Cell structure Flashcards

Question

Na+/K+ pump

Answer 1

* Transmembrane pump moves 3 Na+ out, 2 K+ in * ATP hydrolysis drives conformational change (active transport)

Answer 2

Uses energy of electrochemical gradient for work (ATP only used indirectly) Example: Na+/glucose co-transporter Na+ goes down gradient into cell (favorable) Coupled to glucose moving up gradient (unfavorable) Symport = molecules go in same direction Antiport = molecules go in opposite direction

Answer 3

Endocytosis: membrane can pinch off and engulf things Internalization of small or big things (e.g., macrophage eats bacteria) \*\*significant becuase liek with exocytosis, nothing is crossing a membrane; budding process that goes on, whatever that thing is that is being brough into vesicle never had ot go through membrane\* its being brought into teh cell without crossing a membrane\*

Answer 4

Exocytosis: vesicles fuse with the plasma membrane and release contents extracellularly The inside of a vesicle/organelle = lumen Topologically, ER lumen = Golgi lumen = outside of cell important becuase stuff doesnt have to thread itself through the membrane on its own

Answer 5

**Structural anchoring of cells to each other, but molecules can still pass between cells; do not do much but keeps cells together grouped there!** Like plastic rings that hold together a six-pack Desmosome: like a spot rivet, connected to cytoskeleton Adherens junctions: zipper of adhesion proteins, connected to cytoskeleton

Answer 6

Receptor mediated endocytosis involves a transmembrane receptor; so whatever it is we want to be endocytosed it has to first be attached to a receptor\* so then you get internalize it on receptor, has to bind to receptor and bring that into cell; depends on having right receptors on surface of cell, would not be possible if the receptor was not there; after this happens eventually receptor has to be recycled, receptor has to go back to plasma membrane in order to keep bringing in more substrate\* ex. from mcat, one example of this is LDL Example is cholesterol uptake Cholesterol packaged into low-density lipoprotein (LDL) that circulates in blood LDL receptor binds LDL outside, brings it into cell via vesicle LDL receptor is recycled to membrane, LDL releases cholesterol in the cell this is bad cholesterol- we are able to bring those into our cells only if LDL receptor on surface of our cells binds LDL and does this process of bringing LDL in, then have to send empty receptor back to plasma membrane to pull in more LDL\*\* if don't make enough of these LDL receptors can't pull LDL into their cells enough which means they have way too much LDL suck in blood stream meaning they have really really high cholesterol as a result of this receptor problem\* cells need cholesterol in membrane good side to cholesterol; bad side is that it can contribute to deposits in the arteries that narrow the arteries, athroschlorisis narrowing and hardening of arteries there are a bunch of things that happen in that situation, inflammation whole process LDL sticks to the spot and creates a plaque and if that plaque gets too big, it can block off an artery and cause heart attack!! If going for artery heading toward brain or heart, can choke off blood supply to an important organ, lifetime of eating very fatty foods or having high cholesterol in general can raise the risks of clogged or blogged arteries so the real danger is in terms of cardiovascular disease\*

Answer 7

A tight seal that does not allow passage of materials between cells Seals off body cavities such as intestines and stomach Important in blood-brain barrier very important- seal in lumens! individual cells that make up lumen means space in between cells so specific molecule could slip right through, if toxin not a good thing to happen enter straight into blood stream, so this makes sure seal off different separate environments. prevents anything from slipping through in those cells there\* so they essentially block this from happening make sure nothing slips through cells into blood stream, meaning if molecule wants to get into cell very selective process if particular channel or transporter can go right through and enter cell if it wants to

Answer 8

A protein channel (hole) between cells Allows ions and small molecules to move freely, permits electrical coupling (e.g., heart) need ions to move from one cell to another! Allows for cell to cell communication! * Meaning if a molecule in the cell is connected via gap junction can just pass through neighboring cell through gap junction and you are in as long as small enough to get through gap junction * Heart really utilizes this! Action potential of cardiac muscle cell is signal to have heart contraction, would not want some cells to be activated to have an action potential, if have all different parts of heart activated firing different action potentials, heart having different contractions all over th place and will not get good pumping of heart, want one cardiac muscle cell firing action potential, that sodium will flow into cell, nice strong contraction heart pumps all at once and get nice efficient blood contraction\* Bone also can use this

Answer 9

**Surface area of a sphere is 4πr2** **Volume of a sphere is 4πr3/3** **As radius increases, volume increases faster than surface area** Surface area: volume ratio is a limit to cell size Surface area supports key cell processes (e.g., transport of things across a membrane) Beyond a certain surface area: volume ratio, cannot sustain the metabolism of the cell Cell indentations increase surface area (e.g., microvilli of intestinal epithelial cell) Skinny and flat cells maximize surface area: volume ratio (e.g., neuron)

Answer 10

1. All transcription takes place in nucleus 2. All translation begins in the cytosol * if you are cytosolic protein, you finish translation in the cytosol\*\* * but if you are a secreted protein, transmembrane protein, lysosomal protein= you will finish translation in the ROUGH ER\*\*\* or ER/golgi resident\*

