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MIR Deck 12 Quiz > CTO Quiz #1 > Flashcards

CTO Quiz #1 Flashcards

1
Q

What is the chemical composition of the lipid part of the cell membrane? What is the most common lipid?

A

They are phospholipids (two fatty acid chains attached to a glycerol molecule that is, in turn, attached to a polar side chain by a phosphate group). The most common type is Phosphatidylcholine.

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2
Q

What determines whether something will pass the lipid bilayer?

A

The ability to cross the lipid bilayer is dependent on lipid solubility and size of the molecule. Things that are highly fat soluble and small cross the membrane. Large molecules and charged particles (such as ions) do not. Small polar molecules are in between.

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3
Q

What factors stiffen the plasma membrane? What makes it more fluid?

A

Cholesterol in the membrane functions to stiffen it up, while the unsaturation of the phosopholipids makes the layer fluid.

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4
Q

What enzymes are responsible for distributing phospholipids in the correct side of the membrane?

A

Flipases function to selectively transfer certain lipids from one side of the bilayer to the other.

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5
Q

Where are new membranes made?

A

Golgi and sER are responsible for making new membrane.

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6
Q

What is the role of the Golgi in creation of membrane?

A

The Golgi will glycosylate some membrane phosphlipids (glycolipid) and will also glycosylate proteins in the membrane.

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7
Q

When vesicles of membrane are added to the plasma membrane, which side winds up facing the outside of the cell?

A

The side inside the vesicle will be on the outer surface of the plasma membrane lipid bilayer.

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8
Q

What is the role of the glycocalyx?

A

Glycocalyx has cell recognition and protective properties.

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9
Q

What are the functional types of transmembrane proteins? (5)

A

Transporters, anchors, receptors, enzymes and pumps.

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10
Q

What is the role of integrins?

A

These are anchor proteins that attach cytoskeletal elements to extracellular elements.

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11
Q

Are there more proteins associated with the inner or outer leaflet of the lipid bilayer? Why?

A

There are more attached to the inner leaflet since many of the proteins attached to that side have enzymatic or regulatory functions within the cell.

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12
Q

What is a lipid raft and why is it important?

A

A lipid raft is a domain within the cell membrane within which are clustered proteins of complimentary function. This allows them to function efficiently.

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13
Q

What is the most common shape of protein that permits it to exist within the plasmalemma?

A

Proteins that span the plasma membrane or that insinuate themselves in one side of the membrane usually have an alpha-helical structure.

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14
Q

What functional type of protein typically has multiple transmembrane spanning regions? Why do they do this?

A

Ion channels create fluid-filled (hydrated) pores through which ions can cross the membrane.

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15
Q

What are the two types of endocytosis?

A

Pinocytosis and phagocytosis.

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16
Q

What are the two types of pinocytosis?

A

Receptor independent and receptor mediated, clathrin dependent pinocytosis.

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17
Q

What is constitutive pinocytosis?

A

This is a continuous process of pinocytosis that occurs in the absence of any outside stimulus. It is a way for the cell to sample it’s environment. This can be clathrin dependent or independent.

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18
Q

Describe the process for Receptor Mediated Endocytosis.

A

The receptor binds to adaptin (AP-2). Adaptin binds to clathrin. The triskelion form of clathrin assembles into a coated pit. The coated pit has a narrow neck that pinches off by dynamin (which uses GTP).

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19
Q

What happens to clathrin and adaptin?

A

Clathrin and adaptin detach from the coated vesicle and are recycled. There are several molecules in the cell that promote this disassociation.

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20
Q

What is the localizing signal protein that allows recognition of the vesicle by the endosome?

A

The Rab5 protein is recognized by a receptor protein on the surface of the endosome and SNARE proteins interact to dock the vesicle.

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21
Q

Where do you find acid hydrolases in the cell?

A

Acid hydrolases are in the late endosome and the lysosome.

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22
Q

What is the pH in the early endosome? In the late endosome? In the lysosome?

