Glucose and amino acids are reabsorbed from PCT or absorbed from intestinal lumen by
**Core Concept**
The transport of glucose and amino acids across the renal proximal convoluted tubule (PCT) and intestinal epithelium is a crucial process for maintaining proper metabolism and electrolyte balance. This is mediated by specific transport proteins that bind to these molecules and facilitate their movement across the cell membrane.
**Why the Correct Answer is Right**
Glucose and amino acids are reabsorbed in the PCT and absorbed in the intestinal lumen by sodium-coupled cotransporters. The sodium-glucose cotransporter 2 (SGLT2) is primarily responsible for glucose reabsorption in the PCT, while the intestinal peptide transporter 1 (PEPT1) and amino acid transporters such as PAT1 facilitate the uptake of amino acids. These transporters utilize the sodium gradient to drive the uptake of these molecules against their concentration gradient.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it does not specify the type of transport involved. While glucose and amino acids are indeed reabsorbed through facilitated diffusion, the sodium-coupled cotransporters are the primary mechanism in the PCT and intestine.
**Option B:** This option is incorrect as it is too vague and does not specify the type of transport or the location. Facilitated diffusion is indeed a mechanism for glucose and amino acid transport, but it is not the primary mechanism in the PCT and intestine.
**Option C:** This option is incorrect as it is not a specific type of transport protein. The sodium-coupled cotransporters (SGLT2 and PEPT1) are the specific transport proteins responsible for glucose and amino acid reabsorption in the PCT and intestine.
**Clinical Pearl / High-Yield Fact**
In the PCT, the reabsorption of glucose occurs until the renal threshold is reached, which is approximately 180 mg/dL. This is an important clinical correlation as it highlights the importance of maintaining proper glucose homeostasis to prevent diabetes mellitus.
**Correct Answer: D. Sodium-coupled cotransporters.**