Answer 11

* what do paritcular amino acids have to be shipped over to finish translation * they have a signal sequence, differentce btw two! if no singal sequence nno indicaton to cell they are going anywhere, will just finish translation in ctyolsol * BUT if happen to be translating mrna strand and a cople of amino acids end up translating happen to be signal sequence, that is indciation will be shipped over to rough er to finish translation! * if secreted protein, lysozomal protein distinct signal sequence\* so in case of secreted protein or lysozomal protein the signal sequence will be the first amino acids * signal sequence 1. first couple of amino acids that get translated, 2. signal is removed when translatin is complete you chop it off! * signal sequence is literallya couple amino acids cell recognizes as signal sequence, distnct combination that happens to get recognized as a signal sequence

Answer 12

1. doesnt have to be first couple of amino acids that gets translated, can be anywhere in amino acid sequence, doesn't have to be finally hit signal sequence indication to finish translation at rough ER another thing to note about membrane bound proteins is signal sequence can appear several times in amino acid sequence whereas previously it only appeared once 2. can appear severeal times in the amino acid sequence 3. signal remains as membrane bound part of protein

Answer 13

once finally sent out to cyutosol why only produces one protein product, once sent out mRNA will bind to free ribosome, depending on i fyou stay there bound to that free ribosome is if you do or do not have a signal sequence, if no signal sequence finish translation onf ree ribosome in cytosol wil not go anywhere.... secretory pathway will be endoplasmic R and golgi apparatus, how to package up proteins into vesciles to be sent to outside of cell, or can be fused with the membrane because as we will talk about its pretty hard to get across the membrane, we have a very nonpolar region; making a peptide which happens to have some polar amino acids in it, there is no way its getting outside of the cell or making particular protein embedded in membrane need some way to weave self inside and otuside membrane, so how does the cell overcome that? follow secretory pathway! take free ribosome once produce that signal sequence of a couple of amino acids cell will recognize that, has a signal sequence recognition particle takes free ribosome and directs it, detors over to rough ER\*, free ribosome docks at rough ER to continue translation pushes it into lumen of er or weave peptide insie and outside of membrane so that once it is done we can then ship that finished product, package it up in vesicles from one structure to the next

Answer 14

once that particular strand of amino acids is strung together through translation happen to create a signal sequence those free ribosomes can get directed to ER where it will then dock, first couple of amino acids translated were the signal sequence, signal sequence will be embedded in the membrane of the ER here membrane is cytosol of cell, Endoplasmic reticulum will get embedded into the membrane of the ER - composed of nonpolar or hydrophobic amino acids becuase otherwise would not be able ot exist and not be very happy being in that inner portion, nonpolar amino acids - once have signal sequence resumse rest of transaltion, see growing strand being pushed into lumen of ER; acting as achor for peptide, need whole protein to be in lumen, embed signal sequence into membraen of ER to push transaltion into lumen so then once done can then remove it and have final protein product\* needs to get packd into vesicle then dumped otuside of cell

Answer 15

* ribosome directed over to ER here is its mRNA that it has been reading, steps will look the same, said signal sequence doesnt have to be the same amino acid some getting translated, then hit signal sequence which directs you over to rough er, once signal sequence embedded in membrane continue * once hit signal sequence and every time push translation to the other side of the membrane here, look on image, how get for instance a channel, channels usually composed of proteins how you get them woven in and out of the membrane, because otherwise it would be very hard to get passed those phospholipids have translation pore to weave peptide in and out of membrane * so signal sequence DOES NOT GET REMVED\* green lines and protein woven in and out of membrane here, can still form those vesicles and this will ultimately fuse with plasma membrane to have final locatioN! * ex. in image, phospholipids that make up membrane will pinch off and fuse with next structure

Answer 16

it will be hte ER lumen side! not cytosol, can think of environment as Er lumen as synonymis with otuside of cell, environments are very very similar, whatever is cytosol will remain cytosol side!

Answer 17

* dont want fatty acids to stack up and pack together super tightly with saturated fatty acids very tight can rupture cell, want give with membranes so why cell will add cholesteroL!!! to make sure that those fatty acid tales do not pack together! * cholesterol is really a cool molecule, not only prevents them from sticking together and keeps if fluid, stabilizing this membrane on both ends, when it gets very hot stops it from melting/ keeps them in tact * at the same time, if very cold stops it from being too rigid b/c of tendency to stack up! so very very great buffer for membrane, does more than inc fluidity maintains that fluidity at all temperatures very similar to a buffer in a sense, stabilizes membrane and increases its fluidity

Answer 18

1. phospholipids 2. 2 choleserol- stabilizes membrane and increases fluidity 1. fatty acid tails cannot pack up as nice and neat because of cholesterol molecule getting in the way, keeps quite fluid 3. proteins- allow membrne to be dynamic structure, get things across, and allow movement of certain things across membrane but not all things, allows membrane to be a dynamic structure, can transport polar proteins etc 1. ex. channels can be selective only allowing a certain ion to get across, once charged ion can be allowed to get through membrane once shown, or don't even have molecules get across cell, bind to receptro G proteins then activating a whole chain of response inside of the cell to have your desired effect there 4. carbohydrates- serve as unique cell surface markers, **find only on extracellular side\*\*\*\* will not be finding them in intracellular side\***