A

Early Endosome: pH 6; Late Endosome: pH 5.5-6; Lysosome: pH 5.

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23
Q

What causes the decreased pH in the endosomes and lysosome?

A

There are proton pumps in the membranes.

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24
Q

How are pseudopods formed in order to phagocytose particles or bacteria?

A

Receptor activation results in assembly of actin in order to push out the membrane and cytoplasm to engulf particles.

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25
Q

Approximately how thick are actin filaments? Intermediate filaments? Microtubules?

A

Actin: 7nm, ATP; Intermediate Fibers: 10nm; Microtubules: 25nm.

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26
Q

What filaments form the core of microvilli?

A

Bundled actin filaments form the core of microvilli.

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27
Q

where in the cell are you most likely to find actin filaments?

A

You are most likely to find actin filaments near the plasma membrane.

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28
Q

Which cytoskeletal elements are polarized?

A

Both actin filaments and microtubules are polarized, with a + and a - end.

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29
Q

What motor protein is associated with actin?

A

Myosins are the motor proteins associated with actin.

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30
Q

What molecule, when bound to g-actin, promotes polymerization?

A

ATP (adenosine triphosphate).

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31
Q

What integral membrane protein will bind to actin inside the cell and to connective tissue outside of the cell?

A

Integrins will bind actin to extracellular matrix proteins.

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32
Q

What drugs prevent polymerization of actin? What prevents it from depolymerizing?

A

Cytochalasins prevent polymerization and phalloidin prevents depolymerization.

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33
Q

What is the structure of microtubules?

A

A microtubule is a hollow tube composed of 13 linear, tubulin dimers (made of alpha and beta tubulin).

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34
Q

How are microtubules organized in the cell?

A

Most microtubules radiate from the MTOC near the nucleus. There are other microtubules in structures like cilia or flagella.

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35
Q

What is the microtubule organizing center of most eukaryotic cells?

A

This is the site from which microtubules radiate. It is the centrosome, and is located near the nucleus.

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36
Q

What is unique about the tubulin near the MTOC?

A

There is a concentration of stable gamma-tubulin rings near the MTOC

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37
Q

What pair of structures is found at the centrosome?

A

A pair of centioles that are at right angles to one-another.

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38
Q

What are the motor proteins associated with microtubules? Which direction do they move?

A

Kinesin moves things toward the plus end of the microtubule. Dynein moves things toward the minus end of the microtubule (i.e., toward the MTOC).

39
Q

What is the structure of cilia?

A

There is a ring of 9 doublet microtubules, with a core of two independent microtubules. These are anchored at a basal body (that does not have the two core microtubules and has a ring of 9 triplet microtubules).

40
Q

How do cilia move?

A

There are dynein motors attached to the microtubules that bend them and then they snap back due to the structural rigidity of the microtubules.

41
Q

What is the effect of adding Taxol to a cell?

A

Adding Taxol caps the + ends of the MT and will result in stabilization.

42
Q

What two drugs will prevent polymerization of microtubules?

A

Colchicine and Vinblasine will prevent polymerization of microtubules.

43
Q

What is the main function of intermediate filaments?

A

Structural support/tensile strength of the cell.

44
Q

What is the structure of intermediate filaments?

A

Two coiled dimmers make a staggered tetramere. Eight of these polymerize into the intermediate filament.

45
Q

What are the chief types of intermediate filaments and where are they found?

A

Keratin (epithelia); GFAP (glia); Vimentin (CT, mesechyme); Desmin (skeletal muscle); Neurofillaments (neurons); Lamins (lining this inside of the nuclear envelope).

46
Q

Where in the nucleus is most RNA being synthesized?

A

The nucleolus is the site of most rRNA synthesis. A small fragment is synthesized in the rest of the nucleus.

47
Q

What is happening in the dense fibrillar zone of the nucleolus?

A

The dense fibrillar zone is the site of rRNA transcription

48
Q

What is happening in the granular zone of the nucleolus?

