Liver Flashcards
(25 cards)
What does an amino acid consist of?
- Amino group (NH2) 2. Carboxyl group (COOH) 3. R-group side chain
How are amino acids metabolised in the body?
- Some are free in the blood
- Form proteins in the liver or peripheral tissues
- Harvested to remove C-backbone or nitrogen
How are amino acids stored in the body?
They are not stored, all are metabolised
What are enterocytes?
Intestinal absorptive cells
Describe how dietary protein is broken down and absorbed after entering the stomach
- Dietary protein enters the stomach and is denatured by HCL and pepsin
- These denatured proteins are then broken down in the SI by chylomytrypsin and trypsinogen into oligopeptides and AA’s
- These enter enterocytes and form AA’s in the blood after action of enterocyte peptidases
What is the function of albumin?
- Maintains oncotic plasma pressure (preventing oedema)
- Carries hormones + ions
What is a glucogenic amino acid?
An AA with a C-backbone that produces glucogenic/TCA cycle intermediates (glucose)
What is a ketogenic amino acid?
An AA with a C-backbone that produces acetyl CoA
What is transamination and what enzyme is required?
Taking an amino group from one AA to give to another
amino poop acid 1 + a-ketoglutarate -> alpha ketoacid + amino acid 2
(Catalysed by aminotransferase)
Why must ammonia/ammonium be removed from the body quickly?
Toxic
What two things can be used to get rid of faulty/ obselete proteins
- Proteosome (ubiquitin)
- Lysosome
What is the function of ubiquitin?
Ubiquitin is a small protein which binds to another protein to make a proteasome destroy the protein
Describe the Glucose-alanine cycle
- Alanine in muscle moves to a hepatocyte (liver), giving up a N atom, forming pyruvate
- Pyruvate is converted into glucose (gluconeogenesis) to be used in a muscle cell for energy
- Glucose reformed into pyruvate in the muscle (glycolysis)
- As pyruvate is the a-ketoacid of alanine, alanine can be produced which can then be reused again (transamination)
What is the benefit of the glucose-alanine cycle?
- Prevents buildup of nitrogen in muscle
- Allows alanine to be recycled when not needed or made when needed
What is catabolism?
The metabolic pathways involved in breaking down larger molecules (e.g. proteins) into smaller ones (e.g. AA’s)
What is ferritin?
A large protein containing iron found in cytoplasm of (mostly liver) cells
Conc. of ferritin is directly proportional to total iron stores
Low ferritin can be due to iron deficiency (anaemia)
What is vitamin C needed for?
Vitamin C is water soluble so passes more readily through the body
Used in collagen synthesis, antioxidants, iron absorption
Deficiency - scurvy (easy bruising/bleeding, teeth gum disease)
What is vitamin A needed for?
Lipid soluble
Forms rhodopsin in rod cells, spermatogenesis, prevention of foetal reabsorption of female
Deficiency - blindness
What is vitamin E needed for?
antioxidant, stored in non-adipose tissue
What happens at the end of a red blood cells lifetime?
- Iron from hemoglobin is recycled
- Porphyrin ring (globin) compunds are broken down to form bile pigments (e.g. bilirubin)
What is bilirubin?
- The most predominant bile pigment
- Yellow in colour
- Fat soluble but becomes water soluble before excretion in faeces or urine
What are common symptoms of jaundice?
Yellow discoloration of the skin and eyes
What is jaundice caused by?
Caused by excess of the bile pigment bilirubin in the plasma of the blood
- Prehepatic jaundice - excessive breakdown of RBC
- Hepatic jaundice - Inflammation of liver preventing conversion of fat-soluble to water soluble bilirubin (excretion)
- Posthepatic jaundice - Obstruction of the biliary tree
What are the functions of bile?
- Lipid digestion and absorbtion
- Cholesterol homeostasis
- Excretion of waste e.g. bilirubin, drug metabolites, metals etc.
