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Cytology
Histology
| Question | Answer |
|---|---|
| What does a chaotropic agent do? | removes membrane bound proteins from eukaryotic cells. |
| what are the three main types of membrane proteins? | transport proteins, receptors/signaling proteins, and structural/anchoring proteins. Some proteins will belong to more than one of these categories. |
| Describe the states of phosphorylation of the Na/K pump. | in its non phospyorylated form, the pump binds an ATP molecule and 3 sodium molecules, binding of the sodium induces a conformational change that transfers a phosphate group from ATP to a aspirate residue on the pump and moves the sodium ions out of the c |
| What ions is the acetylcholine receptor a channel for? | na and k |
| Can anchoring proteins also function as signaling proteins? | yes |
| Can integral membrane proteins be seen in thin slice electron microscopy? | no, they must be freeze fractured and coated with a heavy metal. |
| Name the three cytoskeleton systems. | actin (thin-filament), microtubule, and intermediate. |
| What are the two forms of actin? | soluble, monomeric and globular G-actin and F-actin which is a double stranded helical filament of G-actin. 7nm in diameter. |
| Which pole of the F-actin filament polymerizes faster ? | the + pole |
| What motor is associated with actin filaments? | |
| Towards which pole does myosin move? | towards the + pole of actin filaments. |
| What is the only myosin that forms bi-polar filaments? | type II myosin, conventional myosin |
| What is the only conventional myosin? | type II, all others are non-conventional |
| What type of myosin may be involved with shaping membranes? What characteristic allows it to accomplish this? | type I myosin has a short tail and frequently contains a lipid binding area or a non-contractile actin binding domain. DO NOT FORM DIMERS. |
| Describe the myosin responsible for vesicle movement along the cytoskeleton. | type V myosin has a short tail which forms dimmers. The tails interact with vesicles and the heads with actin filaments. |
| What would a mutation in type VII myosin lead to? | deafness |
| Describe the steps involved with actin/myosin powerstroke. | binding of ATP causes the myosin head to release from the F-actin. Hydrolysis of the ATP results in movement of the myosin head (cocking) and a weak binding of the head to the F-actin filament. Release of the phosphate causes the powers stroke; tight b |
| What are the differences in regulation and execution of the power stroke contraction between muscle cells and non-muscle / smooth muscle cells? | Both depend on Ca, however in muscle cells the Ca binds to tropomyosin and troponin inducing a conformational change that exposes the actin filament to the myosin head. In non-muscle and smooth muscle cells, the Ca stimulates myosin light chain Kinases t |
| How would you increase the viscosity of a cell’s cytoplasm? | increase the activity of G actin sequestering agents. |
| Inhibition of actin sequestering proteins may lead to what? Why? | increased F-actin polymeration because F-actin and G-actin are in equilibrium. |
| What is nucleation? | it is the formation of a trimer of actin molecules. |
| What are several ways to modify the levels of actin in cells? | actin sequestering, increase nucleation, cleave an F-actin, bind to the sides of F-actin, crosslink the F-actin, crosslink in parallel arrays, and cap the F-actin. |
| Why are they actin filaments in muscles so long lived? | capped F-actin ends. |
| What form of actin filament is found in microvilli? Where else is this form found? | crosslinked parallel arrays. Also in filopodia and stress fibers. |
| What cytoskeletal system is involved in organelle and vesicle movement, chromosome movement during mitosis/meiosis and beating cilia/flagella? | microtubules. |
| Describe the structure of a microtubule. | dimer of a-tubulin and B-tubulin polymerize head to tail to form protofilaments which align laterally to form cylinders of 13 protofilaments. |
| Which pole of which cytoskeletal system is associated with the centriole and pericentriolar “microtubule organizing center”? | the negative pole of microtubules. |
| Would the “+” pole of a microtubule be found closer to the tip or base of a cilia or flagellum? | ”+” pole of the microtubule is near the tip of the cilia and flagellum. |
| What motor protein moves towards the “-“ pole of microtubules? | dyneins |
| What principal fnxs do deneins serve? | transport vesicles towards negative pole and drive flgellar and ciliary beating. |
| Which motor molecules drive towards the “+” pole of microtubules? | kinesins |
| How are kinesins similar to myosins? | they consist of a relatively fixed head and a variable tail and are powered by ATP. |
| What higher order structures do actin filaments form? | stress fibers and microvilli. |
| How do the number of “A” tubules and “B” tubules molecules compare in an axoneme? | there are 13 A and only 9 or 10 B tubules in the doublet. |
| What structures do microtubule-associated proteins attach to in an axoneme? | they connect doublets to doublets and doubles to the central microtubules. |
