Tpic 1: Cell Bilgy (Student) 1.2 Essential Idea: Eukarytes have a much mre cmplex cell structure that prkarytes. 1.2 Intrductin t Cells i. Prkarytes have a simple cell structure withut cmpartmentalizatin. All prkarytes have a cell membrane and a cell wall surrunding the utside membrane. The cell wall is made frm peptidglycan. The entire interir f the cell is filled with cytplasm (nt cmpartmentalized) as n membrane-bund nucleus is present. Many different enzymes are present, thus cmplex in terms f bichemicals. ii. Eukarytes have a cmpartmentalized cell structure. Eukarytes have a much mre cmplicated cellular structure. The inside f the cell als cntains cytplasm but it is separated by cmpartments that allw fr specializatin. The cmpartments are membrane bnd rganelles such as the nucleus and the mitchndria. Sme advantages f cmpartmentalizatin are: Advantages f cmpartmentalizatin in eukarytic cells. Enzymes that serve a specific functin r catalyze a specific reactin can be cncentrated within the cmpartment instead f being spread thrughut the cytplasm. Ideal cnditins r particular prcesses can be maintained within the cmpartments such as ph. Organelles with their cntent can be mved arund the cell. Damaging substances such as digestive enzymes (lyssme) can be cntained within their rganelle. Prkarytic Cells Eukarytic Cells Small - less than 10µm Larger cells greater than 10 µm DNA free within the cytplasm DNA cntained within the nucleus DNA in a ring free f prteins (naked DNA). DNA assciated with prteins Appears lighter in clr and called nucleid. N membrane bund rganelles Membrane bund rganelles N mitchndria Mitchndria present 70S ribsmes (Svedberg units) 80S ribsmes N internal cmpartmentalizatin t frm rganelles Internal membranes that cmpartmentalize their functins Reprductin thrugh binary fissin Reprductin thrugh mitsis and meisis iii. Prkarytes divide by binary fissin Binary fissin is the frm f asexual cell divisin that results in the prductin f tw genetically identical prkarytic cells. All prkarytic cells divide by binary fissin. The chrmsme replicates and tw cpies mve t ppsite ends f cell. Divisin f cytplasm fllws. 1
iv. Electrn micrscpes have a much higher reslutin than light micrscpes. The limit f reslutin is the minimum distance that can be bserved befre tw bjects merge tgether t frm ne bject. The smaller the limit f reslutin the higher the reslving pwer. Electrn micrscpes have a greater reslutin (abut.001 µm) when cmpared t a light micrscpe (abut 0.2 µm) The reslutin f light micrscpes is limited by the wavelength f light (400-700 nm). If the magnificatin becmes t great the image becmes blurry Electrns have a much shrter wavelength s they have much greater reslutin (abut 200x greater than a light micrscpe) Skill: Drawing f the ultrastructure f prkarytic cells based n electrn micrgraphs 2
Electrn micrgraph f prkarytic cell Draw the prkarytic cell here and anntate yur drawing. Here are the specific details f the functins f a eukarytic animal cell Organelle Functin Sketch Nucleus Knwn as the cntrl center f the cell. The nucleus regulates cell activities thrugh gene expressin. Cntains the majrity f the cell s DNA. It is surrunded by a duble membrane called the nuclear envelpe, which has small nuclear pres t allw mlecules t mve in and ut f the nucleus. Rugh End- Site f prtein synthesis (attached ribsmes) fr secretin ut f the cell. plasmic rer tubules are cntinuus with the uter layer f the reticulum nuclear envelpe. Glgi apparatus Organelle fund in mst eukarytic cells that prcesses and packages macrmlecules such as prteins. 3
Prteins are usually mdified fr secretin ut f the cell. Lyssme Cntains hydrlytic enzymes that digest wrn-ut rganelles, fd particles, and viruses r bacteria. Frmed frm the Glgi apparatus. Bunded by a single membrane. Mit- Membrane-bund rganelles that carry ut aerbic chndrin cellular respiratin t create ATP. Cntain highly flded inner membranes called cristae which increase the surface area t enhance the mitchndrin s ability t prduce ATP (xidative phsphrylatin takes place here). Space enclsed by the inner membrane is called the matrix. This is where the Kreb s cycle takes place. Cntain their wn DNA genme. Ribsmes Prduce prteins. Free ribsmes within the cytplasm prduce prtein that will be used internally within the cell. Ribsmes attached t the rer prduce prteins that will be secreted Chlrplast Duble membrane with stacks f thylakids. Prduces glucse by phtsynthesis. Vacules Single membrane with fluid inside. Large in plants. Absrbs and fds frm utside in sme animals. Unicellular can expel vesicles water. Micrtubul es and centriles Cilia and flagella Label the rganelles belw: Vesicles used t transprt In cytplasm, cylindrical fibers. Mves chrmsmes, anchrs, helps during cell divisin, inside cilia and flagella. Whip-like structures that prject frm cell surface. Cntain ring f nine duble micrtubules and tw central nes. Used fr lcmtin r t create current arund cell. 4
Skill: Interpretatin f electrn micrgraphs t identify rganelles and deduce the functin f specialized cells. Identify as many structures and rganelles yu can frm the tw micrgraphs belw. Als, practice with the 3 micrgraphs in yur bk n page 25 Animal cell Plant Cell 5
Can yu identify the rganelles frm the electrn micrgraphs belw? What rganelle is this? Hw did yu knw? Is this a plant r animal cell? Label all the structures yu can Chlrplast, nucleus, vacule Label the lyssme and glgi apparatus What is this rganelle? 6
Label the nuclelus, nucleus, nuclear membrane and ER Applicatin: The structure and functin f rganelles within palisade mesphyll cells f the leaf. Palisade Mesphyll cells carry ut mst f the phtsynthesis in the leaf. They have many chlrplasts t allw the cell t carry ut the maximum levels f phtsynthesis. The cells are surrunded by a cell wall t hld the shape f and prtect the cell and a plasma membrane t allw substances in and ut f the cell. They als have mitchndria which are membrane-bund rganelles that carry ut aerbic cellular respiratin t create ATP. They have vacules which are a large cavity in the middle f the cell that stres water and disslved substances, e.g. sugars and metablic by-prducts They are basically plant cells with many chlrplasts. Refer t page 24 in yur bk. Applicatin: The structure and functin f rganelles within excrine gland cells f the pancreas. Excrine Gland Cells f the Pancreas These are animal cells that are specialized t secrete large quantities f digestive enzymes. They will have all the rganelles f an animal cell but will have many ribsmes and rugh ER t create the enzymes which are prteins and transprt them utside the cell. They have many mitchndria t supply the ATP needed fr these prcesses. Refer t page 24 in yur bk Skill: Drawing f the ultrastructure f eukarytic cells based n electrn micrgraphs. The diagram abve shws a animal cell like a liver cell which cntains many ribsmes, rugh endplasmic reticulum (rer), lyssmes, Glgi apparatus, many mitchndria and the nucleus. Liver cells cntain many mitchndria fr energy and rugh endplasmic reticulum with ribsmes fr secretin purpses. 7