What can you label To know the structure

What can you label?

� To know the structure of the liver � Describe with the aid of diagrams and photographs, the histology and gross structure of the liver

� Know about the function of the liver � Describe the formation of urea in the liver, including an outline of the ornithine cycle � Describe the roles of the liver in detoxification

RECAP - STARTER 1. What is the functional unit of the liver called? 2. What are the main functions of the liver? 3. What is the triad? 4. What is the sinusoid? 5. What fills the bile canaliculi? 6. What is the name of the phagocytic cell in the liver and where would we find it? 7. Name two products release from the hepatocytes into the blood 8. Name two products removed and metabolised from the blood by the liver.

� Write out the equations for: � Deamination � Formation of Urea � Detoxification of alcohol

Vital role in maintaining blood glucose levels controlled by pancreas FATS FOR ENERGY • • • Fats released from adipose tissue and released into blood. Hepatocytes split triglyceride molecules into fatty acids and glycerol. Fatty acids converted to acetyl coenzyme A Kreb’s cycle. CONVERTING XS PROTEIN AND CARBS TO FATS (TAG’S) CHOLESTEROL Transported in the blood as lipoproteins Cholesterol is needed for: -cell membranes -Lipid and steroid based hormones such as sex hormones

FATS FOR ENERGY • • • Fats released from adipose tissue (GLUCAGON) and released into blood. Hepatocytes split triglyceride molecules into fatty acids and glycerol. Fatty acids converted to acetyl coenzyme A Kreb’s cycle. G L Y C E R O L COOH Liver: break down of the triglyceride FA’s: acetoacetate to blood COOH Absorbed by tissues Acetyl co. A COOH Used in Krebsproducing ATP

� Detoxification can take place by the oxidation, reduction or methylation of toxins � Detoxification of alcohol, antibiotics, steroid hormones etc � Example catalase Hydrogen peroxide water and oxygen 2 H 2 O 2 2 H 2 O + O 2

� Alcohol is broken down into ethanoate by the enzymes alcohol dehydrogenase and aldehyde dehydrogenase. � Ethanoate (acetate) combines with coenzyme A and becomes acetyl coenzyme A. � Hydrogen ions are released and reduced NAD is produced. � Acetyl coenzyme A enters the Krebs cycle and is metabolised to produce ATP.

� NAD is used to oxidise and break down fatty acids (for use in respiration) in the liver (by hepatocytes) If NAD is reduced (from already having to detoxify alcohol, there is insufficient NAD to oxidise the fatty acids. The fatty acids are converted back to lipids and are deposited in the hepatocytes which then causes the liver to become enlarged If it persists the liver tissue is converted to fibrous tissue and can lead to cirrhosis

� Damaged hepatocytes are replaced by fibrous tissue � Structure of blood supply is lost �Blood flows from hepatic artery into hepatic vein without flowing through sinusoids � Effects �Increase in ammonia concentration which can cause major damage to the central nervous system

How does SALT affect liver metabolism?

QUESTION �What type of reaction will be involved in converting glucose to glycogen?

ANSWER �A condensation reaction; glycosidic bonds will be formed between glucose molecules.

� Describe in three or four bullet points the key features about the gross structure of the liver. � Describe and explain the important differences in the liver’s blood supply (compared to most organs of the body) � Briefly describe the role of the following structures in liver tissue: 1. 2. 3. 4. Bile canaliculi Phagocytic Kupffer cells Central vein Sinusoids

Proteins are made of long chains of amino acids. When amino acids are metabolised and broken down during deamination, ammonia is released; This is a poisonous substance which must be rapidly converted into something less harmful. In the liver, the ammonia is converted in urea. After the urea has been synthesized it is carried in the blood to the kidneys, where it is excreted in the urine.

The ornithine cycle

AMINO Oxygen is required, and along with ammonia, hydrogen peroxide is produced. Ammonia is highly toxic and very soluble, so as soon as the ammonia is made, it enters the next stage of the process.

keto acids Respired Lipids and cholesterol

UREA Urea is soluble and can be excreted from the body in the form of urine. The ornithine cycle was discovered by Krebs 5 years before the TCA cycle. The first stages occur in the mitochondria, the second half of the cycle occurs in the cytoplasm.

Transamination – transferring an amino group from one molecule to another. Transaminase is the catalyst

� Explain what deamination is and why it is so important. � Why should excess amino acids not be excreted? � What is the ornithine cycle? � Why are there so many symptoms associated with liver disease? � Why might you want to include liver in your diet?

� On print out Ornithine Cycle

HOMEWORK: TEST YOURSELF Define the term excretion � What are the main 2 substances to be excreted by humans? � Define the term deamination. � What can excess carbon dioxide in the blood cause? � Write down the chemical equation formation of urea from ammonia? � What is the scientific name for a liver cell. � Name the 2 blood supplies to the liver � What is the function of the Kupfer cell � Name the enzyme that initially breaks down alcohol in the liver � What happens to the acetly co enzyme A that has been produced by the break down of ethanol in the liver? �