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36 Cards in this Set
- Front
- Back
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Membrane transport:
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1. Diffusion
2. Facilitated diffusion 3. Active transport (primary and secondary) |
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Examples of diffusion
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water, oxygen molecule, and carbon dioxide
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Examples of facilitated diffusion:
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Aquaporin, porins, Gramacidin A
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Facilitated diffusion is also known as
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Passive Transport
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Primary Active Transport
Key: |
-Against concentration gradient
-Necessary ATP, PEP,or other high energy compounds |
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Examples of primary active transport:
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Na+/K+ pump
Ca2+ pump |
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Secondary Active Transport
Examples: |
Na+ glucose symport
Lactose/H+ gradient? |
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Electrogenic antiport
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Na+/K+ pump
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Electroneutral antiport
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H+/K+ pump
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Passive Transport:
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Carriers: Valinomycin
Channels or pores: Gramicidin A, porins, and ion channels Transport proteins: Erythrocyte glucose transporter (GLUT1) |
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Ionophores
Classification |
a) Carrier Ionophore
b) Channel-forming ionophore |
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Valinomycin
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Valinomycin carries K+ across the membrane
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Monensin
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Monensin is the Na+ binding ionophore
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Gramicidin
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Gramicidin A forms helical transmembrane channels
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Aquaporins
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Rapid water transport
Highly selective to water Highly expressed in tissues such as kidneys, salivary glands, and lacrimal glands |
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K+ channels
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-Facilitates the diffusion of K+ from the cytoplasm to the extracellular space
-Important for cellular osmotic balance, neurotransmission, and signal transduction -Highly selective to K+ ion -K+ channel is a tetramer |
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Cl- channels
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-Basic amino acids form a selective funnel for anions
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Active Transport
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-Transport ions and neutral molecules against the conc. gradient
-Often coupled to hydrolysis of ATP (ATPase activity) |
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Types of ATPases
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-Cation Transporters
P-Type ATPases F-Type ATPases V-Type ATPases -Anionic Transporters A-type ATPases |
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P-Type ATPases
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Located in plasma membrane
Autophosphorylation of ATP Transport H+, Na+, K+, Ca2+, Cu2+, Cd2+, and Mg2+ Inhibited by vanadate |
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F-Type ATPases
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Translocate H+ into mitochondria and bacterial cells
Power ATP synthesis |
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V-Type ATPases
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Located in plant vacuolar membranes and acidic vesicles
Homologous to F-type ATPases |
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Na+/K+ ATPase
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Regulation of osmotic pressure
Maintaining membrane potential Maintaining sodium and potassium gradients Pumps 3 Na+ ions out and 2K+ ions in (electrogenic) |
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Inhibits Na+/K+ ATPase
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Cardiac glycosidies (or cardiotonic steroids). Ex. digitoxin, and oubain
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Secrete HCl in the gastric mucosa
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Parietal cells
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Carbonic anhydrase reaction
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CO2 + H2O <---> H2CO3- + H+
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Regulation of gastric acid secretion
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-Acetylcholine
-Histamine -Gastrin |
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Treatment of acid reflux or heartburn:
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-Histamine antagonists: cimetidine, ranitine, famotidine
-Proton pump inhibitors: omeprazole, esomeprozole |
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Group Translocation
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Simultaneous chemical modification of transporting molecules
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Simultaneously transports and phosphorylates sugars including glucose, fructose, mannose, N-acetylglucosamine, etc
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Phosphoenolpyruvate-dependent phosphotransferase system (PTS)
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Stimuli to open gated channels:
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-Mechanosensitive channels
-Ligand-gated channels -Signal-gated channels -Voltage-gated channels |
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Types of synapses
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-Electrical synapses: rapid signal transduction; direct electrical coupling
-Chemical synapses: Release of neurotransmitters from the presynaptic membrane; receptors on the postsynaptic membrane |
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A ligand-gated cation channel
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Acetylcholine receptor
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Neurotransmitters
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Dopamine
Norepinephrine Epinephrine GABA Histamine Serotonin |
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Technique to study channels
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Patch-clamp technique
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Pyruvate Dehydrogenase Complex (PDH) requires 5 coenzymes:
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TPP
lipoic acid CoA FAD NAD+ |
