Term
| Describe the path vesicle lipids take from synthesis to the membrane |
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Definition
1. Synthesis at ER
2. Transport through golgi
3. Budding and fusion through vesicles, picking up material
4. Exocytosis |
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Term
| How is assymetry of lipids and proteins maintained during vesicle mediated transport? |
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Definition
| The cytoplasmic domains always face inside, and the lumenal domains become extracellular domains |
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Term
| What are the four types of lipid anchors? |
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Definition
Palmitate, myristate, pyranyl groups (farnesyl or geranylgeranyl), and GPI
Used to anchor proteins to membrane |
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Term
| What does the palmitate lipid anchor link to? |
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Definition
| Internal cysteine or serine |
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Term
| What does the myristate lipid anchor link to? |
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Definition
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Term
| What does the pyranyl lipid anchor link to? |
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Definition
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Term
| What is the only reversible lipid anchor? |
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Definition
Palmitate (the link can be removed to allow reversible association)
The others are permanent |
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Term
| What is significant about prenylated proteins (proteins attached to farensyl/geranyl group)? |
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Definition
They are key regulators of cell growth
More than 30% of cancers have to do with one of these proteins, the Ras-superfamily GTPases
Statin drugs block prenylation
Involved with sleeping sickness and malaria |
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Term
| What are the four types of lipid anchors? |
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Definition
Palmitate, myristate, pyranyl groups (farnesyl or geranylgeranyl), and GPI
Used to anchor proteins to membrane |
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Term
| What are the two types of glycoproteins |
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Definition
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Term
| Describe O-linked glycoproteins |
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Definition
Bound to serine or thereonine in golgi
Sugars added step-wise |
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Term
| Describe N-linked glycoproteins |
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Definition
Bound to asparagine in ER
Sugars already attached all at once |
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Term
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Definition
An example of a glycoprotein
A transmembrane protein in red blood cells
Once protein is N-linked in ER lipids, the protein is modified through O-linked glycosylation in the golgi
Proper orientation is established once in the membrane (N-terminal outside because that is the side modified by glycosylation) |
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Term
| Define proteoglycan and describe its structure |
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Definition
A glycosaminoglycan covalently attached to a membrane or secreted protein
Major components of connective tissue
Many repeated dissacharides (ex. GAG) attach via a trisaccharide to a serine
The disaccharide segment is the major component, the area of biological activity |
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Term
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Definition
A membrane proteoglycan (with many repeating dissacharides)
Alternating sufate-rich and low-sulfate areas
Biological activity is in the high sulfate (S domain) areas |
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Term
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Definition
Integral membrane proteins with 3 heparins and 2 chondrotin sulfate chains
S domains mediate biological activity |
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Term
Define conformational activation in a proteoglycan
Give an example |
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Definition
A conformational change is induced upon binding to an S domain
Ex. Thrombin can be reduced to reduce clotting (why heparan is anti-coagulating) |
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Term
Define enhanced protein-protein interaction on a proteoglycan
Give an example |
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Definition
Binding of two proteins nearby causes interaction
Ex. thrombin and AT interaction inhibits blood clotting |
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Term
Define co-receptor for extraceullular on a proteoglycan
Give an example |
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Definition
NS domains interaction with both the factor and its receptor, bringing the complex together and increasing the effectiveness of the factor
Ex. Fibroblast growth factor and its receptor |
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Term
Define cell surface localization/concentration on a proteoglycan
Give an example |
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Definition
The high density of negative charges on heparin attracts positively charged molecules and holds them electrostatic and sequence-specific interactions with NS domains
Ex. lipoprotein lipase |
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Term
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Definition
A proteoglycan extracellular matrix
The largest biological membrane known (up to 50,000 dissacharides)
Core protein with keratin and chondroitin
Important in extracellular matrix of connective tissue |
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Term
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Definition
Major structural heteropolysaccharides of bacterial cell walls, very strong, prevents swelling and lysis
Alternating N-acetylglucosamine and N-acetylmuramic acid |
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Term
| What antibiotics involve peptidoglycan? |
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Definition
Hydrolyzed by lysozyme (in tears and saliva)
Formation (via transpeptidases) inhibited by penicillin, cephalosporins, and other β-lactam antibiotics |
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Term
| What are the functions of the cytoskeleton? |
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Definition
| Structure and organization of the cytoplasm, controls cell shape, and mediates movement of cells and cell contents |
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Term
| What are the three types of cytoskeleton? |
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Definition
1. Actin
2. Microtubules
3. Intermediate filaments |
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Term
| Describe actin cytoskeleton |
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Definition
Asymmetrical helical arrays that form microfilaments
Work with myosin for contractile motion
