B2.1 細胞膜與膜運輸（細胞）：練習題

What is the primary structural component of the plasma membrane?

A cell is actively secreting insulin into the bloodstream. What is the immediate effect of this exocytosis on the cell's plasma membrane?

Considering the chemical properties of the phospholipid bilayer, which of the following substances would show the lowest rate of simple diffusion across the membrane?

Phospholipids are described as amphipathic molecules. How does this property determine the structure of the plasma membrane?

A sample of plant tissue is placed in a solution of \( 0.6 \text{ mol dm}^{-3} \) sucrose. After two hours, the mass of the tissue is found to have decreased significantly. What does this indicate about the initial state of the tissue?

Contrast integral proteins and peripheral proteins based on their physical arrangement and positioning within the phospholipid bilayer.

Contrast the movement of ions through channel proteins in facilitated diffusion with their movement via protein pumps in active transport, specifically regarding the energy requirement and the direction of the concentration gradient.

Explain how evidence from freeze-etched electron microscopy was used to falsify the Davson-Danielli "protein sandwich" model and support the fluid mosaic model of membrane structure.

Passive transport allows substances to cross the plasma membrane without the expenditure of energy.
a) Distinguish between simple diffusion and facilitated diffusion in terms of the types of molecules transported.
b) Explain why both processes are considered passive transport mechanisms despite the use of channel or carrier proteins in one of them.

A student places an animal cell and a plant cell into two separate beakers containing a hypotonic solution.
a) Predict the net direction of water movement for both cells and name the transport process involved.
b) Explain the likely physical outcome for the animal cell compared to the plant cell after 30 minutes, referencing the role of the plant cell wall.