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Learning about Active Transport - Biology Revision


All metabolic processes like Photosynthesis, Respiration etc in the living organisms involve movement of substance in and out of the cells. The substance move in and out of the cell either by Active Transport or Passive Transport. Passive transport takes place in the cells by the process of diffusion or osmosis

Active transport can be defined as the movement of ions or molecules into the region of higher concentration through the semi permeable membrane with the help of enzymes. Now you must be wondering, technically the ions or molecules move from higher concentration to lower concentration through the process of diffusion but here it is moving into higher concentration.


 Schematic diagram representing the movement of molecules from a region of high concentration to a low concentration across a semi permeable membrane. Image source: sparknotes.com.
As we can see in the diagram above the cell membrane has a high concentration of particles on one side and a low concentration of particles on the other side. Scientists call this a concentration gradient. Generally the ions and molecules travel from a region of higher concentration to a region of lower concentration. But what if the cell wants to bring in a molecule which is already present in high concentration inside the cell ? This is when active transport comes into action.

So now we can describe active transport as the process in which substance are absorbed against the concentration gradient (or we can say substance move from a region of lower concentration to a region of higher concentration) with the help of an enzyme. This process requires energy from respiration.

Schematic representation of a cell membrane depicting the movement of molecules from a region from low concentration to high concentration with the use of ATP. Image source: quit.com 
Active transport is different from the process of diffusion in two ways:

Diffusion
Active transport
Particles move down the concentration gradient i.e from s region of higher concentration to a region of lower concentration
Particles move against the concentration gradient.
This process does not require any energy from respiration.
Active transport requires energy from respiration to move the particles against the concentration gradient.

Active transport takes place both in animal cells and plant cells. In animal cells, it takes place in the small intestine while absorbing food. In plants cells, it takes place in the root hair cells which absorb water and minerals.




Active Transport in Animal Cells 

The cavity of small intestine where the food is digested is called lumen. Glucose molecules are produced in lumens when food is digested. Now that the concentration of glucose molecules in the lumen is much lower than that in the cells, they are transported inside the cells by active transport against the concentration gradient. Further those molecules can be transported to blood stream with 
the concentration gradient.


Active transport in Plant Cells 

Root hair cells found in the roots of the plant transports ions such as magnesium (Mg) from the soil into the cells as these ions are needed to make chlorophyll in the leaves. The concentration of Mg ions is lower in the soil than in the root cells so active transport is used to transport the ions into the cells. These ions are then moved to xylem vessels and eventually the leaves where chlorophyll production takes place.

Hence, we can say that active transport is critical in both plants and animal cell and also in both the examples the cell contained mitochondria as mitochondria is the site of respiration and active transport requires energy from respiration.


Respiratory Inhibitors 

Cyanide is a poison which is called the respiratory inhibitor as it doesn't let mitochondria perform the aerobic respiration. This in turn badly affects the energy availability in the cells which causes the active transport to either slow down or stop.
Mahima Laroyia, is an Oxford Postgraduate in Integrative Biosciences who has more than 8 years of tutoring experience in tutoring students Maths and Sciences from KS2 up to A-levels. She specializes in providing custom and tailor made study materials to school students to make Maths and Sciences easier and fun.Find me at: www.expertguidance.co.uk 

About Will Green

A student in England studying Automotive Engineering with Motorsport, Will created Ask Will Online back in 2010 to help students revise and bloggers make money. You can follow AskWillOnline via @AskWillOnline.

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