Unit 5- Intracellular Activities Flashcards
All internal workings within cells must be _______.
Organized
What are the methods of organizing the cell?
Large, Multi-protein complextes Membrane-Enclosed Organelles
Nucleus
contains main genome, surrounded by nuclear envelope, nuclear pores facilitate communication between interior of nucleus and cytosol
Endoplasmic Reticulum
interconnected network of sacs and tubes, continuous with nuclear envelope; site of synthesis of membranes for cell and major site of protein modification (ER lumen)
Rough ER
has bound ribosomes, nascent proteins are delivered to rER membrane or into ER lumen
Smooth ER:
no ribosomes, major functions vary between cells types
Endocrine cells function:
Steroid Hormone Synthesis
Liver Cells Function:
Detoxification of alcohol and other organics
Muscle Cells Function
The site of Ca2+ Storage
Gogli Apparatus
receives proteins and lipids from ER and modifies them, dispatches them to destination
Lysosomes
degrade worn out organelles (autophagy), macromolecules and engulfed material
Endosomes
sort and dispatch engulfed material to destination, also may recycle it back to plasma membran
Peroxisomes
break down lipids and destroy toxic molecules using variety of oxidative reactions
Mitochondria
Energy synthesis
Membranous Organelles are held in place by the _______
cytoskeleton: serves as tracks along which organelles move
Membranous Organelles are Thought to have evolved in _________ through series of ________.
Eukaryotic Ancestor Invaginations
Non-membranous organelles treat interior of organelles as ______
Exterior
The Endomembrane system is composed of:
Composed of Nuclear Envelope, ER, Golgi, Lysosomes, Endosomes, Peroxisomes
Interiors of ES organelles communicate with each other via ______ that bud from one organelle/plasma membrane and fuse with next organelle or to plasma membrane
Vesicles
Protein content, both in lumen and membrane proteins, of organelles determines ______
Functions
Protein sorting occurs by what 3 mechanisms?
Through nuclear pores Transported across membranes Transport by vesicles
Pritein sorting is controlled by ___ ____ ______ of cargo proteins themselves (____ _____)
Amino Acid Sequence Signal sequences
Describe Transport through nuclear pores
Movement in/out of nucleus Pores penetrate both inner and outer nuclear membranes andfunction as selective gates that actively transport material across
Describe Transport across membranes
• Movement into ER, Mitochondria, some entry into Peroxisomes • Requires protein translocators, which facilitate movement
Describe Transport by vesicles
• Movement from one compartment of ES to next • Requires transport vesicles which carry cargo proteins and pinch off from one membrane and fuse with the next
Define: Signal Sequence
stretch of few (4) up to 50 AA in primary sequence of protein that directs protein • Often removed from sorted protein
The Nuclear Envelope is double-_______
membraned.
Inner Membrane of Nuclear Envelope:
Contains attachmetn sites (proteins) for certain regions of chromosomes and is associated with nuclear lamina
nuclear lamina
cage-like network of proteins, give shape to nucleus
Outer Membrane of Nuclear Envelope:
continuous with and similar to ER Membrane
The nuclear evelope is perforated by ____ ____ which facilitate active entry and exit of large molecules
Nuclear Pores
True or False: Small, soluble molecules can freely diffuse through nuclear pores
True
Nuclear pores are composed of ___ different proteins
30
True or False: Proteins lining pore have large, unstructured regions that form soft, tangled meshwork that prevents large molecules passage but allows small molecules
True
Tentacle-like fibrils extend from nuclear pore on the _____ side and failitate entry of approriate large molecules.
Cytosolic
Proteins destined for the nucleus are called
Cargo
Cargo Proteins contain what signas?
Nuclear Localization Signals (NLS)
the NLS is bound by ____ _____ _____ in the cytosol
Nuclear Import Receptors
Nuclear Import Receptors facilitate interaction within the meshwork of the _____ ______
Nuclear Pore
•Short, repeating AA sequences of non-folded proteins in meshwork interact with _____ ______ ______, “bumping” into one protein fiber and the next, making passageway for nuclear import receptor and cargo
Nuclear Import Receptor
Once it’s in nucleus, nuclear import receptor binds
Ran-GTP
NIR binding to Ran-GTP stimulates what?
