Prokaryotic and Eukaryotic Cells: structure and Function

Set: Prokaryotic and Eukaryotic Cells: structure and Function

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All 91 Terms

	Term	Definition
	organelles	little organs. many of which are housed inside of prokaryotic cells. these are not bounded by lipid membranes
	nucleoid	an organelle containing the DNA of a prokaryotic cell that occupies an irregularly shaped region. as opposed to in a eukaryotic cell which the DNA is contained in a well-defined membrane bound nucleus
	peptidoglycan	a macromolecule tha makes up virtually all prokaeyote's cell wall
	surface-to-volume ratio	small cells have relatively more surface area for the same volume as larger cells. the larger the surface area, the more rapidly nutrients can enter. the larger the volume, the more nutrients that are needed. prokaryotic cells meet their needs for nutrients quickly and grow rapidly.
	envelope	consists of as many as three layers (outer membrane, cell wall, and cytoplasmic membrrane/inner membrane). the three groups of bacteria (gram +, gram -, glycoplasmas) differ with respect to the number of layers that comprimise their envelopes.
	Gram-negative bacteria	contain all three layers of the envelope. because they have two membranes (outer and cytoplasmic), they have extracellular compartment that lies between the two membranes.
	periplasm	a compartment in gram-negative bacteria that lies between the outer and cytoplamic membranes
	gram-positive bacteria	a bacteria whose envelop is made up of a cell wall, and cytoplasmic membrane. these lack the outer membrane.
	mycoplasmas	bacteria that lack the outer membrane as well as the cell wall. their envelope is made up of the cytoplasmic membrane only
	acid-fast bacteria	a bacteria whose outermost covering is a highly unusual waxy layer, this bacteria includes the Mycobacterium tubuerculosis and M. leprae.
	outer membrane	a bi-layer protective covering of gram-negative bacteria. the inner is composed of phospholipid amd the outer is composed of lipopolysaccharide (LPS). the outer layer also contains small amount of phospholipid to which some components of capsule are attached
	LPS	an unusual compound found only in the outer membrane of gram-negative bacteria. it is a combination molecule with a lipid moiety on one end and polysaccharide on the other. the lipid end is hydrophobic and the polysaccharide talil is hydrophilic. this serves as a barrier to polar and nonpolar molecules...as a resul, only water and a few gases can cross the lipid par of the outer membrane.
	PORES	small wholes in the outer membrane of a gram-negative cell
	porins	proteins that form the pores along the membrane of gram-negative cells. these enable small molecules to diffuse through....some of these pores are selective
	lipoprotein	the outer membrane is anchored to the rest of the envelop of the gram-negative cell by these molecules. they are bonded to the cell wall at one end and the other end carries a lipid that inserts into the inner surface of the outer membrane
	periplasm	the space that lies just inside of the outer membrane and cytoplasmic membrane in gram-negative bacteria. it contains the cell's peptidoglycan wall within it. it is filled with gelatinous material, including two types of proteins. One is enzymes, which can pass through the cytoplasmic membrane, and the second protein are binding proteins....which bind cerain nutrients and facilitate their passage across both the outer membrane and the cytoplasmic membrane
	cell wall	strong rigid wall that are made of peptidoglycan, contained by all bacteria except mycoplasmas. this lies within the periplasm in gram-negative bacteria and just outside the cytoplasmic membrane of gram-positives. the thickness of this layer differs between + and -. the Gram-neg. consists of a peptidoglycan mesh that is only one layer thick. as opposed to a gram-pos. which consists of many layers, and may also consist of a second component teichoic acid-glycerol and ribitol units linked by a phosphate.
	lysozyme	an enzyme that destroys peptidoglycan, commonly found in tears. is able to convert rod-shaped bacteria into a sphere (the shape of wall-less objects)
	cocci	sphere shaped, singular
	bacilli	rod-shaped, singular. When plural, only in the lowercase does it refer to the size of
	spirilla	spiral-shaped, singular
	vibria	short, coma-shaped spirillum
	coccobacillus	short rod-shaped
	autolysins	enzymes produced by bacteria when they want to enlarge in order to break the across-bonds in the peptioglycan cell walls
	transpeptidases	enzymes that are used in bacteria to reseal the breaks in the broken cell wall by adding new peptidoglycan monomers. this enlarges the peptidoglycan sac and increases the cell size. penicillin blocks this reaction in order to kill bacteria
	penicillin-binding proteins	the name of penicillin and related antibiotics which inactivate transpeptidases by binding to them. inactivated transpeptidases cannot close the breaks in the cell wall that autolysins make in order to enlarge the cell. the wall becomes too weakened to hold the turgor pressure and the cell bursts (or lyses)
	mycoplasmas	they lack a cell wall but they do not lyse because they don't have significant turgor pressure. they maintain a nearly equal concentration of solutes that exists in their external environment. If they are deprived of an energy source and are therefore unable to pump out, they swell and lyse. their turgor pressure are not exactly at zero since their cytoplasmic membranes are strengthened by containing sterols. sterols are lipids found in membranesof eukaryotes but not in membranes of most bacteria.
	cytoplasmic membrane	the membrane that encloses the cytoplasm of any cell. the functions of this membrane are to contain the cytoplasm and to regulate what comes in and what goes out of the cell.
	unit membranes	the cytoplasmic membrane of bacteria and eukaryotes...this is much different from the outer membrane of Gram - bacteria and cytoplasmic membranes of archaea are chemically distinct. this membrane is composed of phospholipids (hydrophilic head and a hydrophobic tail)
	transmembrane proteins	proteins that penetrate through the membrane...contained in the eukaryotic and prokaryotic phospholipid bilayers
	peripheral membrane proteins	proteins that are merely stuck to the surface of the membrane...contained in the eukaryotic and prokaryotic phospholipid bilayers
