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1 Outcomes A and G Chapters 3, 4, and parts of 7 Unit 2: Cell BiologyOutcomes A and GChapters 3, 4, and parts of 7Prepared by: Wendy Vermillion Columbus State Community CollegeReformatted for use atG.P. Vanier by Ilene Yeomans
2 A. Cellular Level of Organization 1. Cells are the smallest unit of lifeExhibit all characteristics of lifeAre highly organizedMany become specialized for complex functions2. Cell theoryAll living things are composed of cellsCells are the functional and structural units of organismsAll cells are derived from previously existing cells3. Discovery of cellsa) Antonie van Leeuwenhoek- invented the light microscopeb) Robert Hooke- first observed cells in cork (actually saw the cell walls of dead cells)c) Schleiden and Schwann-proposed cell theory
3 Cellular level of organization, cont’d. 4. Cell sizeMost cells are smaller than 1 mm in diameterSurface area/volume ratio determines cell size:
4 Cell Size, cont’d. determining surface area to volume ratios Cell DimensionsSurface AreaVolumeSA/VolSA:Vol1 cm x 1 cm2 cm X 2 cm6 cm x 6 cmLet L be the length of one side= L x L x 6= L x L x L:1:1:1
5 Cell Size continuedAs the cell size increases, the volume increases faster than the surface area doesTherefore small cells have a greater surface area to volume ratio than larger cellsNutrients from the environment must cross the surface of the cell to enterCells must be small in order for the surface area to be adequate to supply nutrientsThis is one reason why we are made up of lots of cells instead of just one big one
7 B. Eukaryotic cells Eukaryotic cells have a membrane-bound nucleus Cell Membrane (or Plasma Membrane)
8 Eukaryotic cells, cont’d. OrganellesSubcellular structures which perform specific life functions for the cellMany organelles are found in both animal and plant cellsSome are found exclusively in plants or animalsPlantschloroplasts, large central vacuole, cell wallAnimalscentrioles
10 Eukaryotic Cells cont’d NucleusContains the genetic material (DNA)Nucleoplasm -semifluid within nucleusChromatin -threadlike DNA which has a grainy appearanceNucleoli (Nucleolus) -dark regions of chromatinThese produce rRNA which makes up the two subunits of ribosomes when combined with proteinNuclear membrane - double layered, surrounds nucleus and has large pores
12 C. Animal Cell Organelles 1. Ribosomes-Site of protein assembly (“Protein Synthesis”)Composed of rRNA and protein subunitsExist either as free ribosomes (in groups called polysomes) or bound to endoplasmic reticulum (ER)Polysomes produce multiple copies of the same protein for use inside the cellProteins produced at the ER’s ribosomes are destined for export from the cell
13 2. Rough endoplasmic reticulum (RER) Organelles, cont’d.2. Rough endoplasmic reticulum (RER)Complex system of sacs and channelsHas attached ribosomesServes as site of assembly of proteins for exportAssembled proteins enter channels for processinge.g. addition of sugar chains to form glycoproteinsReleased in vesicles3. Smooth endoplasmic reticulum (SER)No ribosomesSynthesizes lipid products such as phospholipids and steroids AND is used to detoxifyProduct released in vesicles
15 4. Golgi Apparatus (or Golgi Body) Organelles, cont’d.4. Golgi Apparatus (or Golgi Body)Packaging and processing center for cell productsReceives the vesicles from ERVesicles fuse with Golgi and products are released insideFurther modification of proteins occursProducts are packaged into secretory vesicles and released to travel to the cell membraneGolgi also produces lysosomesEasier to remember the functions withMRS Golgi =M (modify), R (repackage), S (sort)
16 The Endomembrane System Smooth ERRough ERFig 3.6
17 5. Lysosomes Contain hydrolytic enzymes (very powerful enzymes) Organelles, cont’d.5. LysosomesContain hydrolytic enzymes (very powerful enzymes)Three functions of lysosomes:Intracellular Digestionlysosome fuses with a vesicle and digests its contentsAutodigestionlysosomes fuse with worn out organelles or cell components and digest them (e.g. mitochondria)Autolysislysosomes sometimes called “suicide sacs” because they release their enzymes into the cell causing cell death
