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BMSC 220 CELL BIOL > Gauvrit Section > Flashcards

Gauvrit Section Flashcards

1
Q

What kind of samples can electron microscopy visualize?

A

dead fixed cells

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2
Q

What are the four components of cell theory?

A
  • all organisms are composed of one or more cells
  • cells are the structural unit of life
  • cells only arise from division of a pre existing cell
  • cells contain genetic information to pass on to the next generation
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3
Q

Who are the first cells cultured froma tumor of a cancer patient called?

A

HeLa cells (Henrietta lacks)

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4
Q

What is the ancient cell that all life is derived from?

A

LUCA

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5
Q

What are three characteristics that distinguish prokaryotic and eukaryotic cells?

A

eukaryotic cells have a membrane bound nucleus
- eukaryotic cells divide by meiosis or mitosis where prokaryotic cells divide by binary fission
- eukaryotic cells use cilia and flagella where prokaryotes only have flagella

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6
Q

What are viruses that infect bacteria called?

A

bacteriophages

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7
Q

What are viruses that are pathogens and interfere with host cells called?

A

Viroids

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8
Q

What are the two types of viral infection?

A

Lytic infection - makes more virus particles then pops the host cell open to release them
Integration - virus integrates its DNA (provirus) into host cell chromosome

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9
Q

What are the four classes of macromolecules?

A

proteins
lipids
nucleic acids
polysaccharides

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10
Q

What macromolecule is long lived?

A

DNA

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11
Q

What is the difference between glycogen and starch?

A

glycogen is in animals, starch is in plants

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12
Q

What do lipids dissolve in?

A

organic solvents, not water

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13
Q

What is the difference between saturated and unsaturated fatty acids?

A

Saturated has no double bonds

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14
Q

What are the building blocks of proteins?

A

Amino Acids

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15
Q

What is the primary structure of a protein?

A

linear amino acid sequence

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16
Q

What is the driving force for protein folding?

A

hydrophobic interactions

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17
Q

What disease results froma single amino acid change in hemoglobin?

A

sickle cell anemia

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18
Q

What is the secondary structure of proteins?

A

conformations of portions of polypeptide chain
- alpha helices and beta sheets

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19
Q

What is the tertiary structure of a protein?

A

entire 3d conformation

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20
Q

What are prions?

A

misfolded proteins that can transmit their misfolded shape

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21
Q

can proteins be similar at the tertiary level but not primary level?

A

yes

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22
Q

What determines if proteins have quaternary structure?

A

if they have subunits

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23
Q

Can all proteins self assemble into tertiary structure?

A

No, some need helper proteins or molecular chaperones

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24
Q

What disease is from protein misfilding?

A

Alzheimers

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25
Q

What is the main differing function between DNA and RNA?

A

RNA transfers genetic information, DNa stores it

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26
Q

What base is swapped in DNA and RNA?

A

T (DNA) for U (RNA)

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27
Q

Which nucleotides bind to eachother?

A

A binds to T, C binds to G

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28
Q

Does denaturation affect amino acid sequence?

A

no

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29
Q

What does it mean when we say membranes are amphipathic?

A

contain both hydrophobic and philic regions

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30
Q

What are the three membrane lipids?

A

Phosphoglycerides, sphingolipids and cholesterol

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31
Q

What are phosphoglycerides?

A

Lipids with a phosphate group are phospholipids
phospholipids with a glycerol backbone are phosphoglycerides
hydophobic

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32
Q

What determines a persons blood type?

A

glycolipid carbohydrates of red blood cell plasma membrane

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33
Q

What are integral membrane proteins?

A

proteins that span the membrane
- function as receptors, channels or transporters
- are amphipathic

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34
Q

What are peripheral membrane proteins?

A

only associate on the edge of a membrane via weak electrostatic bonds
- can be added or removed as needed

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35
Q

What are lipid anchored proteins?

A

covalently bonded to lipid group within a membrane
- can be on internal or external side of mem
- external called GPI proteins

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36
Q

What is homology modelling?

