M5C15 Exam questions Flashcards
What property of thr hormone hCG allows it to be detected in urine?
hCG has a molecular mass of less than 69,000
Compare the processes occurring in the proximal and distal convoluted tubes:
Similarities:
-Both undergo co-transport
-Both involve selective reabsorption
-Both use active transport
Differences:
-DCT involves Ca2+ ions
-Co-transport in DCT involves ions only.
State and explain one symptom observed is cells of collecting duct no longer responded to ADH:
-Large volume of dilute urine would be produced.
-Due to less aquaporins in wall of collecting duct.
Explain why podocytes are usually unable to undergo mitosis:
-If cells divided there would be fewer fenestrations for ultrafiltration.
-Cells are already specialised so can’t divide.
-Shape is too irregular to divide.
What features of adult stem cells make them suitable for regeneration of tissues in the kidney?
-Adult stem cells are multipotent.
-So can differentiate into any cells within kidney tissue.
Describe the similarities and differences between ultrafiltration and the formation of tissue fluid:
Similarities:
-Both under high hydrostatic pressure.
-Both involve basement membranes
-Small molecules are filtered in both
-Many molecules (water, sugars) are reabsorbed into capillaries.
Differences:
-Filtrate enters Bowman’s capsule whereas tissue fluid enters intracellular space.
-Molecules not reabsorbed form urine in the kidney, molecules not reabsorbed in tissue fluid become lymph.
Explain why the presence of the protein albumin in the urine indicates kidney damage?
Large proteins should remain in the blood.
State one function of the distal convoluted tubule
Reabsorption of water/ions
Describe the function of the structures in the proximal convoluted tubule
Contains villi which increase surface area for reabsorption.
Explain why some foods affect urine production
-Salted/sweet foods decrease water potential due to high sugar/salt content.
-Osmoreceptors detect decrease and release ADH.
-ADH causes production of aquaporins in collecting duct so more water is reabsorbed.
Describe how the endocrine and nervous sytems work together to increase water absorption in collecting duct.
Nervous system:
-Hypothalamus is part of nervous system.
-Osmoreceptors detect change in water potential.
-Hypothalamus synthesises ADH.
-ADH released from pituitary gland.
Endocrine system:
-ADH binds to receptors on cells of collecting duct.
-Increases permeability of water
-Role of cAMP - triggers vesicles containing aquaporins to fuse with membrane.
-Example of negative feedback.
ornithine cycle
What is the method by which ornithine moves into the mitochondria and citrulline moves out and why?
Facilitated diffusion
-Not lipid soluble molecules so require protein channels.
Why is it important that NAD is made from converting pyruvate into lactate in anaerobic respiration?
-NAD is needed for glycolysis to take place.
-There is a limited amount of NAD in the cell.
What are the 3 functions of the liver?
-Protein metabolism - Transamination, deamination.
-Carbohydrate metabolism - glycogenolysis, glycogenesis, gluconeogenesis.
-Detoxification
What is ultrafiltration?
When blood passes through the glomerulus and small molecules are filtered from the blood to the Bowman’s capsule.
Describe the basic process of ultrafiltration
-Blood in glomerular capillaries is under high hydrostatic pressure, forcing small molecules into Bowman’s capsule.
-Bowman’s capsule contains podocytes (wrap around capillaries and prevent plasma proteins passing through).
-Gaps in endothelium of capillary allow small molecules to pass through basement membrane (layer of collagen between capillary and podocyte).
-Podocytes are adapted for ultrafiltration - Extensions (pedicels) wrapped around capillary, only allow small molecules through.
What is selective reabsorption?
Where useful molecules are moved out of the blood in ultrafiltration are returned to the blood.
Describe the process of selective reabsorption of useful molecules:
Occurs in PCT
1) AT transports Na+ out of epithelial cells lining the PCT into the bloodstream.
2) Epithelial cells now have a low conc of Na+, so Na+ diffuse in from fluid in PCT through carrier proteins (facilitated diffusion).
3) At the same time, carrier proteins transfer useful molecules from PCT into epithelial cells. - This is co-transport: As transport of useful molecule is coupled with Na+. Each carrier protein co-transports a different molecule.
4) Useful molecules diffuse out of epithelial cells into bloodstream.
How are epithelial cells in PCT adapted for efficient absorption?
-Membrane on lumen is lined with microvilli (Large SA)
-Infoldings on membrane near sapillary (Large SA).
-Contain many mitochondria
What is the role of the loop of Henle?
Lower the water potential in the tissue in the medulle
Describe the role of the loop of Henle:
1) As fluid moves up the ascending limb, Na+ & Cl- are pumped out and transferred to interstitial region by AT (ATP provided by cells of ascending limb). Interstitial area now has high levels of Na+ = low water potential.
2) Loop of Henle is adapted to reduce energy needed - descending limb has a high conc of water due to permeability of limb. Water diffuses out of medulla and into blood, fluid becomes more concentrated down limb.
3) As concentrated fluid moves up ascending limb ions diffuse out then move out by AT further up.
This is the counter-current multiplier hypothesis: Fluid moves in opp directions - increases efficiency of ion transfer.
What happens in the collecting duct?
Water moves from fluid to medulla via osmosis so low water potential in medulla is needed, water is reabsorbed into blood.
How is the water reabsorbed from the collecting duct controlled?
Osmoregulation and ADH - important as the water potential of blood must be kept within a certain range.
Describe the role of the hypothalamus in osmoregulation
Hypothalamus synthesises ADH which is then transported to posterior pituitary gland where it is stored.
Hypothalamus also contains osmoreceptors which are sensitive to the water potentialof blood.
