Exam 3 Flashcards
What are the tubular membranes in the ER called?
Flattened sacks
Cisternae
What is the space called within the ER lumen?
Cisternal Space
List the two types of ER
Rough
Smooth
Is the smooth ER associated with synthesis?
No
Where are the proteins made by the RER destined?
Secretion or membrane bound proteins
Which side are the ribosomes attached to on the RER?
Cytosolic side
Is the rRNA charge positive or negative in the RER?
Negative
Where do the proteins destined for secretion go after the RER?
Golgi
Proteins made by the RER ribosomes are generally imported into the RER cisternal space by a process known as…..
Cotranslational Import
How are the proteins made by the RER transported to the cisternal space?
Translocon
What are the 3 different protein signal sequences?
ERSS
Internal Stop transfer sequence
Internal Start transfer Sequence
Where does the ERSS direct import?
Translation of the ribosome
N-terminal
Once the ERSS is made where does the ribosome dock?
Translocon via SRP and temporarily blocks translation
What is the job of SRP
Direct to translocon
Which side of the ERSS protein is cleaved off?
N terminus
List the steps of cotranslational import
SRP binds to ERSS SRP takes polypeptide to translocon Dock GTPs bind to SRP and unblocks translation GTP to GDP release SRP ERSS is cleaved off (N terminus) C terminus leads polypeptide to ER lumen
What does insulin regulate?
Blood glucose levels
Where is n-linked
RER
Where is o-linked?
Golgi
What is the job of the Internal Stop Transfer
To stop the translocation at the site. iN and C cytosol
What is the job of the internal Start Transfer?
Signals SRP to dock with the translocon
What is the main job of the Smooth ER?
Drug detox
Cabohydrate metabolism
Calcium storage
Hormone biosynthesis
What is the Golgi involved in?
Processing and Packaging
How many cisternae does the Golgi have?
3-8
What are the two sides of the Golgi?
Cis- forming
Trans- maturing
What is the Cis Golgi closest to?
RER
Define compartmentalization.
Processing enzymes in the intracisternal space of the golgi
What are the two models for material flow through the Golgi?
Stationary model and Maturation model
What is the most supported model of material flow in the Golgi?
Maturation model
What is the ERGIC tubulovesicular structure?
The space between the Golgi and the ER
Which way do materials move in the Golgi?
CGN toward TGN
All known Golgi-specific proteins are ______ proteins many with just a single transmembrane domain.
Integral membrane
What are the 3 main fates for transport vesicles from the Golgi?
Secretory vesicles, endosomes (lysosomes) or retrograde transport
What is the function of the lysosome?
digestion
How does a lysosome form?
Endocytic vesicles and early endosomes
Late endosomes
Mature lysosome due to pH lowering in lumen
V pump
Protein modification in the RER
N linked to asparagine
Protein modification in the golgi
O linked to serine and threonine
What does protein sorting depend on?
Sequence tags
Transmembrane domain length
Constitutive secretion
continuous secretion, unregulated
Regulated secretion
concentration of materials in the vesicle
ex insulin
What is a specific example of a protein destined for the regulated secretion pathway. Hint: glucose balance
GLUT 4
Where is GLUT 4 synthesized?
RER
What are the two main mechanisms for cell signaling?
Electrical and Chemical
Which system utilizes electrical signals?
Nervous system
What are the two main categories of cells in the nervous system?
Neurons and Glial cells
Define membrane potential
An unequal distribution of ions across a cellular membrane.
Vm
inside with respect to outside of the cell
Quantitative electrical difference across the membrane
What are the three ions that membrane potential relies on?
Na, K, Cl
Electroneutrality
The charged particles can be separated
How many of each ion does the Na/K pump out/in?
3 Na out 2 K in
Equilibrium potential
The voltage difference across the membrane
What is the resting membrane potential for mammals
~-70–80
At rest, is the membrane polarized or depolarized?
Polarized
Graded potentials
A signal that is of varying magnitude
True or False. Graded potentials dissipate with distance along a membrane and time
TRUE
Action potential
an all or nothing response. magnitude invariable
Does action potential dissipate as it travels along the membrane?
No
What causes changes in permeability of the cell membrane?
Opening or closing of some ion channel
Integral membrane proteins that form ion-conducting pores across the membrane are_________
gated
Ligand-gated
Will open in response to binding of ligand
Voltage gated
Will open in response to a change in membrane potential
What mechanism is used in the Inactivation gate?