A

used to learn abput strucutres and function of a protien family

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37
Q

What are lipid rafts?

A

outer specialized region of PM where cholesterol and sphingolipids pack tightly to form favorable environment for surface cell receptors

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38
Q

What enzyme can flip a phospholipid from one side of the membrane to the other?

A

flippases

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39
Q

How will membrane proteins diffuse after cell fusion?

A

concentrations will be uniform throughout cell

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40
Q

Is phospholipid diffusion restricted within a bilayer?

A

yes

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41
Q

What are the names and functions of the three membrane domains?

A

Apical - absorbs stuff from lumen
Lateral- cell contact and adhesion
Basal - substratum contact and generation of ion gradients

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42
Q

cells swell in a _ solution and shrink in a _ solution

A

hypotonic, hypertonic

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43
Q

What are the names and functions of 3 gated channels?

A

Voltage gated channels - state depends on difference in ionic charge on either side of the membrane
- Ligand gated channels - conformation state depends on ligand binding
- Mechano gated channels - conformation depends on mechanical forces applied to membrane

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44
Q

NaK ATPase is an example of what?

A

Active transport, uses ATP to pump 2 K in and 3 Na out

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45
Q

What are the three kinds of pumps in active transport?

A

P type pump - uses phosphorylation
V type pump - transport H - vacuolar, lysosomes
ABC transporters

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46
Q

What is secondary active transport?

A

coupling an energetically unfavorable reaction with an active transport reaction

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47
Q

What occurs to generate an action potential?

A

When cells are stimulated, Na channels open causing depolarization, triggering the action potential

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48
Q

What type of behaviours do action potentials exhibit?

A

All or none

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49
Q

Do APs lose intensity travelling down the nueron?

A

no

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50
Q

What sites on a neuron are where action potentials can be generated?

A

Nodes of ranvier

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51
Q

Where do neurons communicate with eachother?

A

the synapse, across the synaptic cleft
- chemicals, neurotransmitters, released from the presynaptic cleft diffuse to receptors on the post synaptic cell
- depolarization of pre synaptic cell causes ca channels to open, stimulates fusion of vesciles within membrane
- neurotransmitter binding to ion channel receptors can either stimulate or inhibit action potentials

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52
Q

What do acetylcholine, glutamate and GABA do?

A
  • Acetylcholine inhibits heart but stimulates muscle contractility
  • Glutamate is primary excitatory neurotransmitter
  • GABA is primary inhibitory neurotransmitter
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53
Q

Facilitated diffusion is (2)

A

much slower transport than diffusion across a channel
- similar to an enzyme catalyzed reaction

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54
Q

can mitochondria fuse and split with one another?

A

yes

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55
Q

Four points about mitochondria function:

A
  • are often associated with fatty acid oil droplets from which they derive raw materials to be oxidized to make ATP
  • are the sites of synthesis of amino acids and heme groups
    -play a role in uptake and release of calcium ions
  • regulate events involved in cell death
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56
Q

What is contained in the mitochondrial matrix?

A

ribosomes
mitochondrial DNA

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57
Q

strong oxidizing agents have a _ affinity for electrons?

A

high

58
Q

strong reducing agents have a _ affinity for electrons?

A

weak

59
Q

What two components compose the electron gradient?

A

ph and electric potential

60
Q

What is the glycocalyx and what are its four functions?

A

formed by carbohydrate projections on the outer surface of the plasma membrane
- mediator of cell cell and cell substratum interactions
- mechanical protection
- barrier to molecular movement towards plasma membrane
- regulatory factor binding site

61
Q

What is one of the best defined extracellular matrixes and what does it do?

A

basement membrane - surrounds muscles nersves and fat cells
underlies the epidermis on skin

62
Q

What shape of proteins are in the ECM?

A

fibrous, globular is inside cells

63
Q

What is collegen, list some shit abt it

A

Collagens are a large family of fibrous glycoproteins in ECM
- triple helix of three a helical chains
- most abundant protein in the human body
- produced by fibroblasts
- 28 types
-

64
Q

What disease can result from collegen deficency?

