43. Explain the relationship between initial rate of diffusion and substrate gra
ID: 197975 • Letter: 4
Question
43. Explain the relationship between initial rate of diffusion and substrate gradient in facilitated diffusion vs simple diffusion. 44. What are the functions of different classes of ATPases? 45. What stimuli gate ion channels? Explain how they do it. 46. What do you measure in voltage clamp experiments? 47. Explain different configurations of patch clamp experiments. 48. How do you make an amplitude histogram for single channel recording experiment? 49. You have 2 pA, 4 pA, and 7 pA channels in your patch. Draw an amplitude histogram 50. Explain the mechanism of maintaining mucus fluidity and the role of CFTR in it.Explanation / Answer
Answer 43: The hudrophobic nature of cell membranes restricts the passage of molecules across them. Hence the movement of molecules is governed by several forms of transport viz. simple diffusion, facilitated diffusion and active transport. Simple diffusion occurs down a concentration gradient. It is not saturable i.e. rate of diffusion occurs linearly with the increase in substrate concentration. Facilitated diffusion is carrier mediated, and an initial rate of diffusion is high and the diffusion rate changes linearly with substrate concentration.
Answer 44. the different classes of ATPase are:
i) F-ATPases - they are present in mitochondria, chloroplasts and bacterial plasma membranes. They are the prime producers of ATP, using the proton gradient generated by oxidative phosphorylation or photosynthesis.
ii)V-ATPases (V1VO-ATPases) are primarily found in eukaryotic vacuoles, catalysing ATP hydrolysis to transport solutes and lower pH in organelles like proton pump of lysosome.
iii) A-ATPases are found in Archaea and function like F-ATPases.
iv)P-ATPases (E1E2-ATPases) are found in bacteria, fungi and in eukaryotic plasma membranes and organelles, and function to transport a variety of different ions across membranes.
v)E-ATPases are cell-surface enzymes that hydrolyze a range of NTPs, including extracellular ATP.
Answer 45: Ion channels are present in excitable cells viz. neurons, muscles and touch receptor cells. Ion channels are regulated by ion channels receptors that are proteins located in the plasma membrane. The stimuli for the opening and closing pof these ion cahnnels are usally mechanical or chemical. For example, the the concentration of sodium ions in the cytoplasm is far lower than that in the cell's exterior environment. Conversely, potassium ions exist at higher concentrations within a cell than outside it. Such differences create a so-called electrochemical gradient, which is a combination of a chemical gradient and a charge gradient. The opening of ion channels permits the ions on either side of the plasma membrane to flow down this dual gradient.
Answer 46 The voltage clamp technique was used by Hodgkin and Huxley to determine the behavior of the ionic conductances responsible for the generation of the action potential. electrophysiologists to measure the ion currents through the membranes of excitable cells, such as neurons, while holding the membrane voltage at a set level.
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