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Final Exam Flashcards

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1
Q

Secretory pathways

A

proteins moving from ER to Golgi to PM for secretion

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2
Q

Modifications of proteins in the ER

A

Folding and Glycosylation

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3
Q

Folding modification

A

formation of disulfide bonds through oxidation of cysteine residues which stabilized the 3D shape.

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4
Q

glycosylaiton modification

A

addition of carbohydrate groups to the proteins
-an oligosaccharide (14 sugar) is added to asparagine residues by olygosaccahrly transferase. Stars at ER but can be modified in Golgi for diverse sets of glycoproteins

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5
Q

Can proteins leave the ER if misfolded?

A

No, it is monitored, through the direction of chaperon proteins for proper folding

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6
Q

What happens if l there is a large amount of unfolded proteins?

A

the unfolded protein response is triggered
-upregulates the production of chaperon protein s
-slows down generalized protein production
-increase growth of ER

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7
Q

Where are properly folded proteins transported?

A

the Golgi via vesicles

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8
Q

How do proteins travel to the Golgi?

A

merging cis-face of Golgi travel through cisternae towards the trans face
1. budding vesicles
2. maturation of Golgi cisternae migrating through stack cis-> trans

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9
Q

How does protein processing happen in the Golgi

A

enzymatic modification of oligosaccharides on glycoproteins
and specific proteins get sorted into specific vesicles and then buds off the trans face of the Golgi

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10
Q

What are the types of exocytosis and secretion?

A

Constitutive/unregulated exocytosis
regulated exocytosis

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11
Q

Constitutitive/ unregulated exocytosis

A

a constant stream of vesicles from the Golgi fusing with the PM
-refreshing lipid and membrane proteins
-enables PM to expand before cell division in mitotic cell

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12
Q

Regulated exocytosis

A

specialized cells for secretion
eg. glandular cells eg. secretion of hormones, digestive enzyme, mucus
-Products are stored in vesicles until the cell receives the signal for relaxation.

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13
Q

Endocytic Pathways

A

processing of materials brought into the cell in vesicles
1. phagocytosis
2. pinocytosis
3.receptor-mediated endocytosis

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14
Q

Phagocytosis

A

ingestion of larger particles like microorganisms, cellular debris, food
-cells must be specialized
eg. protozoans use phagocytosis to eat

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15
Q

In animals what is the use of phagocytes

A
  1. immunity
  2. clearing debri
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16
Q

How do phagocytes play a role in immunity?

A

white blood cells capable of phagocytosis through neutrophils and macrophages

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17
Q

neutrophils

A

have receptors that can recognize the foreign body or antibodies bound to the foreign body, once the receptor of the neutrophil binds to a foreign body, pseudo extend and engulf the paticle. phagosomes fuse with lysosomes and lysosomal enzymes destroy the foreign body.

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18
Q

Pinocytosis

A

“Cell drinking” nonspecific
-ingestion of small droplets of ECF through the formation of clathrin-coated vesicles( reclaims PM in cell with a lot of exocytosis)
used as a mechanism to balance the size of PM, especially in secretory cells
-when the vesicles come from the PM they fuse with an endosome

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19
Q

Receptor-mediated endocytosis

A

↳ membrane receptors bind specific solutes; solute binding
Initiates the formation of vesicles
-> Selective form of endocytosis
↳ specific for one type of molecule eg. LDL
-> Vesicle fuses with the Endosome: receptor and cargo
often dissociate
↳ receptor returns to PM in a vesicle that
buds from Endosome

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20
Q

endosome

A

sort and process incoming material

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21
Q

what is the general role of endosomes with endocytic pathways

A

-vesicles coming from PM form into an early endosome through the fussion of membranes
-5-15 minutes later the same material is now in a late stage endosomes
-maturation occurs as early endosomes fuse or pre-existing late endosomes
-late endosome fuses with preexisting lysosomes or late endosomes become a lysosome when lysosome enzymes are delivered from Golgi

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22
Q

What are the conditions inside an endosome?

