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Ethan Kenny Organelles Project

Page history last edited by PBworks 16 years, 4 months ago

Organelles Project

 

 Organelle- a specialized structure inside a cell that has a particular function

 

Plastid (Chloroplast)-

 

  • plastids are membrane bound organelles
  • they have an inner membrane system
  • found only in plants and algea - mainly  functions in photosynthesis
  • photosynthesis- the conversion of light energy into chemical energy
  • there are many types of plastids that have many functions-
    • chloroplasts- conduct photosynthesis, contain the plant cell's chlorophyll, providing the green color
    • amyloplasts- store starch
    • proteoplasts- contain chrystalline, fibrillar, and protein, and sometimes starch grains
    • chromoplasts- store and synthesize pigment
    • leucoplasts- colorless, synthesize monoterpenes
    • elaioplasts- store fat
    • statoliths- detect gravity
  • plastids are found in the cytoplasm of cells, usually unattched to other structures
  • structure- they come in many different sizes and shapes, including branched, unbranched, cup-shaped, flat-plated, spherical, and more
  • all plastids have one similar structual detail - a double envelope of 2 concentric sheets of membrane

 

                chloroplast structure                                                      plant cells with chloroplast

              (micro.magnet.fsu.edu)                                                        (www.wikipedia.org)

 

 

 Mitochondria-

 

  • mainly involved with aerobic respiration
  • aerobic respiration- oxygen is used to oxidize organic substrates into CO2 and water and yield energy
  • make most of cell's supply of ATP (adenosine triphosphate), which is used as a source of chemical energy
  • contains inner and outer membranes made of phosolipid bilayers and protein with an intermembrane space (the space between the membranes)
  • function- mitochondria, other then converting organic materials into ATP, are used in many metabolic tasks:
    • apoptosis- programmed cell death
    • cellular proliferation
    • regulation of cell's redox state
    • heme synthesis
    • steroid synthesis
  • they are believed to have originated from endosymbiotic prokaryotes, because they have many similar features
  • structure- other than the inner and outer membrane and the intermembrane space, mitochondria contains:
    • the cristae- space formed by foldings of the inner membrane
    • the matrix- the space within the inner membrane

 

 

 

                       (www.cartage.org.lb)

 

 

Cytoskeleton-

 

  •  the cytoskeleton is the skeletal framework of the cell
  • it consists of  three different kinds of protein filament that form networks
  • these networks give the cell its shape and provide for cellular movement
  • structure-
    • there are three types of cytoskelaton fibers that make up the cytoskeleton-
        • microtubules
            • stiff, hollow rods
            • about 25 nanometers in diameter
            • made of protein called tubulin
        • actin (or micro) filaments
            • thin, flexible double-stranded helical polymers
            • about 5 nanometers in diameter
            • made of globular actin molecules
        • intermediate filaments
            • tough, strong filaments
            • 10-11 nanometers in diameter
            • composed of a family of insoluble proteins
    • thet cytoskeleton connects to the plasma membrane and the organelles insid ethe nucleus and cytoplasm by inker proteins
    • The Microtubule Organizing Center (MTOC)-
        • found in all cells where microtubules are present
        • microtubules extend in a radial array from the MTOC
        • generally, the MTOC is near the nucleus
        • the MTOC organizes the microtubules into a network of microtubule tracks where the plus (fast-growing) ends of the microtubules are near the cell surface and the minus (slow-growing) ends are associated with the MTOC
        • helps microtubules serve as tracks along which membrane-bound vesicles move
  • function-
    • control the shape, movement, elasticity, and division of the cell
    • molecular motors, are able to ratchet along the cytoskeleton to change cell shape and move components around the cell
    • provide backbone for cell

 

                                         the cytoskeleton in animal cells

                               (the blue areas are the nucleus of the cells)

                                                 (www.bscb.org)

 

 

Extracellular Fluid-

 

  • extracellular fluid is the body fluid outside of the cell
  • structure-
    • contains proteins and electrolytes
    • conatins sodium, potassium, calcium, chloride, and hydrogen carbonate
    • extracellular fluid makes up 20-25% of a person's body weight
  • function- they are made by cells so they have a better enviroment to function in
    • in some animals, it has two subcompartments:
      • blood plasma
      • interstitial fluid
    • the regulation of extracellular fluid help avoid edema (excessive accumulation of fluid in tissues) and for the maitenance of arterial pressure
    • extracellular fluid filters into the extracellular matrix (the space that seperates cells in tissues from one another) and flows with the cells transporting nutrients and chemical messangers
    • from the cells it recieves metabolites, ions, proteins, and other substances
    • these substances are reabsorbed by  the venous or lymphatic capillaries

 

 

                                                 (www.micelleproducts.com)

 

 

Nuclear Membrane-

 