A

Scurvy - technically due to vitamin C but vitamin C lets collagen retain structure

65
Q

What is special about type IV collagen?

A

contains non helical segments and globular domains at each end
- allows for flexibility and lattice like character

66
Q

What are proteoglycans?

A

component of ECM
- protein polysaccharide complex
- have repeating A B A B structure
- common in basement membranes and cartilidge
-act as filler

67
Q

What is fibronectin?

A

Component of ECM
- linear array of FN domains
- found in blood clotting factors and membrane receptors
- binds to numerous ECM components
- Binds to cell surface receptors to attach cell to ECM
- important for cell adhesion

68
Q

What is laminin?

A

Component of ECM
- 3 polypeptide chains
- role in potential for growth, migration and differentiation
- role in neuronal outgrowth
- strengthen basement membrane

69
Q

Explain the dynamic properties of the ECM in space and time

A

Spatially - ECM fibrils can stretch to several times their normal length
Temporally - ECM components are under continual degradation and reconstruction to allow ECM remodelling

70
Q

What degrades ECM components?

A

Matrix metalloproteinases (MMP)

71
Q

What is integrin?

A

family of membrane proteins unique to animals
- composed of two membrane spanning polypeptide chains , a and b chain
- activated integrins become clustered and strengthen cell - ECM interactions

72
Q

What are the two conformations of integrin?

A

Bent - corresponds to inactive state
upright - active with a bound ligand

73
Q

What are the two major functions of integrin?

A
  • adhesions of cells to ECM or other cells
  • transmission of signals between external environment and cell interior
    — intracellularly, integrins bind ligands such as Talin causing inside out signalling
    — extracellularly - integrins bind differenct ECM components such as collagen, laminin and fibronectin causing outside in signalling
74
Q

What does outside in signalling by integrin do?

A

can cause a conformational chainge in talin (intracellular)
- actin filament polymerization
- cytoplasmic protein kinases activation to phosphorylate other proteins - life saving signals
- signals influence cell differentiation, motility, growth and survival

75
Q

What are focal adhesions?

A

scattered, discrete sites of cell anchorage
- play a key role in locomotion
- dynamic structure
- create mechanical forces or respond to forces form the environment
- actin filaments are the source of these forces

76
Q

What are hemidesmosomes?

A

Cell-ECM attachment seen at basal surface of epithelial cells
- contain dense cytoplasmic plaque with keratin filaments
- keratin filaments are linked to ECM through integrins

77
Q

How do separated organ cells redistribute themselves?

A

each cell will readhere to the same type of cell

78
Q

Cell cell adhesion is mediated by (4)

A
  • selectins
  • members of the IgSF
  • members of the integrin family
  • cadherins
79
Q

What are selectins?

A

family of membrane glycoproteins that bind to specific oligosaccharides
- have small cytoplasmic segment, single membrane spanning domain and a large extracellular portion
- on platelets, leukocytes

80
Q

What are selectins involved in?

A

cell cell adhesion
- transmembrane signal transduction
- signalling for cell growth, differentiation, migration or survival

81
Q

What is the IgSF?
Ca dependent or not?

A

immunoglobulin superfamily
- 765 distinct domains in genome
- involved in immune functions
- developmental roles in neuronal growth and circuitry
- Ca independent

82
Q

What are cadherins?

A

membrane glycoprotein family
- typically join cells of a similar type to one another
- Ca dependent
- possibly the single most important factor in molding cells into cohesive tissue in embryos and holding them together in the adult

83
Q

What two junctions are cadherins found in?

A

adherins junctions and desmosomes (both Ca dependent)
- adherins junction - actin filaments
- desmosomes - intermediate filaments

84
Q

What are tight junctions?