Answer 19

properties that depend on the number of solute paritcles but not on their identity 4 colligative propertes: 1. freezing point, 2. vapor pressure, 3. boiling point, 4. osmotic pressure change on addition of solute: if have water then add salt to it, what will happen to these colligative properties- in case of Fp will always dec\*\* vapor pressure= decreased boilin gpoint= ALWAYS INC osmmotic pressure= always increased

Answer 20

definition: free ions in solution that are produced as a result of dissolving ionic substances\* so basically does it break apart when you throw it into something, does salt remain as nacl or break apart into sodium ions and chloride ions, can it ionize or not? **Ex. # of ions produced** NaCl --------\> Na+ and Cl- --------\> (produce 2 ions) CaCl2 ----\> Ca2+ and Cl- and Cl- ---\> 3 ions produced tied to electrolytes call it van hoff vector (i): the numbers of ions produced per molecule of an electrolyte for NaCl, i= 2; for CaCl2 i=3 so per molecule what is dissolved when through in water\*

Answer 21

* when starting to get colder solvent starts to form a nice orderly manner and starts to crystalize, need solvent molecles to arrange themselves in an orderly manner; but the second you throw in solute particles prevents them and interfers with the ability of solvent molecules to form nice orderly manner, to foce that alignment have to make it even colder becuase of solutes you added\* * colder temp is required to force alignment * ex. 1 kg of H20 by itself freezes at 0 C- no solutes added, zero degrees celsius start to form nice crystalized manner of wate rmolecules, when start to add in different types of solutes= Kf water = 1.9 C, if ad din 1 mole of glucose considering what van hoff factor will be with k= 1.9 what is the new freezing poitn for water containign 1 mole of glucose: =-1.9 degrees celsius is new freezing point, will have to make it even colder now if want solution to freeze! * know formula FP depression: change T_f= -k_f i m

Answer 22

new FP of sucrose when add to 1 kg of H20, sucrose is a dissachride! Succorse does not IONIZE!!! it doesn't break down into its individual components, so if had sucrose in even if dissachride still -1.9 C becuase van hoff factor i impacting colligative properties here\* they will ask you about a beaker solution that has sucrose or glucose added, which oen will freeze first?? trick question will freeze at exact same time because they both do not ionize\*\* so thinking back to previous slide doesn't depend on identity, depends if solutes can ionize\*

Answer 23

-3.8 C when salt roads when snows becuase adding salt to water on that road means it has eto be even colder to freeze that water that is located on those bridges and road ways!

Answer 24

when gas molecules come into equilbirum above surface of liquid, as starts to boil off comes into equilibrium how have vapor right above paritcular solution, if added glucose sucrose etc those solute particles will act as anchors, means if hold on creating interaction btw water molcules prevents them from evaporating, which means by adding in particular solutes the vapor pressure will go down because not as much will evaporate definition: gas molecules in equilbirum above hte surface of liquid; particles in solution act like "anchors" to solvent moelcules and prevent them from evaporating think molecules pushing up to become a gas\* Vapour pressure is a measure of the tendency of a material to change into the gaseous or vapour state, and it increases with temperature. The temperature at which the vapour pressure at the surface of a liquid becomes equal to the pressure exerted by the surroundings is called the boiling point of the liquid.

Answer 25

must inc kinetic energy of solvent so that they can escape their solute "anchors" and evaporate change in Tb= kb i m if kb of water= 0.5 C; boiling point of water all by itself is 100 C: -if add 1 mol of NaCL= bp is 101 C sodium chloride breaks down, two in for i value and how we get up to 101 C -if add 1 mol of glucose= still has van hoff factor of 1, so when add that in its 100.5 C\*\* why add salt to water becuase makes water boil faster\* not true, actually inc bp to 101 so nacl ensures cook pasta perfectly makes water hotter won't have it under cooked, makes pasta water taste better- SO NO IT WILL NOT LOWER BP

Answer 26

pie= i M R T so still affected by van hoff if can ionize\*\*

Answer 27

Equal solute inside and outside of cell for osmosis

Answer 28

Isotonic: Equal solute inside and outside of cell Hypertonic: more solute outside of cell. Water flows out of cell, shrinking it Hypotonic: less solute outside of cell. Water flows into cell, swelling or lysing it

Answer 29

Hypertonic: more solute outside of cell. Water flows out of cell, shrinking it

Answer 30

less solute outside of cell. Water flows into cell, swelling or lysing it

Answer 31

will go to side B! because it has more particles, van hoff ffactor will be 2 vs side A is 1 here! dont forget van hoff factor! need to know water will go towards NaCl becuase its whichever one has higher van hoff factor is where wate rwill go towards! sucrose i nthis case only has 1 mol of particles, sodium chloride would have 2 moels these two have same tonicity- those have to od with concentrations, they do start off with same concetrations but NaCl will ionize; so cant say one is hypertonic one hypo b/c they have hte same concetration! this is about osmosis!

