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Unformatted text preview: Mitochondria − Structure: − has 2 membranes, like nucleus − Outer membrane covers entire organelle − Inner membrane is extensively infolded, folded back and forth − inner membrane: folded into cristae − Compartment inside both membranes: matrix − part on the inside of the inner membrane − Has own circular DNA; can reproduce − mitochondria can divide and reproduce itself − Function: − Energy metabolism (cellular respiration) − manufacturing, digesting, processing of energy molecules − Structure/function relationship important for respiration − some cells have more mitochondria than others, muscle cells burn a lot of energy so they have a lot of mitochondria − Plants and animals both have mitochondria − Figure 4.17 − outer membrane − inner membrane is folded back and forth forming the crista − space between membrane—intermembrane space Plastids − Plastids: plant specific organelles − synthesizes/stores chemical compounds − often contains pigments (color) − pigments store light energy − stored and manufactured here − Only in plants − Types − Leucoplasts (colorless): store starch and fats, not pigments − Chromoplasts: contain nonchlorophyll pigment, can be any color and can change color depending on season/pigments being made − Chloroplasts: contain chlorophyll type pigments, contain pigments used for harvesting of light energy and production of energy molecules in plants Chloroplasts − Structure: − Outer membrane covers entire organelle − Inner membrane folded into stacked disks − thylakoid: single disk or single fold of inner membrane − grana: stacks of thylakoids − stroma: soluble material around grana − kinda like intermembrane space − Function − Site of photosynthesis in plant cells − convert light energy to chemical energy − structure/function similar to mitochondria − both harvest energy − double membrane is key to process energy molecules − No animals have chloroplasts, only in plants − Figure 4.18 − Grana is a stalk of thylakoids, space between granum is between stroma Vacuoles − Primarily found in plants (rarely in animals) − Prominent part in plant cells − Storage organelle − Store food, water, or waste − usually specific, don't store food & waste in the same vacuole..specific vacuoles have specific jobs − Central vacuole − Stores water: has water channels called aquaporins (specialized channel which help move water) in membrane − Involved in cell shape/water balance (osmosis) − vacuole gives cell its shape/structure − It pushes on the cell wall from the inside and gives it its shape − resist any pressure coming from the outside − pressure – turgor pressure − Involved in cell growth: grow by adding vacuolar volume, not cytoplasm − plant cells grow because central vacuole's size increases − animal cellscytoplasm increases; plant cells vacuole increases Structural support for cells − Eukaryotic cells are relatively large: − cytoskeleton needed for internal support − More important in animals than plants for support − Plants use cell wall and turgor pressure (pressure from vacuole) − cell walls don't change their shape − Cytoskeleton is a dynamic structure − lengthen, shorten, rearrange, disassemble − animal cells can change their shape − Allows cell to move, change shape − gives structure and shape to cell − Multiple types of fibers involved − they are proteins − have specific jobs, specific locations, different properties within the cell Microtubules − Structure: − Largest cytoskeletal element (in terms of diameter) − they are tubes, cylinders − Hollow, unbranched tubes made of alphatubulin and betatubulin monomers − take individual proteins, put them together in a hollow tube, that makes a microtublue − Has different ends (+ and ); dynamic − we can add and subtract monomers to one side and to the other, we cannot − add monomers to the front/positive end − can't add monomers to the negative end − cell can rapidly build up and break down microtubules as needed − Functions: − Forms spindle that separates chromosomes – spindle apparatus − involved in cell division by helping seperate chromosomes on spindle apparatus − Movement: cilia and flagella − outside the cell − propels cell − Transport within the cell − vesicles move along the microtubles, like a pathway − Structural support for cell Microfilaments − Structure: − Smallest cytoskeletal element (in terms of diameter) − Long unbranched fibers of actin monomers − actin: long, round, globular proteins linked end to end − Two strands of beads wound together (like a rope) − Also has different ends (+ and ); dynamic − can break it, build it, rearrange it rapidly, … − build rapidly on positive end − break rapidly on negative end − Located near the inner surface of the cell membrane − Functions: − Signaling: scaffold for signaling molecules − since they're near the membrane, they can rapidly diffuse out − Movement: − all cell movement involves microfilaments − Give structural support to cell Intermediate filaments − Structure: − Intermediate in size (in terms of diameter) − Fibrous subunits (lamins) that are arranged into a solid cylinder − stable and durable filaments that form a branched network − don't break down or break up − once it's built up, it stays − Functions: − gives structure and stability − Gives shape to cell. − Form the nuclear lamina − Figure 4.20 − Model of cytoskeleton − micurotubles hollow, unbranched tube − intermediate filamentssolid rod, branched, form stable and rigid structure − actin filaments strands wound closely together, found close to inner layer of cell membrane Cell movement − Move using external structures: cilia and flagella (swimming movement) − made of microtubules − Move using microfilaments to change shape (amoeboid movement) − Like if you got in a giant balloon and someone in the balloon is walking − move cytoskeleton and push on one side of cell membrane, cell rolls forward − Both kinds of movement require motor proteins − convert chemical energy to mechanical − chemical energy: energy stored in chemical bonds (ex ATP) − mechanical energy: energy of movement − convert checmical energy to movement − Dynein used in cilliar/flagellar movement − Dynein & kinesin also “walk” along the microtubules − Myosin associates with microfillaments − muscles are primarily made of myosin, which does the movement − actin provides the structure Extracellular matrix (ECM) − ECM includes two parts: − interstitial matrix—present in between cells − basement membrane—dense, sheetlike deposits on which epithelial cells are anchored − skin is partially made of epithelial cells which are anchored by basement − Consists of interwoven matrix of structural proteins and carbohydrate polymers − Secreted by surrounding cells − Cells in the matrix make the ECM − Cellular integrin proteins connect cytoskeleton to ECM − Type of ECM depends on surrounding cells − Dynamic structure—has many different functions, very complex − Anchored to one another and to the proteins on the outside. − Ex: bone tissue − ligaments, tendons − primarily made of carbs and proteins − few cells − Functions: − Provides structure, support, protection to cells; separates different tissues − keeps the same types of cells types together and separates them from different tissues and cell types − Intimately involved in regulating cellcell communications − When a cell sends a signal, it has to go through the ECM. − Depot for growth factors (protein hormones) − growth factors are very complex − stimulated cell division in cell − do lots of things − Cells will make growth factors, then put them on the ECM. They go when the cell tells them to go because they're already ready to go. − Release of GFs by ECM causes local and rapid response by cells. − GF regulate many cellular processes − Instead of having the whole body respond, only a few cells in a certain location respond. − ECM key to growth, wound healing, angiogenesis (making new blood vessels), bone formation, tumors, … − ECM controls everything around it. Cell video: http://aimediaserver4.com/studiodaily/videoplayer/? src=ai4/harvard/harvard.swf&width=640&height=520 ...
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This note was uploaded on 03/25/2010 for the course BIO 11000 taught by Professor Friedman during the Spring '10 term at Purdue University-West Lafayette.
- Spring '10