Your liver is important for cleaning up any potentially dangerous substances you consume. But how does it do it?—With a little help from some complex chemistry. Within your liver, as within every tissue in the body, many chemical reactions occur. Often these reactions require "help" to happen at a faster speed, and this can be supplied by enzymes—tiny types of proteins.
The liver uses specialized enzymes to help it break down toxic substances and make them safer for the body to process. But an enzyme, just like the chemical reactions it modifies, needs certain conditions to do its work. So, some environments can make a liver enzyme effective, whereas others can prevent it from working at all.
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A chemical reaction occurs when compounds come together and their molecules interact to form new compounds. Sometimes these reactions happen by themselves, are usually very fast and spontaneous, and give off energy. Other chemical reactions need energy, without which they would proceed very slowly or not at all. Enzymes can help speed up these types of chemical reactions.
Enzymes are large proteins that speed up the rate of a chemical reaction by acting as a catalyst. A catalyst provides the necessary environment for the reaction to occur, thereby quickening it. Certain catalysts work for certain kinds of reactions; in other words, each enzyme has a particular type of reaction that it can activate. Enzymes can be very fussy and sometimes need to be in certain environments or conditions to work well—or at all. Some enzymes can even be damaged, such as when exposed to too much heat. A damaged enzyme may no longer work to catalyze a chemical reaction.
Catalase is an enzyme in the liver that breaks down harmful hydrogen peroxide into oxygen and water. When this reaction occurs, oxygen gas bubbles escape and create foam.
Extra: Try experimenting with other conditions. For example, try freezing some blended liver or mixing it with salt and then test the enzyme's activity. Or you could try adding more than one teaspoon of vinegar or baking soda and then test the enzyme. Under which conditions does the enzyme work well, and under which ones does it work poorly?
Extra: You could try this activity again using another enzyme, called bromelain, which digests proteins and can be extracted from pineapples. One protein that is fun to digest using bromelain is gelatin, which is found in many puddings and gelatinous desserts. How do different conditions affect the ability of bromelain to digest proteins?
Observations and Results
When exposed to hydrogen peroxide, did the blended liver bubble less when mixed with either the vinegar or baking soda compared with when it was untreated? Did it bubble even less after it was microwaved?
An enzyme needs certain conditions to work, and the ideal environment can be a hint as to where the enzyme normally works in the body. And because different body tissues have distinct environments—acidic or warm—each enzyme is tuned to work best under specific conditions.
Different tissues in the body have different pHs (pH is a measure of how basic or acidic a solution is). The liver maintains a neutral pH (about pH 7), which is easiest for its enzymes, such as catalase, to work in. Consequently, when exposed to hydrogen peroxide the liver should have produced more bubbles (oxygen gas), and at a faster rate, when it was untreated than when exposed to vinegar or baking soda. (It may have bubbled more when treated with baking soda, compared with vinegar, because it might have been better able to return the pH to around 7.)
Similarly, enzymes in the liver are also used to functioning at body temperature (37 degrees Celsius), so microwaving the blended liver to a temperature hotter than that should have damaged the catalase enzyme and clearly decreased the amount of bubbles when it was exposed to hydrogen peroxide.
More to Explore"Enzymes Make the World Go 'Round" from Rader's Chem4Kids.com
"Your Liver" from KidsHealth
"Catalase" from David Goodsell and RCSB Protein Data Bank
"Liver Stinks!" from Science Buddies
"Which Fruits Can Ruin Your Dessert?" from Science Buddies
Teisha Rowland, PhD, Science Buddies
Science Buddies |
Chemistry, acids, bases, temperature, physiology, molecular biology
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