A

occur between neighboring epithelial cells
- prevent solute distribution where different solute concentrations are in adjacent compartments
- points of cell cell contact where integral proteins if two adjacent membranes meet within the extracellular space
- major proteins are claudins

85
Q

What are gap junctions?

A
  • sites between animal cells that are specialized for intercellular communication
  • plasma membranes of a gap junction contain channels that connect the cytoplasm of one cell with the cytoplasm of the adjoining cell
  • plasma membranes come close but DO NOT make direct contact at a gap junction
  • composed of several integral membrane proteins connexin, and organized into multi subunit complexes called connexons that span the membrane
86
Q

What is the role of cell cell adhesion in inflammation?

A

white blood cells can get to the cells they need to be in to fight infection
- recruitment focused on selectins, integrins and IgSF proteins

87
Q

What is the role of cell cell adhesions in metastasis?

A

cancer can escape the normal growth control mechanisms
- have special cell properties that allow it to escape

88
Q

What 5 structures make up the endomembrane system?

A

ER, golgi complex, endosomes, lysosomes, and vacuoles

89
Q

Generally, what is the endomembrane system doing?

A

materials are packaged in small membrane bound vesicles
- bud off from a donor membrane compartment
- move via motor proteins on cytoskeleton
- fuse with the membrane of the acceptor compartment
-

90
Q

What are the three pathways in the endomembrane system?

A

Biosynthetic pathway
Secretory Pathway
Endocytic Pathway

91
Q

What are the two secretion modes in the endomembrane system?

A

Constitutive secretion - materials are transported in secretory vesicles and discharged in a continual manner
Regulated secretion- materials are stored in vesicles and discharged in response to a stimulus
– occurs in endocrine cells and nerve cells, used in biosynthetic or secretory pathway

92
Q

What is the biosynthetic pathway?

A

Pathway in endomembrane system
- proteins are synthesized in the ER, modified at the Golgi complex and transported to various destinations

93
Q

What is the secretory pathway?

A

Proteins synthesized in the ER are discharged from the cell

94
Q

What is the endocytic pathway?

A

Pathway in the endomembrane system
- materials move from the outer surface of the cell to compartments, such as endosomes and lysosomes

95
Q

What does autoradiography do?

A

visualizes biochemical processes by radioactively labelling molecules

96
Q

What does GFP tagging do?

A

allows microscope viewing of protein movement in living cells
- cells are infected with VSV which has a viral-GFP gene infusion

97
Q

What are microsomes?

A

vesicles derived from the endomembrane system during homogenization

98
Q

What are liposomes?

A

used for studying proteins
- vesicles whos surface consist of an artificial bilayer that is created from purified phospholipids

99
Q

What is the endoplasmic reticulum?

A

network of membranes that penetrates the cytoplasm and has a lumen separated from the cytosol by the ER membrane
- highly dynamic structure 2 compartments
- RER/ SER

100
Q

Three distictions between the RER and SER

A

RER has ribosomes bound to its cytosolic surface, SER lacks ribosomes
- RER has flattened sacs (cisternae) SER membranes are highly curved and tubular
- RER is continuous with outer membrane of nuclear envelope, SER is continuous with RER

101
Q

What are the functions of the SER? 3

A
  • Steroid hormone synthesis in endocrine cells of the gonad and adrenal cortex
  • detoxification of organic compounds in the liver via oxygenases including cytochromes
  • calcium ion sequestration and regulated release
102
Q

What is the function of the RER

A

Has ribosomes to make proteins
- starting point of biosynthetic pathway for secretory proteins
- one third of proteins are synthesized here and released into the ER lumen via co translational translocation

103
Q

What determines protein synthesis on the RER?

A

site of protein synthesis is determined by sequence of amino acids in N terminal portion of polypeptide
- secretory proteins contain a signal sequence at N terminus that direct emergind polypeptide and ribosome to ER membrane
- polypeptide moves to cisternal space of ER cotranslationally
- proteins contain built in address codes for protein trafficking pathways (signal hypothesis)

104
Q

What determines the synthesis of secretory, lysosomal or vacuolar proteins?