19 6. Mitochondria Site of aerobic cellular respiration Organelles, cont’d.6. MitochondriaSite of aerobic cellular respiration= production of ATP (energy)Uses oxygen we breathe and food that we eat to produce energy for every action in and of our bodyUp to 38 ATPare made per glucose molecule6 O2 + C6H12O6 6 CO2 + 6 H2O
21 7. Peroxisomes Specialized vesicles Smaller than lysosomes Organelles, cont’d….7. PeroxisomesSpecialized vesiclesSmaller than lysosomesContain powerful oxidative enzymesUse oxygen to strip H’s from certain moleculesProduce peroxide (H2O2), hence the nameRole is detoxificationFound in large numbers in liver cells
22 8. Vaults Serve as cellular transport vehicles (we think) Organelles, continued8. VaultsServe as cellular transport vehicles (we think)Discovered in the early 1990s (do not show up with normal staining techniques)Shaped like octagonal barrels, hollow, 3X size of ribosomesIntriguingly, vaults are the same size and shape as nuclear poresResearch supports vaults’ role in transport from the nucleus to the cytoplasmUnknown cargo, BUT are the right size to accommodate the two ribosomal subunits!
23 D. Cytoskeleton The Cytoskeleton Maintains cell shape Allows cells to move or allows organelles to move within cellsMade of proteinComponents include microfilaments and microtubules:Microfilaments are slender fibers that often occur in bundlese.g. ACTIN which works to contract musclesMicrotubules protrude from the centrosome and form centrioles, cilia, and flagella
24 Eukaryotic cells, cont’d. Centrioles see p60Short tubules with 9+0 pattern of microtubule tripletsIn animal cells, centrosome is composed of 2 centriolesBelieved to be involved in microtubule formation including mitotic spindleBasal BodiesFound at the bases of both cilia and flagellaOrganize the microtubules in the cilium or flagellumHave a 9+0 arrangement of microtubules.
26 E. Cellular Movement Cilia and Flagella Cilia are generally multiple and hair-likeMove mucus (phlegm) up the tracheaMove the egg (or zygote) along the oviductFlagella occur single or double and are whip-likePropel the spermBOTH have a 9+2 pattern of microtubules
29 F. Cell (Plasma) Membrane 1. Membrane StructureFluid-Mosaic Membrane Model (FMMM)Phospholipid bilayerHydrophilic heads face surfacesHydrophobic tails face inwardProteinsIntegral proteins- embeddedPeripheral proteins- surfaceGlycoproteins and GlycolipidsCell markers (antigens)CholesterolChanges fluidity of the membrane
30 Fluid-Mosaic Model of Membrane Structure Fig. 4.1
31 Functions of the Cell Membrane Cell Membrane cont’dFunctions of the Cell MembraneFunctions as a barrier between the cell and its environmentRegulates what enters or exits the cell (Regulates transport of substances into and out of the cell)Contains receptors that determine how a cell will respond to stimuli in the environmentContains proteins that are important in immune responsesIt is a very dynamic, fluid structure
33 G. Permeability of Cell Membrane Cell membrane is selectively permeableSome substances pass through the membrane freely while others do notCrossing depends on factors like:size and shape of molecule,molecule’s chemical nature (e.g. lipid soluble?)temperaturenumber of passages (channel proteins, carrier proteins, etc.)Rate depends on:concentration gradient of substancepermeability of membrane to substancesurface area of membranemolecular weight of substancedistance travelled (thickness of membrane)
34 H. Passive Movement Passive Mechanisms (of crossing the cell membrane) = no cellular energy requiredKinetic energy drives passive mechanismsMovement is always from high concentration to low concentration( = DOWN a concentration gradient)
35 Diffusion For instance: Passive mechanisms….For instance:DiffusionThe movement of substances from an area of high concentration to an area of low concentrationDrink crystals in waterPerfume in a roomThe movement of lipid-soluble substances directly through the phospholipid bilayer from an area of high concentration to an area of low concentrationGases (oxygen and carbon dioxide)Alcohol
