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53 Cards in this Set
- Front
- Back
Nuclear protein import steps
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1) Nuclear localization signal-short amino acid sequence that directs a protein to the nucleus
2) nuclear transport receptors bind nuclear localization signal 3) Receptor interacts with nuclear pore fibrils 4) Receptor and protein pulled into nucleus 5) Receptor returned to cytosol |
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Protein translocation
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1) Proteins enter mitochondria and cholorplasts
2) Protein is unfolded during transport 3) Signal peptide cleaved after translocation 4) Chaperones refold the protein |
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Purpose of vesicle coating
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Helps shape vesicle
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Purpose of protein glycosylation
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1) Protection from degradation
2) Hold in ER for folding 3) Help guide to appropriate organelle 4) Cell recognition |
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Protein Glycosylation steps
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1) Polypeptide enters ER
2) Membrane lipid (dolichol) linked to oligosaccharide 3) Oligosaccharide from dolichol transferred to asparagine residue of incoming protein |
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ER-retention signal
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C-terminal sequence that signals a protein to stay in the ER
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Protein sorting steps
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1) Proteins are tagged
2) Proteins are sorted 3) Vesicles bud 4) Proteins interact with receptors 5) Delivery |
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Constitutive secretory pathway
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1) Continual operation in all cells
2) Bud from golgi 3) Fuse with plasma membrane 4) Deliver protein to membrane or extracellular fluid |
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Regulated secretory pathway
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1) Only in specialized cells
2) Secretory vesicles accumulate near the plasma membrane 3) Extracellular signal stimulates fusion with membrane |
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Cystic fibrosis
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1) Production of thick mucus in lungs and digestive tract
2) Autosomal recessive inheritance 3) Caused by protein misfolding |
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Vesicle docking steps
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1) Rab proteins - on surface vesicle
2) Tethering proteins - on cystolic surface of target membrane 3) v-snares - on vesicle membrane 4) t-snares - on target membrane |
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Types of endocytosis
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1) Phagocytosis
2) Pinocytosis 3) Receptor-mediated endocytosis |
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Steps of phagocytosis
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1) Solid particle enters pseudopodium
2) Becomes phagosome in cell |
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Steps of Pinocytosis
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1) Small particle enters pseudopodium
2) Becomes engulfed by vesicle in cell |
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Steps of receptor-mediated
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1) Specific particles enter coated pit on receptor
2) Turns into coated vesicle with coat protein in cell |
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How does tuberculosis trick the immune system
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It is taken up by macrophages but blocks fusion of phagosome and lysosome
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Cholesterol absorbtion
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1) LDL binds cell receptors
2) LDL enters cell via receptor-mediated endocytosis 3) LDL fuses with endosome 4) LDL dissociates from receptor 5) LDL delivered to lysosomes 6) Receptor returned to plasma membrane |
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Endosomes
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- Sorting station for endocytic pathway
- Acidic environment causes receptor and cargo to dissociate - Digestion of cargo begins |
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Lysosomes
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- Principle site of intracellular digestion
- Formed by fusion of transport vesicles from the golgi and endosomes - Contain hydrolytic enzymes - Acidic environment |
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3 types of cell signaling
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- Endocrine
- Paracrine - Neuronal |
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How endocrine cell signaling works
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The hormone enters the blood stream, finds target cell and binds to the receptor
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How paracrine cell signaling works
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Local mediator leaves signaling cell and binds to receptor of target cells
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How neuronal cell signaling works
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Neurotransmitter from neuron attaches to target cell at synapses
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How contact-dependent cell signaling works
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membrane bound signal molecule binds to target cell directly
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3 examples of signaling molecules
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- Hormones: glucagon and insulin
- Local mediators: epidermal growth factor (EGF) - Neurotransmitters: acetylcholine |
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3 types of receptors
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- G-protein coupled receptors
- Enzyme-linked receptors - Intracellular receptors |
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Steroid hormone binding
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- Bind outside nucleus in cytosol or in nucleus to receptor protein
- Hydrophobic molecules - Transcription regulators - Hormone-receptor complex binds to DNA |
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Cell surface receptors
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- Transmembrane proteins
