Active Transport

Keywords

Active transport, transfer, substances, energy, low concentration, high concentration, concentration gradient, vesicles, nutrients, minerals, cell membrane, partially permeable.

Introduction

Substances can move between the inside and outside of cells. This is done through the cell membrane. Although you would think that a cell membrane just holds all the organelles inside and stops them from escaping, but the cell has molecules at certain points that allow the transport of particles within the cell to the outside.

How It Works

To start, your cell has vesicles. These vesicles are small packets of protein that have been processed by the golgi apparatus, and they sit ready to be used by the cell at a later point.

Our cells have a cell membrane, also known as a plasma membrane. This membrane is partially permeable. This means it allows certain components to travel between the cell and the external area. But it keeps other components that are larger within the cell.

Active transport happens by the movement of these vesicles and other particles within the cell to another part, outside the cell. This is called moving from a region of low concentration to a high concentration.

This is linked to the concentration gradient. A concentration gradient is how concentrated a solute is. There are three ways this can be changed - through diffusion, through osmosis, and active transport.

Some examples of active transport include:

• uptake of glucose by epithelial cells situated in the small intestine
• uptake of ions from soil water by root cells in plants

Interesting fact: there are two types of active transport - primary active transport being used by energy called ATP, and secondary that uses electrochemical ions.

Active Transport in Plants

Plants also require active transport systems which are mainly involved in the transport of materials. This happens through the root hair cells underground, and transports water, minerals, and nutrients that are then delivered around the rest of the plant.

Again, like animal cells and human cells, the active transport in plants moves against the concentration gradient. The plant absorbs water and nutrients in the roots.

Examples of this happening in plants includes:

• phagocytosis of bacteria by Macrophages
• sugars moving from leaves to fruit
• minerals traveling through a stem to other parts of the plant

Active Transport in Humans

A great example of how active transport works in humans is to look at the white blood cell. What do they do? They literally eat pathogens that are in your body that shouldn't be there.

So, your white blood cell will travel around your circulatory system, seeking out the pathogens. When it gets to them, it will only allow that pathogen to enter the cell. This is through active transport. When it does this, it doesn't allow anything to escape the cell at the time, and often, the white blood cell will get slightly bigger.