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124 Cards in this Set
- Front
- Back
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Where does Membrane Lipid Biosynthesis occur? |
ER |
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5 Steps of Membrane Lipid Biosynthesis in ER |
1. Insertion of Fatty Acid into cytosolic face 2. Addition of CoA to Fatty Acid 3. Attachment of glycerol 3-P to FA-CoA 4. Removal of phosphate group 5. Addition of a polar group |
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What catalyzes the 5 Stops of Membrane Lipid Biosynthesis in ER? |
Embedded enzymes in the ER membrane |
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Which side of the ER are Phospholipids Synthesized? |
Cytosolic Face |
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What does scramblase prevent/counteract? |
Asymmetry of the bilayer (since phospholipids are only added on one side) |
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What does Scramblase do? |
"Randomly" moves phospholipids across the bilayer |
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Is Compoitional Asymmetry Desirable? |
Yes, the different phospholipid composition helps function |
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What Role does Flippase and Floppase Play? |
Maintains Compositional Asymmetry |
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What do Flippase and Floppase do? |
Flip specific phospholipids across the bilayer. Flippase in one direction, Floppase in the other. |
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Do things/proteins/sugars stay on their same side even during transport? |
Yes |
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How do membrane bound organelles that don't make their own phospholipids get them/? |
Proteins in the cytosol take them there |
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4 Functions of Membrane Proteins |
1. Transport and Channels 2. Anchors 3. Receptors 4. Enzymes |
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Types of Membrane Protein Attachments |
1. Transmembrane 2. Monolayer Associated alpha helices 3. Lipid Linked 4. Protein-Attached |
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Name the Integral Protein Attachments |
1. Transmembrane 2. Monolayer Associated 3. Lipid Linked |
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Name the Peripheral Protein Attachments |
Protein-Attached |
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Are the outsides of Tranmembrane Proteins Hydrophilic or Hydrophobic? |
Hydrophobic |
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What does the Protein Bacteriorhodopsin do in Archae? |
Light causes a conformational change in it, which moves a proton across the membrane, creating a proton gradient that can be used to generate ATP |
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Beta Barrel |
Beta Sheets arranged in a Barrel shape. Inside is Hydrophilic, outside is Hydrophobic |
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Membranes Diffuse Laterally: T/F |
True |
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How did the human-mouse experiment work? What did it prove? |
A hybrid human-mouse cell was made and the colored proteins from each mixed together. Proved lateral protein diffusion. |
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How did the Fluorescence Recovery After Photobleaching (FRAP) experiment work? What did it prove? |
A small area of the cell was bleached. After some time there was no visible bleached area. Proved lateral protein diffusion. |
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4 Ways Movement of Membrane Proteins Can be Restricted |
1. Linked to cell cortex 2. Linked to ECM 3. Linked to Membrane Proteins in another cell 4. Tight Junctions Restrict the area of diffusion |
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Cell Cortex |
Provides support, is on the inside face on the membrane |
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How can we isolate membrane proteins? |
Use detergents and the proteins will aggregate |
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What is the cell surface coated with? |
Carbohydrates |
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What do the carbohydrates on Neutrophil do? |
They act as signal that let the cell squeeze between cells and fight infection |
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Diffusion |
Spontaneous net movement of particles down a concentration gradient |
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Particles that will diffuse across the membrane |
Small Nonpolar Molecules (O2, C02, N2) *Slowly* Small Uncharged Polar (H20) *SUPER Slowly* Large Uncharged Polar (Amino Acids) |
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Particles that won't diffuse across the membrane |
*Effectively* Large Uncharged Polar (Amino Acids) Ions |
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Partition Coefficient |
Measure of Hydrophobicity |
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A High Partition Coefficient = ... |
More Hydrophobic |
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4 Key Points about Concentration Gradients |
1. Takes NRG to establish them 2. Free NRG is stored in them 3. Free NRG is released when molecules move down them. 4. Amount of NRG released depends on magnitude of gradient |
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Electrochemical Gradient = ____ + _____ |
Concentration Gradient + Membrane Potential |
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What's faster Transporters or Channels? |
Channels |
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What's the distinguishing feature of a Transporter? |
A binding reaction occurs that causes a conformational change in the transporter |
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Saturable |
A maximum substrate velocity |
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Is Facilitated Diffusion Saturable? |
Yes, it has a maximum substrate velocity |
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Is Simple Diffusion Saturable? |
No |
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Is the Partition Coefficient relevant for Protein Mediated Transport? |
No |