| What is different about an primary cilia? | it contains no central doublet and does not beat. |
| What structure provides the nucleation site for an axoneme? | the basal body |
| What are the primary structural differences between a centiole and an axoneme? | centriole has 9 triplets of shorter microtubules in a cartwheel formation and lacks the central microtubules. |
| What essentially is the centrosome? | the microtubule organizing centers. |
| What is at the negative pole of microtubules in the pericentriolar material? | y-tubulin |
| what is the primary role of centrioles in mitosis? | recruit the MTOC from which astral microtubules can grow and establish the axis for the mitotic spindle. |
| What region of a chromosome to astral microtubules attach to? | the kinetochore |
| Where to microtubules move chromosomes to before division? | the metaphase plate |
| What motor proteins are involved in separation of daughter chromatids? | dyneins and kinesins |
| How does taxol work? | inhibits microtubule polymerization |
| What is the diameter of intermediate filaments? | less than 10 nanometers. |
| What is the diameter of microtubules? | 24nm |
| Describe the structure of an intermediate filament. | alpha helical monomers form coiled-coil dimmers which align into side-to-side tetramers. They bond in an antiparallell fassion, therefore no polarity. |
| Which cytoskeleton system is suspected to have tensile strength responsibilities? | intermediafilaments. |
| Which sytoskeleton system has no motor proteins? Why? | intermediate because no polarity |
| What are the four classes of intermediate filaments? | lamins, keratins, vimentin-like filaments and neurofilaments. |
| What is the only intermediate filament associated with all cell types? | lamins |
| Where are lamins found? | inner surface of the nuclear membrane. |
| ____________ of the __________ during ___________ leads to breakdown of the _________. | phosphorylation of the lamins during mitosis leads to breakdown of the nuclear membrane. |
| Where aer keratins found? | in epithelial cells? |
| Do all epithelial cells have similar intermediate filaments? | no, the keratins are specific to the type of epithelium. |
| What constitutes the dimer of keratins? | 1 acidic monomer and 1 basic monomer. |
| What is the intermediate filament produced by fibroblasts? | vimentin |
| What tissue is likely to contain vimentin? | connective tissue |
| What is the intermediate filament of muscle? | |
| Is vimentin found in muscle? | no, found in connective tissues |
| Glial fibrilary acidic proteins are found where? | glial support cells of CNS |
| What unique structural fiber is found in glia cells? | |
| What intermediate fibers are formed from 3 closely related proteins which can co-polymerize? | neurofilaments |
| What intermediate filament has variable spacing between parallel bundles? | neurofilaments |
| What is the principal protein comprising the membrane cytoskeleton? | spectrin |
| What is the structure of the membrane cytoskeleton protein? | it is spectrin, an alpha helical molecule that forms long tetramers. |
| How does spectrin form a network around the cellular membrane? | by binding to short actin filaments, peripheral proteins and integral proteins. |
| What is the structural cause of spherocytosis? | mutation in spectrin gene causes spherical and fragile RBCs |
| What is the specific membrane cytoskeletal protein of muscle cells? | dysprophin |
| A mutation to dystrophin may cause what? | muscular dystrophy |
| Can Myosin II bind directly to cellular membrane proteins? | No, but Type I can, and lipids. |
| What class of proteins are involved in cell-cell transmembrane binding? | cadherins |
| In general, what are the different connection points of cadherins? | they are transmembrane molecules which bind to the extracellular domain of other extracellular molecules and to peripheral proteins on their cytoplasmic domain. |
| What types of structures combine to form a zonulae adherens? | cadherins and actin filaments. Aka, adherins junctions. |
| What type of structures combine to form a desmosome? | cadherins and intermediate filaments. |
| Only 1 in is in the cell, 2 ins and your out.. | lamin, cytoplasm, laminins extracellular |
| Integrins form which two types of extracellular structures? | focal adhesions and hemidesmosomes |
| What is the difference between desmosomes and hemidesmosomes? | desmosomes are formed between cadherins and intermediate filaments while hemidesmosomes are formed between integrins and intermediate filaments |
| Hemidesmosomes create cell to cell connections, t/f? | false. |
| What are two common extracellular matrix proteins? | lamININs and fibronectin |
| Are inclusions light microscope visible? Are they organelles? Name some. | yes and no. they are not membrane bound…could be free ribosomes or glycogen particles. |
| What protein coat is found on plasma membranes, on the trans-Golgi network and on membranes derived from these organelles? | clathrin |
| What protein coat is found on the Golgi apparatus? | COP-I |
| What protein coat is found on the endoplasmic reticulum? | COP-II |
