Filtration And Reabsorbtion

Question 1

State how ultrafiltration works

Answer 1

1) blood enters afferent arteriole (wider) into glomerulus. Exits efferent arteriole (narrower) therefore creating high hydrostatic pressure in glomerulus.
2) forces smaller molecules out of bowman’s capsule through three layers which it is filtered
3) layer 1 - endothelium cells which filter out RBC and WBC
4) layer 2- basement membrane which prevents large proteins
5) layer 3- the epithelium has podocytes have slits which make sure no small molecules can pass through
6) glomerular filtrate is formed, amino acids, glucose, urea, inorganic ions and water

Question 2

What molecules are reabsorbed by nephron into blood

Answer 2

1) glucose
2) water
3) amino acids
4) salts

Question 3

State how reabsorption happens in proximal convulated tube

Answer 3

1) glucose, AA, hormones move out by active transport with ATP
2) Na+ also moves out by active transport followed by water by osmosis
3) water potential lowered therefore cl- ions move out after water by diffusion

Question 4

How does reabsorption happen in descending limb of loop of Henle

Answer 4

1) water moves out by osmosis because it’s permeable to water
2) therefore water potential decreases as increase of ions like NaCl
3) NaCl can’t move out because it’s impermeable to ions

Question 5

How does reabsorption happens in ascending loop of henle

Answer 5

1) ascending loop is permeable to NaCl
2) its got low water potential therefore NaCl can move out by diffusion until reaches isotonic point
3) after that uses active transport to remove ions

Question 6

Reabsorption in distal convoluted tube

Answer 6

1) only reabsorption ions if the body needs it for example if water potential to high
2) only reabsorbs water by ADH if body needs it for example water potential too low

Question 7

Reabsorption in collecting duct

Answer 7

1) reabsorbs water by ADH, aqua porins inserted into membrane, allowing water to go back to blood stream
2) na+ from tissue fluid steepens concentration gradient allowing more water reabsorption if needed
3) all that is left is urine: urea, excess water and excess salts

Question 8

Mechanism of ADH if water is in short supply

Answer 8

1) low water potential is detected by osmoreceptors in hypothalamus (where ADH is made)
2) hypothalamus sends signals to posterior gland which causes it to secrete the ADH into the bloodstream to cells of collecting duct
3) ADH binds to receptors on cell membrane and triggers CAMP ( second messenger)
4) vesicles fuse with the cell surface membrane
5) the membranes of the vesicles contain aquaporins which are inserted and make the collecting duct more permeable
6) provides a route for water to move out of tubule cells and back into capillaries by osmosis

Question 9

Mechanism of ADH when to much water

Answer 9

1) osmoreceptors of hypothalamus detect this and send signals to posterior gland to reduce the release of ADH
2) very little water is re absorbed to maintain water potential

Question 10

How do you make monoclonal antibodies

Answer 10

1) a mouse is injected with hCG so that the appropriate antibodies can be made
2) the B cells that produce the antibodies are removed from the spleen and fused with myeloma ( cancer cell that divides rapidly)
3) this is called hybridoma
4) these hybridoma cells divide rapidly producing the required antibodies
5) antibodies are purified and used

Question 11

Adaptations of pct

Answer 11

1) many microvilli - increases SA for reabsorbtion
2) many mitochondria - provides ATP for the active transport processes.
3) many co transport proteins- each carry different substance across membrane