Why we need to breathe: Part I – carbon dioxide

What exactly is the big deal with breathing?  Why do we breathe?  Always.  It must be pretty important….so important that most of the time our body does it automatically.  Respiration (a fancy-pants word for breathing) is more than just breathing in oxygen and breathing out carbon dioxide.  The nutrients (sugars, proteins and fats) that you eat travel through the circulatory system to the cells and are broken down and their energy converted into ATP (adenosine triphosphate) through stacks of complicated processes that go under the banner cellular respiration.  ATP is kind of like the universal energy currency of cells.  Australia has the dollar, Europe the euro and cells have ATP.  Most things that happen inside cells (like moving, replicating and making things) have a cost that is paid in ATP.  Each cell even has its own money mints to print the ATP – the mitochondria.

Cell with mitochondria

The sugar glucose is the major energy source of most animals and plants.  Carbon dioxide and water and produced as wastes when it is broken down.  While excess water can be removed via the urinary system (peed out), getting rid of the carbon dioxide waste can be a bit more problematic.  In liquids like blood, or cellular fluids, carbon dioxide combines with water to form carbonic acid.  Our body (and other vertebrates) has a system (bicarbonate buffer) in place can stop small increases in carbonic acid in the bloodstream from being harmful.  But cellular respiration is happening constantly so ultimately the carbon dioxide needs to be removed from the body so that the cells (and blood) don’t become more and more (and more) acidic.  Changes in the acidity of the blood (and cells) can stuff up lots of important things (like moving, replicating and making things) and even make things fall apart (change protein conformation).   So, the carbon dioxide is transported to the lungs (or gills, or skin or however the particular animal/plant does this) in the blood (buffered by the bicarbonate system in vertebrates) and breathed out.

Cellular respiration - glucose is broken down into carbon dioxide and water

But when we breathe, we breathe in oxygen….right?  What does oxygen have to do with anything?  Find out Friday.

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5 Responses to Why we need to breathe: Part I – carbon dioxide

  1. Pingback: Whaaaat……eggs breathe? Part II: How bird, reptile and monotreme eggs exchange gases | to breathe, or not to breathe

  2. Pingback: So what’s all this oxygen about? Why we breathe part II | to breathe, or not to breathe

  3. Pingback: Can you stop breathing? Frogs can………for winter | to breathe, or not to breathe

  4. Pingback: Do plants breathe? | to breathe, or not to breathe

  5. Pingback: Why don’t birds breathe like the rest of us? | to breathe, or not to breathe

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