| How are caveolea vesicles different from other membrane vesicles? | the motive force bending the membrane is supplied by an integral protein, not a peripheral protein coat. |
| What two proteins are responsible for vesicle binding its destination? | v-SNAREs on the vesicle and t-SNAREs on the target. |
| t/f SNAREs come in specific pairs. | true |
| what comprises the 70S particle? | rRNA and a large number of proteins. Two busunits form the larger (70S) particle. About the same diameter as microtubules. |
| Define a polysome | a cluster of ribosomes |
| What is the charge on RNA? | negative |
| Do ribosomes stain with H or E? | hematoxylin |
| Are ribosomes visible in the light microscope? | no, but clusters stain with basic dyes |
| Free ribosomes synthesize what types of proteins? | cytoplasm, nuclear proteins, peroxisomal proteins and some mitochondrial proteins. |
| Where might mitochondrial proteins have been synthesized? | cytoplasm and within the mitochondria |
| RER-bound ribosomes synthesize proteins destined for where? | plasma membrane, lysosomes, and secretion |
| What is the organelle order for protein secretion? | ER, Golgi, plasma membrane |
| What are structural differences between RER and SER? | SER tubular and few ribosomes while RER forms cisternea and is covered in ribosomes. THEY ARE CONNECTED. |
| What organelle uses what compound for oxidizing what type of compounds? | SER uses cytochrome P450 enzymes to oxidize aromatic compounds |
| Why is SER prominent in the adrenal gland? | becuase SER is prominent in steroid synthesizing cells |
| What might a habitual barbiturate user show histologically? | increased SER in liver cells |
| What structure in muscle cells is similar to a tubular organelle seen in steroid synthesizing cells and what function do the two share? | the sarcoplasmic reticulum is similar to SER and they both store Ca. |
| How are proteins being synthesized on free ribosomes but destined for secretion halted? | a string of hydrophobic amino-acids are bound so the SRP or signal recognition particle formed by proteins and RNA on the ribosome |
| What induces RER pore formation during protein synthesis? | the ribosome/SRP/SRP-receptor interaction |
| What is co-translational transport? | after the SPR/SRP-receptor have released from the ribosome/SRP/SRP-receptor complex, RER ribosomes resume synthesis of the nascent protein through a channel formed by RER proteins. |
| What is the relationship of RER channel proteins to integral protein synthesis? | hydrophobic start and stop sequences in the mRNA induce opening and closing of the channel wall, allowing for synthesized proteins to embed in RER membrane |
| Where do the first steps in glycosylation of secreted and transmembrane proteins happen? | in the RER, later steps occur in the Golgi |
| What is the only code that would prevent a protein from leaving the RER? | KDEL “ER-retention” |
| The cis-Golgi network is related to what organelle? | the RER |
| What happens in the Golgi? | modification of the carbohydrate portion of the glycoprotein |
| Why would you see a COP-I coated vesicle between the Golgi and RER? | retrograde transport from Golgi to RER |
| What is one of the principal sorting signals for lysosome bound vesicles? | mannose-6-phosphate |
| What is the mutated enzyme I-cell disease? | N-acetylglucoseamine-phospotransferase |
| What are the stages/types of lysosomes? | primary, secondary, lipofucin granules (residual bodies) |
| How would residual bodies appear in a person with I-cell disease? | they wouldn’t appear at all because no primary lysosomes |
| What might small vesicles in the trans-Golgi network be destined for? | secretion |
| What steps can be taken to mature a secretory vesicle? | small molecule transport, pinch of excess membrane, proteolytic processing of secretory product. |
| What happens to proteins that lack a sorting signal in the Golgi app? | they are secreted via the constitutive pathway. |
| Is a sorting signal necessary for constitutive secretion? | no, but some proteins signal for apical or basolateral secretion |
| What is transcytosis? | use of the endocytic pathway to move material across the cell. Can be retrograde. |
| What are the stops along the endocytic pathway? | endocytic vesicle, early endosome, multivesicular bodies and late endosomes, lysosomes (from where? GOLGI) |
| What generates the invaginating forces for phagocytosis? | |
| What generates the invaginating forces for pinocytosis? | clathrin or caveolin |
| Lamellipodia and pseudopds do what? How? | they use the actin cytoskeleton system to engulf membrane bound bacteria or dying cells |
| What are clathrin coated vesicles associated with? | trans-Golgi, endosomes, and plasma membrane (this is correct) |
| What do adaptins insert between? | clathrin molecules and transmembrane receptors for hormones and nutrients. |
| Hormones have bound to receptors on a cell’s pitted surface. What caused the pitting and what will finish it off? | clathrin bound to adaptin bound to the receptor started it, dynamin will complete the formation of an endocytic vesicle from the plasma membrane pit |