  •  the nuclear membrane is also known as nuclear envelope, perinclear, nucleolemma,  or karyotheca
  • it is the outer part of a cell's nucleus that seperates it from the cytoplasm
  • cytoplasm- the jelly-like part of the cells that holds all of the cell's other structures (than the nucleus)
  • function-
    • is the boundary for the nucleus, forcing the nucleus to keep its shape
    • acts as the control center for all of the cells activities
    • contains the chemical instructions (DNA) needed for all of the cells processes to work propwely
    • it also allows controls what passes between the nucleus and cytoplasm by using its pores
    • the pores only allow small particles in and out of the nucleus
    • the porers also allow select larger molecules
    • also help cells in the process of mitosis (when the cell makes a copy of itself)
  • structure-
    • it is a double-layer membrane
    • composed of lipid bilayer

 

the nuclear membrane surrounding the nucleus of a cell from the cytoplasm

                                        (www.galenet.com)

 

 

Endoplasmic Reticulum-

 

  • the endoplasmic reticulum is a network of membranes in a cell through which materials move
  • it is also involved in the pruduction of proteins
  • found in all eukaryotic cells
  • structure-
    • network of folds, tubes, and sacs
    • through a microscope, the endoplasmic reticulum looks like flat, tubular membranes that connect to the nucleus and are spread through the inside of the cell
    • there are two types of endoplasmic reticulum-
      • rough endoplasmic reticulum- appears to have a rough surface because it is covered with ribosomes (structures that make protein)
      • smooth endoplasmic reticulum- has no ribosomes on its surface, making it appear smooth
    • the smooth endoplasmic reticulum curves around the cells cytoplasm, while the rough endoplasmic reticulum is stacked and flattened
    • both types connect directly to other organelles in the cell
  • function-
    • both the rough and smooth moves material to where they are need act as a conveyer belt that moves material throughout the cell
    • moves material to where they are need
    • the smooth endoplasmic reticulum packages and distributes material for making proteins and other substances
    • the smooth endoplasmic reticulum also detoxifies any substance in the cell that is poisinous
    • without the endoplasmic reticulum, cells would not be able to function

 

the endoplasmic reticulum (both rough and smooth) surrounding

                        the nuclear membrane (envelope)

                                   (computer.act.ac.th)

 

 

Golgi Apparatus-

 

  • the golgi apparatus is a collection of flattened membrane stacks (called cisternae) that process, package, and sort a variety of cellular products
  • in both plant and animal cells
  • structure-
    • each golgi apparatus is made of 4-8 cisternae stacked on top of eachother
    • many cisternal stacks connected by tubules and transport vesicles make up a golgi complex
    • the golgi complex if often near the nucleus of the cell
    • each golgi stack has a induvidual orientation
  • function-
    • the cis (or entry) face of the golgi apparatus is where transport vesicles dock and add their synthesized products from the endoplasmmic reticulum to the golgi cisternae
    • a network of membrane tubules attach to and cover the cisternae on the cis face
    • the network also serves as a docking site for the transport vesicles
    • from the cis face, vesicles transport proteins back to the endoplasmic reticulum, where further processing takes place
    • the products that the vesicles brought move to the trans (or exit) face where they undergo final processing and packaging into vesicles
    • the vesicles carry the products to the cell surface for secretion, or to other organelles for storage
    • complex oligosaccharides are also synthesized in the golgi apparatis

 

 

                (www.molecularexpressions.com)

 

 

Ribosome-

 

  •  play a key role in the manufacturing of proteins in both prokaryotes and eukaryotes
  • ribosomes are sites of protein synthesis
  • in bacterial cells, ribosomes are scattered throughout the cytoplasm
  • in eukaryotic cells, they can be both free and bound, depending on the fuction of the cell
  • ribosomes can exist as a single ribosome (one ribosome translating an messanger RNA or mRNA) or as polysomes ( two or more ribosomes translating the same mRNA in order to make multiple copies of the same protein
  • structure
    • large RNA-protein complex
    • about 20-30 nanometers in diameter
    • it is formed fron two unequally sized subunits (the small subunits and the large subunit)
    • for the ribosome to synthesize protein, the subunits must come together
    • in prokaryotes, the small subunit contains one RNA and around 20 different proteins
    • the large subunit conatins two different RNAs and about 30 different proteins
    • in eukaryotic ribosomes, the small subunit contians one RNA and over 30 different proteins
    • the large subunit contains three RNAs and about 50 proteins
    • ribosomes, from all organisms, are very similar in their structure
  • function-
    • free ribosomes manufacture proteins that will function as soluble proteins in the cytoplasm or form structual elements within the cytosol
    • proteins made by bound ribosomes are incorporated into the membranes, used for storage, or exported out of the cell
    • ribosomes mediate the transfer of genetic information from DNA to protein
    • they translate this code using an intermediary, the mRNA
    • the mRNA is a copy of the DNA that can be interpreted by ribosomes
    • to begin the translation, the small subunit identifies the point in  the RNA sequence where it should begin linking amino acids (the building blocks of protein
    • after the small subunit is bound to the mRNA, the large subunit joins and the translation begins
    • the amino acid chain grows, until the ribosome recieves a signal to stop

 

 

a diagram of a ribosome growing an amino acid chain

                   (publications.nigms.nih.gov)

 

 

Plasma Membrane-

 

