MDS PREP
What is the threshold for glucose excretion in the urine in a healthy individual?
1) 100 mg/100 ml
2) 180 mg/100 ml
3) 200 mg/100 ml
4) 250 mg/100 ml
The threshold for glucose excretion in the urine in a healthy individual is approximately 180 mg/100 ml, above which glucose appears in the urine.
The glomerular filtration rate (GFR) is determined by which two factors?
1) Blood pressure and urine osmolarity
2) Blood flow rate and tubular reabsorption
3) Net filtration pressure and glomerular capillary filtration coefficient (Kf)
4) Hormonal levels and urine volume
The glomerular filtration rate (GFR) is determined by net filtration pressure and the glomerular capillary filtration coefficient (Kf), which are critical for kidney function.
What is the normal ratio of glycine to taurine conjugates of bile acids in the bile?
1) 1:1
2) 2:1
3) 3:1
4) 4:1
Physiology
Answer: 3
The ratio of glycine to taurine conjugates of bile acids is normally 3:1.
What happens when the transport maximum for glucose is exceeded?
1) All excess glucose is reabsorbed
2) Some glucose is reabsorbed and some is excreted
3) All excess glucose is excreted in the urine
4) No glucose is excreted regardless of the amount
Physiology
Answer: 2
When the transport maximum for glucose is exceeded, the excess glucose is not reabsorbed and appears in the urine, known as glucosuria.
What is the primary mechanism of H+ secretion by parietal cells?
1) Active transport via the sodium-hydrogen exchanger (NHE3)
2) Secretion through H+-K+ ATPase pump
3) Secretion through a chloride-bicarbonate antiporter
4) Secretion through a sodium-bicarbonate cotransporter
E) Secretion through a sodium-hydrogen antiporter
The primary mechanism of H+ secretion by parietal cells is through the action of the H+-K+ ATPase pump, also known as the proton pump. This enzyme is responsible for actively transporting H+ ions into the gastric lumen while moving K+ ions into the cells, thereby acidifying the gastric content.
What is the role of carbonic anhydrase in the reabsorption of bicarbonate in the renal tubules?
1) It facilitates the formation of carbonic acid in the tubular lumen.
2) It catalyzes the conversion of carbon dioxide and water to carbonic acid in the tubular cells.
3) It enhances the secretion of hydrogen ions into the tubular lumen.
4) It accelerates the dissociation of carbonic acid into carbon dioxide and water in the tubular cells.
E) It is not involved in the reabsorption of bicarbonate.
Carbonic anhydrase is present in the tubular cells and accelerates the reaction of carbon dioxide and water to form carbonic acid, which then dissociates into bicarbonate and hydrogen ions. This facilitates the reabsorption of bicarbonate into the blood and maintains the acid-base balance.
Which of the following inhibits gastric acid secretion?
1) Low pH in the stomach
2) High pH in the duodenum
3) Secretion of gastrin
4) Both A and B
Both low pH in the stomach and high pH in the duodenum inhibit gastric acid secretion, helping to regulate the digestive process.
What is the primary site of vitamin B12 absorption in the intestine?
1) Stomach
2) Duodenum
3) Jejunum
4) Ileum
The primary site of vitamin B12 absorption in the intestine is the ileum, where it binds to intrinsic factor for absorption.