Answer 32

**RULE: OSMOTIC PRESSURE= PARTICLE CONCENTRATION** when see this think always water driven toward more concentrated area\*\* all abotu particle concentraiton, high particle concentraiton ewater will be driven toward that side, low concetration will not be driven and will remain where it i sat driven where it is currently sitting! why need 0.9% NaCl in bags, if alter from that will take on too much water or lose water\*\*\* so need to make sure when giving IVs or any sort of injections you get this right otherwise big lawsuit on your hand!

Answer 33

1. pore- water has a pore, nonspecific holes in the membrane\* if smal enough to get through yiu are getting in 2. channels- highly specific! highly specific holes in the membrane, ex. Na channel only allows sodium to pass through, K can only pass through K channels, HIGHLY SPECIFIC HOLES IN MEMBRANE allow particular ions to move down concentration gradient 3. porters- not holes left open, way they will actually get molecule to move down concentration gradient, confirmational change to move molecule across, molecule binds to porter and by simply binding to porter causes it to change shape and as it changes shpae molecule will be dumped to the other side of membrane, once binds changes shape of porter and mvoes to the other side - undergo conformation change to mvoe molcules across "shape shifters"

Answer 34

moving moelcules AGAINST their concetration gradients! 2 types: 1. primary active transport- uses atp directly to move molecules against its concentration gradient ex. Na/K ATPase, in process of doing so costs pump 1 atp to do so\* 2. secondary active transport- using atp but indirectly! when say uses it indirectly means it usually takes advantage of concentration gradient set up by ATPase once use energy in order to drive these moelcules against this concentration gradient other molecules can take advantage of that

Answer 35

what is moving out= NA, 3 what is moving= K, 2 potassium broguht in "pumpKin" word out has 3 lettres in it, in has two letters in it out= 3 in =2 \*\*\* so remember pump K in\*\*\* out 3 Na, 2 in

Answer 36

B/c these are not moving against concnetrationg radient! movign down concenration gradient= so this is faciliated diffusion, seems like atp being used indirectly, **but IF NOT MOVING AGAINST ITS CONCENTRATION GRADIENT IT IS NOT ACTIVE TRANSPORT\*\*\*** ATPase causes us to lsoe 1 net ion otuside of cell here, means inside of cell becomes more negative! in addition to that we have a potassium link channel which always remains open, not effected by any sort of volages what so ever just constantly left open, allow potassium ot move down concetration gradient, lose another positive ion to the outside world making inside more negative **if answer q is it movign against concentration gradient or going down concentration gradient, then can distinguish active from passive\*\*\* this is an ex of faciliated diffusion**

Answer 37

1. maintains osmotic balance, in case of osmotic cell no rigid cell mebrane to prevent from taking on too mcuh water- problem we could take on too much water, if take on too much will ultimately lyse, so how we prevent ourselves from taking on too much water\*\*\* 1. by constantly moving ions across membrane here- always movign ions, prevents from taking on too much water prevents lysing and bursting how animal cells do this without cell wall move ions across memrbane to rpevent taking on too much water 2. establishes electrical gradient- all cells will be doing this, resting mmebrane potential approximately -70mV 3. sets up sodium graident for secondary active transport

Answer 38

- uses atp indirectly - relies on gradien set up by primary active transport - epithelial cells which take in nutrients and absorb can then dump into blood stream/connective tissue where it can then be delivered to the rest of the body\* - second that sodium and glcuose bind to transport, dump acros into inside of eptihelial cell, say had nice meal pretty sugary all that sugar is going by all that glucose going by in lumen, cant eat somethign sweet without salty, so salty snack has all that sodium passing by, one thing body wants to do is always wans to be picking up new glucose! doesnt want ot just let glucose get passed through, want to pick up and store it incase go through period of fasting, if not movign down concentrationg radient but sodium! actually does want to go into cells because they would be movign down their concentrationg radient so what happens if you bind both a sodium molecule and a glucose molecule that will case the cotransproter to change shapes adn dump molecules across the membrane, so when thsi happens dump molecules across the membrane adn notice that sodium is moving down its concentration gradient but glucose is essentially hitching a ride and movign against concentration gradient in this particular case; so in case of glucose still being pushed against cocnentration graident, using gradient established by primary active transprot to do this in case of glucose still psuehd against concenrationg radient, sodium moving down /constantly pumpign out sodium becuase of sodium atpase\*

Answer 39

* as alpha subunit dissociates and travels down to adenylyl cyclase and turns that protein on saying hey now operate you can now work! * adenylyl cyclase- takes atp and converts it into cyclic amp\*\*\*\* so in cell start to see rising levels of cyclic amp\*\* so levels start to drastically increase insdie of our cell * cAMP then goes around adn starts to ativate cAMP dependent\* protein kinases (kinase phosphoralytes\* ) so goes around phosphoralting all these diff enzymes * one way can regulate enzymes is add a phosphate group onto those enzymes or remvoe it, so if have this protein kinase going around adding phospahte groups turns on or off enzymes! so essentially changed enzyme activity in teh cell * ligand didn't ven have to come across our membrane here, just boudn ourselves to protein linked receptor and caused all these things to take place

Answer 40

ex. of g protein when ephinephrine is released glucose concentration is= release epin. when LOW blood glucose levels! so epinehprhine can act as ligand and bind to G protein linked receptor, step 1 in this case; causing gdp to dissociate off of alpha subunit 2. gtp binds to alpha subunit 3. once gtp is bound to alpha subunit, alpha subunit goes and turns on adenylyl cyclase takes atp and covnerst to camp 4. atp converted to camp 5. camp goes around and phiosphoraltes enzymes, truning on enzymes that cause us to break down glycogen stores inc amount doing in that case and turning off enzymes forming glycogen\*\*\* which makes sense if releasing ephinephrine as a result of low blood glucose levels, dont want to take little bit of glucose in blood will drop even lower, so want to break down glycogen stores so can get glcusoe up in blood

Answer 41

remember cyclic amp is second messenger!

