Membrane Transport Flashcards

1
Q

4 Major Classes of Membrane Lipids:

  1. Phosphoglycerides: derived from _ carbon ___ backbone; _ FA chains attached to backbone; _ major types.
    - 1 FA is usually _____, leading to ____, which increases _____.
    - Head group consists of ___, ____, then ___ group.
    - PTE an PC enriched in _____ membranes
  2. Sphingolipids: derived from _____ backbone; ____ is major one.
    - can contribute to formation of ___ ____ alongside cholesterol
  3. Glycolipids: often ______ backbone; _____ always on ____ face.
    - enriched in _____
    - Example: ____ ganglioside used for entry of _____.
  4. Sterols: primarily ____
    - contains _____, _____, and _____
A

4 Major Classes of Membrane Lipids:

  1. Phosphoglycerides: derived from 3 carbon GLYCEROL backbone; 2 FA chains attached to backbone; 3 major types.
    - 1 FA is usually UNSATURATED, leading to KINK, which increases FLUIDITY.
    - Head group consists of GLYCEROL, PHOSPHATE, then POLAR group.
    - PTE an PC enriched in INTRACELLULAR membranes
  2. Sphingolipids: derived from SPHINGOSINE backbone; SPHINGOMYELIN is major one.
    - can contribute to formation of LIPID RAFTS alongside cholesterol
  3. Glycolipids: often SPHINGOSINE backbone; CARBOHYDRATE always on EXTERNAL face.
    - enriched in MYELIN
    - Example: GM1 ganglioside used for entry of CHOLERA TOXIN.
  4. Sterols: primarily CHOLESTEROL
    - contains ALIPHATIC REGIONS, STEROL RING, and POLAR OH LOCATED NEAR MEMBRANE SURFACE IN BOTH LEAFLETS
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2
Q

PS has net ____ charge

A

PS has net NEGATIVE charge

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3
Q

Lipid rafts have ____ structure and can ______ subsets of membrane proteins to ____ function.

A

Lipid rafts have THICKER structure and can SEQUESTER subsets of membrane proteins to SEGREGATE function.

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4
Q

Integral membrane proteins are typically made up of _________ or _______.

Peripheral membrane proteins have lipid _____ attached that can ____ interact with membrane. Others associate with membrane via ___.

A

Integral membrane proteins are typically made up of 15-20 AA ALPHA HELIX or BETA BARREL.

Peripheral membrane proteins have lipid COVALENTLY attached that can REVERSIBLY (BC CAN BE REGULATED VIA CLEAVAGE) interact with membrane. Others associate with membrane via CHARGED-INTERACTIONS.

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5
Q

Things that can affect channel function:

  1. ___ channel blockers such as
    • ________, which abolishes neuro-muscular transmission
    • ________, which can also treat tachycardia
  2. ___ channel blockers, which are used to treat arrhythmias
    - _____ or ____ toxins
  3. _____ receptor at neuromuscular junction
    • affected by ____, which is an antagonist at ___ binding site.
A

Things that can affect channel function:

  1. NA channel blockers such as
    • TETRODOTOXIN, which abolishes neuro-muscular transmission
    • LIDOCAINE, which can also treat tachycardia
  2. K channel blockers, which are used to treat arrhythmias
    - SCORPION or CONE SNAIL toxins
  3. NICOTINIC ACH receptor at neuromuscular junction
    • affected by CURARE, which is an antagonist at ACH binding site.
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6
Q

Example of uniporter:

____ ____ transporter.
-Transport rate depends on _____, _____, and ____

A

Example of uniporter:

GLUT1 GLUCOSE transporter.
-Transport rate depends on CONCENTRATION GRADIENT, KM OF SOLUTE, AND FLIPPING RATE (VMAX)

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7
Q

Example of Symporter:

  • ___/___ symporter
  • _____ binding occurs so that binding of __ increases affinity of symporter for ____.
  • Both sites need to be ______ for conformational switch that opens ____ _____ to other side of membrane.
  • Allows transport of _____ _____ concentration gradient without ______.
A

Example of Symporter:

  • NA/GLUCOSE symporter
  • CO-OPERATIVE binding occurs so that binding of NA increases affinity of symporter for GLUCOSE.
  • Both sites need to be OCCUPIED for conformational switch that opens SOLUTE BINDING SITES to other side of membrane.
  • Allows transport of GLUCOSE AGAINST concentration gradient without DIRECT ENERGY EXPENDITURE.
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8
Q

Glucose transport from GI system through epithelial cells uses 2 different glucose transporters:

  1. _____; __ moves down gradient, ____ dragged inside. Located on ____ side of epithelial cell.
  2. ____; _____ moves down gradient.

