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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-
- 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
- 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)
Ethan Kenny Organelles Project
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