1 What is the relationship between the composition of the cell membrane and the movement of substances across it?
2 Must the cell membrane be composed of lipid-soluble (or non-water-soluble) molecules? Explain.
3 The outermost layer of a virus is composed of proteins. Are these proteins water-soluble?
4 Why do you think the cell membrane is composed of a bilayer of phospholipid molecules instead of a single layer?
5 Human bones are primarily composed of phosphorus and calcium. Why do we generally only emphasize calcium absorption during dietary intake and not phosphorus?
6 In reality, modern diets can sometimes lack phosphorus. What might be the possible reasons for this?
7 Phospholipid molecules are not tightly connected to one another. Why is this characteristic important?
8 In the fluid mosaic model, what does "fluid" refer to? What does "mosaic" refer to?
9 How do phospholipids differ from triglycerides in terms of structure and properties?
10 How many functions do the proteins in the cell membrane have?
11 Which proteins in the cell membrane are responsible for transporting substances in and out?
12 What are the differences between channel proteins and carrier proteins in terms of the molecules they transport and their characteristics?
13 What types of substances can easily pass through the phospholipid bilayer?
14 Are lipid-soluble (or nonpolar) molecules or water-soluble (or polar) molecules more likely to pass through the cell membrane? Explain.
15 Give an example of receptor proteins on the cell membrane and their functions.
16 Give an example of antigen proteins on the cell membrane and their functions.
17 The discovery of the structure of the cell membrane is closely related to advancements in scientific technology. Provide two examples of such relationships.
18 How does temperature affect the permeability of the cell membrane?
19 How do organic solvents affect the permeability of the cell membrane?
20 Alcohol can kill bacteria. What is the principle behind this?
21 However, compared to bacteria, alcohol has a greater effect on human cells. Explain why.
22 The cells of beetroot contain red pigments. When heated, the red pigments are released into the surrounding solution. Explain why.
23 There are four basic ways in which substances cross the cell membrane. Which of these require energy?
24 What is the relationship between diffusion and osmosis?
25 Can osmosis occur outside of cells?
26 How does temperature affect the rate of diffusion? Explain.
27 If a dialysis tube containing a sugar solution is placed in distilled water, will water continuously flow into the tube over time? Why or why not?
28 Based on the principle of osmosis, why does honey not easily spoil (i.e., support the growth of microorganisms)?
29 However, when exposed to air for a period of time, microorganisms still grow on the surface of honey. Why?
30 On Earth, there are some environments where food does not easily spoil. What are these environments, and why?
31 What molecules can pass in and out of human cells solely by diffusion? Why do they not require active transport?
32 After heavy rainfall, farmland becomes waterlogged, and most crops die. Why might this happen? (Note: it is not simply because of excess water.)
33 Some terrestrial plants grown in soil can also be cultivated hydroponically. What needs to be added to the water for this to succeed?
34 What is the principle behind using salt to preserve food?
35 Does active transport require living cells? Explain.
36 When applying artificial fertilizers, why are both excessively high and excessively low concentrations unsuitable? Explain.
37 When consuming food while drinking large amounts of water, how is the rate of nutrient absorption affected? Explain.
38 When preparing herbal medicine, why is it inappropriate to add too little or too much water? Explain.
39 When the body absorbs glucose, it utilizes both diffusion and energy-consuming active transport. What are the benefits of doing so?
40 In mangrove swamp environments, the salt concentration in seawater is much higher than in the root cells of plants, making it impossible for most plants to survive. Explain why.
41 However, some plants can still survive in swamp environments. How might they achieve this?
42In diabetic patients, blood sugar levels are much higher than normal. What effects does this condition have on the body?
43 When a potato is cooked, osmosis stops. However, aren't channel proteins supposed to allow free movement of water? Explain why cooked potatoes can no longer allow water to pass through the cell membrane.
44 Normally, the water potential of human blood does not fluctuate significantly. If it does change significantly, what might happen to red blood cells?
45 Changes in water potential inside cells also affect the rate of chemical reactions. Explain why.
46 In the process of human respiration, most of it occurs within the membrane-bound mitochondria. What are the benefits of this?
47 In plant cells, one of the functions of the vacuole is to regulate the water potential of the cytoplasm. How does it achieve this, and what are the benefits?
48 If the water potential outside a cell is very high, such as in freshwater, amoebae (single-celled organisms) cannot prevent water from continuously entering their cells. How might freshwater amoebae resolve this issue?
49 In freshwater, algae or plant cells do not face the same problem as amoebae. Why?
50 active transport always required for the absorption of minerals by plant roots? Explain.