	Appendages of bacteria	pili and flagella
	pili	straight hairlike appendages made up of protein molecules called pilins which are arranged helically around a central hollow core. the principle function of pili is attachment. adhesins are interspersed amung the pilin molecules in this. virtually all gram neg bacteria have this. amd many gram-pos do not. aka fimbriae
	flagella	an appendage that extends from the surface of the envelop. the function is locomotion, not attachment. they are helical (cork-screw shape) and they rotate to propell the cell. contains three distinct parts: flagellin, hook. and basal body
	flagellin	protein subunits which are arranged within the flagella, much like the pilin molecules are arranged within pili.
	hook	a short thickened bent region, which acts as a universal joint to the flagella, allowing the filament to point in defferent directions
	basal body	an elaborate structure that anchors the hook. This penetrates the cell's envelope and causes the flagellum to rotate. it has a motor that turns the flagellum and a set of bearings, called rings, that allow the flagellum to turn within the stationary envelope
	rod	the core of the flagellum, which is free to rotate
	taxis	the behavior of bacteria to seek out favorable environments and avoid harmful ones
	chemotaxis	bacteria sense certain chemicals and swim toward regions that contain more nutrients and avoid regions with toxic materials.
	axial filaments	instead of the flagella sticking out from the cell, they are trapped within the periplasm, where they form two bundles, each of which is anchored near one end of the cell and wraps around the cell body, extending about halfway up the cell. together they form a helical buldge in the outer membrane that moves like a corkscrew as the entrapped flagella turn. this moving buldge propels the cell/ ex. Treponema pallidum, the cause of syphilis, which live on mucous membranes
	aerotaxis	movement of bacteria to regions that contain favorable concentrations of dissolved oxygen
	phototaxis	photosynthetic bacteria swim to regions of optimal light intensity and quality.
	magnetotaxis	bacteria which are capable of traveling along the magnetic lines of force
	capsule	a slimy or gummy substance that most bacteria, secreted by both gram positive and negative, that becomes the outermost layer of the cell. most are made of polysaccharides, but some are made of proteins. they function for protection but it can also help a cell adhere to a surface where conditions are favorable for growth (Streptococcus mutans...tooth decay) and it can also protect disease-causing bacteria against phagocytosis (like Streptococcus pneumoniae which can cause a mild pneumonia when its capsule is thick, and a deadly pneumonia when the capsules are thickest)
	nucleoid	an irregular mass of DNA within the cytoplasm.
	bacterial chromosome	in most bacteria, the majority of DNA is arranged in this single circular molecule
	plasmid	in addition to the bacterial chromosomes, there are usually smaller circular DNA within the bacteria, if a bacteria has linear rather than circular chromosomes, the bacteria also will have linear DNA within the bacteria vs. circular.
	ribosomes	small structures that manufacture protein. their small size and great number give the cytoplasm its grainy appearance. these structures are smaller when found in prokaryotes. some antibiotics bind to the smaller prokaryotic disease-causing bacteria with out damaging the larger eukaryotic host.
	inclusion bodies	the most abundant of these are the storage granules that hold the cell's reserve supplies of nutrients. some species of bacteria store carbon, some poly-beta-hydroxyalkanes (carbon in granules composed of lipids), polyphosphate (phosphate...essential component for ATP)
	other kinds of inclusions found in bacteria	gas vacuoles (contained by some photosynthetic aquatic bacteria in order to allow the bacteriunm to float at the water level that provides the best conditions for photosynthesis), chlorosomes (structures just inside the cell membrane that house pigments necessary for photosynthesis), and magnetosomes (has iron-containing structures necessary for magnetotaxis)
	endospores	the most resistant biological structures that are known and produced by some bacteria. they can withstand harsh environmental conditions becasue they contain such little water.
	resting structures	nongrowing structures, describes endospores, which can survive up to hundreds of years, withstanding extreme hear, dehydration, toxic chemicals, and radiation. they form only when nutrients are exhausted or other conditions become unfavorable for growth.
	vegetative cells	cells that grow and reproduce, this is found when favorable condition return and they are the result of endospores
	sporulate	the formation of an endosporm, usually triggered by bacterial cells' unfavorable conditions or starvation. it is the unequal division of the cytoplasm. the larger part engulfs the smaller one, aka the forespore, which eventually becomes the endospore
	microtubules	proteins capable of movements, they are found within the flagella of eukaryotes (which are longer and more complex than prokaryotic flagella)
	kinetodesma	fibers that interconnect the basses of the cilia and move the eukaryotic cell by beating in coordiinated waves. the movements of the cilia also aid buchal activities that involve sweeping food matter into their mouth
	cell wall of eukaryotic cells	most animals lack one of these, humans never have these, fungi and algae typically do, and protozoa do not have one. SOme have a pellicle outside which functions as a flexible wall. these are made up of the polysaccharide cellulose, nitrogen-containing polysaccharides, and other cellulose
	mitochondria	found in all aerobic eukaryotes in the organelles, as opposed to being located in the prokaryotic cytoplasmic membrane. they are located in the intracellular membranes of this eukaryotic cells
	cytoskeleton	the internal structure of the eukaryotic cell that prokaryotes lack. it is composed of microtubules, microfibrils, and intermediate filaments
	microtubules	the largest portion of the cytoskeleton which are made of the protein tubulin, just like flagella and cilia. they form during cell division to ensire that each daughter cell receives one complete copy of the genetic blueprint