A

-interior of late endosomes is acidic.(H+ pumps pump H+ into endosome)
-An acidic interior can cause some of the dissociation of cargo from reporters

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23
Q

Lysosomes

A

contain hydrolytic enzymes capable of digesting unwanted material
-releasing amino acids, nucleotides, monosaccharides, and fatty acids to the cytosol they can be used to build macromolecules
-optimal activity in acidic conditions of the interior of lysosomes

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24
Q

Types of lysosomal enzymes

A

-proteases
-glycosidase
-nucleases
-lipase
-phosphatase
-phospholipase

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25
Chemical Signaling
-> A signaling cell releases a Specific Chemical Signed (Extracellular Chemical Signal = ECS) -> ECS is recognized by target cells that express the Specific Protein receptor that will bind the ECS -> The binding of ECS to the receptor initiates a sequence of Events (signal transduction) that brings about a cellular response
26
Different forms of chemical signals
1. Endocrine 2. Paracrine 3. Neuronal 4. Contact-Dependent
27
Endocrine Signaling
ECS/Hormones are released by Endocrine glandular cells and are taken up by the bloodstream, delivered through the body by circulatory system, and brings about the response at a relatively distant target cells.
28
Paracrine Signaling
-ECS is released and diffuses to act on local target cells -Autocrine: acts on the cell that secretes it. Or Other cells close by of the same cell type.
29
Neuronal Signaling
-an electrical signal that travels along an upon extension, and is converted into a chemical signal released from the axon terminal. ECS = Neurotransmitter ECS binds to receptors at nearby target cells.
30
Contact dependent signaling
-> Chemical Signal is embedded in PM of Signaling cell -> receptor is embedded in PM of the target cell -> When the chemical signal binds it creates a a physical connection between those cells
31
How does the ECS know where to bind?
Target cell express the specific receptor protein that will specifically bind the ECS
32
Receptors can be found in?
Cell surface intracellular
33
cell surface receptors
PM proteins with ligand binding domain facing ECF, mostly hydrophilic ECS's
34
intracellular receptors
located within the cell -usually bind small or hydrophobic ECSs
35
Cellular can vary in terms of timing, what are the types of responses?
fast response (seconds): usually involves activation/deactivation cascade of existing protein to bring about cellular response slow response( minutes to hours) Usually involves signal transduction pathways that involve altered protein production
36
Amplification in cell signaling is?
A small # of ECSs can trigger a robust cellular response because several intracellular signals are activated in the pathway amplification
37
What are the main charactericitis of a cell surface receptors
-> Span the PM -> Binding region faces ECF -> Bind majority of ECS's -> Binding of ECS on the outside of cell is relayed by receptor to a signal transduction pathway inside the cell
38
signaling transduction
usually a cascade of biochemical activations and deactivaitons
39
activation/ deactivation
protiens in the signaling cascade is often controlled by altering phosphorylation and dephosphorylation reaction
40
kinase
mediate phosphorylation reactions ( addition of phosphate) eg. serine/threonine: phosphorylate protein at serine or threonine residues tyrosine kinase
41
phosphatases
enzymes that mediate dephospho-rylation( removal of PO4)
42
What are the three types of cell surface receptors
1. Ion- channel coupled receptors 2. G-protein coupled receptors 3. Enzyme coupled receptors
43
Ion-channel coupled receptors
-> the receptor is Chemically (ligand)gated ion channel > the ECS binds, which causes a conformation change and open the Channel the channel allows specific ion to move passively down its electrochemical gradient ↳ often leads to an electrical Signals (EPSP's, IPSP's) ↳ eg. Na, K, Cl, Ca
44
G-protein coupled receptors: GPCR's
> the GPCRs are conserved evolutionally > all have same basic structure > a single polypeptide that crosses back and forth through the phospholipid bilayer of PM 7 times -> GPCR is coupled to a G-protein G-proteins are Heterotrimeric proteins ↳ composed of 3 different Subunits G alpha, beta , gamma) -> Stay tethered to the phospholipid bilayer ↳ but subunits are able to move laterally in the membrane
45
What does the activation process of GPCR look like?
1)ECS specifically binds to the receptor 2)the binding of ECS to the receptor causes a conformational change in receptors at cytosolic Side -> now able to interact with the alpha Subunit of G-protein. Sidenote: Inactive alpha subunits are associated with GDP 3)When alpha Interacts with the receptor, the alpha will dissociate from GDP, and a new molecule of GTP is bound alpha is now activated 4)activated alpha subunits dissociate from beta and gamma, which now activates them 5)Both active alpha and active beta and gamma can interact with effector molecules to initiate signal cascades, eventually bringing about cellular response
