L 2 Flashcards
How do the majority of drugs act on the body?
Answer: The majority of drugs act by binding to specific protein targets, which can include receptors, ion channels, enzymes, and carrier molecules (transporters).
- What are the four main types of protein drug targets?
Answer: The four main types of protein drug targets are:
Receptors
Ion channels
Enzymes
Carrier molecules (transporters
- What are receptors and how do they function in pharmacology?
Answer: Receptors are proteins involved in chemical communication. They function as “sensing elements” that bind to chemical messengers such as hormones, neurotransmitters, or other mediators (e.g., growth factors). When a drug or chemical binds to a receptor, it can either activate it (as an agonist) or block its activation (as an antagonist).
- What is an example of a receptor-drug interaction?
Answer: An example of a receptor-drug interaction is the β-adrenoreceptor in the heart. Noradrenaline acts as an agonist, activating the receptor and increasing heart rate. Propranolol, a drug used to treat hypertension, acts as an antagonist by blocking receptor activation, thereby reducing cardiac contraction
- How do ion channels function as drug targets?
Answer: Ion channels are proteins that allow ions to flow across the cell membrane. Ligand-gated ion channels open when occupied by an agonist, while voltage-gated ion channels open in response to changes in cell membrane voltage. Drugs can affect ion channels by binding to them and either facilitating or blocking ion flow.
- What is an example of a drug that affects ion channels?
Answer: Local anesthetics like lidocaine bind to the voltage-gated sodium channels, blocking ion permeation and reducing neuron firing. Benzodiazepines act on the GABA receptor/chloride channel complex, facilitating the opening of the channel by the neurotransmitter GABA.
- How do drugs interact with enzymes?
Answer: Drugs can act as competitive inhibitors of enzymes by mimicking the natural substrate or as false substrates, producing abnormal products. For example, aspirin inhibits the enzyme cyclooxygenase, and fluorouracil acts as a false substrate in nucleotide synthesis, blocking DNA synthesis and cell division.
- What is a pro-drug, and how is it activated?
Answer: A pro-drug is an inactive form of a drug that requires enzymatic degradation to convert it into an active form. The drug becomes pharmacologically active after being metabolized by enzymes in the body.
- What are carrier molecules (transporters), and how do drugs interact with them?
Answer: Carrier molecules, or transporters, are membrane proteins that transport ions and small molecules across cell membranes. Drugs can inhibit transporters, such as tricyclic antidepressants and cocaine, which inhibit noradrenaline uptake, making more noradrenaline available to bind to receptors.
- How do toxins and toxicants interact with molecular targets in the body?
Answer: Toxins and toxicants interact with the same molecular targets as drugs, such as proteins, lipids, and nucleic acids. They can cause symptoms by interacting with these targets, either directly or through downstream effects. For example, toxins may inhibit enzymes, act as agonists or antagonists for receptors, or damage DNA, causing mutagenic effects.
- How does colchicine act on the body, and why is it an exception to typical protein targets?
Answer: Colchicine is used to treat gouty arthritis and acts by inhibiting neutrophil migration. It binds to tubulin and depolymerizes microtubules, causing neutrophils to develop a “drunken walk,” which prevents their migration. Unlike most drugs that target receptors, ion channels, enzymes, or transporters, colchicine acts by disrupting the microtubule structure.
- Describe the mechanism of action of agonists and antagonists at receptors.
Answer: Agonists bind to receptors and activate them, mimicking the effect of natural chemical messengers such as hormones or neurotransmitters. This activation can trigger a direct physiological effect or initiate a cascade of intracellular signals. In contrast, antagonists bind to receptors but prevent their activation by blocking the binding of natural agonists or drugs. This inhibits the receptor’s normal function.
- What role do ligand-gated and voltage-gated ion channels play in cellular communication, and how do drugs modulate their function?
Answer: Ligand-gated ion channels, also known as ionotropic receptors, open when a specific ligand (such as a neurotransmitter or drug) binds to them, allowing ions to flow across the cell membrane and change the membrane potential, initiating cellular responses. Voltage-gated ion channels open in response to changes in membrane voltage, allowing ions like sodium, potassium, or calcium to pass through. Drugs can modulate ion channels by either blocking them (e.g., local anesthetics like lidocaine) or enhancing their function (e.g., benzodiazepines acting on GABA receptors).
- Explain how local anesthetics such as lidocaine affect voltage-gated sodium channels and the implications for neuronal activity.
Answer: Local anesthetics like lidocaine bind to the pore region of voltage-gated sodium channels, blocking ion permeation through the channel. This prevents sodium ions from entering the neuron, reducing the neuron’s ability to depolarize and fire an action potential. As a result, the sensation of pain is diminished because the signal cannot be transmitted along the nerve.
- What are false substrates in enzyme interactions, and how do they affect normal metabolic pathways? Provide an example.
Answer: False substrates are drug molecules that mimic the natural substrate of an enzyme but are transformed into an abnormal product that cannot complete the normal metabolic pathway. This disrupts the biological process. An example is fluorouracil, an anticancer drug that acts as a false substrate for enzymes involved in nucleotide synthesis. Fluorouracil replaces uracil in the pathway but cannot be converted into thymidylate, thereby blocking DNA synthesis and preventing cell division.