A

The granular zone is the site of ribosomal packing and processing.

49
Q

What is the structure of the nuclear envelope?

A

The nuclear envelope has a double membrane. It is continuous with the endoplasmic reticulum and the cisternal space is continuous with rER lumen.

50
Q

How are proteins created in the cytoplasm delivered to the nucleus?

A

Proteins destined for the nucleus contain a “nuclear localization sequence” that labels them for the nucleus. This binds to importins that bind to proteins of the nuclear pore complex. Ran (RAs-related Nuclear protein) is a GTP binding protein that is located throughout the cells but is needed for movement in and out of the nucleus. RanGTP is in high concentration in the nucleus and RanGDP is in high concentration in the cytoplasm. Importin moves proteins from the cytoplasm toward a region of high RanGTP (i.e., into the nucleus). Conversely, exportin moves proteins out of the nucleus.

51
Q

What is the importance of lamin?

A

Lamin is an intermediate filament lining the inside of the nuclear envelope. It attaches to chromatin and keeps it in place n relation to the envelope. It is phosporylated during mitosis, which results in a disruption of the lamins and the attached envelope (into numerous, lamin bound vesicles.

52
Q

How is DNA packed?

A

DNA consists of a pair of helices wraped around two tetramers of histone proteins. These nucleosomes are coiled into a solenoid (one wrap of nucleosomes) and these are folded into chromosomes.

53
Q

How is the cell cycle regulated?

A

The cell cycle is regulated by the appearance and disappearance of cyclins. Cyclins interact with cyclin-dependent kinases (Cdks) that phosporylate a large number of proteins that contribute to the progress of the cycle. Cyclins will activate different CDKs (M-cyclin for mitosis, S-Cdk for DNA sythesis, for example). At the end of its part of the cycle, the cylin will be bound to ubiquitin, that will tag it for destruction by proteosomes.

54
Q

What are the components of interphase in the cell cycle?

A

G1 (Gap 1; growth of cell), S (DNA replication), G2 (Growth of Cell and replication of organelles).

55
Q

What are “checkpoints” and when do they occur?

A

These are places at which the cell cycle may be interrupted if things are not right. The checkpoint at G1 detects signals saying that the environment sufficient for division, that DNA is undamaged. The checkpoint at G2 evaluates if the cell is big enough and the DNA is replicated. The checkpoint at M, metaphase, evaluates if all chromosomes lined up at the metaphase plate

56
Q

What is the role of p53?

A

This protein is phosporylated in the presence of damaged DNA. It turns on the gene for p21, which produces a protien that will arrest the cell cycle until the DNA is repaired.

57
Q

What occurs during prophase?

A

In prophase there is condensation of chromosomes (which have been replicated in S-phase). The centrosomes separate and there is the beginning of the formation of the spindle poles.

58
Q

What occurs during prometaphase?

A

There is breakdown of the nuclear envelope with phosphorylation of nuclear lamins. Spindle fibers (microtubules) attach to the kinetechores of the chromosomes (kinetochore microtublues).

59
Q

What occurs during metaphase?

A

Chromosomes are lined up at the metaphase plate. Kinetochore microtubules are attached to spindle poles (centrosomes) and the (inter)polar microtubules are overlapping with those form the other spindle pole.

60
Q

What happens during anaphase?

A

The paired sister chromatids separate, moving toward the spindle poles (centrosomes). Dynein on the astral microtubules pull, kinesins on the (inter)polar microtubules push the chromosomes apart and progressive depolarization of the kinetochor microtubules pull the chromosomes apart.

61
Q

What occurs during telophase?

A

Chromosomes approximate the centrosomes. The nuclear envelope reforms as lamins are dephosphorylated and associated vesicles reform. Cytokinesis (division of the cytoplasm) is complete.

62
Q

What process is necessary for cytokinesis?

A

A contractile ring comprised of acting filaments can interact with myosin to pinch off the cell into two daughter cells.

63
Q

What is apoptosis and why is it important?

