Transport across cell membranes：練習題

Which statement correctly describes a feature of the fluid-mosaic model regarding transport across cell membranes?

The fluid-mosaic model describes the cell-surface membrane. Which statement correctly describes the role of glycoproteins within this structure?

Regarding transport across cell membranes, if the concentration of a respiratory inhibitor is increased, the uptake of which of the following substances would be most significantly reduced?

The fluid-mosaic model describes the cell-surface membrane as a dynamic structure. Which component of the membrane is primarily responsible for preventing the leakage of water-soluble ions out of the cell while maintaining membrane flexibility?

A graph of the rate of uptake of a substance into a cell against the external concentration of that substance shows that the rate increases linearly at first, but then reaches a maximum plateau despite further increases in concentration. Which mechanism of passive transport is most likely being demonstrated?

In the context of the fluid-mosaic model, explain why the presence of cholesterol is essential for the function of mammalian cell-surface membranes at high temperatures.

In the mammalian ileum, glucose is moved from the lumen into the epithelial cells against its concentration gradient. Describe the role of sodium ions \( (Na^+) \) and the specific membrane protein involved in this co-transport mechanism.

The graph shows the rate of uptake of glucose into a cell via facilitated diffusion compared to the rate of uptake of oxygen via simple diffusion. Explain why the rate of glucose uptake eventually reaches a maximum (plateau) while the rate of oxygen uptake continues to increase linearly with external concentration.

The movement of substances across the cell-surface membrane is essential for cell survival.

a) Describe the fluid-mosaic model of membrane structure and explain why it is described as both 'fluid' and a 'mosaic'. (2 points)
b) Compare the mechanisms of facilitated diffusion and active transport. Your answer should include references to carrier proteins and energy requirements. (3 points)
c) Cells lining the small intestine are adapted for rapid transport. Explain how the presence of microvilli and a high density of mitochondria facilitate this. (2 points)