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71 Cards in this Set
- Front
- Back
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2 major classes of membrane transport proteins |
1. Transporters 2. Channels |
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Binds the specific solute to be transported and transfer them across the lipid bilayer by undergoing a series of conformational changes |
Transporters |
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Interact with the solute to be transported much more weakly; form continuous pores that extend across the lipid bilayer |
Channels |
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Type of transport that allow solutes to cross the membrane only PASSIVELY ("downhill") |
Passive transport |
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Difference in the concentration on the 2 sides of the membrane |
Concentration gradient |
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Net driving force |
Electrochemical gradient (formed from the concentration gradient and the electrical gradient) |
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Adds an energy source to a transporter to move AGAINST the concentration gradient, coupled with a favorable reaction; UPHILL |
Active transport |
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T/F: Active transport can use a channel/hole |
FALSE. They CANNOT use a channel/hole |
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T/F: You can use ANTIPORT mechanisms in active transport |
True |
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Active transport is mediated by _________ coupled to an energy source |
Transporters |
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3 types of transporters in Active Transport |
1. Coupled transporter 2. ATP-driven pump 3. Light-driven pump |
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Couple uphill transport of one solute with the downhill transport of another; downhill to uphill solute |
Secondary active transport (coupled transporter) |
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Uses an electrochemical gradient – generated by active transport – as an energy source to move molecules against their gradient |
Secondary active transport |
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Example of a coupled transporter |
Na+/Glucose Transporter |
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In Na+/Glucose Transport, which is the secondary transport molecule? |
Glucose |
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Glucose is transported by? |
Facilitated diffusion |
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Na+/glucose are co‐transported by? |
Electrochemical gradient |
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Transport of glucose against its gradient (uphill) is driven by? |
Na natural gradient (downhill) |
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Glucose is pumped from a region of (low/high) concentration to a region of (low/high concentration) |
Low; high |
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Glucose molecules are transported _________ their concentration gradient |
Against |
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T/F: The energy that drives glucose across a membrane against its concentration gradient comes from ATP |
False. Comes from energy stored in a Na+ ion gradient, which was created using ATP |
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Na+ concentration is (lower/higher) in the extracellular space than in the cytosol |
Higher |
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Example of where you can find Na+/Glucose transporter |
Small intestines |
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Na+/Glucose Transporter in the Epithelial Cell |
1. Glucose is transported across the apical surface into the cell 2. Glucose molecules diffuse to the basal surface 3. Carried by a glucose facilitative transporter out of the cell and into the bloodstream |
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T/F: 2:1 Na/Glucose provides a lesser driving force than a 1:1 ratio |
FALSE. 2:1 Na/Glucose provides a MUCH GREATER driving force than a 1:1 ratio |
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Couple uphill transport couple to the hydrolysis of ATP |
Primary active transport |
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Directly uses a source of chemical energy (e.g., ATP) to move molecules across a membrane against their gradient |
Primary active transport |
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Transporter used in primary active transport |
ATP-driven pump |
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Types of ATPases |
1. P-type pump 2. F-type and V-type proton pump 3. ABC transporter |
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Ions phosphorylate themselves during the pumping cycle |
P-type pump |
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In a P-type pump, ion pumps are responsible for setting up and maintaining which gradients? (4) |
Na+, K+, H+, Na2+ |
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Use H+ ion to synthesize ATP from ADP to Pi (normally works in reverse) |
F-type pump |
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F-type pumps are most commonly known as? |
ATP synthases |
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Where can you find the F-type pump? (3) |
Plasma membrane in the bacteria Mitochondria Chloroplasts Light-activated H-pump |
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T/F: F-type pumps use ions to synthesize ATP but CANNOT work in the opposite direction |
FALSE. They can also work in the opposite direction. |
