Which of the following functions is NOT performed by the liver?
a) Storage of vitamins and minerals b) converts glucose to glycogen c) converts toxins to harmless chemicals d) produces bile
I chose b and got it wrong, any help?
Liver does all those functions as far as I know. The liver hepatocyctes are stimulated to create the enzyme glycogen synthase which promotes the conversion of glucose to glycogen in the presence of insulin. Glycogen is stored in the liver after its production for further use. The whole process is explained in detail in this page. Regarding the storage of vitamins and minerals, I have a paper which details the absorption and storage of Vitamin A in rat liver. I am also linking another paper that details the presence of Vitamin B12 in the human liver.
21.2: Homeostasis and Disease
- Contributed by Suzanne Wakim & Mandeep Grewal
- Professors (Cell Molecular Biology & Plant Science) at Butte College
Imagine driving on this seemingly endless road. Hopefully, your imaginary car is equipped with cruise control. Cruise control can help keep you safe as well as help you avoid a speeding ticket by keeping the speed of the car at the speed limit. Cruise control works by monitoring the car&rsquos speed and adjusting the throttle as needed to keep the speed within a narrow range around the set speed limit. If the car starts to go faster than the set limit, it causes the throttle to release less gas until the speed drops back down to the setpoint. The opposite happens if the car&rsquos speed starts to fall below the set speed limit. Cruise control on a car is a good analogy for physiological mechanisms that maintain the human body in a steady state.
- : Inflammation of the liver, usually caused by viruses like hepatitis A, B, and C. Hepatitis can have non-infectious causes too, including heavy drinking, drugs, allergic reactions, or obesity. : Long-term damage to the liver from any cause can lead to permanent scarring, called cirrhosis. The liver then becomes unable to function well. : The most common type of liver cancer, hepatocellular carcinoma, almost always occurs after cirrhosis is present. : Liver failure has many causes including infection, genetic diseases, and excessive alcohol. : As cirrhosis results, the liver leaks fluid (ascites) into the belly, which becomes distended and heavy. : If a gallstone becomes stuck in the bile duct draining the liver, hepatitis and bile duct infection (cholangitis) can result. : Hemochromatosis allows iron to deposit in the liver, damaging it. The iron also deposits throughout the body, causing multiple other health problems. : A rare disease with unknown causes, primary sclerosing cholangitis causes inflammation and scarring in the bile ducts in the liver. : In this rare disorder, an unclear process slowly destroys the bile ducts in the liver. Permanent liver scarring (cirrhosis) eventually develops.
Liver inflammation is a reaction that occurs when liver cells are attacked by a disease-causing microbe or substance. The liver is an organ in the digestive system that assists the digestive process and carries out many other essential functions. These functions include producing bile to help break down food into energy creating essential substances, such as hormones cleaning toxins from the blood, including those from medication, alcohol and drugs and controlling fat storage and cholesterol production and release.
The word hepatitis refers to liver inflammation. Most forms of hepatitis result from viral infection, although in some cases it is caused by an autoimmune disorder, in which the body’s immune system attacks liver cells because it cannot tell the difference between harmful invaders and healthy liver tissue. Damage to the liver from alcohol, toxins, and certain drugs can also result in inflammation. Some inherited diseases can cause inflammation and hepatitis, along with prolonged obstruction of bile flow. Some forms of liver inflammation produce mild symptoms, while others can be serious or life threatening.
Several types of viral hepatitis are known, the most common of which are designated as hepatitis A, B, C, D and E. Depending on the type, viral hepatitis can be spread through food or water contaminated by feces from an infected person contact with infected blood through infected needles or contaminated blood transfusions through sexual contact with an infected person or passed from mother to child during childbirth.
The severity, treatment and outcome of liver inflammation depend largely on the type of hepatitis you have. The initial symptoms of inflammation are similar to flu, but with the addition of jaundice, a yellowish discoloration of the skin and whites of the eyes. Left untreated, liver inflammation will begin to interfere with liver function and may progress to end-stage liver disease and liver failure. The liver damage caused by any inflammation is worsened by drinking alcohol. Fortunately, vaccines have been developed to protect against hepatitis A and B, two common causes of liver inflammation.
Seek immediate medical care (call 911) for serious symptoms associated with complications of liver inflammation, such as confusion, hallucinations, extreme fatigue, fainting, fever (especially if combined with a swollen abdomen), vomiting blood, or severe mood changes (especially agitation).