	microfibrils	portion of the eukaryote's cytoskeleton that is made up of the protein actin
	intermediate filaments	portion of the eukaryote's cytoskeleton that is commonly made of a variety of proteins like keratin which add rigidity to the cytoskeleton.
	pseudopods	false feet, a type locomotion for certain eukaryotic organisms
	nuclear envelope	the double membrane structure that encloses the eukaryotic nucleus, unlike the prokaryotic nucleoid
	nucleoplasm	the gelatinous matric of the nucleus which is found in the interior of hte nucleus.
	nucleoli	dense masses of RNA and protein that manufacture ribosomes, several of these are located in the nucleus.
	histones	basic proteins associated with eukaryotic DNA that form a DNA-protein structure called a nucleosome....which are organized into paired structures called chromosoms, which are visible under the microscope around the time of cell division.
	mitosis	an essential feature of cell division fr growth. one of the two complex nuclear divisions that eukaryotic cells undergo. there are four phases: interphase, prophase, metaphase, anaphase which resilt in each daughter cell receiving one pair of each type of chromosomethat the mother cell contains.
	meiosis	an essential feature of cell division leading to sexual reproduction of eukaryotes. during this, the chromosomes split, each cell only one copy of each chromosome, resulting in haploid gametes, and later fuse with another haploid gametes in order to create a zygote, which is a diploid cell that develops into a new organism
	cytomembrane system	connects iwth the nuclear envelop, but not with the cytoplasmic membrane, this complex membrane system sorts, organizes, and packages the different kinds of molecules that the cell produces. major two forms within the cytoplasm and the endoplasmic reticulum and the golgi apparatus
	endoplasmic reticulum	double membrane that folds back on itself creating a complex pattern of tunes and latered sacs. some are smooth and others appear rough, they have different functions
	smooth endoplasmic reticulum	the major sites of phospholipid synthesis and repairing membranes
	rough endoplasmic reticulum	a region that is recognized by the grainy appearance of the ribosomes on their outer surface, where the cell's proteins are made
	golgi apparatus	an organelle made of flattened stacks of membranes, proteins that leave the RER become packaged, in membrane-found vesicles that bud from the ER and then fuse with this which in turn modifies and concentrates the molecules. they are repackaged in new vesicles, which are then sent on their way to their final destination, either insider or outside the cell. it functions as a packaging and distribution center.
	lysosome	a small but powerful packet of enzymes that can destroy many kinds of molecules and microbial cells captured by phagocytes, this is a specialized vesicle that leaves the Golgi apparatus
	endosymbiotic theory	the fact that mitochondria and chloroplasts are derivitives of gram-negative bacteria that were captured by an ancient organism when eukaryotic cells first evolved. evidnese includes that the mitochondria and chloroplasts are the same size as prokaryotic cells, they both contain DNA, the DNA is arranged in the prokaryote's single circular chromosome, both contain the 70S ribosomes, the double membranes resemble the cytoplasmic and outer membranes of gram-negative bacteria, the external membrane contains pores that resemble the portins in the outer membrane of gram-neg, and they multiply by binary fission...the way prokaryotic cells do.
	diffusion	the random movement by which molecules collide with molecules nearby and eventually distribute themselves uniformly throughout the space available to them in attempt to reach equal concentrations on either side of a membrane
	concentration gradient	the driving force of the net flow of molecules in or out of a cell, no energy is needed to drve the flow since all the movement is due to the greater concentration of molecules on one side than the other.
	osmosis	water crosses a membrane toward the side with the higher concentration of solute molecules and therefore the lower concentration of water molecules.
	turgor pressure	an increase in the internal pressure of a cell as water flows into it.
	hypertonic	the environmet has a higher concentration of solutes than does the cell's interior. water is therefore drawn out of hte cell by causing the membrane-bound volume to decrease and eventually it collapses
	hypotonic	an environment that has a lower concentration of solutes than the cells interior, so water enters the cell's interior which increases the cell's turgor pressure, and can cause the cell to lyses.
	isotonic	an environment that is a happy medium and has the same concentration of solutes in and out of the cell and, there is therefore no osmotic effect on the cell
	facilitated diffusion	passage from higher concentrations to regions of lower concentrations mediated by highly specific carrier proteins embedded in the membrane. these proteins bind a compound on one side of the membrane and release it on the other
	active transport	a process necessary to bring essential nutrients into the cell when the concerntations outside are low. this movement of molecules against the concentration gradient requires energy. energy can be supplied inthe form of ATP or a concentration gradient of ions, usually protons.
	group translocation	a vatiation of active transport that occurs onlu in bacterial cells and only with certain molecules. a molecule is transported into the cell and at the same time it is chemically changed into a slightly different molecule. it requires energy, but the chemical modification prevents the molecule from leaving the cell. in a sense it is a trapping mechanism. phosphorylation ( the addition of a phosphate group) is one variation of how bacteria do this
	endocytosis	the process of solid material being engulfed. the cytoplasmic membrane folds in on itself and surrounds a foreign particle. inside it releases a separate membrane-bound structure called a vacuole.
	phagocytosis	the process of cells being taken in by certain types of white blood cells
	pinocytosis	"cell drinking", the process of liquid material being taken in.
	exocytosis	the expulsion of material, by the reverse process of endocytosis.