A

This is programmed cell death. It is not inflammatory and is due to activation of intracellular mechanisms that cause destruction of the cell from the inside, with phagocytosis of the resultant debris. It is important for normal development, since it will get rid of unwanted cells withut damaging surrounding tissue.

64
Q

What intracellular signaling molecule is key in induction of apoptosis?

A

Caspases are the most important signaling molecules for apoptosis. These can be activated by signals from outside the cell or by various intracellular processes (such as release of cytochrome c from the mitochondria).

65
Q

What are the functions of epithelia?

A

The functions of epithelia include protection, absorption, secretion and sensory reception.

66
Q

What are the two side of an epithelium called?

A

Epithelia are polarized with an apical domain on the side facing the surface, and a basal (basolateral) domain facing underlying connective tissue.

67
Q

What are microvilli?

A

These are projection of the cell surface with an actin core that increase surface area for absorption. Actin filaments are anchored in the terminal web. They are not motile in themselves, although if the terminal web is moved, the microvilli spread apart.

68
Q

What cell surface structure is motile?

A

The vast majority of ciilia are motile (microvilli and stereocillia are not). These have a (9+2 microtubules organization; axoneme). Dynein is critical for moving the arms. There are some “primary cilia” that are not motile (and are lacking the central microtubules). Some cells (such as sperm cells) have a single flagella that has a similar structure to a large, long cillium).

69
Q

What is a stereocillia?

A

These are not motile and are essentially long microvilli. They are found in the inner ear and the epididymus.

70
Q

What does the junctional complex of epithelial cells consist of?

A

The junctional complex is comprised of three different junctions. The one that is closest to the apical surface of the epithelial cell is the zonula occludens (aka tight junction). This goes all the way around the cell and is a site where the plasma membranes of adjacent cells are tightly opposed. The tight junction limits the ability of materials to pass between adjacent epithelial cells (paracellular pathway). The main channel proteins that connect the adjacent cells are occludin and claudin. The zonlula adherens is the next junction; actin filaments of adjacent cells are linked with transmembrane proteins of the cadherin family. Desmosomes are the third junction that are located a little further from the surface of the cell. These are “spotwelds”, where cadherin proteins are liked to intermediate filaments.

71
Q

What is the basement membrane?

A

All epithelia rest on a basement membrane. It is a layer between epithelium and connective tissue that stains well with PAS because it has lots of glycoproteins. It has type IV collagen fibers, laminin, proteoglycans and many other components. It is important for support and migration of epithelial cells.

72
Q

What are hemidesmosomes?

A

These are structures that bind intermediate filaments to the basement membrane with integrins.

73
Q

What is the definition of a simple epithelia and what are the types?

A

A simple epithelium has every cell resting on the basement membrane. The types include: simple squamous, with cells of flattened shape; simple cuboidal, with box-shaped cells; simple columnar, with tall cells, usually having microvilli or cilia; pseudostratified, where every cell touches the basement membrane even though there appear to be several rows of nuclei.

74
Q

What are the types of stratified epithelia?

A

Stratified squamous epithelia are found in places wehre there is exposure to abrasion or other physical trauma. In moist places it is non-keratinized, while in dry places it is keratinized. Stratified cuboidal is quite rare, though it is found in certain large ducts. Stratified columnar is very rare, only appearing in epithelial to mucous membrane transitions (anus).

75
Q

Which type of epithelium is most likely to be ciliated?

A

Pseudostratified columnar is usually ciliated, being most common in the respiratory system.

76
Q

Which type of epithelium is found in the urinary bladder?

A

Transitional epithelium (urothelium) can change shape depending on stresses placed upon it. Stretching of the organ flattens cells, while a relaxed organ results in pillow-shaped cells.

77
Q

What are the two main types of glands?

A

Exocrine (secrete onto a surface or into a duct) and endocrine (secrete into the circulation) glands.

78
Q

What are the modes of secretion of exocrine glands?