Seek prompt medical care if you experience any of the following symptoms, including yellowing of the skin or whites of the eyes (jaundice) abdominal pain nausea, vomiting or diarrhea constant weakness or dizziness difficulty thinking or understanding and low-grade fever. Also seek prompt medical care if you are being treated for hepatitis but your symptoms persist or recur.
What are the symptoms of liver inflammation?
Symptoms of liver inflammation can involve a variety of body systems, with effects ranging from decreased energy level to skin irritation to abdominal and gastrointestinal symptoms. You should contact your health care provider if you have any of these symptoms, and seek immediate attention for symptoms associated with more serious forms of the disease.
Common symptoms of liver inflammation
There are various types of liver inflammation, and symptoms vary depending on the type. At times, any of these symptoms can be severe:
How does the liver detoxify?
Toxins enter the body in food, water, through the skin and by inhalation. These toxins – such as pesticides, pharmaceutical drugs, chemicals and water-borne pollutants – end up in our bloodstream, and our liver filters the blood to remove them. Toxins are also created by biochemical reactions in the body. Toxins affect us in many ways, from drunkenness caused by alcohol to the side-effects of certain medication.
The liver transforms fat-soluble toxins into a water-soluble form. This enables them to be released through the kidneys for elimination in urine, or into bile for elimination through the colon. Enzymes chemically break down toxins which have been absorbed through the intestines. The toxins are either neutralised, or converted into a more chemically active form which is then neutralised, to be safely excreted.
A healthy liver will manufacture approximately one litre (1.75 pints) of bile per day to transport toxins out of the body. If the liver is sluggish, toxins can build up, causing inflammation and oxidative stress. Toxins which are not eliminated return to the bloodstream and are eventually stored in fatty tissues where they pose less of an immediate threat. In the longer term, however, the slow release of these toxins back into the bloodstream can lead to a number of diseases.
A chemical reaction is when chemicals come together and their molecules interact to form new chemicals. Sometimes chemical reactions happen by themselves. These reactions are usually very fast and spontaneous, and give off energy. Other chemical reactions need energy to happen, and without energy proceed very slowly or not at all.
These types of chemical reactions can be helped to occur more quickly by using enzymes. Enzymes are made out of protein and they speed up the rate of a chemical reaction by acting as a catalyst. A catalyst provides the necessary environment for the chemical reaction to occur, which speeds up the reaction. Certain catalysts work for certain kinds of reactions. In other words, each enzyme has a particular type of reaction that it can activate.
Enzymes are proteins, which are molecules that are very large and dynamic. They can be very fussy, and sometimes need to be in certain environments or conditions to work, and the ideal conditions are usually reflective of where the enzyme must normally function in the body. In other words, different tissues are home to different enzymes, and an enzyme should be able to function in the conditions that surround it in the tissue it's supposed to function in. Some enzymes can be damaged under certain conditions, such as heat. A damaged enzyme will no longer work to catalyze a chemical reaction.
One source of enzymes is the liver, which needs to break down many substances in the body. Catalase is one enzyme from liver that breaks down harmful hydrogen peroxide into oxygen gas and water. When this chemical reaction occurs, you can see the oxygen gas bubbles escaping and causing the reaction to foam, as shown in Figure 1 below.
Figure 1. When blended liver is exposed to hydrogen peroxide, the catalase enzyme in the liver reacts with the hydrogen peroxide to form oxygen gas, which creates the visible bubbles in this photograph, and water.
In this science fair project, you will use fresh (or frozen) liver as a source of catalase and investigate how the activity of the enzyme can change under certain conditions. What does catalase do? Under which conditions does it work best? Why do we need catalase in our liver?
- Abdominal Ultrasound (American College of Radiology, Radiological Society of North America) Also in Spanish
- Computed Tomography (CT) - Abdomen and Pelvis (American College of Radiology, Radiological Society of North America) Also in Spanish
- Elastography(National Library of Medicine) Also in Spanish
- Liver Biopsy(National Institute of Diabetes and Digestive and Kidney Diseases) Also in Spanish
- Liver Function Tests(National Library of Medicine) Also in Spanish
- Magnetic Resonance Cholangiopancreatography (MRCP) (American College of Radiology, Radiological Society of North America) Also in Spanish
- MRI of the Body (Chest, Abdomen, Pelvis) (American College of Radiology, Radiological Society of North America) Also in Spanish
- Smooth Muscle Antibody (SMA) Test(National Library of Medicine) Also in Spanish
- Milk Thistle(National Center for Complementary and Integrative Health)
- Transjugular Intrahepatic Portosystemic Shunt (TIPS) (American College of Radiology, Radiological Society of North America) Also in Spanish
The Bladder [back to top]
The collecting ducts all join together in the pelvis of the kidney to form the ureter, which leads to the bladder. The filtrate, now called urine, is produced continually by each kidney and drips into the bladder for storage. The bladder is an expandable bag, and when it is full, stretch receptors in the elastic walls send impulses to the medulla, which causes the sphincter muscles to relax, causing urination (or micturition). This is an involuntary reflex response that we can learn to control to a certain extent when we are young.