| What coating protein is associated with “receptor mediated endocytosis?” | clathrin |
| Lipid rafts (cholesterol rich) are associated with what invaginating force molecule? | |
| Where are clathrin and caveolin located? | clathrin is a protein coat, caveolin is in integral membrane protein |
| Dynamin has just pinched off an uncoated plasma membrane vesicle, how is this possible? | likely a caveolea formed by caveolin |
| Have early endosomes just been pinocytosed? | no they are the first stop and sorting station for endocytic vesicles. |
| Material destined for destruction is sent to _______ endosomes while material not destined for destruction is sent to _____. | late endosomes and the plasma membrane |
| Early endosomes use ____ to sort ligands and their receptors into ________ and ________ respectively. | Early endosomes use pH to sort ligands and their receptors into late endosomes and plasma membrane bound vesicles respectively |
| Where are late endosomes headed? | to lysosomes |
| The ____ level in the ______ is sufficient to remove iron from _________, but not ________ from _______. | The pH level in the early endosome is sufficient to remove iron from transferrin but not apotransferrin from its receptor. |
| A cell’s cytoplasmic contents are being digested. | What is this organelle called? |
| In what type of cells may cristea be tubular? | cells specializing in steroid synthesis |
| How does the number and depth of cristea relate to their function? | increased numbers with greater depth represent cells with greater ATP demands…muscles |
| What are some residents of mitochondrial matrix? | kreb’s cycle enzymes, mitochondrial DNA and ribosomes, Ca binding proteins |
| Mitochondrial DNA is _____ and encodes for _______, _________, and _____________. | Mitochondrial DNA is circular and encodes for rRNA, tRNA and 13 proteins. |
| Post-translationally, cytoplasmic mitochondrial proteins are bound to _______ in what state? | bound to chaperones in an unfolded state |
| Proteins destined for the inner mitochondrial membrane are always fed through the IMM into the matrix before returning to the IMM t/f. | false, some have a stop signal that keeps them in the IMM |
| What is the enzyme associated with peroxisomes? | catalase |
| What is the end product of ethanol oxidation in __________ . | the end product ethanol oxidation in peroxisomes is hydrogen peroxide and free radicals. |
| What enzyme degrades the end products of ethanol oxidation? Where? | catalase in peroxisomes |
| What three enzymatic reactions are unique to peroxisomes? | B-oxidation of long chain fatty acids, a-oxidation of phytanic (titanic) acid, and synthesis of plasmolagen |
| Adrenoleukodystrophy is caused by? | a defect in b-oxidation of long chain fatty acids in peroxisomes |
| Refsum’s disease is caused by? | a defect in a-oxidation of phytanic acid |
| Zellweger syndrome is caused by? | a defect in plasmolagen synthesis in peroxisomes |
| Was Refsum the captain of the titanic? | yes, disruption of a-oxidation of phytanic acid causes refsum’s dz |
| What class of proteins are responsible for peroxisome transport? | the peroxins |
| Are peroxisomal matrix and membrane proteins use the same signal to bind to _________. | false, they use different signals to bind to peroxins |
| Protein-DNA complex | chromatin |
| What are the components of an histone? | two each of H2A, H2B, H3, H4 |
| What is the diameter of DNA “beads on a sting?” | 11nm |
| What is wrapped around H1? | a fiber of necleosomes with a diameter of 30nm |
| What is the smallest resolved formation of DNA by electron micrographs? | 30nm fibers |
| A cell is highly metabolically active. How would the chromatin appear? Why? | light staining euchromatic bc it is transcriptionally active. |
| How does heterochromatin appear compared to euchromatin? | heterochromatin is darker staining and located on the periphery why euchromatin is lighter staining and centrally located. |
| What is the nuceuolus? How does it appear? | the nucleolus is the ribosomal RNA transcribing region located centrally to some chromatin but not in the center of the nucleus. Stains darkly. Oval or ovoid in shape has distinct regions. |
| What three levels do nuclear pores penetrate? | outer nuclear membrane (continuous with ER membrane), perinuclear space (continuous with ER lumen) and inner nuclear membrane. |
| Nuclear pore inport/export is mediated by _____/_____ ________ and powered by _____. | Nuclear pore inport/export is mediated by inport/export signals and powered by GTP |
| Binding to a nuclear pore involves binding to this “ase.” | GTPase |
| What are transcription factors? | they are proteins that bind to DNA to cause transcription of the gene to which the protein has bound. |
| Histones bind DNA into chromatin. Do they also bind chromatin to lamins? | no, non-histone proteins do. |
| The molecules of a lamin meshwork were just phosphorylated, is it going to decompose or reassemble? | phosphortylating the lamin meshwork will lead to depolymerization and breakdown of the nuclear membrane. |
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natejansen
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