A

co translational translocation deposits protein in ER lumen
- polypeptide signal sequence targets polypeptide to ER membrane
- signal sequence is recognized by signal recognition particle (SRP)
- SRP binds polypeptide and ribosome - stopping synthesis
- complex is recruited to ER membrane
- ribosome is handed off to translocon, a protein channel in ER membrane, upon recognizing signal sequence, polypeptide is inserted into translocon channel

105
Q

What regulates the synthesis and trafficking of secretory proteins?

A

binding or hydrolysis of GTP
- SRP and receptor are G proteins that interact with eachother in GTP bound states, GTP hydrolysis triggers release of signal sequence by SRP

106
Q

How are signal peptides removed and how are carbohydrates added in ER?

A

signal peptide is removed by signal peptidase and carbs are added by oligosaccharyltransferase
- both enzymes are integral membrane proteins associated with the translocon

107
Q

How are integral membrane proteins synthesized on ER bound ribosomes

A

cotranslationally, hydrophobic transmembrane segments are shunted from the translocon into lipid bilayer
- inner lining of translocon orients polypeptide so more positive end faces the cytosol
- in multispanning proteins, transmembrane segments typically have opposite orientations, so arrangement is determined by direction in which the first segment is inserted
- tail anchored proteins lack a signal sequence but are synthesized in cytoplasm and targeted to ER thru GET pathway

108
Q

3 things common to all membranes

A
  • membranes exist from pre existing membranes
  • membranes are enzymatically modified as they move from ER into other cellular compartments
  • membranes are asymmetric with a cytosolic face and luminal / extracelluar face established in ER
109
Q

what do nearly all proteins produced in the RER become?

A

glycoproteins

110
Q

Where does modification of the oligosaccharide after its transfer to the polypeptide occur?

A

In the RER

111
Q

What happens to misfolded proteins?

A

Glucose tagged, mannose deficient and ultimately degraded by proteosomes

112
Q

What does the accumulation of misfolded proteins trigger?

A

Unfolded protein response UPR
- sensors in ER are kept inactive by BiP
- when misfolded proteins accumulated BiP cannot inhibit sensors
- activated sensors send signals to trigger proteins involved in destruction

113
Q

What is the first step in vesicular transport?

A

ER to golgi complex

114
Q

What is the golgi complex?

A

stack of flattened cisternae
- cis face faces Er
- trans face on opposite side

115
Q

What are the functions of the two parts of the golgi complex?

A

cis golgi network - sorts proteins for ER or next golgi station
trans golgi network - functions in sorting proteins to plasma membrane or various intracellular destinations

116
Q

Where does the assembly of carbs found in glycolipids and glycoproteins take place?

A

golgi complex

117
Q

What determines the sequence of incorporation of sugars into oligosaccharides?

A

glycosyltransferases

118
Q

What are the two functions of protein coats?

A
  • cause membrane to curve and form a vesicle
  • select the components to be carried by vesicle
119
Q

What are the three types of vesicle transport?

A

COPII-coated vesicles - move materials from Er forward to ERGIC intermediate compartment and golgi complex

COPI-coated vesicles - move materials from ERGIC and golgi backwards to ER, or from trans golgi to cis golgi

Clathrin coated vesicles - move materials from TGN to endosomes lysosomes and plant vacuoles

120
Q

What is ERGIC?

A

endoplasmic reticulum golgi intermediate compartment

121
Q

Explain the properties and use of COPII coated vesicles

A
  • bud off specialized domains of ER called ER exit sites (ERES) - this begins the biosynthetic pathway
  • ER export signals found in cytosolic tails of proteins
    -COPII coats select and concentrate enzymes
  • all vesicles have two distinct layers- an outer scaffold and an inner layer of adaptor like proteins
122
Q

Explain the properties of COPI coated vesicles

A

COPI coat is made of cotamers made of seven proteins
- clearly used in backwards transport
- organelle proteins are maintained by
– retention of resident molecules excluded from transport vesicles
– retrieval of escaped molecules back to normal compartment
- resident proteins of ER contains AA sequence at C terminus as a retrieval signal

123
Q

What does sorting and transport of lysosomal enzymes use?

