BRAINCAKEProximal Convoluted Tubule
The proximal convoluted tubule (PCT) is the first, coiled part of the nephron after the Bowman's capsule, in the cortex. It reabsorbs most of the filtrate: all the glucose and amino acids, and about 65% of the water and sodium ions.
The cells of the PCT wall are adapted for reabsorption:
• microvilli on the surface facing the lumen give a large surface area
• many mitochondria provide ATP for active transport
• many carrier and co-transporter proteins in their membranes
• tight junctions between neighbouring cells, so substances pass through the cells rather than leaking between them
• a folded basal membrane next to the capillaries, giving a large surface area for transport into the blood
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Key terms in this lesson
- bowman's capsule
- The cup-shaped end of a nephron that surrounds the glomerulus and collects the filtrate.
- facilitated diffusion
- The passive movement of a substance down its concentration gradient through a specific carrier or channel protein.
More in Homeostasis
- Osmoregulation in Mammals
- Structure and Function of the Kidney
- Ultrafiltration
- Selective Reabsorption
- Loop of Henle
- Countercurrent Multiplier
- Distal Convoluted Tubule
- Collecting Duct
All 41 lessons in Homeostasis · All Edexcel A-level Biology topics