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What is Km? |
Substrate Concentration at (1/2) Vmax |
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Does a lower Km mean a higher or lower affinity for substrate? |
Higher |
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Does passive transport require NRG? |
Yes, but in the form of a concentration gradient |
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What does active transport require? |
Input of additional energy |
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Are Transporters Active or Passive Transport? |
Either |
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Are Channels Active or Passive? |
Passive |
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Energy sources of Active Transport |
1. Second Substrate Concentration Gradient (Coupled Pump, Secondary Active) 2. ATP 3. Light |
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Uniport |
Moves 1 kind of solute at a time (can move multiple solutes, but must be the same kind) |
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Symport |
The ion and co-transported ion are transported in the same direction across the plasma membrane |
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Antiport |
The ion and co-transported ion are transported in opposite directions across the plasma membrane |
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Gut lumen -> Gut Epithelium is what kind of transport? |
Active, symport, coupled, Sodium Coupled Glucose Transporter (SCGT) because low glucose in gut lumen and high glucose in gut epithelium. High Sodium in gut lumen, low sodium in gut epithelium |
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Gut Epithelium -> Interstitial Fluid |
Passive, Uniport, GLUT |
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Interstitial Fluid -> Blood |
Passive, Uniport, GLUT |
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Blood -> Interstitial Fluid |
Passive, Uniport, GLUT |
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Interstitial Fluid -> Muscle Cells |
Passive, Uniport, GLUT |
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How does Insulin effect [blood glucose]? |
Decreases [blood glucose] |
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Liver, Insulin Effect |
Glucose -> Glycogen (indirect effect on transporters) |
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Muscle, Insulin Effect |
Glucose -> Glycogen (direct effect on transporteres) |
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Adipose, Insulin Effect |
Glucose -> TAG (direct effect on transporters) |
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How does Glucagon effect [blood glucose]? |
Increases [blood glucose] |
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Liver, Glucagon Effect |
Glycogen -> Glucose (indirect) |
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How does insulin directly increase glucose uptake by muscle cells? |
Stimulates vesicles containing glucose transporters to fuse with plasma membrane. Which increases number of glucose uniporters in plasma membrane (which moves glucose into cell). |
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P type ATP Powered Pump |
Phosphorylated Intermediate |
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V type ATP Powered Pump |
On a Vacuole or Lysosome's membrane |
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ABC Superfamily ATP Powered Pump |
ATP binding cassette Most Diverse class Has 2 domains where ATP attaches |
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F type ATP Powered Pump |
Funny because it generates ATP (aka ATP synthase) |
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What type ATP Powered Pumps only move H+ |
V type and F type |
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What do Plants, Fungi, and Bacteria use to establish electrochemical gradient? |
H+ pump, whereas animals use Na+/K+ pump |
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How do animal cells deal with water? |
They use gel-like cytoplasm |
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How do plant cells deal with water? |
They use their cell wall and water vacuoles |
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Characteristics of Non-Selective Channels |
Large diameters Beta Barrels Examples: Porins, Gap Junctions |
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Characteristics of Selective Channels |
Majority of Channels Examples: Aquaporins, Ion Channels |
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Gap Junctions |
Membrane channels allow material go directly from one cell to the other connected cell |
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Adhesion Junctions |
Fibers stick out and attach membranes together |
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Tight junctions |
a specialized connection of two adjacent animal cell membranes such that the space usually lying between them is absent. |
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Are aquaporins specific? |
Yes, they're very specific for water |
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How many aquaporins are in 1 aquaporin? |
4 |
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What part of channels is selective? |
The selectivity filter |
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How does a selectivity filter select? |
1. The ion has to be the required size. Too large ions won't fit and too small won't make the correct bonds 2. The ion has to have the required charge to make the correct chemical bonds. |
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Why doesn’t Na+,which is smaller than K+,pass through the K+ channel? |
Because it doesn't interact correctly with the side chains on the channel, so water will stay attached and make it too large to fit through the channel |
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Name All the Types of Gated Ion Channels |
1. Voltage Gates 2. Ligand Gated (Extracellular and Intercellular) 3. Mechanically Gated |
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Voltage Gated Ion Channel |
Change in membrane potential opens/closes the gate |
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Ligand Gated Ion Channel |