NIR to release the cargo
Ran-GTP facilitates
Exit from the nucleus
In the cytosol, GAP stimulates Ran to hydrolyze
GTP to GDP
GAP
GTPase Activating Protein
Ran hydrolyzing GTP to GDP does what
Stimulates NIR to release Ran and free the receptor to bind new cargo
Proteins destined for the Mitochondria and Chloroplasts have signal sequences where?
N-Terminus
The signal sequence on the N-Terminus mediates the interaction with what?
Import Receptors and Organelle Surface
(when proteins are destined for mitochondria and chloroplasts) , the import receptor is associated with
The protein translocator
Complex of receptor protein translocator, import receptor and signal sequence-containing protein drifts within outer membrane until encountering ___________in ______ membrane
2nd Protein Translocator Inner
When a protein is destined for the Mitochondria and Chloroplasts, the two translocators move the proteins across the membrane, doing what to it in the process?
Unfolding it
Once the proteins are across the membrane in the mitochondria and choroplasts, what occurs?
The protein refolds and the signal sequence is removed
What are the two methods of peroxisomal import?
From the Cytosol From the ER
When proteins are imported to the Peroxisome from the Cytosol, the process requires ___ ____ similar to Mitochondrial Import
Protein Translocators
When proteins are imported to the Peroxisome from the Cytosol, are the proteins unfolded like in Mitochondrial import?
No, but their mechanism is unknown
When proteins are imported to the Peroxisome from the ER, while the proteins are being translated, they enter the ER and
eventually make their way to peroxisome via vesicles
The ER is the entry point for proteins destined for what areas?
ER, other organelles, and outside the cell.
Protein entry to ER occurs in (smooth/rough) ER
Rough ER Region
Two types of proteins are transported into the nucleus:
Soluble Transmembrane
Soluble proteins
Are not attached to the membrane- are completely translocated into the ER Lumen
Transmembrane proteins
Partially transported across the membrane and become embedded in it.
Protein entry to the ER requires
Signal Recognition Particle (SRP) and SRP Receptor
SRP binds ER signal sequence on nascent protein and translating ribosome which does what?
Slows translation
SRP Complex binds to what ____ embedded in the Er membrande
SRP Recetor
After the SRP recpetor is bound in the ER emembrane, wha occurs?
Translation resumes with the new region of the polypeptide being looped into the ER Lumen nd the signal sequence remaining anchored in the translator
Transmembrane Signal ______ cleaves the signal sequence from the completed rotein, releasing it into the ER membrane and Degraded
Peptidase
Cleavage results in what?
The release of protein into the lumen.
True or False: Transmembrane proteins have start and stop sequences.
True
In transmembrane proteins, N-terminal signal sequence gets ______ protein to membrane and then subsequent AA sequences (stop transfer sequence) halt translocation process
Nascent
What way does the translocator release proteins into the ER Bilayer?
Sideways
Some proteins have internal signal sequences and potentially more than one stop transfer sequences resulting in What?
multi-pass transmembrane proteins
In vesicular transport, Cells move soluble proteins and membrane between compartments (organelles) via _____ _____, allowing one to communicate with the other
Transport Vesicles
In vesicular transport, Progress is from ER to _____ to other organelles and/or ______ _____.
Golgi Plasma Membrane
only proteins and membrane components needed at destination should be ______
Transported
Coat proteins help form a ____ and help capture molecules to move to correct organelle
Bud
What is the function of coat proteins?
help form coated vesicles on parent organelle
Clathrin-Coated Vesicles Bud from the _____ and ____ ____
Golgi Plasma Membrane
Clathrin is recruited by
Adaptin
Adaptin binds specific transmembrane proteins in soon-to-be vesicle, forms a basket-like network that helps form an ______ or ___ which will become the vesicle
Invagination/Pit
_______forms a ring around the neck of the pit and eventually pinches it off the membrane
Dynamin
True or False: after Dynamin forms the ring, Adaptin and Clathrin bind the vesicle.
False: They release the vesicle
Vescicles are actively transported by what type of proteins?
Motor Proteins
Although they are transported by motor proteins, vesicles must dock with ____ _____.
