Test: GRE Subject Test: Biology

The interaction between blood pressure and kidney function in humans requires coordination by the renin-angiotensin-aldosterone system (RAAS). This system involves the dynamic interplay of the kidneys, lungs, and blood vessels to carefully regulate sodium and water balance.

A normal human kidney has cells adjacent to the glomerulus called juxtaglomerular cells. These cells sense sodium content in urine of the distal convoluted tubule, releasing renin in response to a low level. Renin is an enzyme that converts angiotensinogen to angiotensin I (AI). AI is converted to angiotensin II (AII) by angiotensin converting enzyme (ACE) in the lung.

AII stimulates aldosterone secretion in the zona glomerulosa of the adrenal gland. Aldosterone then acts to upregulate the sodium-potassium pump on the basolateral side of distal tubule epithelial cells to increase sodium reabsorption from the urine, as well as increasing potassium excretion.


Renin is most likely to drive the formation of angiotensin I from angiotensinogen by doing which of the following?

I. Increasing the concentration of angiotensinogen

II. Lowering the activation energy of the reaction from angiotensinogen to angiotensin I

III. Stabilizing the angiotensin I molecule to lower the energy of the products

I,II, and III

II only

I only

III only

II and III

1/1 questions


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