Ball and Chain
What are action potentials?
Large electrical depolarizations and repolarizations of the plasma membrane
Which channels are involved in the action potentials?
K and Na
AP depolarization
Opening of Na channels
Positive inside
Approaches E na
AP repolarization
Opening of K channels
Negative inside
Towards Ek
AP hyperpolarization
undershoot due to prolonged opening of K channels
What is required in order for AP to occur?
Threshold must be met
What is the resting potential for the Na/K gate?
-60mV
What causes the absolute refractory period?
Na channel inactivation
When can the Na diffuse into the cell for the depolarization period?
Once the cell is depolarized to threshold
When does repolarization occur?
When K diffuses out
Hyperpolarization
When K continues to flow out, overcorrection
Subthreshold depolarization
Depolarization does not reach threshold
Does the membrane potential ever reach the Ena?
NO!
Why can no stimulus cause another action potential in the absolute refractory period?
The na channels cant be opened
What is relative refractory period
Inactivation gate is opened for Na during repolarization and beginning of hyperpolarization
What causes the gates to open and close?
Initial depolarization to threshold
When is deinactivation?
-40 - -80 during repolarization
During repolarization are the Na channels inactivated or closed?
Inactivated
What is the period called when the Na channels are inactivated?
Refractory period
Can an AP occur in the relative refractory period?
Yes but it is more difficult
True or false
The refractory period prevents APs from occurring too close together in time. APs cannot summate
TRUE
How do APs travel on the axon?
Down from the point of origin and spread passively
What is electrotonic or passive spread?
The magnitude of the initial depolarization is lower at sites distant from the initial site
What does lambda represent?
Space that it takes for the voltage to decay to 37%
Is passive electrotonic spread of the depolarization AP conduction?
NO
________ Spread passively to surrounding regions
Depolarizations
Which direction does passive spread occur?
All directions
Anatomy of myelinated axon
multiple intermittently spaced sheaths of membranes wrapped around the axon
Myelinated axon
Sheaths that are wrapped around the axon
What are the gaps between the sheaths called?
Nodes of Ranvier
Myelination allows for more _______ conduction velocities.
Rapid
Which provides faster dispersal?
Myelinated is faster
How is the electrical signal transmitted from cell to cell?
Synapses
post and pre
How many neurotransmitters does each presynaptic cell have?
One main
Depolarization=Excitatory
Excitatory post synaptic potential
Hyperpolarization=inhibitory
Inhibitory postsynaptic potential
(Pre or post synaptic cell?)
AP causes voltage gated Ca channels in the membrane to open at the terminal bulb
Pre synaptic
Pre or post synaptic?
Ca 2+ diffuses into the cell and causes synaptic vesicles to fuse to the presynaptic membrane
Neurotransmitter is released into the cleft
Pre synaptic
Pre or post synaptic?
Neurotransmitter binds to its receptor
Post synaptic
Pre or post synaptic?
Induces a change in membrane conductance (ESPS or IPSP which are graded potentials)
Post synaptic
What mechanism is used to fuse the synaptic vesicles and the presynaptic membrane?
Ca 2+ induced exocytosis
What are the three main vesicles present in the terminal bulb?
Undocked
Docked
Docked and primed
On the vesicle there are V snares and synaptotagmin
Found in the vesicle
True or false
Docking proteins are tethering proteins
True
What does priming involve?
Interactions of v-snares and t-snares
What are toxins that interfere with vesicle release?
Botox, tetanus and presynaptic blockers
Ionotropic
The receptor is the channel
Metabotropic
The receptor communicates with a channel indirectly
Ionotropic receptor example
nachr opens the Na+ channel
Ionotropic receptor example
GABAa opens the Cl- channel
Metabotropic Receptor example
GABAb leads to opening of K channels, hyperpolarization
Are postsynaptic potentials additive?
Yes! Time and space
How can the activation state of the postsynaptic cell be determined?
Net influence of all the excitatory and inhibitory influences
What type of potentials are the incoming electrical signals at the dendrites and soma?
Graded IPSP and EPSP
Do IPSP and EPSP potentials degrade with time?
Yes
Why can’t the dendrites or soma fire APs?
Because of the channel types that they are.
Can neurotransmitters be removed from the synapse by transport into the cells?
Yes
True or False
All neurotransmitters are simply degraded like Ach.
False