37 2. Facilitated Transport Passive mechanisms….2. Facilitated TransportThe movement of small, lipid-insoluble substances such as simple sugars and amino acids across a cell membraneUses a carrier proteinMovement is down a concentration gradientHighLow
39 Movement of Molecules Across Cell Membranes Table 4.1
40 Passive Mechanisms Cont’d 3. Osmosis-A special case of diffusion = movement of WATER from an area of low solute concentration to an area of high solute concentration.The water moves to an area of high ‘saltiness’ in order to dilute the areaWater moves through protein-lined pores (“aquaporins”) in the cell membrane.Osmotic pressure- force that causes water to move in a direction
41 Tonicity Isotonic solutions-no change Hypotonic solutions-cause cells to swell and burstHypertonic solutions-cause cells to shrink, or crenate
44 Permeability of plasma membrane, cont’d. I. Active Mechanisms= require ATPActive TransportUses ATPRequires a carrier proteinTransports molecules from an area of low concentration to an area of high concentration= (UP or AGAINST a concentration gradient)Example:sodium/potassium pump in nerve cellsIodine accumulation in the thyroid glandLowHigh
47 Active Mechanisms, cont’d. 2. ExocytosisRequires ATPVesicle usedTransports cell products and wastes (big stuff) out of the cell by vesicle formationVesicles fuse with plasma membraneProducts are releasedVesicle membrane becomes part of the plasma membrane
49 Active Mechanisms, cont’d 3. EndocytosisRequires ATPVesicle usedTransports substances (big stuff) into the cell by vesicle formationmembrane invaginates and surrounds a substance, then pinches off to form a vesicle
50 Pinocytosis-”cell drinking” material is liquid or small Endocytosis, cont’dPinocytosis-”cell drinking”material is liquid or smallReceptor-mediated endocytosis is a specific type of pinocytosis which occurs in response to receptor stimulationb) Phagocytosis-”cell eating”material taken in is large like bacteria or cell debris
52 POINTS TO PONDER1. The stomach has two different types of secretory cells. The chief cells secrete pepsinogen (the inactive form of the enzyme pepsin), while the parietal cells secrete hydrochloric acid. Both of these cell types have lots of mitochondria to make ATP. The chief cells use ATP to make pepsinogen. Parietal cells use ATP to actively transport H+ and Cl- from the blood into the cells. Only one of these cell types also has extensive RER and Golgi. Which one and why?
53 POINTS TO PONDER2. One type of the affliction epidermolysis bullosa is caused by a genetic defect that results in production of abnormally weak keratin. Based on your knowledge of the role of keratin, what part of the body do you think would be affected by this condition?
54 POINTS TO PONDER3. Colostrum, the first milk a mother produces, contains an abundance of antibodies (infection-fighting proteins). By what means would you suggest these Ab’s are transported across the cells of a newborn’s digestive tract into his or her bloodstream?
55 Clinical-1Kevin J and his wife have been trying to have a baby for the past three years. On seeking the help of a fertility specialist, Kevin learned that he has a hereditary form of male sterility involving non-motile sperm. His condition can be traced to defects in the cytoskeletal components of the sperm’s flagella. Based on this finding, the physician suspected that Kevin also has a long history of recurrent respiratory tract disease. Kevin confirmed that he has had colds, bronchitis and influenza more frequently than his friends. Why would the physician suspect this?
56 Clinical-2When William H was helping victims in an earthquake-ravaged region, he developed severe diarrhea. He was diagnosed as having cholera, a disease transmitted through unsanitary water supplies that is spread by fecal contamination. The toxin produced by the cholera bacteria leads to the opening of Cl- channels in the lining of the intestine. Cl- then floods into the intestine. How does this account for the diarrhea that is severe enough to kill many who have cholera?