# How does the cell membrane change over time?

Mar 27, 2017

The ratio of lipids and proteins in a cell membrane can change over time.

#### Explanation:

$\textcolor{red}{\text{The cellular membrane}}$
The main components of the cellular membrane are:
- phospholipids
- cholesterol
- proteins.

The currently accepted model of the cellular membrane is the fluid-mosaic model. This model states that membranes are very dynamic structures with different components. The lipids that make up the double layer of the membrane and the proteins they harbor can flow freely in the plane of the membrane.

$\textcolor{red}{\text{Changes over time}}$
The fluidity of the membrane also means that there is room for changes. The cellular membrane is crucial for the cell and has to be able to adapt to the circumstances

Some of the possibe changes:

• amount of cholesterol : cholesterol helps to maintain the fluidity of the membrane.
$\textcolor{red}{\text{Example}}$: when the temperature decreases, the concentration cholesterol increases

• the number of proteins : proteins in the cell membrane perform various functions, the need for these proteins can change.
$\textcolor{red}{\text{Example}}$: some proteins help to anchor the cells to their surroundings, when the cell needs to move/migrate there will be less of these proteins compared to when the cell needs to stay anchored.

• the type of protein: the cell membrane receives and transmits signals, different signals require different proteins. This can also change over time.
$\textcolor{red}{\text{Example}}$: immune cells need to be able to 'present' different antigens on the surface to initiate an immune response.

During the lifetime of a cell the proteins and lipids will be damaged by certain molecules in the body (reactive oxygen species, ROS). Due to this aging the membrane will lose some of its integrity.