The Liver: Helping Enzymes Help You!
Your liver is important for cleaning up any potentially dangerous substances you consume. But how does it do it?&mdashWith 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&mdashtiny 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.
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&mdashor 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.
&bull Raw liver (fresh or frozen, thawed one quarter pound)
&bull Cutting board
&bull Medicine dropper
&bull Large plate
&bull Hydrogen peroxide (new or recently purchased bottle works best)
&bull Measuring teaspoon
&bull Two bowls
&bull Baking soda
&bull Microwave-safe bowl (with a cover)
&bull Microwave oven
&bull Completely disinfect any surface that the raw liver touches during this activity.
&bull On the cutting board, carefully cut the liver into little, cube-shaped pieces, about one to two centimeters long. Be careful using the sharp knife. (An adult may need to help with this.)
&bull Place the liver cubes into a blender and add an equal volume of water. Blend on high speed, pulsing when necessary, until the liver is smooth and no chunks are present. Be careful of the sharp blades in the blender.
&bull Keep the blended liver in the refrigerator.
&bull Put one drop of the blended liver on the large plate. To the blended liver drop, add one drop of hydrogen peroxide. You should see a lot of bubbles! What do you think the bubbles are made of? This shows that the liver enzyme catalase is working to start the chemical reaction that breaks down the hydrogen peroxide that would be harmful to the body into less dangerous compounds.
&bull To test the effect of an acid on the liver enzyme, put one teaspoon of the blended liver in a bowl and mix it well with one teaspoon vinegar. What is the color and consistency of this mixture? Put one drop of the mixture on a clean part of the large plate and add one drop of hydrogen peroxide to it. Compared with the untreated blended liver, did more, less or about the same amount of bubbles form? Did they form more slowly, more quickly or at about the same rate?
&bull To test the effect of a base, put one teaspoon of the blended liver in a bowl and mix it with one teaspoon baking soda. What is the color and consistency of this mixture? Put one drop of the mixture on a clean part of the large plate and add one drop of hydrogen peroxide to it. Did more, less or about the same amount of bubbles form? Did they form more slowly, more quickly or at about the same rate?
&bull To test the effect of heat, put one teaspoon of the blended liver into a microwave-safe bowl. Cover the bowl and microwave it on high for 20 seconds. How does the blended liver look after heating? Remove a drop-size amount of the heated liver and put it on a clean part of the large plate. Add one drop of hydrogen peroxide to it. Did more, less or about the same amount of bubbles form? Did they form more slowly, more quickly or at about the same rate?
&bull Based on your observations, under which condition(s) does it look like the enzyme works best? Which condition(s) makes it work the worst? Why do you think this is so?
&bull 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?
&bull 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&mdashacidic or warm&mdasheach 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.
Safely dispose of any raw liver meat used in this activity by putting it in the trash when you are done. Completely disinfect any surfaces that the raw liver meat touched during this activity, and be sure to thoroughly wash your hands with soap and warm water.
This activity brought to you in partnership with Science Buddies
You can lower your chances of getting cancerous liver lesions if you exercise, stay at a healthy weight, and drink only in moderation (up to two drinks a day for men and one for women).
And you can do a few things to keep from getting hepatitis B or C, which cause 80% of liver cancer cases. You can get vaccinated against hepatitis B, wear condoms when you have sex, and don’t share needles if you use them to do recreational drugs.
American Liver Association: “Benign Liver Tumors.”
Cleveland Clinic: “Malignant Hepatic Lesions.”
California Pacific Medical Center: “Metastatic Liver Lesions Diagnosis and Treatment,” “Non-Cancerous Liver Lesions Diagnosis and Treatment.”
Memorial Sloan Kettering Cancer Center: “Liver Cancer Prevention & Risk Factors.”