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Leaving Cert Biology Revision: Blood & Circulatory System

Blood and Circulatory System



Transport in the human


Imagine your body is like a big city, and blood is the transportation system that keeps everything running smoothly.


The Blood System


The blood system is like a network of roads, carrying important stuff like oxygen, nutrients, and waste products to and from different parts of your body.


Composition of Blood Tissue


Now, let's talk about what blood is made of. It's like a special fluid that's made up of different parts. First, there's plasma, which is like the liquid part of blood. It's mostly water, but it also carries proteins, salts, and other important substances.


Types of Blood Cells


Then, there are the blood cells, which are like the workers in this transportation system. 

There are three main types:


  1. Red blood cells: They carry oxygen like delivery trucks and have a protein called hemoglobin.

  2. White blood cells: They defend the body by fighting off germs.

  3. Platelets: They help stop bleeding and form scabs when you get a cut.




Cell metabolism and enzymes


Anabolism: The process by which the body builds new molecules and energy.


Catabolism: The breakdown of molecules in the body to produce waste products and energy is known as catabolism.


Metabolism: The entire process by which the body uses and changes food and energy is called metabolism.


Properties of Enzymes


  • Our bodies contain small molecular machines called enzymes that aid in accelerating chemical reactions. 

  • They are extremely particular, akin to keys that precisely fit locks, guaranteeing that only specific reactions take place at the appropriate times. 

  • Enzymes can also be recycled, indicating that they are reusable. 

  • Their activity may be controlled to match the demands of the body, and they function best in particular environments like pH and temperature. 

  • Without enzymes, to sustain human life, many vital bodily functions would proceed too slowly.




Mechanism of Enzyme action - The active site theory


In our bodies, enzymes function as little assistants that speed up chemical reactions. They achieve this by attaching themselves to particular molecules and transforming them into others.

The "active site theory" is a unique theory regarding the functioning of these enzymes. 


According to this theory, enzymes have a unique region known as the "active site" where they attach themselves to the molecules they wish to catalyze.


Similar to a lock and key, only specific molecules (the key) can fit into the lock, which is the active site.

The enzyme can function after the proper molecule enters the active site. It may disassemble the molecule, combine various components, or alter its structure. This occurs because the molecules and the active site fit together like a jigsaw.


According to the active site theory, enzymes bind to particular molecules within their active sites and alter them to speed up chemical reactions.


Denatured Enzyme


In our bodies, denatured enzymes function as little machines that assist with vital processes like food digestion. 

Enzymes that are denatured have structural abnormalities that impair their ability to function as intended. When exposed to specific chemicals, extremely acidic or basic conditions, and extremely high temperatures can all induce this.


What would happen if you disassembled a toy and could not assemble it correctly? 


Enzymes that become the denatured type lose their structure and become unable to function as intended.

An enzyme is like a broken toy permanently after it is denatured since it usually cannot return to its former shape.


On the other hand, in certain cases, the enzyme may continue to function somewhat if the denaturation isn't too severe, much like a broken toy that may still move somewhat.


Denatured enzymes are occasionally used by scientists in tests and research, however, they can be harmful to human health. Enzymes can be denatured by high fevers or specific infections, which can disrupt vital bodily functions.



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