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Transfers H+ ion into organelles to ACIDIFY the interior of these organelles |
V-type pump |
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Which organelles do the V-type pump transfer H+ ion into? |
Lysosomes (pump hydrogen in the lumen) Synaptic vesicles Plant or yeast vacuoles |
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Pump SMALL MOLECULES across cell membrane, in contrast to the other types that pump ions exclusively |
ATP-Binding Cassette (ABC) transporters |
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How much ATP do ABC Transporters need? |
2 ATP (one on each side) |
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Examples of P-type ATPases |
Ca2+ pump H+/K+ pump Na+/K+ pump ABC Transporters |
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Gradient of Ca+ pump |
Going in |
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Where can you find Ca+ pump? |
Muscles (sarcoplasmic reticulum; sliding filament model), bones |
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Functions to acidify the stomach |
H+/K+ pump |
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Where can you find the H+/K+ pump? |
Stomach, obviously |
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What is the acid-blocking drug in the H+/K+ pump? |
Zantac, Pepcid, Tagamet * Histamine causes gastric secretion which produces acid in the stomach |
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Na2+/K+ pump goes _______ the gradient |
Against, like the Ca+ pump |
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Na2+/K+ pumps (Na/K) out of the cell and (Na/K) in |
Na; K * Coupled anti-port (2K in: 3Na out) |
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What mechanism can tell what will bind in Na+/K+ pump? |
Association of ATP |
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2 types of ABC transporters |
1. Bacterial ABC transporter 2. Eukaryotic ABC transporter |
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On which side of the membrane can you find ABC transporters? |
Cystolic |
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What brings the 2 ATPase domains together? |
ATP binding |
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What dissociates the 2 ATPase domains together? |
ATP hydrolysis |
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Common structure of a bacterial cell |
Gram negative * bacteria with double membranes |
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How many phospholipid layers does a gram negative structure have? |
2 (very thin peptidoglycan layers) |
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What do you call the space in between the 2 layers? |
Periplasmic space |
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What structure do bacteria with single membranes have? |
Gram positive |
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What is the difference between a gram negative and a gram positive structure (besides the number of membranes)? |
- Gram negative: 2 VERY THIN peptidoglycan layers; thin membrane - Gram positive: 1 phospholipid layer, but VERY THICK peptidoglycan; thicker cell wall |
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Explain the ABC Transporter mechanism |
* Extracellular space --> Periplasmic space --> Cytosol 1. Molecule binds to PERIPLASMIC SUBSTRATE-BINDING PROTEIN (PSBP) in periplasmic space 2. Binding of PSBP complex to ABC transporter causes CONFORMATIONAL CHANGE 3. Molecule is brought into CYTOSOL |
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Example of ABC transporter that is also called the P-glycoprotein |
Multidrug resistance (MDR) protein |
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What is the other name for the MDR protein? |
P-glycoprotein |
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What is the function of the MDR protein? |
Makes the cell simultaneously resistant to a variety of chemically unrelated cytotoxic drugs (cancer chemotherapy) |
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Where can you find the MDR protein? |
HEPATOCYTES --> efflex of drugs |
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What do you call the protist that causes malaria? |
Plasmodium falciparum |
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What protein (mutation) causes cystic fibrosis? |
(mutation of) Cystic Fibrosis Transmembrane Conductance Regulator (CFTR) protein - increases viscosity of mucus --> chronic lung infection, inflammation |
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What channel does the CFTR use and where can you find them? |
Cl- channel in the plasma membrane of epithelial cells |
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Type of transporter in Active Transport that couple uphill transport to an input of energy from light (instead of NADH and FADH) |
Light-driven pump |
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Where can you mainly find light-driven pumps? |
Bacteria, archaea |
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Example of light-driven pump |
Bacteriorhodopsin |
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Each bacteriorhodopsin molecule is folded into how many closely packed transmembrane alpha helices? |
7 |
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The 7 alpha helices in bacteriorhodopsin contains a single light-absorbing retinal group called a? |
Chromophore * Gives the protein its purple color |
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Explain the mechanism in bacteriorhodopsin |
Protons move from the cytoplasm to the cell exterior through a central channel in the protein |