Target Membrane
Rab Proteins:
GTPases bound to surface of vesicle and recognized by tethering protein attached to target membrane
GTPase
Are a large family of hydrolase enzymes that can bind and hydrolyze guanosine triphosphate (GTP). The GTP binding and hydrolysis takes place in the highly conserved G domain common to all GTPases.
Each organelle and vesicle have unique Rab and ____ proteins
Tethering
SNARES
once Rab/tethering protein interaction links vesicle (v) to target (t) membrane, these proteins facilitate docking and membrane fusion
vSNARE on vesicle surface interacts/intertwines with _______ on target membrane, providing energy for and driving process of membrane fusion, which is energetically (Favorable/Unfavorable)
tSNARE Unfavorable
Signal Transduction:
Conversion of external signal to internal signal
Extracellular Signaling Molecule
Molecule used by one cell to stimulate another
What are the various mechanisms for cellular communication?
Endocrine (Long Range) Paracrine (Short Range) Synaptic Contact-Dependent
Cells respond (or dont) based on what
Receptors they express
True or False: Response to same extracellular signaling molecule can vary from cell to cell
True
Cell’s overall behavior depends on what?
Signals from other cells
Endocrine signals are (long/short range)
Long Range
How do steroid hormones transmit their signals?
diffuse through membrane, bind nuclear receptors
Paracrine signals are (long/short) range
Short or Local Mediators
Dissolved gases transmit their signals by
Diffusing through the membrane, binds to ad regulates specific proteins in a target cell.
How do proteins, peptides, amino acids, and nucleotides use extracellular signaling?
bind various cell-surface receptors
What are some examples of proteins, peptides, amino acids, and nucleotides using extracellular signaling?
G-protein-coupled receptors (GPCRs), Receptor Tyrosine Kinases (RTKs), ionchannel-coupled receptors
Synaptic Extracellular Signaling
Neurotransmitters: bind ion-channel-coupled receptors
What is an example of Contact-Dependent Extracellular Signaling?
Various • Example: Glycoproteins from one cell bind leptins on another
Steroid hormones are ____ (Lipid-Based) and (passs/cannot pass) directly though membrane
Hydrophobic Easily pass
Steroid Hormone Singlaing: In cytosol or nucleus, hormone binds _____ _______, changing receptor’s conformation such that it now binds DNA and regulates transcription
Nuclear Receptors
True or False: NO (nitric oxide) cannot pass directly through membrane of cells
False: Nitric Oxide passes directly through the membrane.
Nitric Oxide works only locally. Why?
because it easily interacts with O2 and H2O, which are abundant, resulting in loss of activity
Nitric Oxide is produced by what type of cells?
endothelial cells that line blood vessels and stimulates smooth muscle cells (SMCs) in vessel walls
Nitric Oxide binds and activates ______ ______, which produces cGMP which through its own set of activities stimulates relaxation of SMC
Guanylyl Cyclase
What are cell-Surface Receptors?
Transmembrane receptors that take message from outside of cell and convert it into an internal signal of a different form
Upon Binding by ligands, cell-surface receptor proteins initate what?
intracellular signaling process(es) where message is passed “downstream” from one intracellular signaling molecule to another • Functions and results of intracellular signaling pathways vary
What are the various types of Cell-Surface Receptors?
GPCRs RTKs
What is a GPCR
G-Protein Coupled Receptor
True or False: There are only 3 trypes of GPCRs
False: There are over a thousand different types of GPCRs.
The seven-pass transmembrane protein functions as what?
functions as receptor • When activated, binds and activates accessory G-proteins (G = GTPase), alpha & beta-Gamma
Before activation, GPCR and G Proteins are ____, may or may not be associated prior to activation
Inactive
Upon Ligand binding, ____ conformation changes, which in turn alters G-Protein’s conformation
GPCR’s
Aleration of the Alpha subnit of the G-Protein does what?
Allows for exchange of bound GDP for GTP, activating the Alpha and Beta-Gamma Subunits
Activated Alpha and Beta-Gamma subunits may or may not ____ befre interacting with tragets/effector proteins.
Dissociate
In the G-Protein inactivation, what controls the duration of the response?
The Alpha Subunit
The Aplha subunit eventually hydrolyzes What into What in G Protein Inactivation?