Answer 42

1. cAMP is the second messenger 2. signal amplification-by binding one ephienphrien huge series of events, all that camp got made, going around and activating kinases, turning on glycogen rbeak down HUGE SIGNAL AMPLIFICATION 3. that means v fast but also very temporary- gtp which cases al[ha subunit to dissociate does hydrolysis, breaks down into gdp then everything is resent so it is temproary adn doesnt last forever! 4. exactly how peptides work off of secondary mesenger ssytems like insuliN! ex. type 1 diabetes have to keep injecting thesmelves with insulin, its v fast but temporary will not last forever!!

Answer 43

proteins: alpha and beta tubulin\*\* largest diameter by far think railroad system throughout cell, if need to be sending something somewhere else allow it to attach to microtiubules like if jumped on train takes you to wherever you want to go in the cell used in= mitoic spindle, intracellular trnasport, cilia and flagella \*only cell that has flagella cilia and flagella cross section 9+2 arrangement\*; 9 pairs of microtiubules inside have 2 pure number 1 pair\* dumb fucking name

Answer 44

proteins: made of actin- muscle contractions use this actin diameter: small \*smallest uses: muscle contraction, pseudopod formation, cell adhesions, cytokinesis, help cell move - thinest of 3, often found beneath cell ’s plasma membrane where they strengthen it and give it shape - quite strong even though thin and flexible take out if do not need to know-filamentous actin= F-actin, made up of globular actin G-actin monomers, rate limiting step in actin filament formation, once nucleation has occurred can -an monomers of actin will join together to form an actin polymer, then twist together to form an actin filament INVOLVED IN GROSS MOVEMENT OF CELL\*\* they are dynamic\* what we mean by that is they can lengthen and shorten very frequently, become longer in process known as actin polymerization\* and actin depolymerization = helps to move the cell, so one example of where these help gross movement of cell is during cell division, cell will be pinched in the way and then eventually separate into two different cells, microfilaments help cell make pinched shape and move to create two separate cells\* also in an amoeba cell, we will say that it is trying to capture that piece of food to do that has to extend its pseudopods in that direction and move it around that molecule, what helps pseudopods move those microfilaments\*

Answer 45

proteins: several different protein types so for that reason you dont have to know them diameter: medium uses: structural roles for skin and hair!

Answer 46

smooth ER= lipid and fatty acid synthesis, also detoxification of toxins rough ER is involved in translation of proteins\*

Answer 47

good for antibiotics! tetrachycline antibotic that works tha way, gos after prokaryoic ribosomes good becuase prokaryotic ribosomes are differnet than ukaryotic ribosomes which is good meaning tetrachyline doesnt destroy all of our ribsoomes doens't kil us, more sesletively tarcting bacteria infection eu 40S and 60S pro 30S and 50S

Answer 48

when translation begins it always begins on a ribosome in the cytosoplasm, always initally on free ribosome (ribosomes can be free or bound attached to membrane of ER) initially when ribosomal subunits come otgehter around mRNA always free ribosome translation starts to happen, polypeptide starts to poke out of hte ribosome and made, and sometimes hte beginning of the polypeptide has a signal sequence and that is a series of amino acids on the amino terminus which is the part that is translated first so poking out of the ribosome you would have a stretch of amino acids called signal sequence, if that emerges as the beginning of the polypeptide, the cell will pause translation adn move the ribosome over to the membrane of the ER\* and then when translation continues again, the polypeptide that is being produced is going to be pushed across the membrane into the interior lumen of the ER\* look in campbell page can see how ribsoome is going over to the ER can then see how protein polypeptide chain is going into lumen of ER pushed in there\* so the idea is that we are changing where the protien is going to end up and where hte protein is being targeted to\* and when there is a signal sequence hte significance of that is really that the protein is going to end up going through this pathway where it goes into inside of ER into vessicle called golgi, adn then to an another vesicle form tehre 3 places it can go, it cna be exoctyosed, release from cell; it can be inserted into plasma membrane, or it can be targeted to a lyzosome\* so summary version is when a polypeptide has a signal sequence means wil lbe inserted into cell membrane, exocytosed from cell or sent to a lyzosome\* so for an example if have pancreatic cell producing insulin a protein hormone and it has to be exoctyzed secreted from cell, insulin wuld be tranaslted haave signal sequence and go through this pathway; anytime cell has to make receptor that lvies in plasma membrane that protein also goes through this pathway, and then for the lyzosoome the proteins to think about would be the enzymes that do the work of lyzosomes\*\* in lyzsosome there are a bunch of enzymes that break things down using hydrolzysis enabled by low pH acid hydrolzyes anytime cell needs to make one of those the cell would use this pathway if no sequence something called nuclear localization signal, as name suggests means protein will be sent to the nucleus, there is another signal that tells the protein to go to the mitochondrian how the cell organizes it so that proteins go to teh right location after they are transalted if no signal sequence and no local nucelar sequence, if nothign special for mitochondira then protein ends up in ctyoplasm as degault location

