簡介Introduction
在本活動中，你會利用提供的材料來製作一個細胞膜模型。你需要應用關於細胞膜結構的知識。你還有機會展示你在工程學上的技能、創意、團隊合作性和溝通技巧。
In this activity, you will use materials provided to make a cell membrane model. During the activity you will need to apply your knowledge about the structure of cell membrane. You will also have a chance to demonstrate your engineering skills, creativity, team work and communication skills.
背景知識：細胞膜的結構、特性和功能Background knowledge: the structure, properties and functions of the cell membrane
1.
細閱以下内容以重温細胞膜的結構、特性和功能。
- 細胞膜的結構能以流動鑲嵌模型來描述（圖1）。
- 細胞膜由磷脂雙層組成，並有蛋白分子散佈在其中。
- 「流動鑲嵌模型」這名字的由來是基於細胞膜的磷脂雙層具流動性，磷脂分子與一些蛋白質分子可作橫向移動。
- 「鑲嵌」則是指蛋白質分子散佈在磷脂分子之間，有如瓷磚鑲嵌的圖案。
1.
Study the content below to revise the structure, properties and functions of the cell membrane.
- The structure of the cell membrane can be described by the fluid mosaic model (Figure 1).
- The cell membrane is made up of a bilayer of phospholipid molecules with protein molecules interspersed among them.
- The cell membrane is ‘fluid’ in nature. The phospholipid molecules and some protein molecules can move laterally within the bilayer.
- Due to the fluid nature of the membrane, proteins are found to intersperse within the bilayer distributed in a mosaic pattern.
- 磷脂分子可形象化為具有親水的「頭部」和兩條疏水的「尾巴」。
- 磷脂分子疏水的尾部指向膜的內部，而親水的頭部則指向細胞內外的水溶液。
- 膜蛋白具有不同功能，如下表所示：
| 膜蛋白的種類 |
位置 |
功能 |
| 通道蛋白 |
貫穿細胞膜 |
形成孔道讓水分子、離子和水溶性分子通過 |
| 載體蛋白 |
貫穿細胞膜 |
是主動轉運的載體 |
| 酶 |
附在細胞膜的內或外表面 |
能加快生物體內的化學反應 |
| 受體蛋白 |
附在細胞膜的外表面，能與特定的化學物質結合 |
可以激發或抑制某些細胞活動 |
| 糖蛋白 |
附在細胞膜的外表面 |
作為細胞的識別標記 |
- 細胞膜的韌度足以包裹細胞內所有物質。細胞膜具流動性，因此可斷開及融合，這使細胞在生長、進行分裂和吞噬時能改變形狀。
- 細胞膜具差異透性，能控制物質進出細胞。
- A phospholipid molecule can be represented as a hydrophilic ‘head’ with two hydrophobic ‘tails’.
- The hydrophobic tails are pointing inwards, while the hydrophilic heads face the watery environment inside and outside the cell.
- Membrane proteins serve many different functions as shown in the table below.
| Type of protein |
Location |
Function |
| Channel proteins |
Across membrane |
Forming pores through which water, ions and other water-soluble molecules can pass |
| Carrier proteins |
Across membrane |
Involved in active transport |
| Enzymes |
Outer or inner surface |
Speeding up chemical reactions |
| Receptor proteins |
Outer surface, binding with specific chemicals |
Triggering or inhibiting certain cellular activities |
| Glycoproteins |
Outer surface |
Acting as recognition markers |
- The cell membrane is strong enough to hold the cell contents. The cell membrane can break and fuse due to its fluidity. This allows cells to change shape during cell growth, cell division and phagocytosis.
- The cell membrane is differentially permeable. This allows the control of the movement of substances into and out of the cell.
活動Task
老師會把同學分成三至五人的小組。與組員合作設計和製作一個細胞膜模型。設計細胞膜模型時，要注意以下各項︰
Your teacher will divide the class into groups of three to five. Collaborate with your group members to design and make a cell membrane model. Remember that the model:
- 模型應合乎比例。
- 模型應能表示細胞膜的結構。
- 模型應能表示細胞膜的特性和功能。
- should be to scale.
- should represent the structure of the cell membrane.
- should illustrate the properties and functions of the cell membrane.
設計細胞膜模型Design the cell membrane model
1.
老師會提供下表列出的物料供你製作細胞膜模型，你可自由組合不同的物料，也可以自備物料。列出你的設計所需的物料。
Your teacher will give you the materials listed below to make the cell membrane model. You may choose materials in any combination or even bring your own materials. List the materials your group will use.
| 乒乓球ping-pong balls |
吸管drinking straws |
黏土modelling clay |
| 水缸a plastic container |
油oil |
水water |
2.
繪畫並標示你的設計。扼要地描述製作模型的步驟。
Draw and label your design. Briefly describe your steps in making the model.
3.
寫出設計模型時，所參考的資料來源。
Write the source(s) of any reference you used when designing your model.
製作及展示模型Make the model and communicate results
1.
經老師准許後，你和組員便可收集所需物料和製作細胞膜模型。
3.
老師會根據以下評核準則來評核你的表現。
| 評核準則 |
水平 |
| 優異 |
良好 |
平平 |
差劣 |
生物學知識的應用
- 模型合乎比例
- 模型展示了細胞膜的結構和特性︰
磷脂雙層、正確的磷脂分子排列方向、細胞膜的流動性
|
4 | 3 | 2 | 1 |
|
解難能力
|
4 | 3 | 2 | 1 |
|
創新的設計
|
4 | 3 | 2 | 1 |
|
報告及演示
|
4 | 3 | 2 | 1 |
|
引用參考資料
|
4 | 3 | 2 | 1 |
|
整體水平
|
4 | 3 | 2 | 1 |
1.
After getting your teacher’s approval, you can collect your materials and make the cell membrane model.
2.
Present and display your model to the class.
3.
Your teacher will evaluate your work based on the following grading rubric.
| Assessment criteria |
Quality of work |
| Excellent |
Good |
Fair |
Poor |
Application of biological knowledge
- Model in scale.
- Model illustrates the structure and properties of the cell membrane:
phospholipid bilayer; correct orientation of phospholipid molecules; fluidity of the cell membrane.
|
4 | 3 | 2 | 1 |
Practical solution
- Appropriate use of all the materials provided to make a model.
|
4 | 3 | 2 | 1 |
Innovative design
- Innovative use of extra materials and original design.
|
4 | 3 | 2 | 1 |
Presentation
- Clear and well-organized oral presentation, proper use of scientific language.
|
4 | 3 | 2 | 1 |
Reference acknowledgement
- Any references used are properly acknowledged.
|
4 | 3 | 2 | 1 |
|
Overall quality of work
|
4 | 3 | 2 | 1 |
4.
What modifications can you make to improve your cell membrane model?
問題Questions
1.
解釋為甚麼細胞膜具「流動性」和「鑲嵌」性質。
Explain why cell membrane is described as ‘fluid mosaic’.
2.
解釋磷脂分子如何構成細胞膜的結構。
Explain how phospholipid molecules contribute to the structure of the cell membrane.
3.
寫出使用模型來展示細胞膜的一項優點和一項限制。
State ONE advantage and limitation respectively of using a model to represent the cell membrane.
延展部分Extension
除了實物的模型，模型亦可透過圖像展示。我們可以利用電腦程式，例如BioRender，來繪畫圖像模型。如果你會使用一些繪圖工具，你也可以嘗試設計自己的細胞膜圖像模型。
Besides scale models, models can be represented through graphics. A graphical model can be created using computer programs, such as BioRender. You can use computer programs that you are familiar to create your own cell membrane model in graphics.