Excretion Flashcards
What is the lining of a capillary called?
Endothelium
What three layers do substances have to pass through to get from the capillary to the Bowman’s capsule?
- Endothelium (fenestrations)
- Basement Membrane (contains fibrous collagen- sieve)
- Podocytes
What goes into the Bowman’s capsule? (Glomerular filtrate)
- Water
- Ions
- Urea
- Glucose
What does not go into the Bowman’s capsule?
- Cells
- Proteins
Describe ultrafiltration.
Ultrafiltration occurs when blood enters the glomerulus, the efferent arteriole has a smaller diameter than the afferent arteriole which causes high hydrostatic pressure which causes water, glucose, urea and ions to be filtered out into the Bowman’s capsule. It is now called the glomerular filtrate. Cells and proteins remain in the blood.
What are three functions of the liver:
- Detoxification
- Deamination
- Stores glycogen
What is the definition of excretion?
Removal of waste products (byproducts from normal cell processes) from the body. Helps to maintain pH and osmotic pressure within the body
What five things need to be excreted from the body?
- CO2
- H2O
- Bile pigments (bilirubin)
- Salts
- Urea
What is the definition of secretion?
Movement of materials within the body
What happens when blood glucose is too high in the liver?
- Beta cells in the Islets of Langerhans release insulin which bind to receptors on target cells on hepatocytes. This induces tyrosine kinase to phosphorylate inactive enzymes to become active enzymes. A cascade of enzyme controlled reactions causes vesicle containing glucose transporter proteins to implant within the cell surface membrane. Extra glucose enters the cell and is converted to glycogen, conversion to fats and used in respiration.
What happens when blood glucose is too low in the liver?
- Alpha cells in Islets of Langerhans release glucagon which binds to receptors on target cells in hepatocytes. This stimulates activation of a G protein to activate adenylyl cyclase. Adenylyl cyclase stimulates conversion of ATP to cAMP (second messengar)
How is alcohol broken down by the liver?
Ethanol diffuses through he membrane and is converted to ethanal in the cytosol by ethanol dehydrogenase. The 2H produced are used to reduce NAD. Ethanol enters the mitochondria and is converted to ethanoate and releases 2H which reduces NAD.
How does fatty liver form?
Reduces too much NAD in alcohol breakdown so cannot use fatty acid in respiration. Deposited in liver as lipids and cause fatty liver. Acidity can cause damage leading to liver cirrhosis.
In what ways are the cell lining in the PCT specialised?
- PCT is folded to have a high S for facilitated diffusion/ active transport/ osmosis/ diffusion
- Mitochondria
- Basolateral membrane has high numbers of Na+/K+ pumps
- Membrane has cotransporter proteins
What happens to hepatocytes when blood glucose is too high.
Beta cells in the Islets of Langerhans release insulin which binds to complementary receptors on hepatocytes. This stimulates tyrosine kinase to phosphorylate inactive enzymes to form active enzymes. A cascade of enzyme controlled reactions occurs, causing vesicles containing glucose transporter proteins to undergo exocytosis, implanting glucose transporter proteins into the plasma membrane. Glucose enters the cell and is used up in respiration or converted to glycogen/fats.