A

clathrin coated vesicles
- lysosomal proteins are tagged in cis golgi with phosphorylated mannose residues
- tagged lysosomal enzymes are recognized and captured by mannose 6 phosphate receptors

124
Q

What are the four steps that occur between vesicle budding and fusion?

A
  • movement of besicle towards specific target compartment mediated by microtubules and associated motor proteins
  • tethering vesicles to target compartment - mediated by tether proteins
  • docking vesicles to target compartment, membranes come in close contact via interations between integral proteins
  • fusions between vesicle and target membranes
125
Q

What are Rabs?

A

family of small g proteins that cycle between active GTP bound and inactive GDP bound states
- GTP bound rabs associated with membranes by lipid anchor
- over 60 diff rabs genes
- used for vesicle sorting

126
Q

What are SNAREs?

A

family of integral proteins that bring the vesicle and target compartment in close contact
VSNARES found in transport vesicles
TSNARES in target compartments

127
Q

What is exocytosis?

A

discharge of secretory vesicle after fusion with PM
- triggered by Ca
- forms a fusion pore
- luminal part of vesicle becomes outer surface, cytosolic part becomes inner surface

128
Q

why are extracellular vesicles useful maybe for drug delivery?

A

can move thru body unnoticed and pass thru blood brain barrier but have short half life before phagocytosis

129
Q

What are lysosomes? What is autophagy?

A
  • white blood cells digest shit by fusing phagosomes and lysosomes
  • play role in autophagy - organelle turnover
  • a phagopore envelopes an organelle to produce a double membrane vesicle called an autophagosome
  • this fuses with a lysosome generating an autolysosome, degrading all contents
130
Q

What are the two ways to get shit into the cell?

A

Endocytosis - cell internalizes cell surface receptors
Phagocytosis - uptake of particulate matter

131
Q

What are the two categories of endocytosis?

A

bulk phase - non specific
receptor mediated - specific

132
Q

What do coated pits do in receptor mediated endocytosis?

A

substances that enter cell become bound to coated pits on PM, pit regions invaginate and then pinch free of cytoplasm via clathrin
- contain adaptors between clatherin lattice and surface like AP2
- adaptors engage tails of specific receptors to do different things

133
Q

What is the structure of clathrin

A

used in coated pits
- 3 heavy chains and 3 light chains called a triskelion
- triskelions overlap

134
Q

What is dynamin?

A

G protein required for fission of vesicle from membrane that it forms on
- assembles into a helical collar around invaginated coated pitq

135
Q

What are vesicle bound materials called after internalization?

A

endosomes

136
Q

What are LDLs?

A

Low density lipoproteins
- complex of protein and cholesterol
- receptors transported to membrane and bound to coated bit
- taken up by RME and taken to lysosomes releasing cholesterol for use by cells

137
Q

How does phagocytosis work?

A

folds produce a vacuole called phagosome that pinches off inwardly of PM and fuses w lysosome (phagolysosome)

138
Q

What are peroxisomes? And they import proteins —— Ttranslationally

A

small membrane bound organelles that contain enzymes
- proteins are imported postranslationally ( same in other organelles but not RER which is cotranslationally)
- two subcompartments
- possess targeting signal for matrix or membrane
Various metabolic functions

139
Q

What is the TOM complex? What is the TIM complex?

A

outer mitochondrial membrane protein import complex
- TIM compex is for proteins destined for inner mito membrane

140
Q
A
141
Q

Integrins
Selectins
Cadherins
Igsf
All do what kind of interaction, what does integrin also do, what kind of things are they

A

Cell cell
Cell ecm
Membrane proteins

142
Q

4 ecm components

A

Collagen
Fibronectin
Proteoglycans
Laminin

BMSC 220 CELL BIOL (6 decks)

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