Found immediately under the plasma membrane and in microvilli |
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Term
| Define the microtubule cytoskeleton |
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Definition
Heterodimers of alpha and beta subunits extending from a centrosome (near the nucleus) towards the membrane
Dynamic structures, grow and dissociate
Motor proteins (dyneins/kinesins) move cargo along the microtubules |
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Term
| Define the intermediate filament cytoskeleton |
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Definition
Parallel dimers in coiled-coils associated into longer filaments
The least dynamic cytoskeleton structure
Form nonliving skin and hair |
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Term
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Definition
| A cytoskeleton protein on the inner membrane that provides stability and scaffolding |
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Term
| What is a "membrane raft"? |
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Definition
A cholesterol-sphingolipid microdomain that associates in the membrane and forms a thick area
Dynamic, associate and dissociate (can take up as much as 50% of the membrane)
Attract lipid-anchored proteins (type 5, especially palymilated proteins) that can increase reaction rates |
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Term
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Definition
A transmembrane protein that mediates a physical continuum between the fibrils of the extracellular matrix and the cytoskeleton of the cytoplasm
Has an alpha and beta protein, required for calcium, associated with I-CAM |
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Term
| Describe the cytoskeleton "fences" that form immediately inside the membrane |
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Definition
Inhibit movement
Actin, spectrin, and adapter proteins (such as ankyrin) |
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Term
| Describe the plasma membrane adhesion proteins |
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Definition
All type I
Integrin, cadherin, N-CAM, Selectin |
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Term
| What are homotypic cell adhesion proteins? |
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Definition
| Membrane proteins such as N-CAM and I-CAM that bind to the same proteins on other cells |
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Term
| Give an example of selectin and integrin action in the immune system |
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Definition
The cell secretes cytokines that attract T lymphocytes
The lymphocytes bind to integrin and selectin in a rolling motion, then adhere and can undergo extravasation to the site of inflammation |
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Term
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Definition
| Specific sulfated glycoproteins |
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Term
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Definition
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Term
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Definition
| Other cadherins on other cells |
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Term
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Definition
| Other N-CAMs on other cells |
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Term
| How do protein transporters mediate diffusion? |
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Definition
They reduce the activation energy of transport by forming noncovalent reactions with the solute to replace the hydrogen bonding with water
Also, by providing a hydrophilic transmembrane passage |
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Term
| Describe the kinetics of carrier-mediated transport |
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Definition
| It can be saturated, analogous to Michaelis-Menten analysis of enzymes |
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Term
| Can simple or channel-mediated diffusion become saturated? |
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Definition
No
Channels don't become saturated because no binding is involved |
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Term
| Describe the glucose transporter |
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Definition
A type III membrane carrier protein with 12 domains
Have much more polar residues than most, so form amphipathic helices
The polar side of the helix faces inside and can stably interact with glucose
Two-form model for function |
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Term
| How does insulin regulate glucose transport via carriers on muscle and fat cells? |
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Definition
| When insulin levels are high and interact with insulin receptors, vesicles with glucose carriers fuse with the plasma membrane |
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Term
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Definition
| A channel protein for water (very important in red blood cells and in nephrons) |
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Term
| Define ion-selective channels |
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Definition
| Channels that control permeability to specific ions, often regulated |
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Term
| Describe the K+ channel. Why does it only let K+ inside even though Na+ are smaller? |
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Definition
| Eight transmembrane helices (2 from each of four identical subunits), rate is almost diffusion limited
Backbone carbonyl oxygens form a cage that fits K+ precisely |
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Term
| What sort of membrane proteins do neurotoxins often affect? |
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Definition
| Ion channels (because they are involved in neurotransmission) |
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Term
| Give an example of symport |
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Definition
| Sodium symport allows glucose and amino acid uptake in intestine |
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Term
| Give an example of antiport |
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Definition
| Sodium-calcium antiport in heart |
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Term
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Definition
Reversibly phosphorylated ATPases
Ex. Na-K+ ATPase, sarcoplasmic Ca-pump, gastric H-K+ pump |
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Term
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Definition
Maintains low intracellular Na+ and high intracellular K+
Uses 25% of energy consumption at rest
Three Na+ pumped out per two K+ pumped it
Very important in the heart |
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Term
What are the inhibitors of Na+-K+ ATPase?
How is this significant medically? |
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Definition
Vanadate and ouabain
Used in digoxins to allow Na+ to increase in the heart, reducing the activity of Na+-Ca antiporter, increasing Ca and strengthening heart contractions |
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