Membranes
Review
Review
These are the macromolecules found in/on the cell membrane.
What are proteins (integral and peripheral), carbohydrates (glycolipid and glycoprotein), and lipids (phospholipids)
A hydrophobic substance moves from low concentration to high concentration across the membrane. List the method of transport and if ATP is required.
What is passive diffusion with no ATP?
This type of receptor works with hydrophobic messengers and is found inside the cell.
What are intracellular receptors?
A hydrophilic hormone cannot cross the plasma membrane. Identify which receptor class it will use and where on the cell it binds.
What is an extracellular receptor on the cell surface?
These extensions of the cell body serve as the receptive sites for electrical signals arriving at the neuron.
What are dendrites?
This would be the effect of removing the Na/K pumps from a neuron's membrane.
What is a lack of excitability (no membrane potential)?
These factors of Fick's diffusion are positively proportional to diffusion.
What are permeability, surface area and concentration difference?
A cell is placed in a hypertonic solution. List the direction water is moving and what happens to the cell.
What is water moving out of the cell to the area of higher solute concentration, causing cell shrinkage?
This is the molecule produced from ATP when the G-protein pathway activates adenylyl cyclase.
What is cAMP (cyclic AMP)?
These two molecules work to activate Protein Kinase C (PKC).
What are DAG and Calcium ions? (tip: look at the PLC diagram and pay attention to the small arrows)
This is the threshold potential range that triggers an action potential.
What is -55 mV to -50 mV?
Name the period when an action potential needs a higher initial depolarization voltage to reach the threshold and the channel that facilitates it.
What is the relative refractory period facilitated by slow-closing VGKCs?
These make up the four types of protein junctions in the cell membrane.
What are desmosomes, adherens junctions, tight junctions, and gap junctions?
This type of transport moves chemicals against their concentration gradient.
What is Active Transport?
In the G-protein pathway, name the nucleotide bound to the alpha subunit when it is at rest, and name what replaces it when activated.
What is GDP (at rest), and what is GTP (when activated)?
A drug blocks adenylyl cyclase. Starting from messenger binding, identify every step of the G-protein pathway that will NOT occur as a result.
cAMP will not be produced; protein kinase A (PKA) will not be activated; target proteins will not be phosphorylated; cellular response will not occur.
These labels and units are given to the X-axis and Y-axis of the action potential graph.
What are
X-axis: Time (msec)
Y-axis: Membrane Potential (mV)?
A graded potential is triggered in a dendrite. Name the type of channel that opens, the ions that could flow in, and the type of potential those ions cause.
Ligand Gated Channels
Na+ and Ca2+: Excitatory Postsynaptic Response
Cl-: Inhibitory Postsynaptic Response
These are the characteristics of osmosis.
What is the passive diffusion of water through a membrane from an area of high concentration to an area of low concentration?
A channel is phosphorylated by ATP, indicating that this type of active transport is occurring.
What is Primary Active Transport?
Name the two products formed when PLC cleaves PIP₂, and name what each product activates.
What are...
IP₃ — triggers release of intracellular calcium storage
DAG — activates protein kinase C (PKC)
An intracellular receptor binds and forms a complex within the nucleus; this cellular event occurs next.
What is the complex binding to the promoter region of DNA?
Name the two cells that produce myelin, identify where each is found.
What are Schwann cells (PNS) and oligodendrocytes (CNS)?
List the processes, ions, and structures involved in neurotransmitter release at the axon terminals.
AP arrives → voltage-gated Ca²⁺ channels open → Ca²⁺ mobilizes neurotransmitter-filled vesicles → neurotransmitter released by exocytosis into the synaptic cleft.
This is the main difference between active and secondary transport.
Active: direct usage
Secondary: indirect usage through another chemical's concentration gradient
A polar molecule needs to enter a cell. List the structural feature of the cell that prevents simple diffusion and the two transport mechanisms that could move it instead.
What is the hydrophobic nonpolar region of the phospholipid bilayer? What is facilitated diffusion (with gradient) or active transport (against gradient)?
What are adenylyl cyclase (AC) and phospholipase C (PLC)?
These molecules phosphorylate proteins in receptor cell signaling pathways.
What are protein kinases (Tyrosine Kinase, PKA, PKC, and CAMK)? (Tip: kinases indicate phosphorylation)
State the resting membrane potential of a neuron and the pump that maintains it.
What is −70 mV (maintained by the Na⁺/K⁺ pump)?
Novocaine blocks voltage-gated sodium channels. Name the phase of the action potential prevented by this drug, and why it would be prevented.
What is depolarization? (VGSC cannot open so Na⁺ cannot rush in; the membrane cannot reach peak potential (+30 mV) and no action potential is generated.)