GTP to GDP, inactivating the Aphla Subunit.
in G Protein inactivation, the Aplha subunit binds active ___ ____ , resulting in that subunut’s inactivation.
Beta-Gamma
When both subunits are inavtivaed in G-Protein inavtibation, they are raeasdy for what?
Re-Activation
What toxins work by impacting the duration of Alpha Subunit Activity?
Pertussis, Cholera
G Proteins vary depending on type of _____ _____ they activate, which often produce secondary messengers that impact other cellular components
Effector Proteins
What are the types of G-Proteins
Ion-channel activating • Gs • Gi • Gq
Gs activates
activates adenylyl cyclase whichconverts ATP to cAMP
Gi function:
Inhibits Adenylyl Cylcase
Gq Function:
activates Phospholipase C which generates inositol triphosphate (IP3) and diacylglycerol (DAG), both of which function as secondary messengers
IP3
Inositol Triphosphate
Diaglycerol
DAG
phosphodiesterase
comverts Camp into AMP
Camp is produced by
Adenylyl Cylcase
Camp activates what?
cAMP-dependent protein kinase (aka PKA)
PKA phosphorylates various _____ and _____ AAs in various proteins resulting in activation or deactivation.
Serines Theronines
In Gq-mediated activation of Protein Kinase C , activated Gq activates what?
PLC/Phospholipase C
Phospholpiase C produces ______ and souble IP3
Diaglycerol (DAG)
IP3 diffuses Ligand-gated ___ channels in the ER membrane , opening them.
Ca2+ Binds Protein Kinase C (PKC)
In Gq-mediated activation of Protein Kinase C , DAG binds ___.
PKC
In Gq-mediated activation of PKC, the Combination of Ca2+ and DAG binding PKC (activates/Inactivates) PKC
Activates
Active PKC has similar (in terms of variety) activities to activated ____.
PKA
Enzyme-coupled Receptors
Transmembrane receptors that have enzymatic activity associated with intracellular regions OR that associate with enzymes upon activation
What are the types of Enzyme-Coupled Receptors’ responses?
Slow(Hours) Rapid
Slow ECR responses?
responses that often involve changes in gene expression • Signaling molecules causing this type of response are often growth factors
Rapid ECR Repsonse
responses that alter cytoskeleton and potentially cell movement • Signaling molecules causing this type of response are often attached to ECM
What is a common type of Enzyme-Coupled Receptor?
Receptor Tyrosine Kinase (RTK)
Ras
Small, membrane-bound, monomeric GTPase that is activated by all RTKs
Ras is active when has _____ bound, eventually hydrolyzes GTP to ____, inactivating it (similar to Ga)
GTP
Ras-Guanine Exchange Factor (Ras-GEF)
Ras-Guanine Exchange Factor (Ras-GEF) stimulates exchange of GDP for GTP • Active RTK recruits and activates Ras-GEF, resulting in Ras activation
• Ras-GTPase-activating Protein (Ras-GAP)
stimulates GTPase activity of Ras
Activated Ras results in several Serine/Threonine phosphorylation events which helps ?
send signal from RTK to nucleus
MAP
mitogen-activated protein
MAP-Kinase is what type of molecule?
Signaling
Ras activates
MAP Kinase Kinase Kinase
MAP Kinase Kinase Kinase activates
MAP Kinase Kinase
MAP Kinase Kinase activates
MAP Kinase
MAP Kinase Activates
several transcription factors associated with proliferation
RTKs may aso activate
PI3K
PI3K Phosphorylates
inositol-lipids in plasma membrane
True Or False: PI3K phosphorylates inositol-lipids in plasma membrane which creates docking sites for various signaling proteins that can activate each other now that they’ve been recruited to membrane
TRUE
AKT is also kown as
PKB
AKT/PKB has various targets with overall effect of promoting cell survival:
Bad TOR
BAd
protein that promotes cellular suicide. PKB inactivates Bad.
PKB inactivates
Bad
Tor
protein that enhances protein synthesis and inhibits protein destruction, ultimate result of which is promotion of cell survival and growth
GPCRs and RTKS
Both types of receptors activate myriad of pathways that may directly or indirectly impact each other