Answer 49

evolution idea came from mitohcondira have doubel membrane around them, they have hteir own ribosomes and own dna which is circular dna so it really looks like an old prokaryote\*\*\* the evolutionary theory

Answer 50

passive -down concentration gradient active- up concentration gradient primary active transport- uses atp directly ex. Na+/ K+ ATPase how get inside of clel being net negative which is important when talked about acting potentials, bsaeline inside of cell is more negative because of sodium potassium pump, atp hydrolzyed to push Na and K against their gradients\* each movign toward the area where they are more concetrated, more Na outside of cell and more K inside of cell\*\*\*\* secondary active transport- uses an ion gradient created by hydrlyzing ATP, ex situation where we know sodium is very concentrated outside of the cell; sodium moving down its concentration gradient is a passive process, gradient wouldnt exist if not for sodium potassium pump and hydrolzysis of atp, when sodium goes back inside cell that is passive, it can drag somethign else with it like glucsoe which woudl then not be favorable on its own. Na+ is going down gradient but glucose is getting pulled up gradient\* and that is secondary active transprot because the energy of atp is being stored in the sodium gradient and then that is being used its an indirect use of atp\* so in this case where sodium and glucose are moving in the same direction across the membrane that is called symport\*\*

Answer 51

ex. Na+ and glucose move in same direction mean both go frm inside cell to outside cell

Answer 52

Na+ moves down gradient, X moves up gradient going in opposite directions sodium going from outside to inside, and X is going from inside to outside so that is also seocndary active transport but it is called antiport as opposed to symport\*

Answer 53

A. sucrose, b. RNA, c. short peptides, d. large anions, e. oxygen OXYGEN\*\*\* simple diffusion is always nonplar solutes, O2 and Co2 winners because small and nonpolar\*\*\*\* but if someting is nonpolra and large ex steroid hormones go right across membrane\*\* How would you expect this molecule to cross cellembrane- of nonpolar answer is diffusion even if it is huge\*\*\*\* really mostly about polarity\*

Answer 54

d. entrance into the ER \* key idea once a protein is in teh ER it does not cross a membrane again, it doesn't cross the membrane again it in the ER then vesicle then golgi.... if look at picture purple peptide pushed across emmberna into blue spaceof ER has to move through membrane that is where protein crosses a membrane; translation is happening pushed through membrane into ER then in vesicle going to golig or vesicle going to plasma membrane or lysozome\* CANNOT PASS MEMBRANE ON ITS OWN, proteins are not hydriphobic have a lot of polar groups so they have to be shoved across that membrane during translation\*\* then from there if they are suppose to be secreted from teh cell the system is set up so they do no have to go through a membrane again, enclosed in a vesicle that meges with golgi then viescle merges with plasma membrane- all this budding, exocytosis very challenging for something large and partly polar to get through membrane\* membrane bubbles around\*

Answer 55

answer is b and c Humans have no cell wall! Nuclear envelope only in Eu, bacteria do not have it so somethign that would be a disaster for us. we are looking for something here that attacks prokaryots but not structures in eu, bacteria has cell walls so b is good Then ribosomes are good becuase we have ribosomes and bacteria have ribosomes but htey are different so could traget!

Answer 56

c. reduces in swelling in certain cells b. is opposite direction of what we are talking about not swelling shrinking\*\* hypertonic= more solute outside, into the blood stream but outside of the cells\*\*\* KEY water wants to rush into the salty area\*\* so if that happens water going from cell out the cell will SHRINK\*\*\* losing some of its volume

Answer 57

c. \*secreted proteins= pathway where protein made on bound ribosome, then goes to ER then goes to golgi in a vesicle, we are NOT talking about a protein made on free ribosome still on cytoplasm loose so anything else that would happen to it is in ER or golgi, or maybe in vesicle, only one of those optiosn given as a choice is ER lumen because it is seceted, being translated and then immediately pushed into interior of ER then goes to golgi then out of cell so any changes that happen post translational modifications that happen along the way, matter where is the protein where those modifications could occur? modifications could occur right in ER, also modifications in golgi extra sugar groups get attached somehwere alogn pathway that protein is taking in its way to being secreted.

