Term
| What are desmosomes and tight junctions? |
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Definition
Desmosomes: Mechanically strong physical connections. (i.e. - skin cells). Holds cells together.
Tight junctions: Leak-proof physical connections. Not as strong as desmosomes but prevents backflow and allows unidirectional movement. (i.e. - glucose out of intestinal cells into blood) |
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Term
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Definition
Large, non-specific ion channels.
- for electrical synchronization between cells (i.e.- between heart cells) |
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Term
| What determines specificity of ligand-receptor binding? |
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Definition
Complementary shapes, 3-D structure of protein.
3-D folding determines shape of binding sites.
- Shape and charge determine binding affinity of ligand for binding site. |
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Term
| Describe competitive inhibition and give example. |
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Definition
When a substance, like a drug, is introduced and binds to a certain receptor but doesn't activate it. This is called an antagonist (competitive inhibitor) and competes with natural ligands. Lowers response to ligand BUT high ligand concentration can overcome competition by inhibitor.
Ex: Alpha-Bungarotoxin in snake venom competitively inhibits Ach receptors in neuromuscular junction and causes muscle paralysis. |
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Term
| Describe non-competitive inhibition and give example. |
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Definition
| Inhibitor causes irreversible inactivation of receptor. High ligand concentration CAN'T overcome this type of inhibition. |
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Term
| Distinguish binding of water-soluble and lipid-soluble messengers. |
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Definition
Lipid-soluble messengers pass through cell membrane and bind to intracellular receptors.
Water-soluble messengers bind to cell surface receptors, coupled with signaling pathways. |
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Term
| Major mechanisms of receptor-coupled cell signaling |
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Definition
1) ligand-gated ion channel: receptor activates ion channel, ion channel opens up.
2) Tyrosine Kinase receptor: ATP hydrolyzed, resulting free phosphate phosphorylates (energizes) protein to activate more substrates later.
3) JAK Kinase: receptor activates JAK Kinase, Kinase activity phosphorylates protein using ATP.
4) GPCR: alpha subunit activated, which activates effector protein to generate membrane potential change or 2nd messengers. |
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Term
| G-protein Coupled Receptor Reactions |
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Definition
1) activation of adenylyl cyclase, uses ATP to produce cAMP, Protein Kinase A activated which phosphorylates protein
2) Phospholipase C activated and splits PIP2 into IP3 and DAG.
- IP3 -> ER -> Ca release -> Calmodulin activation -> activates calmodulin-dependent protein kinase
- DAG -> activates Protein Kinase C -> phosphorylates protein |
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