diverse signaling pathways ○ Modifies substances to make it less toxic ○ Enzymes in liver detoxifies drugs Neutralizes substances GOLGI APPARATUS • Golgi Apparatus: flattened stacks of membrane called cisternae • Vary in # of cisternae depending on organism. ○ Protists have about 1 or few to about 20 in animal cells. • In vertebrates, Golgi link to form Golgi ribbons ○ They are abundant in glandular cells that manufacture and secrete substances. ○ Collects, packages, and distributes substances made in one area to another area to be used Goes with in the cell to other organelles Goes outside of the cell across the membrane • Has a front and back on membrane with diff structures ○ Front (receiving) : has a cis face, near the ER ○ Back: has a trans face, where substances leave in vesicles • There are two methods in Golgi Apparatus process of packaging ○ Vesicular transport ○ Cisternal maturation • Modifies and Packages substance from both the rough and smooth ER • Most common alterations are: ○ Short sugars (modified) ○ Glycoproteins (from sugar chains) ○ Glycolipid (from sugar chains) • Also synthesizes cell wall components Noncellulose polysaccharides in plant cell wall are made from Golgi ○ Noncellulose polysaccharides in plant cell wall are made from Golgi Apparatus Join cell wall through vesicles ○ Other polysaccharides secreted from plants are synthesized in Golgi Apparatus LYSOSOMES • Lysosomes: membrane-bounded digestive vesicles • Come from Golgi Apparatus • Have a lot of degrading enzymes ○ Catalyze rapid break down of proteins, nucleic acids, carbs and lipids ○ Eukaryotic cells: Break down old organelles and recycle their components EX: mitochondria is replaced in some tissues every 10 days. ○ Active at acidic pH. • Need to fuse with vesicle they degrade MICROBODIES • Microbodies: enzyme bearing membrane enclosed vesicles: • Peroxisome: type of microbody that has enzyme that oxidizes fatty acids ○ Enzymes enclosed with fatty acids or would short-circuit entire metabolism of cytoplasm leading to addition of hydrogens to oxygen. ○ Has detoxifying and digestive enzymes-breaks down Hydrogen Peroxide to produce water and oxygen ○ Produces hydrogen peroxide REACTIVE VACUOLES • Vacuole: Membrane- bound organelle found in plant cells, looks like a blank space under microscope • Tonoplast: membrane surrounding the vacuole ○ Has channels for water ○ Maintains tonicity or osmotic pressure. • Doesn't only store water but important molecules such as ○ Sugars, ions, pigments and waste product ○ Was thought to have enzymes that break down macromolecules and detoxify foreign substance Section 4.5: Mitochondria & Chloroplasts- Cellular Generators Wednesday, September30, 29:27 PM Mitochondria Chloroplasts Have a double membrane Have a double membrane Have DNA-protein synthesis Have DNA-protein synthesis Energy metabolism Energy metabolism - in animal cell and plant cell - only in plant cells Produce ATP Absorb Energy from sun (ATP) Cellular Respiration Photosynthesis MITOCHONDRIA • Mitochondria: sausage shaped organelle about the size of a bacteria, found in all eukaryotic cells Mitochondria is not • Has two membrane its own independent ○ Smooth outer membrane cell still has ○ Inner folded membrane with numerous layers called important genetic cristae info stored in • Cristae divides the mitochondria into two parts: nucleus for existence! ○ Matrix: inside the inner membrane ○ Intermembrane space: space b/w the first and second membrane • Inner membrane has proteins that carry out oxidized metabolism, embedded in it. • Oxidative metabolism: metabolism requiring oxygen that energy in macromolecules produce ATP. • DNA in mitochondria help synthesize protein needed in inner membrane to perform oxidative metabolism. ○ Enzymes in oxidative metabolism come from nucleus • Mitochondria reproduce themselves during cell reproduction ○ With help from cytoplasmic ribosome CHLOROPLASTS • Only in plant cells or other eukaryotic cells that perform photosynthesis • Chloroplasts: organelles that generate food and energy through photosynthesisi ○ Has chlorophyll which absorbs all colors but green Reflects green giving plant color • Has two membranes but is more complex than mitochondria ○ Membranes are very close to each other no gap • Grana: compartments of stacked membranes which are in the inner membrane ○ Hundreds of them in chloroplasts • Thylakoids: small disk-like structures surrounding granum • Thylakoids: small disk-like structures surrounding granum (singular of grana). ○ Light capturing pigments ○ Stroma-fluid like matrix surrounding thylakoid that have enzymes that synthesize glucose THEORY OF ENDOSYMBIOSIS • Symbiosis: relation between two diff species living together • Endosymbiosis theory: proposes eukaryotic cells had symbiosis with another free living cell. ○ A prokaryote was engulfed and became part of the eukaryotic cell Explains origin of modern eukaryote ○ These prokaryotes became a part of these eukaryotic cell to gain metabolic advantages. • Mitochondria is believed to be an independent bacteria due to its ability to perform oxidative metabolism . • Chloroplasts are also believed to be originated from photosynthetic bacteria. Mitochondria is not autonomous or independent from the cell!!!
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