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Creator	nicholhm
Created	September 20, 2007
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nicholhm : Changed nuclear envelop → the double membrane structure that encloses the eukaryotic nucleus, unlike the prokaryotic nucleoid to nuclear envelope → the double membrane structure that encloses the eukaryotic nucleus, unlike the prokaryotic nucleoid

nicholhm : Changed surface-to-volume ration → small cells have relatively more surface area for the same volume as larger cells. the larger the surface area, the more rapidly nutrients can enter. the larger the volume, the more nutrients that are needed. prokaryotic cells meet their needs for nutrients quickly and grow rapidly. to surface-to-volume ratio → small cells have relatively more surface area for the same volume as larger cells. the larger the surface area, the more rapidly nutrients can enter. the larger the volume, the more nutrients that are needed. prokaryotic cells meet their needs for nutrients quickly and grow rapidly.

nicholhm : Changed outer-membrane → a bi-layer protective covering of gram-negative bacteria. the inner is composed of phospholipid amd the outer is composed of lipopolysaccharide (LPS). the outer layer also contains small amount of phospholipid to which some components of capsule are attached to outer membrane → a bi-layer protective covering of gram-negative bacteria. the inner is composed of phospholipid amd the outer is composed of lipopolysaccharide (LPS). the outer layer also contains small amount of phospholipid to which some components of capsule are attached

nicholhm : Changed microtubule → proteins capable of movements, they are found within the flagella of eukaryotes (which are longer and more complex than prokaryotic flagella) to microtubules → proteins capable of movements, they are found within the flagella of eukaryotes (which are longer and more complex than prokaryotic flagella)

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