Note: ___/___ transporter on ____ Surface to keep intracellular ___ [] low so the system can work.

A

Glucose transport from GI system through epithelial cells uses 2 different glucose transporters:

  1. SYMPORTER; NA moves down gradient, GLUCOSE dragged inside. Located on APICAL side of epithelial cell.
  2. UNIPORTER; GLUCOSE moves down gradient.

Note: NA/K PUMP transporter on BASAL Surface to keep intracellular NA [] low so the system can work.

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9
Q

2 Types of Active Transporters:

  • P Type Pump: _______ with _ from ___
  • ____ leads to conformational change
  • ____ ions

-ABC Transporter: pumps _____ molecules rather than ____.

A

2 Types of Active Transporters:

  • P Type Pump: AUTOPHOSPHORYLATION with P from ATP
  • PHOSPHORYLATION leads to conformational change
  • PUMPS ions

-ABC Transporter: pumps SMALL molecules rather than IONS.

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10
Q

Important P-Pumps:

__/____, 90% of membrane protein found in muscle cells
-since ___ is []d in ER, how is this reestablished after it’s release into cytoplasm during muscle contraction?

  1. Cavity in non-P-lated transporter binds ___
  2. ATP can bind and contribute _ for ____ of ___.
  3. When ___ is ____, conformation change occurs.
  4. Channel opens to ____ of ___ and releases ___.
A

Important P-Pumps:

CA2+/ATPase, 90% of membrane protein found in muscle cells
-since CA2+ is []d in ER, how is this reestablished after it’s release into cytoplasm during muscle contraction?

  1. Cavity in non-P-lated transporter binds CALCIUM
  2. ATP can bind and contribute P for P-LATION of ASP.
  3. When ASP is P-LATED, conformation change occurs.
  4. Channel opens to LUMEN of SR and releases CALCIUM.
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11
Q

Important P-Pumps:

NA/K ATPase where ___ ____ are transported against their [] gradients.

/ of cellular energy used to maintain this pump

  1. __ binds from inside of cell
  2. _____ of cytoplasmic face induces conformational change
  3. __ then transported and released on ____
  4. When __ outside of cell binds, _____ occurs and induces another conformational change, leading to entry of __ into cytoplasm
A

Important P-Pumps:

NA/K ATPase where BOTH IONS are transported against their [] gradients.

1/3 of cellular energy used to maintain this pump

  1. NA binds from inside of cell
  2. AUTO-PHOSPHORYLATION of cytoplasmic face induces conformational change
  3. NA then transported and released on OUTSIDE
  4. When K outside of cell binds, DEPHOSPHORYLATION occurs and induces another conformational change, leading to entry of K into cytoplasm
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12
Q

ABC Transporters:

  • __ ATPase domains on each protein. Usually _____ bind to _____ bound state.
  • ____ then binds and the _ ATPase binding domains ____, which produces conformational change that exposes the ___ to the ____ side of the membrane.
  • _____ hydrolysis then releases substrate and prepares the transporter for another round.

Examples:
______ are found in tumor cells; more _____ drug is cleared from cytoplasm, reducing drug effects.

_____ resistance; amplified levels of _____ from ____ genome pump drug out.

ATP binding to ______ drives opening and closing of __ channel (exception of ABC transporter regulating ion flow)

A

ABC Transporters:

  • TWO ATPase domains on each protein. Usually SMALL MOLECULES bind to NON-ATP bound state.
  • ATP then binds and the TWO ATPase binding domains DIMERIZE, which produces conformational change that exposes the SUBSTRATE to the OPPOSITE side of the membrane.
  • ATP hydrolysis then releases substrate and prepares the transporter for another round.

Examples:MULTIPLE DRUG RESISTANT (MDR) are found in tumor cells; more HYDROPHOBIC drug is cleared from cytoplasm, reducing drug effects.

CHLOROQUINE resistance; amplified levels of TRANSPORTER from MALARIA genome pump drug out.

ATP binding to CFTR drives opening and closing of CL channel (exception of ABC transporter regulating ion flow)

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