46
What are the pathways of signal transduction into cellular response for GPCR?
activated alpha with GTP bound will interact with effector proteins in PM beta and gamma also interacts molecules
47
What occurs when alpha is free to move laterally and does it ever get back to its complex?
alpha subunits have intrinsic GTPases activity so GTP is hydrolyzed to GDP within seconds -> inactive the alpha will reassocited with beta and gamma
48
G proteins that activated ion channels
↳ when activated by G-protein Subunits the channel opens: ions cross membrane down electrochemical gradient eg. Acetlycholine(ACH): a neurotransmitter. ACH binds to GCPR in heart pacemaker (SA node) ... activated beta and gamma interacts with K + channel -Channel opens; K+ efflax -> leads to decreased Heart Rate
49
G proteins that activate effector enzymes and intiate second messenger signaling systems
-alpha subunits interact with membranes proteins that are enzymes capable that produce second messenger molecule (first messenger: GCS that bound to GPCR) -Small signaling molecules that diffuse and amplify the Signal Within the cell eg. cAMP ↳ triggers the signaling cascade to bring about response
50
How does the cAMP second messenger system work?
1)ECS binds to GPCR 2)G protein binds to receptor 3)activates the alpha, which then exchanges GDP for GTP 4)alpha activates beta and gamma: alpha and beta and gamma dissociate 5)alpha is specifically alpha(s) migrates in PM eventually encountering adenyly cyclax (effector enzyme) -> ATP-cAMP (second messenger) 6)cAMP activates PKA (protein Kinase A) 7)PKA phosphorylate target proteins in the cell that bring about the cellular response ↳ dependent on target cells
51
what happens when PKA is activated by cAMP?
↳ enzymes or CRE binding Proteins (CREB's) ↳ once activated by specific Sequences of DNA in the Promoter regions of target gene. -> altered rates of transcription ↓ can bring about a cellular response
52
Cholera toxin secreted (vibro cholera)
↳ Inhibits the GTPase activity of alpha -locks the alpha in an active state· leads to continious activation of adenylyI cyclate· Increased and Sustained levels of cAMP ↳ leads to continuous flow of Cl- out of cells. water lost to lumen of the gut. => diarrhea disease massive dehydration -> can lead to death if untreated
53
pertussis toxin: Bordetella pertusis
↳ colonizes the lungs ↳ whooping cough ↳ Inhibits the exchange of GDP to GTP. (at alpha(i) ) ↳ alpha(i), when activated inhibits adenylyI cyclase -> adenylyI cyclase is not inhibited -> in appropriate activation build up of cAMP ↳ Symptoms. Causing of a Whooping Cough.
54
Describe how the Inositol phospholipid/ calcium ion pathway leads to a cellular response.
-GPCR activation by the signaling (ECS) -activaiton of alpha q suunit of the G proiten -Alpha(q) activated phospholipase C (PLC) -PLC cleaves PIP2 which produces inositol 1,4,5 triphosphate (IP3) and diacylglycerol(DAG) rxn: PIP2-> IP3 + DAG -IP3 binds to ligand-gated calcium ion channels at the reservoir of the ER -Channel opens, and calcium ions flow out of ER and into the cytosol - DAG, together with calcium ion, activates PKC( protein kinase C) -Phosphorylates target protein in cell => cellular response
55
What is the Calcium/calmodulin system?
-activated by any mechanism that brings about an increase in cytosolic calcium -Calcium is normally kept low in the cytosol by ATPase pumps -this leads to a large difference in an electrochemical gradient that factors calcium when a channel opens in the PM or ER -calcium ion binds to calmodulin which is a calcium-binding protein found in euk cells -activated calmodulin interacts with proteins in cells including CAM kinases which phosphorylate and cause cellular response
56
Enzyme Coupled receptors
-a transmembrane protein that ligand binding at the outer surface of PM -the cytosolic domain of receptors acts as an enzyme itself or forms a complex with another protein that acts as a receptor -role in growth; differentiating ;proliferation and survival of cells -slow response times involved genomic mechanism (transcription/translation) -some fast response as rearrangements of the cytoskeleton -receptor tyrosine kinases(RTK's) largest kinase
57
RTK activation
-Binding signaling molecule often causes dimerization of 2 receptors-> activation of kinase domains on the cytosolic side-> each tail phosphorylates each other specific tyrosines -initiates the formation of protein complex of signaling molecules on the activated tyrosine residues up 20 proteins
58
most RTK will activate Ras proteins; how does that happen, and what is the final response?
1) an adaptor protein will associate with one of the phosphorylated tyrosine of activated RTK 2) The adaptor activates RAS-GEF ( guanine nucleotide exchange factor) 3)Ras GEF: stimulates Ras protein to exchange GDP for GTP, creating an active Ras protein 4) active Ras activates a phosphorylated cascade (e.g., MAP kinase signaling pathway mitogen-activated protein kinase)
59
mitogen
ECS that stimulates cell proliferation through mitosis
60
Ras activates? which leads to what cellular response?