  •  the plasma membrane is a thin sheet than serperates all living cells from the outside enviroment
  • it maintains the enviroment inside the cell
  • allows only certain things to go in and out of the cell
  • structure-
    • the plasma membrane is very strong and flexible
    • it can repair itself
    • extremely thin, so thin that it wasn't proven to exist until recently when the super-powerful electron microscope was invented
    • made up of a phospholipid bilayer
    • gives animal cells the apperance of a small jelly-filled bag
  • function-
    • seperates cells from outside
    • without it, cells couldn't function at all
    • keeps the contents of cells together, prevents parts from floating away
    • plasma membranes are selectively permeable - they only allow certain molecules to enter through its pores
    • sometimes called "living gatekeeper"

 

                                  (www.molecularexpressions.com)

 

 

Endomembrane System-

 

  •  the endomembrane system is a system of internal membranes
  • it is found in eukaryotic cells, not prokaryotes
  • structure-
    • made of phospholipid bilayer
    • proteins are attached to either side of the membrane or transverse the membrane
    • the endomembrane system contains-
        • the cell membrane- seperates the cells from the outside enviroment and regulates what reaches the cell
        • the nuclear envelope- the membrane around the nucleus of the cell
        • the endoplasmic reticulum- a synthesis and transport organelle, an extension of the nuclear envelope
        • the golgi apparatus- the packaging and delivery system for molecules
        • lysosomes- the digestive units of cells, they break down macromolecules
        • vacuoles- storage units for the cell
        • vesicles- small membrane-enclosed units that transfer molecules
  • function-
    • divides the cell into organelles
    • provides a transport system for moving molecules throughout the cell

 

 

                                                   the endomembrane system

                                                         (www.wikipedia.org)

 

Exocytosis-

 

  • exocytosis is a process, not an organelle
  • intracellular vesicles in the cytoplasm fuse with the plasma membrane and release their contents into the extracellular space
  • exocytosis can occur all the time or be regulated
  • exocytosis is important in transporting proteins that function in the plasma membrane
  • membranes do not fuse spontaneously
  • membrane fusion requires energy and special adaptor molecules on both the vesicle and plasma membrane
  • the adaptors are very selective and only allow vesicles to fuse with certain membrane of organelles
  • a fusion pore forms between the vesicle and the plasma membrane, and the contents of the vesicle are released to the exterior of the cell as the pore widens
  • after this process, the vesicle becomes part of the plasma membrane or is recycled back to the cytoplasm
  • many cells also use exocytosis to release molecules that communicate with other cells

 

                                                      (www.linkpublishing.com)

 

 

Endocytosis-

 

  •  endocytosis is a process, not an organelle
  • materials are engulfed and taken into the cell
  • there is an infolding of the cell membrane, which then pinches around the substances, forming a vacuole or vesicle
  • the materials are then transported into the cytoplasm of the cell
  • this process requires energy and therefore considered  a form of active transport
  • there are three types of endocytosis-
    • pincocytosis-
        • the cells engulfes liquids
        • this can occur in many types of cells in multicellular organisms
    • phagocytosis-
        • solid particles are engulfed into the cell
    • receptor-mediated endocytosis-
        • the substances being transported into the cell first bind to specific sites or receptor proteins on the outside of the cell
        • then the substances are engulfed into the cell
  • once substances have been engulfed and used, waste is removed by exocytosis

 

 

 

                         a diagram of the process of endocytosis

                                          (jan.ucc.nau.edu)

 

 

Vacuole-

 

  • the vacuole is a large, fluid-filled sac inside the cell
  • many types of cells have vacuoles, but they are most prominent in plant cells
  • structure-
    • under a microscope, vacuoles appear as large, round, clear structures
    • filled with a watery fluid called cell sap, which is made up of water, salt, and sugar
    • in some plant cells, a vacuole occupies as much as 90% of a cell total volume
  • function-
    • stores all the materials that a cell needs
    • in animal cells, vacuoles can store a variety of substances, such as lipids and carbohydrates
    • provides the necessary internal pressure for a plant to stay upright and not wilt
    • the vacuole presses the cytoplasm against the cell wall, which remains stretched out under the pressure
    • all long as this pressure is applied, the plant stay upright
    • when the vacuole loses its fluid, the pressure descreases and the plant wilts
    • transports materials inside the cell

 

                        (student.nu.ac.th)

 

 

Lysosomes-

 

  • lysosomes are found in the cytoplasm
  • are in all eukaryotic cells
  • the main site where digestion takes place inside a cell
  • structure-
    • lysosomes conatin very powerful enzymes called hydrolases that can break down many types of substances
    • small, round bodies
  • function-
    • break down large food molecules into smaller ones
    • their enzymes, hydrolases, work on food molecules such as proteins, carbohydrates, and fats
    • they break these substances into smaller particles that can be used by the cell
    • the hydrolases are also used to get rid of a damaged or defective within a cell
    • in this case, the lysosomes attack an organelle and quickly destroy it
    • cells can also use lysosomes to destroy itself

 

                    (www.molecularexpressions.com)

 

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