Binding ligands opens/closes the gate |
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Non-gated channels spend most of their time open or closed? |
Open |
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Gated channels spend most of their time open or closed in absence of stimulus? |
Closed |
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Resting Membrane Potential Major Players |
Na+/K+ pump/ATPase (10%) K+ Leak Channels (90%) |
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What type is Na+/K+/ATPase? |
P type |
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What is the net movement of charges from Na+/K+/ATPase? |
+1 to outside the cell |
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What is the result of Na+/K+/ATPase over time? |
High [K+] and low [Na+] |
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What is the most important use of the gradient created by Na+/K+/ATPase? |
It's use for K+ Leak Channels |
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What does the Leak K+ Channel do? |
Moves K+ outside the cell |
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Is Leak K+ Channel Passive or Active? |
Passive? |
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What drives Leak K+ Channels? |
Concentration gradient (High K+ inside, low K+ outside) Voltage gradient (net - inside cell, net + outside cell) |
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Membrane Potential |
Separation of charges across the membrane |
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Action Potential |
Localized, brief, rapid reversal ofthe potential across the plasma membrane |
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Parts of Neuron |
Dendrites Cell Body Axon Axon terminals |
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Dendrites |
Short numerous appendages that receive info |
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Axons |
Usually 1, sends info out of the cell |
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Nerves |
Groupings of neurons |
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In order for an action potential to occur, what must be reached? |
Threshold Potential |
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All or nothing describes... |
Action Potentials (exception: Postsynaptic Potential) |
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What instrument can measure action potentials? |
Electrodes |
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Voltage Gated Na+ Channel States |
Closed Open Inactive |
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Refractory Period |
Open to Inactive State in Voltage Gated Na+ Channels |
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When Voltage Gated Na+ and K+ channels are open where do the ions move? |
Down their concentration gradients. Na+ into the cell. K+ out of the cell. |
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What resets the Concentration Gradient and Voltage Gradient after the Action Potential? |
ATPase |
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Action Potentials are Non-Decrimential. What does this mean? |
It means the peak Membrane Potential (+40 mV) doesn't lose intensity |
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What does a positive feedback loop mean for Na+ Voltage Gated Channels? |
It means that after a couple Na+ gates open, it cause more Na+ gates to open, causing more ..., causing more.......................... |
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How does AP in one region stimulate AP in adjacent region? |
The change in membrane potential caused by the intake of Na+ is the depolarizing event which starts the AP in the adjacent region |
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In an Action Potential, when the Voltage Gated Na+ Channels open, where in the cell are the Na+ ions going? |
Everywhere |
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What gives AP's their uni-directionality? |
The inactive state of Na+ Voltage Gated Channels because they can't open due to a depolarizing event |
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Synaptic Vesicles |
Vesicles filled with neurotransmitters |
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On the post-synaptic cell, what kind of gate does the neurotransmitter receptor use? |
Ligand gated |
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What does the Neurotransmitter do? |
Opens an ion channel, which changes the Membrane Potential in the Post-synaptic cell. |
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When does the Ca++ Voltage Gated Channel open? |
When the Action Potential reaches the axon terminal |
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What does Ca++ cause when it moves into the cell due to an open Ca++ VG channel? |
It causes the exocytosis of the neurotransmitter |
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What re-establishes the [Ca++] in pre-synaptic cell? |
Active Ca++ ATPase |
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Excitatory Synapse |
Increases membrane potential of Post-Synaptic Cell |
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An Example of an Excitatory Synapse |
Na+ |
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Inhibitory Synapse |
Decreases membrane potential in post-synaptic cell |
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An Example of an Inhibitory Synaps |
Cl- |
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Can the pre-synaptic cell secrete more than 1 kind of neurotransmitter? |
No, it can only secrete 1 kind |
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Can the post-synaptic cell receive more than 1 neurotransmitter? |
Yes |
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Do the same neurotransmitters have the same effect in different cells? Why? |
No they can have different effects in different cells because different cells have different neurotransmitter receptors that have different effects |
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How are neurotransmitters re-used? |
After they're done binding to the neurotransmitter receptor on the post-synaptic cell, they're moved back into the pre-synaptic cell by Neurotransmitter reuptake transporters |
