How Substances Cross the Cell Membrane?

Essay Plan

Three main parts to be covered in the essay:

·       Introduction

·       Main body

·       Conclusion

The essay will start with the introduction of the topic; what is membrane transportation and what are the types of mechanisms used by substances to pass through. After that essay structure will be briefly explained. The main body of the essay will include a detailed analysis of various types of substances and their permeability. Methods of cell transport will be analysed to see how the substances cross the cell membrane. In the end, a conclusion will be provided.

Introduction

There are several types of substances in a cell, and their transportation in and out of the cell depends on the specific characteristics of the substances. Some substances don’t need any assistance with the transportation while others might not be able to pass through without help. Depending on the type of the substance, the process of cell transportation varies and these transportations also have different names. For instance, passive diffusion is a process to bring down the free energy of the cell, and this is done without the help of membrane proteins (Antonacci, et al., 2016).

Active transport, on the other hand, is transport with the help of membrane proteins. Seemingly, the process does not require any energy, but hydrolysis from the energy plays a facilitating role in this transport. There are several other subtypes of substance transport in and out of the cell, and this work is based on the analysis of these types of mechanisms used by substances. 

How Do Substances Cross Membrane?

The role of a membrane in a cell is to act as a barrier for the substances that try to pass through. The purpose of this ability of the membrane is to protect the cell from the outer environment and make sure that only the required substance enters into the cell. This is the choice of the membrane to decide what substance crosses the membrane and which one is blocked on the basis of the features of the substance. Some membranes are totally or partially permeable for some substances while it might be totally impermeable to others.  

Membrane proteins are components that facilitate the transport process when required. Moreover, the transport into the cell happens in two directions; concentration and electrochemical gradient or the opposite direction. In case, the transport is towards the gradient, an extra energy from the external channel is not required. For instance, a substance that covers the path from a high concentration to a lower one, the process doesn’t require any external energy. On the other hand, in case the transport is in the opposite direction, the process needs the energy to as a support in the form of metabolic energy. The figure 1 in the appendix illustrates the types of substances and the behaviour of the cell membrane during their transport process