Lesson 6 Membrane Transport
Structure of the Cell Membrane
Before we talk about how materials are transported through the cell membrane, we need to understand the basic structure of it.
A6.2
Fluid-mosaic model
The model we use to describe the structure of the cell membrane is called the fluid-mosaic model. This model suggests the cell membrane is a collection of
proteins floating within the membrane itself and the membrane is fluid in nature. This means
- these proteins can move around in the membrane, depending on their job and the needs of the cell
- the membrane itself can move, vibrate, and change shape when needed
The membrane itself is made of a phospholipid bilayer. This is a fancy way of saying the membrane contains two layers of particles called phospholipids. A phospholipid has a
- round head made of the compound phosphate
- tail made of lipids
A6.3 A phospholipid
A6.4 Structure of phospholipid bilayer
The phosphate head loves water while the lipid tail hates it. This means the two layers of the phospholipid form with the tails on the inside and the heads on the outside. The cell membrane is so strong because the lipid centre really does not want
to get wet and so does everything in its power to keep the heads together as a membrane.
One of the compounds found in the membrane is cholesterol. Cholesterol is important to the structure of the membrane because it keeps the membrane fluid. This allows the other proteins in the membrane to move around and also allows particles that are needed to move into and out of the cell. The cell membrane is semi-permeable, meaning it lets some particles in and keeps others out.
One of the compounds found in the membrane is cholesterol. Cholesterol is important to the structure of the membrane because it keeps the membrane fluid. This allows the other proteins in the membrane to move around and also allows particles that are needed to move into and out of the cell. The cell membrane is semi-permeable, meaning it lets some particles in and keeps others out.
Read This
Please read pages 272 and 273 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on structure of the cell membrane and how it maintains equilibrium. Remember, if you have any questions or you
do not understand something, ask your teacher!
Practice Questions
Complete the following practice questions to check your understanding of the concept you just learned. Make sure you write complete answers to the practice questions in your notes. After you have checked your answers, make corrections to your responses (where necessary) to study from.- Why do you think the model used to explain the cell membrane structure is called the fluid-mosaic model?
Your answer should be a variation of the following: It is called fluid because the proteins in the membrane are floating around, as if they were fish swimming in water. It is called a mosaic because it has many different pieces held
together by the phospholipid bilayer, just like a mosaic tile pattern.
A6.5 Mosaic tiles