- Binding to extracellular signal to receptor initiating intracellular response - Signal relayed from molecule to molecule until desired response is achieved |
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Androgen insensitivity syndrome
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- Genetic males (XY) unable to respond to angrogen due to defective androgen receptors
- X-linked recessive disorder - External female genitalia, internal male genitalia |
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Intracellular signaling pathways
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Relay - pass signal to next moleculeAmplify - make the signal strongerIntegrate - Coordinate signals from multiple pathwaysDistribute - Pass signal to more than one pathway
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3 Classes of cell surface receptors
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- Ion-channel-coupled receptors
- G-protein-coupled receptors - Enzyme-coupled receptors |
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Ion-channel-coupled receptor
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- Simplest and most direct receptor
- Transduces a chemical signal into an electrical signal - Results in alteration of membrane potential - Example: nicotinic actylcholine receptor |
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Structure and function of G-Protein-coupled receptors
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- Seven pass transmembrane protein receptor
- Hydrolysis of GTP |
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G-protein-couple receptor targets
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-Ion Channels
- Binds to ion channels to open them - EG: K+ channel in heart muscle Membrane bound enzymes - Adenylyl cyclase - produces cyclic AMP - Phospholipase C - produces inositol triphosphate and diacylglycerol |
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Cyclic AMP pathway
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1) Activated g-protein subunit activated adenylyl cyclase
2) Increases production of cAMP 3) cAMP activates cyclis AMP-dependent protein kinase (PKA) 4) Kinase phosphorylates a set of proteins 5) Signal terminated by cyclic AMP phosphodiesterase |
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Inositol phospholipid pathway
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1) Phospholipase C cleaves inositol phospholipid into 1,4,5-triphosphate (IP3) and diacylglycerol (DAG)
2) IP3 diffuses into cytosol 3) Binds to Ca2+ channel on ER 4) Ca2+ rushes into cytosol and triggers other pathways 5) DAG activated protein kinase C (PKC) |
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Calcium triggered processes
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- Cytosolic Ca2+ usually low
-Ca2+ stored in cytosol - Influx of Ca2+ into cell triggers calcium responsive proteins |
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Receptor tyrosine kinase pathway
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1) Two receptors proteins form a dimer
2) Activation of receptor tyrosine kinase 3) Intracellular signaling proteins bind the active receptor tyrosine kinase (RTK) 4) Signal relayed to numerous cellular locations 5) Protein tyrosine phosphatase terminates the response |
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RAS Protein
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- membrane bound protein
- active when bound to GTP - activates a phosphorylation cascade |
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3 types of protein filaments
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- Intermediate filaments
- Microtubules - Actin filaments |
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Structure and function of intermediate filament
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Structure
- Long, twisted strands of protein - Tetramers twist into a rope Function - form a network to allow cell to withstand mechanical stress |
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Role of keratins
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distribute stress throughout cells
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Lamin
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Intermediate filaments that make nuclear lamina, must disassemble and reform during mitosis
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Microtubules
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- long, stiff hollow tubes of protein
- guide intracellular transport |
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Growth of microtubules
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- Tubulin subunits added to + end of growing microtubules
- Shows dynamic stabilitiy - packs efficiently when GTP is bound - packs loosely when GDP is bound |
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Antimitotic drugs
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- Colchicine: binds tightly to free tubulin
- Taxol: binds to microtubule to prevent depolymerization |
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Kinesins and Dyneins
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Kinesins: move towards the + end of microtubules
Dyneins: move towards the - end of microtubules |
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Actin filament
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Essential for movement
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Actin filament polymerization
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- Faster addition of subunits at the + end
- Actin monomer to ATP - ATP hydrolyzed after incorporation of monomer into the filament |
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Cell cortex
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Actin rich layer responsible for cell movement
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Myosin
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Head and tail region
- Head: interacts with actin, has ATP hydrolyzing motor - Tail: determines what the motor moves |
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Steps of muscle contraction
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1) Z lines pulled together
2) A band inceases 3) I band, H zone shorter 4) Contraction increases, overlap increases 5) Thick myofilament stationary (myosin) 6) Thin myofilament moves in/out (actin) |
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Rigor Mortis
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- Begins 2-6 hours post mortem- ATP no longer available - actin and myosin remain bound to eachother- Muscles stay rigid until autolysis begins- Onset and duration of rigor affected by: - ambient temp - exertion prior to death - body condition - age
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