MAP kinase Kinase Kinase | Map Kinase Kinase | Map Kinase | Phosphorylates target proteins: enzymes and prescription factors that eventually lead to mitosis
61
What happens if the Ras pathway malfunctions?
involved in many types of cancer
62
Intracellular Receptors
-> ligand (ECS)are small, hydrophobic molecules that can diffuse through PM eg. Steroid hormones, Testostorune, Estradiol, cortisol, aldosterone -> These receptors are often called nuclear receptors ↳ When activated, they interact with the DNA of the genome, acting as a transcription factor -> Genomic mechanism of action: -> ligand diffuses across PM into the cell and binds to the receptor -Bound receptor translocates to the nucleus: receptor binds to hormone response element (HRE) ↳ region of DNA in the promoter area of target genes -> brings about altered rates of transcription of target genes -> cellular response -
63
Cytoskeleton
network of protein filaments -extend throughout the cytoplasm -supports large Vol. Of cytoplasm especially in animals that lack a cell wall -organization of interior components -movement -constantly changing Shape: allow cells to respond to change in enviorment "dynamic"
64
3 different classes of filaments in the cytoskeleton: what are they ?
intermediate filaments microtubules actin filaments
65
intermediate filaments
rope like -most durable -provide cells with Mechanical strength -form a network around and extend out in cell periphery -anchored to PM at the location of desmosomes
66
plactin
An accessory protein that is needed to crosslink intermediate filament to other components of the cytoskeleton
67
microtubules
-widest diameter -hollow tubes with walls composed of tubulin -each tubulin is a dimer of alpha-tubulin and beta-tubulin -13 strands of tubulin dimers form into a hollow microtubule. -(+)end is the beta-tubulin and (-)end has alpha tubulin exposed
68
What is the role of microtubules in the cell?
-create a system of tracks along which vesicles, organelles, and other components can be transported (motor protein) -mitotic spindle, organization, and separation of chromosomes during cell division -provide support and structure for cilia and flagella
69
How do microtubules organize and originate?
> emerge from microtubules -organizing centers' (MTOCs) e.g. centrosomes, basal bodies: cilice and Flagella -> centrosomes ->Dynamic Instability
70
centrosomes
composed of 2 centrials at right angles to each other and a matrix that contains wings of gamma-tubulin -> rings gamma tubulin provide nucleating sites from which the (-)end of a microtubule attaches and grows outward; as it grows the new tubulin dimers add to the (+)end
71
dynamic instability
Microtubules switch between polymerization and depolymerization
72
Drugs that affect microtubules
taxol colchicine, colcemid nacodazole
73
How do microtubules help organize cellular contents?
-together with motor proteins work to organize cellular components (could be organelles, vesicles) -motor proteins interact with microtubules( pathway) -kinesins -dyneins
74
kinesins
Motor proteins that move toward the positive end of the microtubules -attach to growing ER and pull outward
75
dyneins
Motor proteins that move toward the negative end of microtubules -attach to growing Golgi membranes and pull inward toward molecules
76
Type of energy consumed in microtubule and motor proteins?
ATP
77
type of energy consumed in the assembly and disassembly of microtubules
GTP hydrolysis
78
cilia and flagella
-cellular extensions used for motility or to create current in the surrounding fluid -a specific arrangement of microtubules and associated motor proteins -eg. flagella 2 center microtubules with 9 doublet microtubules arranged in circular pathway around the center
79
MTOC for cilia and flagella
called a basal body -contains rings of gamma tubulin to nucleate the formation of microtubules
80
what are actin filaments?
-helical polymers of globular actin -polarized positive end and negative end -assemble and disable is dependent on ATP hydrolysis -assembles at the positive end and disassembles at the negative end
81
what is the function of actin filaments?
involed in cell mocemnt thought the interactions with other binding proteins -> Myosin proteins bind to actin filaments, bringing about, eg. muscle contraction, vesicle movement -> cell cortex -> Actin is part of a ring of proteins that pinches off two new cell at the end of cell division,n "cleavage furrow"
82
cell cortex
network of actin just inside the PM responsible for the shape and movement of the cell surface
83
Describe keratin as an intermediate filament
found in the cytoplasm of epithelial cells -> anchored at desmosomes -resists stretching and tearing in animal epithelial lining and covering -Specialized keratin in nails, feathers, claws, hairs
84
Describe nuclear lamin as an intermediate filament
↳ lamina Fibers found just inside the nuclear envelope ↳ Support the structure of the nuclear envelope ↳ disassemble during the degradation of the nuclear envelope during Mitosis

Cell Bio (3 decks)

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