A

Merocrine glands are the most common. Vesicles fuse and expel contents of the vesicle. Apocrine glands secrete by budding out entire vesicles (e.g., mammary glands). Holocrine glands secrete by disruption of entire cells, with release of all of the cell contents (sebaceous glands).

79
Q

What is the most common unicellular gland?

A

Goblet cells are common in the GI and respiratory tracts. They secrete mucinogen (will make mucus in presence of water).

80
Q

What is a simple gland?

A

A simple gland consists of a secretory portion (e.g. tubular, acinar) and one unbranched duct.

81
Q

What is a compound gland?

A

If the duct of a gland is branched, then it is a compound gland. The secretory portion can be of the tubular type, alveolar type (aka, acini; a ball of secretory cells) or a combination of both (tubuloalveolar - one of the more common architectures).

82
Q

What is the function of fibroblasts?

A

These cells make most of the extracellular matrix (ground substance, fibers, glycoproteins). They are also responsible for making collagen.

83
Q

What cells are transient in connective tissue?

A

Cells of the mononuclear phagocytic system. They come from bone marrow precursors, are phagocytic (with lots of lysosomes) and have surface receptors for immnoglobulins and compliment (opsonin). Most of these are macrophages, which differentiate from monocytes in the blood. Mast cells are important in anaphylactic shock and allergic response. They bind to certain imunoglobulins that are involved in allergies (IgE) and will discharge granules when activated. They contain metachromatic granules containing vasoactive and immunoreactive properties (including SRS-A & heparin). Plasma cells differentiate from B lymphocytes and make antibodies.

84
Q

Where is collagen synthesized?

A

Collagen synthesis is initiated intracellularly in fibroblasts and completed extracellularly.

85
Q

What are the steps in synthesis of collagen?

A

Synthesis begins in rER of fibroblasts, with protein transferred to Golgi exocytotic vesicles (Lys residues get hydroxylated to help in h-bonding). Alpha chains are assembled into triple helix, which is packaged and secreted into fibroblast cove (outside cell). The ends are cleaved to make the propeptides, tropocollagen. The enzyme lysyl oxidase is used to assemble into fibrils (needs vitamin C)

86
Q

What is collagen type I and where is it found?

A

This is the most abundant type of collagen. It is found in connective tissue, tendons and bone. It has a distinctive banding pattern and long fibers.

87
Q

What is collagen type II and where is it found?

A

Collagen type II is found in cartilage (hyaline and elastic).

88
Q

What is collagen type III and where is it found?

A

Collagen type III is found in reticular fibers. It is PAS+ and argyrophillic (like silver stains). It usually provides in internal structure of organs.

89
Q

What is collagen type IV and where is it found?

A

Collagen type IV is important in the basement membrane. It forms a lacy network without definite fibers.

90
Q

What is the structure of elastic fibers?

A

These are fibers comprised of the proteins elastin and fibrillin. Elastin is made up of demosine and isosemosine (unique amino acid sequences that is similar to a thin collagen fiber without hydroxylysine).

91
Q

What is ground substance, and what makes it up?

A

Ground substance is the material between fibers and cells of a connective tissue. It is made of hydrated gel and is essential for transport of nutrients within the tissue. A major constituent is proteoglycans having a protein core with glycosaminoglycans attached (looks like a test tube brush). These are highly hydrophilic.

92
Q

What is the difference between loose and dense connective tissue?

A

Loose CT has lots of cells and ground substance and not a lot of fibers. Dense connective tissue has few cells and ground substance with lots of fibers.

93
Q

What are the two types of dense connective tissue?

A

Dense connective tissue can be regular or irregular (loose connective tissue is always irregular).

94
Q

Which organelle is more prevalent in multilocular (brown) fat than unilocular (white) fat?

A

Mitochondria are much more prevalent in brown fat. The oxidative chain in brown fat cells is uncoupled from the process of producing chemical energy in brown fat cells and, therefore, produces heat.

MIR Deck 12 Quiz (6 decks)

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