Excretion Flashcards
Suggest where ADH is removed from the blood and describe what then happens to the ADH molecule
how ADH is dealt with as a protein
in , liver/hepatocytes;
hydrolysis / acted on by protease ;
deamination/amine group removed /
formation of ammonia / formation of NH3 ;
ornithine cycle /
formation of urea / formation of CO(NH2)2 ;
amino acids / keto acids ,
used in (named) metabolic pathway ;
how ADH or urea is dealt with as a small molecule
in kidney ;
(ultra)filtered from blood / moves from blood into nephron ;
(because) small molecule ;
urea not (all) reabsorbed / ADH not reabsorbed /
(ADH or urea) present in urine ;
excreted
ADH
ADH is a hormone that is produced by specialised nerve cells known as neurosecretory cells. These cells detect changes in the WP of the blood flowing through the hypothalamus. If the WP in the blood is too low ADH is released
ADH is not secreted immediately but passes along the axon of the specialised nerve cells to the posterior pituitary gland from where it is released into the blood
hCG
hCG binds to mobile antibodies from a hormone antibdy complex
Moves up the test stick together
LH complex binds only with immobilised antibodies specific to them ‘
Coloured dye
2 lines - postitive
Why do fish not need to excrete nitrogenous waste in the form of ammonia
Ammonia is highly toxic and highly soluble. Fish can access enough water to dilute the ammonia so it is not toxic.
Mammals live on land and may not have access to enough water to dilute the ammonia sufficiently – so they convert it to a less toxic form and allow a higher concentration in their urine
Why does so much blood need to pass through the kidneys
The kidneys remove metabolic waste – the concentration of metabolic waste in the blood must be kept low. The wastes are concentrated in the urine so a large volume of blood is needed to make a small volume of urine. Many of the cells in the kidney are active – they need a good supply of oxygen
Why are the proximal / distal tubule convoluted
makes the tubules longer so there is a larger total surface area for the selective reabsorption that takes place
Ultrafiltration
Filtration at a molecular level. The pores in the filter are small enough to prevent larger molecules from passing through
Why is it not correct to say that the pressure in the glomerulus is raised
To raise the pressure in the glomerulus would require some form of pumping action. The pressure is maintained at a high level by resistance to flow in the efferent arteriole – the blood cannot escape from the glomerulus easily so there is little drop in pressure
Why are the concentrations of protein in the urine higher than that of the glomerular filtrate
Proteins are not reabsorbed. Water is withdrawn from the fluid in the nephron and this concentrates the proteins
Why must the collecting duct pass through a region of low wp
The wall of the collecting duct is permeable to water. As the duct passes through the region of lower water potential water is drawn out of the urine by osmosis. This conserves water, making the urine more concentrated
Why is it important that terrestrial animals reabsorb as much water as possible
Terrestrial animals don’t have easy access to water so need to conserve water so that they do not have to drink constantly
Why do camels need a long loop of Henle
A long loop of Henle can concentrate the salts in the medulla more and therefore concentrate the urine more effectively
Why do camels need a long loop of Henle
A long loop of Henle can concentrate the salts in the medulla more and therefore concentrate the urine more effectively
Why does the concentration of urea rise as the fluid passes along the distal tubule
Water is reabsorbed from the fluid in the distal convoluted tubule, but urea is not reabsorbed. Therefore the concentration of urea rises. Also, some urea is actively pumped into the distal tubule.
Why does the concentration of sodium stay constant as the fluid passes along the proximal convoluted tubule
Both water and sodium are reabsorbed from the proximal tubule in equal amounts. Sodium is reabsorbed by secondary active transport and water is withdrawn by osmosis.