Answer 58

RBC= do have a nucleus in precursor form, as mature and become true red blood cells lose nucleus and lose mitocondira becuase become specialzied to carry as much emoglobin as posible they become packed with hemoglobiN! white blood cells have different purpose in life, nucleus, dna and mitohcondira, much more normal cells then mature red blood cells are RBC are an eception to EU cells in general, also an exception among other types of blood cells just hte exception\*

Answer 59

30S + 50 S= 70 S= prokaryote 40S + 60 S= 80 S euk what these numbers represnt how they settle out in centrigute S- units of seburge on side of centrifuge how it si callibrated, bigger and heavier things fall more in centritube- corresponds to larger number of S units what these numebrs mean, take small prok ribosome spin in centriuge it will stop at 30 S, take large subunit from prokaryote will stop at 50S level take whole ribosome large and small subunits stuck together and spin it, will settle to the 70S level\*\* so not a linear relationship btw mass and S value units for where the things settles\*\* not normal addition has to do with the behavior of things in a centrifuge\*\*\* why can get 40+60 = 80 on Eu side too its measures of what happens to each of these things if put them in centrifuge tube\* in cytoplasm had normal size of 40 and 60

Answer 60

a single lipid bilayer

Answer 61

which is where ribosomes are assembld from ribosomal RNA and protein

Answer 62

ribosomes are large RNA- protein complexes that mediate protein synthesis in prokaryotic and eukaryotic cells

Answer 63

rough and smooth- which are highly invaginated membrane structures that sequester ribosomes for protein synthesis ## Footnote Inside of the ROUGH ER, the proteins fold and undergo modifications sugh as the addition of carbohydrate side chains. These modified proteins will be incorporated into cellular membranes--the membrane of the Er or those of other organelles-or secreted from the cell The smooth ER makes phospholipids for other cellular membranes, which are transported when the vesicle forms. Invatinated means: FOLDS INWARD does rough ER make phospholipids? NO, The smooth ER also makes phospholipids for other cellular membranes, which are transported when the vesicle forms.? - no smooth er is all lipids incluuding phospholipids Invagination is the infolding of one part within another part of a structure, a folding that creates a pocket. The term, originally used in embryology, has been adopted in other disciplines as well.

Answer 64

is a membranous structure involved in protein translocation within the cell and in facilitating protein secreation at hte plasma membrane When vesicles bud off from the ER, where do they go? Before reaching their final destination, the lipids and proteins in the transport vesicles need to be sorted, packaged, and tagged so that they wind up in the right place. This sorting, tagging, packaging, and distribution takes place in the Golgi apparatus (Golgi body), an organelle made up of flattened discs of membrane. THINK MAIL CENTER/UPS The receiving side of the Golgi apparatus is called the cis face and the opposite side is called the trans face. Transport vesicles from the ER travel to the cis face, fuse with it, and empty their contents into the lumen of the Golgi apparatus. As proteins and lipids travel through the Golgi, they undergo further modifications. Short chains of sugar molecules might be added or removed, or phosphate groups attached as tags. Carbohydrate processing is shown in the diagram as the gain and loss of branches on the purple carbohydrate group attached to the protein. Finally, the modified proteins are sorted (based on markers such as amino acid sequences and chemical tags) and packaged into vesicles that bud from the trans face of the Golgi. Some of these vesicles deliver their contents to other parts of the cell where they will be used, such as the lysosome or vacuole. Others fuse with the plasma membrane, delivering membrane-anchored proteins that function there and releasing secreted proteins outside the cell. Cells that secrete many proteins—such as salivary gland cells that secrete digestive enzymes, or cells of the immune system that secrete antibodies—have many Golgi stacks.

Answer 65

bind cells together facilitates adhesion but different than integrins Cadherin: Cell-Cell think Cs! Also cadherins are calcium dependent and integrins aren't

Answer 66

Integrins bind to ECM, specficially collagen and fibronectin, while Cadherins just bind cells together. facilitate adhesion Integrins anchor the cell to the extracellular matrix. In addition, they help it sense its environment. They can detect both chemical and mechanical cues from the extracellular matrix and trigger signaling pathways in response. Blood clotting provides another example of communication between cells and the extracellular matrix. When the cells lining a blood vessel are damaged, they display a protein receptor called tissue factor. When tissue factor binds to a molecule present in the extracellular matrix, it triggers a range of responses that reduce blood loss. For instance, it causes platelets to stick to the wall of the damaged blood vessel and stimulates them to produce clotting factors.

Answer 67

The first major branch point comes shortly after translation starts. At this point, the protein will either remain in the cytosol for the rest of translation, or be fed into the endoplasmic reticulum (ER) as it is translated. Proteins are fed into the ER during translation if they have an amino sequence **called a signal peptide.** In general, proteins bound for organelles in the endomembrane system (such as the ER, Golgi apparatus, and lysosome) or for the exterior of the cell must enter the ER at this stage. Proteins that do not have a signal peptide stay in the cytosol for the rest of translation. If they lack other "address labels," they'll stay in the cytosol permanently. However, if they have the right labels, they can be sent to the mitochondria, chloroplasts, peroxisomes, or nucleus after translation.

Answer 68

Proteins destined for any part of the endomembrane system (or the outside of the cell) are brought to the ER during translation and fed in as they're made. The signal peptide that sends a protein into the endoplasmic reticulum during translation is a series of hydrophobic (“water-fearing”) amino acids, usually found near the beginning (N-terminus) of the protein. When this sequence sticks out of the ribosome, it’s recognized by a protein complex called the signal-recognition particle (SRP), which takes the ribosome to the ER. There, the ribosome feeds its amino acid chain into the ER lumen (interior) as it's made. WHAT IS IMPORTANT IS SIGNAL PEPTIDE IS AT THE BEGINNING BECAUSE RIBOSOME MOVES TO ER BEFORE TRANSLATION IS FINISHED\*\* NEED TO KNOW AT N BEGINNING OF PROTEIN\*\*\* In some cases, the signal peptide is snipped off during translation and the finished protein is released into the interior of the ER (the lumen). In other cases, the signal peptide or another stretch of hydrophobic amino acids gets embedded in the ER membrane. This creates a transmembrane (membrane-crossing) segment that anchors the protein to the membrane. for image: https://www.khanacademy.org/science/biology/gene-expression-central-dogma/translation-polypeptides/a/protein-targeting-and-traffic

Answer 69

In the ER, proteins fold into their correct shapes, and may also get sugar groups attached to them. Most proteins are then transported to the Golgi apparatus in membrane vesicles. Some proteins, however, need to stay in the ER and do their jobs there. These proteins have amino acid tags that ensure they are shipped back to the ER if they "escape" into the Golgi. In the Golgi apparatus, proteins may undergo more modifications (such as addition of sugar groups) and before going on to their final destinations. These destinations include lysosomes, the plasma membrane, and the cell exterior. Some proteins need to do their jobs in the Golgi (are "Golgi-resident), and a variety of molecular signals, including amino acid tags and structural features, are used to keep them there or bring them back^33cubed. If they don't have any specific tags, proteins are sent from the Golgi to the cell surface, where they’re secreted to the cell exterior (if they’re free-floating) or delivered to the plasma membrane (if they’re membrane-embedded). This default pathway is shown in the diagram above for a membrane protein, colored in green, that bears sugar groups, colored in purple. Proteins are shipped to other destinations if they contain the right molecular labels. For example, proteins destined for the lysosome have a molecular tag consisting of a sugar with a phosphate group attached. In the Golgi apparatus, proteins with this tag are sorted into vesicles bound for the lysosome.

Answer 70

Yes, they do! However, only some of the proteins found in these organelles are made using the internal ribosomes. Most proteins are actually made on ribosomes in the cytosol and imported to the mitochondria or chloroplasts after translation.

Answer 71

First: The endomembrane system (endo- = “within”) is a group of membranes and organelles in eukaryotic cells that works together to modify, package, and transport lipids and proteins. It includes a variety of organelles, such as the nuclear envelope, lysosomes, the endoplasmic reticulum and Golgi apparatus. Although it's not technically inside the cell, **the plasma membrane is also part of the endomembrane system.** As we'll see, the plasma membrane interacts with the other endomembrane organelles, and it's the site where secreted proteins (like the pancreatic enzymes in the intro) are exported. Important note: the endomembrane system does not include mitochondria or peroxisomes. Proteins that are made in the cytosol (don't enter ER during translation) may stay permanently in the cytosol. However, they may also be shipped to other, non-endomembrane destinations in the cell. For instance, proteins bound for the mitochondria, peroxisomes, and nucleus are usually made in the cytosol and delivered after translation is complete. To be delivered to one of these organelles after translation, a protein must contain a specific amino acid "address label." The label is recognized by other proteins in the cell, which help transport the protein to the right destination. As an example, let's consider delivery to the peroxisome, an organelle involved in detoxification. Proteins needed in the peroxisome have a specific sequence of amino acids called a peroxisomal targeting signal. The classic signal consists of just three amino acids, serine-lysine-leucine, found at the very end (C-terminus) of a protein. This pattern of amino acids is recognized by a helper protein in the cytosol, which brings the protein to the peroxisome. Mitochondrial, chloroplast, and nuclear targeting are generally similar to peroxisomal targeting. That is, a certain amino acid sequence sends the protein to its target organelle (or a compartment inside that organelle). However, the nature of the "address labels" is different in each case.

Answer 72

* in contrast to microtubules and microfilaments, made up of very different proteins strung together into different polymers twisted together to make intermediate filaments * pretty much permanent which is what is different than other two, once these are made by cell they stay put as opposed to microtubules and microfilaments that we explained are dynamic\* they constantly change depending on the needs of the cell\* * so what do intermediate filaments do= they provide structural support for the cell\*\* they resist mechanical stress\* like springs of a mattress\*\*\* thanks to size so intermediate filaments act in same way!

Answer 73

Antiporters move two different ions or molecules in opposite directions across a membrane. Here, we know that sodium’s concentration gradient is used to power the movement of calcium. Since sodium tends to be far more highly concentrated outside the cell (due to the action of the sodium-potassium pump), it will flow inward when allowed to move down its gradient. Since Na+ and Ca2+ move in different directions, calcium ions must exit the cell.

Answer 74

A. I and II This answer choice is incorrect B. II and IV This answer choice is incorrect C. III and IV Vitamin A is made from a precursor, beta-carotene, which is a carotenoid. However, vitamin A is fat-soluble. D. I, II, and III D is correct. Vitamin C and the B complex vitamins are the two groups of vitamin that are water-soluble. Vitamin C, also known as ascorbic acid, can function as an antioxidant; it also serves as a cofactor in many enzymatic reactions, including collagen synthesis. The many different vitamin B members can function either as prosthetic groups, such as biotin, or as coenzymes, such as folic acid.